Invertebrate Zoology

ANNE WELLER

C HAPTER 1 - I NTRODUCTION TO Z OOLOGY

Introduction to Invertebrate Zoology

Coral washed up on the beach of Costa Rica. photo credit: Anne Weller

S ECTION 1

W HAT IS Z OOLOGY ?

L EARNING O BJECTIVES 1. Understand what Zoology is and why it should be studied. 2.

Comprehend binomial nomenclature and classification.

3. List the 8 levels of classification in order. 4. Analyze the classification system and its purpose. 5. Identify the different areas of biology that are involved in the study of zoology.

So you’re interested in Zoology? Or maybe you’re not....Or maybe you’re not even sure what Zoology is. Well, little do you know that you have probably been studying Zoology all your life. Have you ever been to a zoo? Have you ever caught an insect? Have you ever watched the ducks at the park? Have you ever played with a cat, dog, or any other pet? Have you ever watched a squirrel in your yard or listened to the birds chirp? All of these things are the beginning steps to the study of Zoology.

Zoology is a branch of biology that studies the Kingdom Animalia. However, Zoology is not limited to the study of the animals at the zoo. There are many animals that you may not even know exist. Did you know that every time you walk in the grass you step on a large number of tiny organisms? Did you know that every time you eat there is a possibility that you consume worm eggs? Hopefully they are dead! Animals, big and small, are all around us and we could not live without them.

Brainstorm: What are 3 ways that you have interacted with animals recently?

2

When considering your relationship with animals, do not forget the most advanced animal of all, YOU! Yes, you are an animal. Humans are mammals, just like dogs, cats, whales and chimpanzees. We will get more into that later, but remember that as we learn about animals, much of what we are learning about applies to you.

Studying Zoology will help you understand the organisms around you. Zoology tells us how animals live and why they live the way they do. Better understanding of these organisms will help us to protect the animals and the environment around us. Brainstorm: What are 5 things that you rely on animals and the environment for?

So now that you know what Zoology is, you should begin to understand why it is important to study Zoology. Throughout this course, we will cover the major principles of Zoology, History of Zoology which include anatomy and physiology, ecology, genetics, evolution, reproduction and development, ethology and con- Humans have always had interest in the animals surrounding servation. us. Ancient cultures left behind documentation of this interest in the forms of carvings, paintings, and textiles.

G ALLERY 1.1 Mammals G ALLERY 1.2 Ancient Chinese Textile

The Standard Poodle, pictured above is a mammal of the Family Canidae.

Ancient Chinese textiles date back as far as the 11th century. Textiles such as the one above were called the Buzi and the animals symbolized the rank of the officers that wore them. Source: www.sccfsac.org

3

The Greek philosopher, Aristotle, was one of the first to leave behind documentation of the study of Zoology. He started by dividing all living things into two groups, plants and animals. He was essentially dividing the study of living things into Botany and Zoology.

G ALLERY 1.3

An orchid, pictured here, would be studied in the field of botany.

Classification of Organisms In addition to Aristotle’s idea of grouping organisms by their similarities, we now have a system for naming these organisms. Carolus Linnaeus developed this system of naming, referred to as binomial nomenclature. In this system, each organism is given two names, their genus and species. For example, you, a human, have the scientific name Homo sapiens. Humans belong to the genus “Homo,” which means “the same.” We then belong to the species “sapiens,” which means “wise.” There is a specific format for writing scientific names. The name is always italicized (or underlined if hand-written). The first letter of the genus is capitalized and the species is not. Before Linnaeus developed this system, scientists used a polynomial system, which would use anywhere from 10100 words to name an organism. For example, a cheetah would have a name like this: Four-legged cat with black spots on yellow fur, long tail, small, rounded ears, aerodynamic body. Although this gives a good description of the animal, it is not a good way to name the animal. Using binomial nomenclature, the cheetah has been named Acinonyx jubatus.

Although Aristotle did not have it completely right, his original system has been adapted to become the system of classification that we use today. 4

G ALLERY 1.4

Brainstorm: Where are 3 places that you can see classification? In order to classify living organisms, scientists have developed a system with eight levels of classification. The largest, most general level is domain. The smallest, most specific is species. The eight levels are as follows: Domain Kingdom Phylum Class Order Family Genus Species

Cheetah -- Acinonyx jubatus Find it! How many domains of living things are there? How many kingdoms of living things are there?

Find it! What does Acinonyx jubatus mean? Giving an animal two names is a great way to keep them organized, but it’s not enough. When scientists classify organisms, they are putting them in groups based on similarities and evolutionary relationships.

When studying Zoology, we will focus only on one domain and one kingdom. Every animal that we study will belong to the Domain Eukarya and the Kingdom Animalia.

5

It may seem easy to classify some organisms (a sponge obviously does not belong in the same group as a cat), but it becomes more difficult as you get to the more specific levels of classification. For example, how do you classify a lion, tiger, panther, cheetah and a house cat? They are obviously similar, but also very different. Sometimes scientists must use very technical methods, such as genetics and embryology. Just looking at an animal is not always enough to determine its classification. Hundreds of years ago, scientists put butterflies and birds in the same group. Why? Because they can both fly. We now know that they could not be more different. Anatomy and physiology has helped us determine that. In order to truly understand Zoology, one must also have a basic understanding of other areas of biology. Refer to table 1.1.

Studying organisms and their classification helps us to understand their evolutionary relationships. Evolutionary relationships are illustrated as phylogenetic trees.

G ALLERY 1.5 Phylogenetic Trees

Table 1.1 Subdisciplines of Biology AREA

DESCRIPTION

Anatomy

Study of the structure of entire organisms and their parts

Ecology

Study of the interactions of organisms with their environment

Embryology

Study of the development of an animal from the fertilized egg to birth or hatching

Genetics

Study of the mechanisms of transmission of traits from parents to offspring

Physiology

Study of the function of organisms and their parts

This phylogentic tree compares eagles, penguins, alligators, crocodiles, turtles and mammals

6

Now that you know what Zoology is and have a basic understanding of classification, you may say to yourself, “I want to be a zoologist!” Well, that’s a pretty broad statement. Just like being a doctor, where you have many fields to choose from (pediatrics, cardiology, neurology, etc.), Zoology can be broken down into more specific fields. See Table 1.2

R EVIEW 1.1 What is Zoology? Question 1 of 4 Zoology is the study of:

A. Life Table 1.2 Subdisciplines of Zoology

B. Animals AREA OF STUDY

DESCRIPTION

Entomology

The study of insects

Herpetology

The study of amphibians and reptiles

Ichthyology

The study of fish

Mammalogy

The study of mammals

Ornithology

The study of birds

C. The Environment D. Space

Check Answer

7

S ECTION 2

What is an Animal?

We know that zoology is the study of animals. We know that animals are classified, like all other living things. However, do you know what an animal is?

G ALLERY 1.6 Animal or Not?

L EARNING O BJECTIVES 1. Identify the characteristics of an animal. 2. Compare and contrast sexual and asexual reproduction. 3. Understand the different methods of obtaining energy. 4.

Identify and understand the different body systems of animals.

5. Analyze the different methods of respiration.

Acropora divaricata

6. Identify stimulus and response. Find it! Find the common name of each of the organisms in Gallery 1.6 and indicate whether or not it is an animal.

8

In order to be an animal and be classified in the Kingdom Animalia, a living thing must have specific characteristics. For an organism to be classified in the animal kingdom, it must have the following characteristics: be motile at some point in their life, be multicellular, consume to acquire energy, respire, grow, develop, reproduce and respond to stimuli.

M OVIE 1.1 Animal Movement

Motile

Analyze: As you watch the video, think about how the two animals are moving and why they move the way they do.

Multicellular Like all living things, animals are made of many microscopic cells. Unlike plants and fungi, animals cells do not have rigid cell walls. In most animals, the cells are differentiated into different types of tissue (muscle, nerve, bone, etc).  These tissues then make up organs, which make up organ systems. For example:

When asked for characteristics of animals, many are quick to list that they move from place to place.  All animals move, however, some animals do not move for the majority of their lives. Sponges and sea anemones, for example, move only during their larval stages. Animals such as Muscle cells sponges swim as larva and attach     Cardiac muscle tissue             themselves to a permanent spot to grow into adults. These animals A cheetah chases a male impala. Heart are said to be sessile. Movement from place to place serves many purposes. Being motile al                                  Circulatory system lows animals to seek food, escape predators and find breeding partners. Find it! The circulatory system is responsible for pumping Brainstorm. What are 5 reasons that you move from place to place?

your blood. Find 5 other body systems and what they are responsible for. 9

The organization of these cells allows animals to be complex organisms and perform complex functions. The cells of multicellular organisms work together to perform functions that are necessary for life.

G ALLERY 1.7 Heterotrophs

Energy Unlike plants, which are able to harvest energy directly from the sun (photosynthesis), animals must consume in order to obtain energy. Because animals must obtain their energy from other organisms, they are referred to as heterotrophs. Refer to Table 1.3 for the methods in which animals feed. Table 1.3 Different types heterotrophs TYPE

DESCRIPTION

Herbivore

Animal that consumes only plants.

Carnivore

Animal that consumes only meat.

Omnivore

Animal that consumes both plants and meat.

Detritivore / Scavenger

Animal that feeds on dead or decaying plant and animal matter.

Filter Feeder

Animals that feed by straining suspended matter and food particles from water.

The giraffe shows in an herbivore.

10

Gas exchange Growth and Development Gas exchange, or respiration occurs in all animals. Whether the animal lives in water or on land, it cycles oxygen in and carbon dioxide out. Oxygen is needed for animal cells to function. When the animal cells use the oxygen, carbon dioxide is created as a waste product. Although all animals must take in oxygen, they do so in many different ways. Animals may use lungs, gills, skin or simple diffusion to obtain their oxygen.

G ALLERY 1.8 Different modes of respiration

When an animal is born, or it hatches,it is not considered an adult. Think about yourself. The average human baby weighs 7.5 lbs at birth. The average adult human weights around 185 pounds. There is a big difference between the two and there is a lot of growth and development that must take place before a baby becomes an adult. In order for a female animal to lay eggs or give birth to young, the offspring must be smaller than the adult, it is simple physics. This means that animals must grow throughout their lifetime. Growth refers to an increase in the mass of an organism. Development refers to changes that take place in and outside of the body. Some animals, such as a butterflies grow and develop during metamorphosis. Other animals, such as dogs, grow and develop without a drastic change in body form. Brainstorm: Can you list 3 animals that go through major structural changes as they develop (metamorphosis)?

The hawksbill sea turtle respires using lungs.

Can you list 3 animals that do not go through major structural changes as they become an adult?

11

Reproduction All animals must reproduce in order for their species to continue. Some animals have adapted to reproduce by way of asexual reproduction. Asexual reproduction usually results in many offspring and little to no parental care. Asexual reproduction also results in offspring that are genetically identical to the parent. Sexual reproduction requires two parents, as opposed to one. Sexual reproduction is generally slower and results in a lower number of offspring. However, the offspring are genetically different than the parents and often receive parental care as they grow and develop.

G ALLERY 1.9 Methods of reproduction

Brainstorm: What are the advantages and disadvantages of sexual and asexual reproduction?

Black swans reproduce sexually and both parents are involved in raising the young.

12

M OVIE 1.2 Response to stimuli Response to stimuli What do you do when you put your hand on a hot stove? What do you do when its cold out and you have forgotten your coat? Your answers to these questions indicate how you respond to stimuli. A stimulus is anything that causes a reaction. A characteristic of animals is the ability to respond to those stimuli. An animal is able to use their senses (sight, hearing, taste, smell and touch) to detect stimuli. An animal’s response to stimuli can depend on instinct, reflex or learned behavior Refer to table 1.4 for examples.

Table 1.4 Stimulus and Response STIMULUS

RESPONSE

Cold

Shivering

Hot

Sweating

Predator approaching

Run away

Thirst

Find source of water

In the video, you will observe cuttlefish, which are closely related to octopi, reacting to various stimuli.

Analyze: What stimulus and response can you identify in the video?

13

R EVIEW 1.2 What is an animal? Question 1 of 8 All animals are motile at some point in their life.

A. True B. False

Check Answer

14

S ECTION 3

How Do Animals Change?

There are an estimated 8.7 million living species on Earth, not including bacteria. This also does not include the species that are no longer on Earth. It is estimated that 99% of all species that have ever existed are extinct. Brainstorm: Can you think of 3 species that are extinct?

L EARNING O BJECTIVES 1. Understand the theories of evolution and natural selection. 2. Analyze how animal adaptations help them survive in their environments.

With new species being discovered everyday, zoologists are asking how so many species have come to exist. How are these species so well adapted to their environments? How are some species similar even though they live on different continents? The theory of evolution provides us with some answers to these questions.

G ALLERY 1.10 Evolution

3. Make connections between different species of animals.

The aardvark is nocturnal species found in Botswana on the continent of Africa.

15

Born on February 12, 1809 (the same day as Abraham Lincoln), Charles Darwin considered himself a naturalist. Although he began his education with the intention of becoming a doctor, his studies took him elsewhere and he is now considered the father of evolution. At the age of 22, Charles Darwin was given the opportunity to board a ship and embark on a 5 year journey. On a ship, named the HMS Beagle, he joined a crew whose mission was to chart the coastline of South America.

G ALLERY 1.11 Darwin’s Finches

Find it! Using the Google Earth app, locate the Galapagos Islands. On his journey, Darwin observed and collected many species of plants and animals. As he studied the organisms at each stop, he began to see similarities and differences. His most famous observations came from the Galapagos Islands. While traveling here, Darwin observed many different forms of small birds, called finches. He noticed that the finches on each island had beaks that were adapted for the specific food that was available there. Darwin theorized that these finches had a common ancestor and as they moved to different areas, they adapted to that environment. His studies of the finches, and other species in the Galapagos, led him to his theories of evolution and natural selection.

The Large Cactus-Finch has a beak adapted for eating seeds, arthropods and parts of the prickly pear cactus.

Darwin’s theory of evolution is centered around the ideas of natural selection and survival of the fittest. Darwin believed that the organisms whose traits make them best suited for the environment will survive and reproduce, passing those traits on to their offspring. Over time, the traits of the welladapted organism become the normal traits for that species. According to this theory, evolution sometimes happens by chance, stemming from a genetic mutation. 16

Find it! Using Google, find another animal that Darwin studied in the Galapagos and describe what makes it unique.

What is an adaptation? What do you know about a polar bear? You probably know that it is large, lives in a cold environment, and is white. But do you know what color a polar bear’s skin is? It’s black. And a polar bear’s hair is actually not white, it is transparent. This is a perfect example of an adaptation. The transparent hair traps heat from the sun and the black skin absorbs the heat. This allows the bear, which is a mammal, to maintain its body heat while living in such a cold environment. You may wonder why the hair isn’t black, since dark colors absorb the most heat. Well, being a black bear in the snow is not very good camouflage, which would make hunting difficult. Adaptations come in many forms. They can be structural or behavioral. Either way, and adaptation is something that increases and organisms chances of survival in a particular area. See Table 1.4 for examples of adaptations.

Table 1.4

ADAPTATION

PURPOSE

STRUCTURAL OR BEHAVIORAL?

Tiger’s Stripes

Camouflage

Structural

Kangaroo’s Pouch

Protect Offspring

Structural

Bat’s hunting at night

Avoiding predators

Behavioral

Mosquitos laying 1000’s of eggs

Ensures the survival of some offspring

Behavioral

Male peacock’s tail

Attracts mates

Structural

17

Evolution is a very slow process, taking place over thousands, maybe even millions of years. When learning about the different animals throughout this course, consider what makes them able to survive in their environment. As you learn, you should also take into consideration what all of the different animals have in common, as well as what makes them different. For example, as humans, we share many characteristics with sponges, such as multicellularity, motility, heterotrophy, and the need for oxygen. However, the characteristic that sets humans apart from all other animals is our brain. No other animal on Earth can think, communicate and plan the way that humans do. But could that all change someday?

R EVIEW 1.3 How Do Animals Change Question 1 of 4 What was the purpose of Charles Darwin’s voyage on the HMS Beagle?

A. To discover new species. B. To fight in a war.

Brainstorm: Think of 3 different animals and explain how they are adapted to live where they do.

C. To chart and map South America. D. To gather food.

Check Answer

18

Chapter 1 Vocabulary Asexual Reproduction Binomial Nomenclature Biology Botany Carnivore Detritivore Development Diffusion Ethology Evolution Extinct Filter Feeder Growth Herbivore Instinct Metamorphosis Motile Mutation Natural Selection Naturalist Omnivore Organ Organ System Phylogenetic Tree Respiration Response

Chapter 1 Summary Scavenger Sessile Sexual Reproduction Stimulus Survival of the Fittest Taxonomy Tissue Zoology

★ Zoology is the study of animals. ★ All animals are given a scientific name using Binomial Nomenclature. ★ Taxonomy classifies living things using 8 levels. ★ Phylogenetic tree shows the inferred evolutionary relationships of organisms. ★ All animals share 7 characteristics (multicellular, motile, heterotroph, need for energy, grow and develop, reproduce, respond to stimuli). ★ Evolution is change over time. ★ Charles Darwin developed the theory of evolution. ★ An adaptation is something that helps an animal survive.

19

C HAPTER 2

Sponges and Cnidarians

Now that you know what an animal is, let’s start from the beginning. Multicellular organisms have been around for nearly 800 million years, but that doesn’t mean animals as we know them have been around that long. Things started pretty simple. Some of the animals you are about the study do not look like anything you would ever call an animal. The members of the phyla Porifera and Cnidaria are very simple organisms, but have all the characteristics necessary to be classified as an animal. Let’s take a look.....

Brain Coral, picture above, is actually not one organism, but colony of many tiny organisms working together. These organisms are members of the phylum Cnidaria and are closely related to jellyfish.

S ECTION 1

Phylum Porifera - Sponges

L EARNING O BJECTIVES

Brainstorm: What are 3 different uses for a sponge? What do you think of when you hear the word sponge? You may thinking of something you have around home that can be used for cleaning. If you have sponges around the house, they are probably the man-made kind that can be purchased at a local store. But did you know that a sponge is also a type of animal? Sponges belong to the phylum Porifera, which has approximately 10,000 species.

G ALLERY 2.1 Phylum Porifera

1. Identify the characteristics of the phylum Porifera. 2. Understand the respiration, reproduction and feeding of sponges. 3. Compare and contrast the different types of sponge reproduction. 4. Understand sponge functions and how they compare to the functions of other animals. 5. Understand the impact that sponges have on the environments in which they live. Sponges come in a variety of size, shapes and colors.

21

Characteristics of Sponges Sponges belong to the phylum Porifera. The word Porifera is Latin for “pore-bearers.” Sponges were given this name because when they are alive, their body is completely covered with pores. Sponges are mostly marine, with the vast majority of the species being found in the ocean. The few freshwater species are generally smaller and less colorful than the marine sponges. Characteristics of sponges include: 1. Asymmetrical body shape. 2. Three cell types: pinacocytes, mesenchyme cells, and choanocytes. 3. No tissues or organs. 4. Body form that includes a central chamber or branching cavities that allow for water flow. What are Sponges Made of? Sponges are animals, so we know that they are made of cells. However, they are made of cells that are very different from your own. Unlike yours, sponge cells do not form tissues and organs. This means that sponges do not have a heart, a brain, muscles, or even blood. Instead, they have different types of cells that perform specific functions. By working together, much like your organ systems do, these cells allow a sponge to function as an animal.

Sponges do not have skin, instead, the outside of their body is lined with thin, flat cells called pinacocytes. These specialized cells protect the sponge, help determine the shape of the sponge, and help regulate water circulation. Some pinacocytes are specialized into tubelike porocytes, which can open and close to control movement of water through the body wall. Just below the pinacocyte layer is the mesohyl. The mesohyl contains amoeboid cells that are responsible for many different functions. These amoeboid cells are also known as mesenchyme cells. Mesenchyme cells are responsible for reproduction, forming skeletal elements, and transporting and storing food. Below the mesohyl is the layer of the sponge that lines the inside chamber(s). This layer is made of choanocytes, also known as collar cells. Choanocytes are cells that have a flagella and a “collar” of finger-like microvilli surrounding the flagella. The flagella whip in the water, creating a current, which pulls water in through the body wall. As the water moves in to the central chamber, the collar of choanocytes filters food particles from the water. CELL TYPE

FUNCTION

LOCATION

pinacocyte

protection, shape, regulate water circulation

outer layer

mesenchyme

reproduction, form skeletal elements, transport and store food

middle layer

choanocyte

keep water moving through body wall, trap food

inner layer

22

G ALLERY 2.2 Sponge Structure Brainstorm: Think of the functions that choanocytes perform. What human organ system(s) could choanocytes be compared to? In order to maintain their shape, sponges must have a support system. Unlike your skeleton, which is made of bone, a sponge’s skeleton is made of spicules or spongin. Spicules are hard, microscopic structures made of calcium carbonate or silica. Spongin is a more flexible network of collagen and is found in the sponges that you can purchase at the store. The sponges that can be purchased at the store have been dried, beaten and washed so that all that remains is the spongin. Whether the sponge contains spicules or sponge, the skeleton is formed by the mesenchyme cells. Find it! What do humans use collagen for? How Do Sponges Work?

A = Flagella, B = Collar, C = Choanocytes (red), D = Pinacocyte (yellow), E = Porocyte (blue arrows), F = Mesohyl (grey)

Do you know what your blood does for you? Your blood carries oxygen and nutrients around your cells, as well as help remove waste from your cells. Sponges do not have blood to perform these functions, so they must rely on water.

23

Brainstorm: Would sponges be considered carnivores, herRespiration bivores or omnivores? Why? Like all animals, sponges require oxygen to survive. When water enters a sponge, it Nervous Functions enters through ostia, or pores Sponges do not have a G ALLERY 2.3 Phylum Porifera in the body wall. As the water brain or central nervous sysmoves through the sponge, tem. However, they are able oxygen diffuses into the cells to respond to stimuli. Most reand carbon dioxide diffuses sponses are generated by indiout. The water then exits vidual cells responding to a through a large hole at the top stimulus. For example, the of the sponge called the oscucells that open and close the lum. porocytes respond to stimuli by opening and closing the osFeeding tia. This causes water flow to Sponges are filter feedstop or start, depending on the ers. As mentioned earlier, as surroundings. water moves through the sponge, the choanocytes filter Brainstorm: Why would a food particles from the water. sponge need to stop the flow of Sponges feed on microscopic The large openings are the osculum where the water exits water into the body? the sponge. particles such as bacteria, algae, and crustaceans. Once Reproduction the food is trapped, it is transMost sponges are monoeferred to a food vacuole in the choanocyte, where digestion cious. This means that the sponge is able to produce both begins. The food is then passed to the amoeboid cells in the sperm and egg. However, sponges do not usually fertilize mesohyl, which complete digestion and deliver nutrients to themselves because they produce sperm and egg at different the other cells. times. At the time of reproduction, sperm and egg from all 24

of the sponges in the area is released. Fertilization occurs in the ocean water. Once the egg hatches, larva are formed, which are free-floating until they attach to a spot and grow into an adult sponge. Asexual reproduction also occurs in some sponges. These sponges are capable of regeneration. When a piece of the sponge is broken off, it is able to grow into a new individual.

R EVIEW 2.1 Sponges: Phylum Porifera Question 1 of 5 What is the meaning of the word Porifera?

Brainstorm: How do you think that sponges benefit the environments in which they live? What are the Different Types of Sponges? Table 2.1 Classification of the Phylum Porifera CLASS

DESCRIPTION

Calcarea

Spicules composed of calcium carbonate; spicules are needle shaped or have 3 or 4 rays; known as Calcareous sponges

Hexactinellida

Spicules composed of silica with 6 rays; often form an intricate lattice; known as Glass sponges

Demospongiae

Brightly colored sponges with spicules made of silica or spongin, or both; includes freshwater and marine species; includes sponges sold for bathing

A. Sponge B. Pore Bearer C. Filter Feeder D. Sessile

Check Answer

Find it! Where on Earth can each of the 3 classes of sponges be found? 25

S ECTION 2

Phylum Cnidaria - SoftBodied Animals

L EARNING O BJECTIVES 1. Describe the characteristics of the members of the phylum Cnidaria. 2. Explain the structure and functions of cnidocytes. 3. Analyze the advantages of alternation of generations. 4. Understand the ecological and environmental importance of cnidarians.

Brainstorm: Would a human be able to survive without a skeleton? Why or why not?

Most animals have some sort of support system, or skeleton. Some animals have a skeleton inside of their body and some have a skeleton on the outside of their body. Members of the phylum Cnidaria, which include jellyfish, coral and sea anemones, do not have a skeleton at all. Instead, these animals rely on water to support their bodies and give them shape. Characteristics of Cnidarians Members of the phylum Cnidaria, or Cnidarians, are named after their stinging cells, or cnidocytes. Each of these animals has the following characteristics: 1. Radial symmetry 2. Jelly-like layer, or mesoglea, between the epidermis and gastrodermis. 3. Gastrovascular cavity 4. Nerve cells organized in a nerve net. 5. Specialized cells, called cnidocytes, used in defense, feeding and attachment.

26

G ALLERY 2.4 Phylum Cnidaria

cytes discharge harpoon-like structures called nematocysts. When the cnidocyte is triggered, it discharges the nematocyst. The inner lining of the cnidarian is the gastrodermis. This lines the gastrovascular cavity, which is where digestion takes place. Between the epidermis and gastrodermis is the mesoglea. Find it! Cnidarians have nematocysts to protect them, but they can still be eaten. Find 2 animals that eat jellyfish.

G ALLERY 2.5 Nematocysts

African Pillow Coral

What are Cnidarians Made of? Unlike the sponges, which have individual cells that perform functions, cnidarian bodies have tissues that carry out specific functions. The body of the cnidarian is organized into three layers, the epidermis, mesoglea and gastrodermis. The epidermis is the outer layer of the animal. In cnidarians, the epidermis contains cells called cnidocytes that are specialized for protection and food gathering. The cnido-

An illustration showing how nematocysts are triggered.

27

How Do Cnidarians Work? Much like sponges, cnidarians do not have blood. This means that they too rely on water to perform many of their body functions. Respiration Cnidarians rely on diffusion to perform many body functions. Because cnidarians are always found in water, they are able to rely on diffusion to bring oxygen into the body. Wastes such as carbon dioxide and nitrogen are able to diffuse out of the body. Feeding Cnidarians are carnivores that feed mostly on small crustaceans. Some, however, are capable of feeding on small fish. The tentacles of cnidarians are where the cnidocytes are located. When prey triggers the cnidocyte, the nematocyst is discharged, entangling and paralyzing the prey. The tentacles then shorten in order to bring the food toward the mouth. The mouth leads to the gastrovascular cavity, which is where digestion takes place. The mouth of the cnidarian is the only opening to their digestive system. Therefore, any undigested material is expelled through the mouth. Find it! What is the deadliest jellyfish? Where is it found? Nervous Functions Cnidarians do not have a brain or central nervous sys-

tem. Instead, they have what is referred to as a nerve net. It is a simple network of sensory cells that cover the epidermis. It allows cnidarians to respond to both physical and chemical stimuli. For example, if the cnidarian senses touch on a tentacle, it may retract that tentacle. If a coral polyp senses chemical changes in the water, it may retract its entire body into the hard structure around it. Zoologists are very interested in the cnidarian nervous system because it may hold clues to the evolution of the more complex animal nervous system. Reproduction Most cnidarians are dioecious, which means that they are either male or female. This is also referred to as having separate sexes. Cnidarians have two body forms, medusa and polyp. The polyp is usually asexual and sessile, although some are able to move, using their tentacles. It attaches to a substrate with its aboral end and has a tube-shaped body with tentacles surrounding the mouth. The medusa reproduces sexually and is free swimming (not sessile). It is shaped like an umbrella with tentacles surrounding the mouth. The mouth faces down. Water currents are mostly responsible for the movement of medusae, but they are also able to pulsate their body wall to help them move. Some species of cnidarians have both polyp and medusa body forms, this is referred to as alternation of generations. Medusae reproduce by releasing sperm or egg into the water. Once the eggs are fertilized, a larva is formed. The larva will eventually attach to a substrate and a polyp will grow. 28

When a polyp reproduces, it generally does so by the asexual process of budding. When this occurs, a medusa will detach from the body wall of the polyp. An exception to the alternation of generations is found in anemones and corals. These animals have only a polyp body form. Some species reproduce sexually by releasing sperm and egg into the water. Other species reproduce by budding and new polyps form from the body wall and generally form a colony.

G ALLERY 2.6 Cnidarian Body Forms

M OVIE 2.1 Alternation of Generations

The common jellyfish reproduces by alternation of generations. The white structures and the polyps and the orange structures are the medusas.

The Lion’s Mane Jellyfish has a medusa body type.

29

Brainstorm: Recall what you know about sexual and asexual reproduction. What is the advantage of alternating between the two?

G ALLERY 2.7 Class Hydrozoa

Other Cnidarians do not have bones or spicules, but they do have a body shape. Cnidarians are supported by a hydrostatic skeleton. A hydrostatic skeleton is formed when water or body fluids fill cavities in the body and provide support. What are the Different Types of Cnidarians? There are over 9,000 species of cnidarians. The phylum Cnidaria has been divided into 5 different classes. Class Hydrozoa Hydrozoans are small, relatively common cnidarians. Most hydrozoans are marine, but this is the one cnidarian class that has freshwater species. Most hydrozoans have a life cycle that displays alternation of generations, but in some species, the medusa stage has been lost. Hydrozoans include Obelia, Gonionemus, and Hydra. These are some of the most well-known species in this class because they are so common and easily found. Hydra are small, freshwater hydrozoans that could even be found in Lake Springfield. The medusa stage of Gonionemus has structures called statocysts, which help the animal determine which way is up. To learn more about these species, see Gallery 2.7.

Obelia are small, marine cnidarians. A colony of polyps is shown here. Some of the polyps are beginning to bud, forming medusae.

30

Class Staurozoa Class Staurozoa contains approximately 100 species of Marine cnidarians. Found mainly in cold ocean water, these cnidarians lack a medusa stage. The polyp attaches to G ALLERY 2.8 Cnidarians the substrate with the aboral end. The mouth is surrounded by eight tentacles. Until recently, these cnidarians were classified in the class Scyphozoa because they were believed to be “stalked jellyfish.”

Find it! What is the largest jellyfish in the world? Class Cubozoa Cubozoans were once classified with the true jellyfish, but are now separate because of their box-like medusa. Cubozoans display alternation of generations with extremely small polyps. these cnidarians are active swimmers and feed in tropical waters. Found mainly near Australia, cubozoans are among

Find it! In what oceans can Staurozoans be found? Class Scyphozoa The members of the class Scyphozoa are all marine and are considered to be “true jellyfish.” The cominant body form is the medusa, although scyphozoans do display alternation of generations Scyphozoans are dioecious. Many jellyfish are harmless to humans, but can deliver painful and even dangerous stings.

Two common jellyfish that are found near the beaches of the United States are Mastigias quinquecirrha (the stinging nettle) and Aurelia. Both types of jellyfish experience an increase in population in late summer, which leads to many vacationers being stung. Most jellyfish stings are a minor irritation and require no medical attention.

Class Staurozoa

the most venomous animals on Earth. The stings are extremely painful and can sometimes be fatal.

31

Find it! What is the difference between venom and poison? Class Anthozoa Anthozoans are marine cnidarians that lack a medusa body form. The polyps can be solitary or form colonies. This class includes anemones and corals. Anemones are large, solitary animals. These have limited locomotion, sometimes gliding on the substrate, walking on their tentacles or thrashing around in the water. Anemones feed on small invertebrates. Their tentacles catch the prey and bring it into the mouth. Anemones display both sexual and asexual reproduction, but do not experience alternation of generations. Corals are anthozoans that are best known for forming coral reefs. The reefs are actually made of calcium carbonate exoskeletons that the corals form for protection. The corals form colonies and build the exoskeletons on top of or next to other corals, therefore building the reef. The corals are able to retract into the exoskeleton for protection. Corals reproduce both sexually and asexually, but do not alternate body forms. Many coral form a symbiotic relationship with algae. The algae live in the epidermis or gastrodermis of the animal. The algae perform photosynthesis, therefore providing the coral with food and oxygen. In return, the algae get carbon dioxide from the coral. Because of this relationship, coral most often have to live in shallow waters where they are exposed to sunlight. A relationship like this, where both organisms benefit, is called mutualism.

Brainstorm: Why do you think coral reefs are important to the worlds oceans?

G ALLERY 2.9 Class Anthozoa

Duncan Coral.

32

M OVIE 2.2 Class Anthozoa

Time lapse video of a sea anemone moving. Research Project Coral bleaching is an environmental problem that is effecting the world’s coral reefs. Using Haiku in your iPad, create a presentation answering the following questions: 1. What is coral bleaching? What causes it? 2. Why is coral bleaching bad for the environment? 3. Where is coral bleaching occurring? 4. How can we solve this problem?

Table 2.2 Classification of the Phylum Cnidaria CLASS

DESCRIPTION

Hydrozoa

Many polyps colonial, mostly marine with some freshwater species. Hydra, Obelia

Scyphozoa

Mostly medusa, polyps small, marine. Aurelia

Staurozoa

Medusa absent, eight tentacles surrounding mouth, sexual reproduction only, marine. Haliclystis

Cubozoa

Box-shaped medusa, polyp small, marine. Chironex

Anthozoa

Colonial or solitary polyps, medusa absent. Anemones and corals

Find it! What class does the Portuguese man-ofwar belong to? Why?

G ALLERY 2.10 Portuguese man-ofwar

What class does this belong in?

33

Chapter 2 Vocabulary

R EVIEW 2.2 Phylum Cnidaria Question 1 of 6 Members of the phylum Cnidaria show what type of symmetry?

A. Asymmetry B. Radial Symmetry C. Bilateral Symmetry D. Trilateral Symmetry

Check Answer

Asymmetrical Mesenchyme Cells Choanocytes Pinacocytes Porocytes Mesohyl Mesenchyme cells Flagella Microvilli Spicules Spongin Ostia Osculum Food Vacuole Monoecious Larva Regeneration Cnidocytes Radial symmetry Mesoglea Epidermis Gastrodermis Gastrovascular cavity Nerve net Cnidocytes Nematocysts Dioecious

Medusa Polyp Aboral Alternation of generations Hydrostatic skeleton Statocysts Symbiotic Relationship Mutualism

34

Chapter 2 Summary ★ Poriferans are the simplest of animals. ★ The cells of sponges work together to perform the functions of an animal. ★ Sponge skeletons are composed of either spicules or spongin. ★ Cnidarians are soft-bodied animals that have tissues and a simple nervous system. ★ Both poriferans and cnidarians are aquatic animals that respire by way of diffusion. ★ Cnidarians are carnivorous animals with specialized cells for feeding and protection. ★ Both poriferans and cnidarians reproduce both sexually and asexually.

35

C HAPTER 3

Worms

What do you think of when you hear the word worms? Most people probably think of earthworms. Although earthworms are common, there are thousands of types of other worms. Worms can be divided into three groups: flatworms, roundworms and segmented worms. Some are harmful to humans, some are helpful, and some are so small that you will likely never know that they exist. Brainstorm: Think of one way that worms could be helpful to humans and one way that they could be harmful.

S ECTION 1

Phylum Platyhelminthes Flatworms

L EARNING O BJECTIVES 1. Describe the function of parenchyma as found in the phylum Platyhelminthes. 2. Understand the nervous system of the Planarian. 3. Describe the life cycle of the beef and pork tapeworm. 4. Analyze the ecological importance of flatworms.

The phylum Platyhelminthes contains over 34,ooo species of worms. Some of those worms are 1 mm long, while others are 25 m long. The flatworms of this phylum have tissue and organs. One particular type of tissue that is characteristic of flatworms is parenchyma. This tissue fills the space between other tissues, organs and the body wall. Parenchyma tissue has different functions in different species. Parenchyma can provide skeletal support, nutrient storage, movement, and oxygen storage, among other things. Flatworms are the simplest animals to have organs. The phylum Platyhelminthes is divided into four classes: Turbellaria, Monogenea, Trematoda, and Cestoidea. Find it! What does the word “Platyhelminthes” mean? Characteristics of Flatworms Members of the phylum Platyhelminthes have the following characteristics: 1. Flattened body, acoelomate, bilateral symmetry. 2. Unsegmented worms. 3. One opening to the digestive system. 4. Show cephalization. 5. Most species are monoecious, complex reproductive system.

37

6. Protonephridia as excretory and osmoregulatory organs. 7. Nervous system with ganglia. How do Flatworms Work? Flatworms are highly specialized to live in a variety of environments. Some are free-living, while others are parasites. This section will cover the basics of how flatworms work. Any special adaptations will be covered in the section on each individual class.

nerve cords that run the length of the body. These nerve cords pick up stimuli from the surroundings and communicate with the ganglia, which serves as a primitive brain. Most flatworms have two ganglia and some may also have statocysts.

G ALLERY 3.1 Phylum Platyhelminthes

Respiration Because flatworms are so simple, and flat, respiration is a simple process. Whether on land or in water, flatworms are always moist. And since most of their cells are so close to the outside of their body, oxygen is simply able to diffuse into the cells, while carbon dioxide diffuses out. If the worm dries out, diffusion can no longer take place, resulting in the death of the worm. Feeding Flatworms are highly specialized to feed in their various habitats. Most have a digestive system with one opening, which takes in food and also excretes the digestive waste. Because flatworms have no blood, they then rely on diffusion to move the nutrients throughout the body. Nervous Functions Free-living flatworms are often highly mobile. Because they are constantly moving, they must also constantly respond to the environment. The flatworm nervous system consists of two

A Turbellarian.

Reproduction Flatworms are able to reproduce both sexually and asexually. They are also capable of regeneration. The mode of reproduction is usually determined by the habitat of the flatworm. 38

What are the Different Types of Flatworms? Class Turbellaria: The Free-Living Flatworms There are approximately 3000 species in the class Turbellaria. Turbellarians are mostly free-living bottom dwellers in freshwater and marine environments. Free-living means that they are not parasites and are able to move around the environment. Most of the Turbellarians are found on the bottom of the aquatic environment where they crawl over stones, sand and plants. There are a few terrestrial species, which are found in the tropics, where it is humid enough for them to stay moist on land.

tubules are able to draw excess fluid out of the cells around them, preventing the cells from exploding. Attached to the protonephridia are flame cells. Together, these two structures help to regulate the internal environment of the Turbellarian. Brainstorm: What organs in the human body perform the same functions as the protonephridia and flame cells?

G ALLERY 3.2 Turbellarian Anatomy

Find it! What does the word “Turbellaria” mean? Turbellarians are either scavengers or predators. Most feed on small invertebrates or larger, dead animals. These flatworms have sensory cells (chemoreceptors) on their anterior end that allow them to sense food. When they locate food, the y extend the pharynx. The pharynx leads to the digestive cavity, which is usually branched. The branched digestive cavity allows food to diffuse easily to all of the nearby cells. Any digestive waste is either diffused out of the cells or expelled through the pharynx. Because Turbellarians are primarily aquatic worms, they must have a way to control the amount of water that is in the body. Protonephridia serve as primitive kidneys. Protonephridia are fine tubules that run the length of the worm. These

The various system of a Turbellarian are shown here. The excretory canals are known as the protonephrida.

39

These free-living flatworms must be able to sense their environment in order to survive. Turbellarians do not have the sense organs that most animals have. Turbellarians do not have eyes, a nose, ears or taste buds, however, they can sense the things around them. As mentioned earlier, flatworms have a nervous system composed of two main nerve cords and two ganglia. These structures coordinate the movement and responses of the worm. In order to sense their surroundings, Turbellarians have two structures on the anterior end of their body. Auricles are sensory lobes that protrude from the sides of the head. These structures help the flatworm to sense touch, water currents and chemicals in their surroundings. Ocelli are eyespots located on the head of many Turbellarians. They do not function as eyes and do not allow the worm to see images. Instead, ocelli are simple structures that detect light and dark.

G ALLERY 3.3 Turbellarian

Freshwater Turbellarian

Brainstorm: Why would a flatworm need to detect light and dark? Many Turbellarians reproduce asexually by way of fission. During this process, the flatworm is able to divide itself in half. The two halves then grow into two identical organisms. Turbellarians are monoecious and can also reproduce sexually. Although these flatworms can produce both egg and sperm, they do not fertilize themselves. Instead, during sexual reproduction, sperm is exchanged between the two worms, resulting in fertilized eggs in both worms.

The most common Turbellarian is the freshwater planarian. They can be found in many bodies of freshwater, although you will most likely not know they are there. To find planarian, one would have to look on the bottom of the body of water, most likely under leaves or rocks. Find it: What is the scientific classification of the freshwater planarian? There are several species, so you should be able to list domain - genus. 40

Class Monogenea cooked fish. The Chinese liver fluke effects as many as 30 milMonogeneans are known as flukes. This class or flatlion people. worms are external parasites of fish. Using a structure known as the opisthaptor, the fluke attaches to the gills of a Find it! What are the symptoms of a Chinese liver fluke infish and feeds on epithelial cells fection? and blood. G ALLERY 3.4 Lorem Ipsum dolor amet, consectetur Schistosomes Find it! What are epithelial Schistosomes are blood cells? flukes that infect more than 200 million people world Class Trematoda wide. Blood fluke infections There are approximately are common in Africa, South 10,000 species of Trematodes. and Central America and Also known as flukes, but unSoutheast Asia. like those in the class Monogenea, Trematodes are internal Find it! How does a human parasites. The flatworms of the become infected with a blood class Trematoda can be found fluke? What are the sympinside vertebrates or invertetoms of blood fluke infection? brates, as well as on plants. Some of the Trematodes are Brainstorm: Why do you Chinese liver fluke under the microscope. Flukes normally able to infect humans. think that fluke infections are measure 1-6 mm in length. Chinese Liver Fluke not common in the United The Chinese liver fluke is a States? common parasite of humans in Asia. Adult liver flukes can be found in the liver of a human, where the flatworm feeds on the epithelial tissue and blood. A human becomes infected by consuming under41

Life Cycle of the Chinese Liver Fluke

Life Cycle of the Blood Fluke

Class Cestoidea The class Cestoidea is made up of approximately 3,500 species of tapeworms. All tapeworms are endoparasites, meaning that they live inside of their hosts. Most tapeworms reside in the digestive system of their hosts and can grow to be up to 25 m long. Because of the harsh environments in which tapeworms live, they are highly specialized. (The acids inside the human digestive system are among the strongest acids on Earth, there is also material constantly moving through the digestive tubes.) Tapeworms do not have a mouth or digestive tract, instead they feed by way of diffusion. Most adult tapeworms consist of a long series of repeating units called proglottids. Inside each proglottid is a complete set of reproductive organs. The tapeworm fertilizes its own eggs within the proglottid, which detaches and is then passed out of the hosts body.

no sensory organs on the scolex simply hooks or suckers to anchor the tapeworm to its host. Because tapeworm live in such as stable, controlled environment, they are relatively simple animals. They have evolved in such a way that they are adapted to infect their hosts, reproduce, and pass on their fertilized eggs.

G ALLERY 3.5 Tapeworm

Find it! Approximately how many eggs does a tapeworm produce? Brainstorm: Most monoecious animals do not fertilize their own eggs. Why do you think a tapeworm would fertilize its own eggs? Beef Tapeworm Scolex Too keep its entire body from being passed out of the digestive system with the waste, a tapeworm attaches to the intestinal wall with a structure called a scolex. There are 44

Many tapeworm species infect humans and some can cause serious damage. The beef tapeworm, Taeniarhynchus saginatus, makes its home in the small intestine of humans. This particular species can grow to be 25 m long. While in the intestine, the tapeworm produces approximately 80,000 eggs per proglottid. Humans become infected with beef tapeworm by consuming undercooked or raw beef. Find it! What are the effects of a beef tapeworm infection? How is it treated? Closely related to the beef tapeworm is the pork tapeworm, Taenia solium. Pork tapeworm can be more serious because it has a tendency to migrate outside of the intestine. Structures called oncospheres travel through the bloodstream and can be fatal if they reach the brain. Pork tapeworm usually grow to be only 2 to 3 m, but have been reported up to 10 m long. Pork tapeworm infects a person when they ingest undercooked or raw beef. A third type of tapeworm, which is common in the northern United States, is broad fish tapeworm, Diphyllobothrium latum. This tapeworm can infect humans, as well as other carnivores when they consume an infected fish. The worms grow to approximately 10 m in length and can produce 1 million eggs a day. Brainstorm: A person orders a rare steak at a restaurant and is infected with tapeworm. Can they sue the restaurant?

Review 3.1 Phylum Platyhelminthes

Question 1 of 5 The cells of flatworms that are able to perform many different functions are:

A. Statocysts B. Parenchyma C. Ocelli D. Auricles

Check Answer

Flatworms and Humans With your group, answer the following questions. These are short answer questions and you should support your answers with what you have learned in this section. 1. How do flatworms benefit humans? 2. How do flatworms harm humans? 3. List and describe 5 animals that would be effected if flatworms disappeared from Earth. 4. Describe a way that flatworms have effected you or may effect you sometime in the future. 45

Table 3.1 Classification of the Phylum Platyhelminthes CLASS

DESCRIPTION

Turbellaria

Mostly free-living, aquatic, ingests food using pharynx. About 3,000 species. Planarian

Monogenea

Ectoparasites of vertebrates, about 1,100 species. Flukes

Cestoidea

Internal parasites of vertebrates, scolex and proglottid, sexual and asexual reproduction. Tapeworm

Trematoda

All parasitic, adapted to attach to host, more than 10,000 species. Flukes

Find it! What is a primary host? What is an intermediate host?

Brainstorm: List 2 animals that would be effected if flatworms did not exist. Explain how they would be effected.

46

S ECTION 2

Phylum Annelida - Segmented Worms

More advanced and more commonly seen than the flatworms are the segmented worms. Annelids, or segmented worms, are believed to share an evolutionary history with molluscs and many other invertebrates. Segmented worms are used by humans for many purposes. They are consumed as food, used to aerate soil and used in medical facilities. Find it! What does the word “Annelida” mean? Characteristics of the Phylum Annelida Members of the phylum Annelida, commonly known as segmented worms, have the following characteristics: 1. Bilaterally symmetry, metameric body plan.

L EARNING O BJECTIVES 1. Understand the concepts of segmentation and metamerism.

2. Coelom present. 3. Paired, epidermal setae.

2. Analyze the structure and function of the closed circulatory system.

4. Closed circulatory system.

3.

6. Metanephridia or protonephridia.

Compare the oligochaete body form to the leech body form.

4. Understand the evolutionary and ecological importance of the annelids.

5. Ventral nerve cords and ganglia.

How do Segmented Worms Work? Unlike the flatworms, segmented worms are adapted for life outside of a host’s body. Although some are parasites, they are ectoparasites. They also possess more complex body systems than the flatworms, which allow them to live in a wider variety of environments. 47

Members of the phylum Annelida have a body plan that is metameric. This segmentation sometimes allows the worms to lose a significant portion of their body without being killed. Inside the each segment of some worms are nervous, digestive, and reproductive organs that allow the segment to work independently, but in cooperation with the segments around it. Segmented worms have a coelom. This is a body cavity that allows room for organs and organ systems. This is why the segmented worms are not flat. Like many of the flatworms, segmented worms are often aquatic. They must have a way to get rid of excess water and liquid waste. Annelids have metanephridia, which are more complex than the protonephridia of flatworms. Brainstorm: As a human, you have 3 bodies cavities. What are they? Respiration Annelids can be terrestrial or aquatic. Whether in water or on land, the worms must remain moist because they obtain oxygen by way of diffusion. Some of the annelids have appendages, known as parapodia, that have evolved into gills in order to increase the surface area for gas exchange. Brainstorm: Other than fish, can you name 3 animals that breathe using gills?

G ALLERY 3.6 Phylum Annelida

Christmas tree worm.

Circulation The simplest of invertebrate animals do not have blood. These animals did not need blood because their body plans were so simple that diffusion was able to circulate all gases and nutrients to the body. Annelids rely on blood to transport oxygen and nutrients throughout the body. In order to have blood, an animal must have a circulatory system. Segmented worms have a closed circulatory system. The circulatory system of the worms contains blood, which may be colorless, green or red. The blood is contained in vessels, arteries and veins. To keep the

48

blood moving, there must be a contractile element to the circulatory system. In humans, that element is the heart, in worms, it may simply be an enlarged part of a vessel. Some worms may have as many as 10 of these “hearts.” Feeding Inside of the body cavity of segmented worms can be found a digestive system. It is a one-way digestive system with two openings, a mouth and an anus. The mouth of the worm has a proboscis, which helps bring food into the digestive system. Depending on the worm, the proboscis is adapted to feed in a variety of ways. For example, the earthworm has a proboscis that is adapted to take in soil as it moves its way through the ground. One type of segmented worm, a polychaete, has primitive jaws that allow it to feed on other animals. Once the food has entered the digestive system, it is broken down and nutrients enter the bloodstream, where they are circulated throughout the body. Digestive wastes, in the form of feces, leave the body through the anus. Segmented worms can be carnivores, parasites or scavengers. Nervous Function Segmented worms must be able to find sense and locate food. The nervous system of an annelid allows it to sense light and dark, chemicals and touch. Controlling the nervous system are the ganglia, many annelids have 4 ganglia, located at the anterior end of the body. Connected to ganglia are nerve

cords that run the length of the body. Connected to the nerve cords are smaller, lateral nerves that help the annelids to sense their surroundings. Locomotion Segmented worms are free-living and motile. Many must move in order to locate and obtain food. The parapodia of some annelids are adapted to be used as gills, as mentioned earlier. However, most annelids use their parapodia for locomotion. Find it! What does the word “parapodia” mean? Segmented worms also possess setae. Setae around bristles, sometimes microscopic, that help annelids move. Annelids move by swimming, walking, crawling or burrowing. Reproduction Annelids are able to reproduce both sexually and asexually. Some segmented worms, such as polychaetes, are hermaphrodites. Other segmented worms, such as earthworms and leeches, are monoecious and reproduce sexually. Segmented worms can reproduce asexually by way of budding or regeneration. When reproducing sexually, they generally exchange sperm with another worm and leave behind a cocoon of fertilized eggs.

49

What are the Different Types of Segmented Worms? Class Polychaeta: The Marine Worms There are approximately 5,300 species in the class Polychaeta, making it the largest class of annelids. Polychaetes live on the ocean floor, under rocks and shells, on coral reefs or burrowed in the sand. Some polychaetes construct tubes in which they live. The tubes are constructed of sand grains and organic materials. Polychaetes are known for their parapodia, which have numerous setae for locomotion. Polychaetes also have numerous sensory organs on their anterior end. Around the mouth are sensory tentacles, as well as eyes and antennae. The eyes do not form images, but are sensitive to changes in light intensity.

Some polychaetes build tubes of sand and other materials that they live in. These annelids are referred to as tube worms. They extend themselves out of the tubes to filter feed and retreat when danger is present. Some of these worms live in the deepest parts of the ocean where very few other living things can survive.

M OVIE 3.1 Polychaetes

Find it! What do polychaetes eat? Polychaetes move in a variety of ways and can be rather active worms. They are able to walk, crawl and burrow in the ocean. Polychaetes are capable of regeneration, which means that they can replace lost parts. They are also able to break off body parts if a predator grabs on to them, allowing them to escape. These worms also use their powers of regeneration to reproduce asexually. During the process of fission, polychaetes split and grow into two separate organisms. They are also capable of budding. When reproducing sexually, fertilization is external, leading to the development of larvae.

This video, taken at the bottom of the ocean, shows tube worms. The white structures are the tubes created by the worms. The red structures are the part of the worm that extends from the tube in order to feed.

50

Class Clitellata The class Clitellata is divided into two groups, earthworms and leeches. These two groups of worms were once classified together and are very genetically similar, but have been separated because of some physical and developmental differences. Subclass Oligochaeta The most well-known of all worms is the earthworm. It is very common on many continents, found after rain or when digging in soil. Earthworms play an important role in the aeration of soil. The subclass Oligochaeta contains almost 3,000 species, so it contains much more than the common earthworm. Members of this subclass can be terrestrial, marine, or found living in freshwater, mud or soil. Oligochaetes move using setae. These bristles are microscopic, but work together to move the worm through the water or soil. These worms are scavengers that feed primarily on fallen or decaying vegetation. Earthworms literally eat their way through the soil. As they burrow, they ingest the soil and obtain their nutrients that way. Earthworms leave behind waste in the form of castings, which help to keep soil healthy. Oligochaetes respire by way of diffusion. Oxygen diffuses through the skin and into the blood, which is circulated throughout the body. Because they rely on diffusion, earthworms must remain moist. When an earthworms dries out, it dies, this is why they can be seen dead on sidewalk after rain.

Oligochates are monoecious and reproduce sexually. Earthworms have a specialized segment called the clitellum. During reproduction, two earthworms join together at the clitellum. The clitellum secretes a mucus and forms a cocoon. The worms secrete the eggs and sperm into the cocoon for fertilization and the cocoon is left behind in the soil. Within one to two weeks, the young worms hatch and emerge from the co-

G ALLERY 3.7 Subclass Oligochaeta

Earthworm setae.

Find it! Why can’t earthworms live in water, such as ponds? 51

M OVIE 3.2 Subclass Oligochaeta

Earthworm moving through its habitat. Subclass Hirudinea There are approximately 500 species of leeches in the subclass Hirudinea. Most leeches are found in freshwater, but there are a few marine species. Leeches feed in two different ways. Some feed on small invertebrates, such as crustaceans, other leeches feed on the body fluids of vertebrates, including humans. Leeches do not have parapodia and most do not have setae. Leech bodies have 34 segments, which can not easily be seen externally. Leeches exchange gases through the body wall, which requires them to be in water.

Leeches that feed on humans are adapted to attach to a host without the host knowing. Leeches have a mouth on the anterior end, which is modified into a sucker so that it stays attached to the host. Once the leech attaches, it secretes an anticoagulant which keeps the host’s blood from clotting. This allows the leech to feed until it is full. To aid in the attachment, leeches also have a sucker disc at the posterior end of their body. This disc simply keeps them attached to the host as they feed. Leeches are monoecious and reproduce sexually. They are not capable of asexual reproduction or regeneration. Reproduction occurs similarly to that in oligochaetes with cocoons being deposited in soil or underwater. Find it! What is the medicinal use for leeches?

G ALLERY 3.8 Subclass Hirudinea

A medicinal leech in the water.

52

Table 3.2 Classification of the Phylum Annelida CLASS

DESCRIPTION

Polychaeta

Largest annelid class, mostly marine, head with eyes and tentacles, parapodia with setae, monoecious or diecious. Nereis

Clitellata

No parapodia, clitellum functions in cocoon, monoecious.

Subclass Oligochaeta

Few setae, no distinct head, primarily freshwater or terrestrial. Earthworms

Subclass Hirudinea

Bodies with 34 segments, posterior and anterior suckers, setae reduced or absent. Leeches

Annelids and Humans

Section 3.2 Review Phylum Annelida

Question 1 of 5 Annelids have blood.

A. True B. False

With your group, answer the following questions. These are short answer questions and you should support your answers with what you have learned in this section. 1. How do annelids benefit humans? 2. How do annelids harm humans? 3. List and describe 5 animals that would be effected if annelids disappeared from Earth. 4. Describe a way that annelids have effected you or may effect you sometime in the future.

Check Answer

53

S ECTION 3

Phylum Nematoda Roundworms

L EARNING O BJECTIVES 1. Compare and contrast the roundworm to other types of worms. 2. Understand the impact of roundworms on humans. 3. Analyze the role of roundworms in the ecosystem.

Members of the phylum Nematoda, or nematodes, are among the most abundant animals on Earth. In every acre of soil, there are approximately 5 million of these roundworms. There are several different phyla of roundworms, however, the members of the phylum Nematoda are those most often encountered by humans, so we will focus on those. Human encounters with nematodes usually occur because the worm has infected the human or an animal, such as a dog. Zoologists believe that there are between 16,000 and 500,000 species of nematodes. These roundworms feed on everything from rotting substances to the living tissues of animals and plants. They live in nearly every habitat, from the ocean, to freshwater, soil and they are even internal parasites.

Characteristics of the Phylum Nematoda Nematodes share the following characteristics: 1. Bilateral symmetry, unsegmented, body cavity. 2. Round body, covered with a tough, elastic cuticle, molting usually accompanies growth. 3. Complete digestive tract, one-way with mouth and anus. How do Roundworms Work? Externally, roundworms appear very simple. Internally, they are more complex. Inside of the round body is a cavity, giving space for organs and system. A roundworms body can 54

be described as a tube within a tube. Respiration Nematodes obtain oxygen and release carbon dioxide by way of diffusion. Because they are often internal parasites, the oxygen must sometimes come from the blood of the host. The oxygen then diffuses throughout the body. Nematodes do not have a circulatory system or blood. Feeding Nematodes may be carnivores, herbivores, omnivores, parasites or scavengers. Those that scavenge feed on decomposing organisms. Parasitic nematodes feed on the blood and tissue fluids of their hosts. The complex digestive system of nematodes begins with a mouth. That mouth may have teeth or jaws that help it obtain the food. The mouth leads to a pharynx, which leads to the intestine, where digestion occurs. Digested food is then passed through a short rectum and anus, through which it leaves the body.

Reproduction Most nematodes are dioecious with the males being smaller than females. Fertilization is external, which is necessary because the nematodes are generally inside the body of a host. Sperm leaves the body through the cloaca. Once the eggs are fertilized, they stay inside of the female’s body until they hatch. The larva then leave the body. The number of larva produced ranges from several hundred to hundreds of thousands a day, depending on the species.

G ALLERY 3.9 Phylum Nematoda

Nervous Function Members of the phylum Nematoda have a very simple nervous system. The system consists of anterior nerve ring with no ganglia or brain. Brainstorm: Why do you think nematodes can function with such a simple nervous system?

A common nematode under the microscope.

55

What Nematodes Infect Humans? Ascaris lumbricoides: The Giant Intestinal Roundworm of Humans As many as 800 million people throughout the world may be infected with Ascaris lumbricoides. Adult Ascaris worms live in the small intestine of humans. They produce large numbers of eggs that exit the body with the feces. When a human ingests the egg, they hatch in the intestine and penetrate the intestinal wall. Once in the bloodstream, they migrate to the lungs, where they develop and migrate up the trachea and are swallowed. The worms return to the intestine where they mature and produce eggs, continuing the cycle. Find it! How does a human become infected with Ascaris lumbricoides? Necator americanus: The New World Hookworm The New World Hookworm or American Hookworm, Necator americanus is found in the southern United States. The adults live in the small intestine, where they hold onto the intestinal wall with teeth and feed on blood and tissue fluids. Individual females may produce as many as 10,000 eggs daily, which pass out of the body in the feces. The eggs hatch in the soil, producing larva, and penetrate the the skin of a human, usually between the toes. Once inside the body, the worms enter the circulatory system and complete a life cycle

similar to that of Ascaris. Trichinella spiralis: The Porkworm Adult Trichinella spiralis live in the small intestine of humans and other carnivores and omnivores. In the intestine, eggs hatch inside the female and young larvae emerge. The larvae then enter the circulatory system and are carried into the muscles of the host. The young larvae form cysts in the muscles and stay infective for years. The disease caused by this nematode is trichinosis. Another host may consume the infective meat and continue the life cycle. Humans often become infected by ingesting raw or undercooked pork. Find it! What is a cyst? Wuchereria spp.: The Filarial Worms In tropical countries, over 250 million humans are infected with filarial worms. The long, threadlike nematodes live in the lymphatic system. Filarial worms make their homes in the vessels of the lymphatic system, often blocking those vessels. When the vessels become blocked, it results in an accumulation of fluids in various appendages, often the legs. This condition is known as elephantiasis. When a human, infected by a filarial worm is bitten by a mosquito, larva enter the body of the mosquito, which becomes the vector. When the infected mosquito feeds on another human, it passes larva into a new host. Find it! What is the function of the lymphatic system? 56

Another filarial worm that is prominent in the United States is Dirofilaria immitis, which infects dogs. This particular filarial G ALLERY 3.10 Nematode Parasites of Humans worm infects the arteries, lungs and heart and causes heartworm disease. Enterobius vermicularis: The Human Pinworm
 Pinworms are the most common roundworm parasites in the United States. Adults become established in the lower region of the large intestine. At night, females migrate out of the rectum to the region around the anus, where they lay eggs. When the females lay the eggs, it produces an itching sensaAscaris removed from the human intestine. tion. When the human itches the anal area, it transfers the eggs to the hands or bedsheets. When the hands touch the mouth and the eggs are swallowed, the infection continues. The eggs can also be transferred to other areas. Pinworm is most common in children and is commonly transmitted in sandboxes and daycares.

Nematodes and Humans With your group, answer the following questions. These are short answer questions and you should support your answers with what you have learned in this section. 1. How do nematodes benefit humans? 2. How do nematodes harm humans? 3. List and describe 5 animals that would be effected if nematodes disappeared from Earth. 4. Describe a way that nematodes have effected you or may effect you sometime in the future.

Brainstorm: Why are parasitic worm infections more common in the tropics? 57

3.3 Review Phylum Nematoda

Question 1 of 5 Which of the following correctly describes the feeding habits of Nematodes?

A. Carnivores B. Omnivores C. Scavengers D. All of the above

Check Answer

Chapter 3 Vocabulary parenchyma acoelomate bilateral symmetry cephalization protonephridia ganglia parasite pharynx flame cells auricles ocelli fission proglottids scolex metameric coelom metanephridia parapodia closed circulatory system proboscis setae hermaphrodites clitellum trichinosis elephantiasis vector heartworm disease 58

Chapter 3 Summary ★ Free living Platyhelminthes, members of the class Turbellaria, are small, bilateral, acoelomate, and show cephalization. ★ Protonephridia are present in many flatworms and are involved in osmoregulation. ★ Members of the class Monogenea are ectoparasites. ★ Trematodes are internal parasites, known as flukes. ★ The class Cestoidea includes the tapeworms, which are generally parasites of vertebrates. ★ Members of the class Polychaeta are mostly marine and possess parapodia with numerous setae. ★ Polychaetes have a closed circulatory system. ★ Polychaetes rely on protonephridia or metanephridia for excretion. ★ The class Clitellata is divided into two subclasses: Oligochaeta and Hirudinea. ★ The subclass Oligochaeta consists of mainly freshwater and terrestrial annelids, including earthworms. ★ The clitellum is a specialized segment of annelids that is involved in reproduction. ★ Members of the subclass Hirudinea are ectoparasites. ★ Nematodes can be aquatic, terrestrial or parasitic. ★ Parasitic Nematodes infect humans in a variety of ways.

59

C HAPTER 4

Mollucs

The process of evolution leads to many changes in animals. Some of the most important changes over time lead to the rapid movement of animals. Rapid movement is seen for the first time in the molluscs. Not all molluscs are capable of this movement (the snail), but those that are show the capability to hunt, hide, and compete for mates (octopi). The phylum Mollusca is made up of a diverse and fascinating group of animals.

Characteristics of the Phylum Mollusca The phylum Mollusca shows many characteristics that are shared with more complex animals, including vertebrates. Members of this phylum share the following charcteristics: 1. Body consisting of two parts: head-foot and visceral mass.

G ALLERY 4.1 Phylum Mollusca

2. Mantle that secretes a calcareous shell and covers the visceral mass. 3. Mantle cavity functions in excretion, gas exchange, elimination of digestive waste and release of reproductive products.

mantle and the foot is a space referred to as the mantle cavity. The mantle cavity opens to the outside of the shell and serves many functions. Molluscs rely on the mantle cavity for respiration, excretion and release of reproductive materials. Most molluscs possess a radula, which is involved in feeding. The radula is essentially a tongue that is lined with rows of teeth. Some molluscs, such as snails, use the radula to scrape food, such as algae, from rocks or other substrate. Brainstorm: Can you name 5 animals that have a shell?

As you continue to study molluscs over the next few sections, keep in mind the differ4. Bilateral symmetry. ences between the worms and 5. Open circulatory system molluscs. Some of these invertein all but one class (Cephalobrates are highly advanced and Curled octopus, a member of the class Cephalopoda. poda). are the first in evolutionary history to show such advanced 6. Radula present and used characteristics. The differences for scraping food. between a tapeworm and an octopus are incredible and amazing and took millions of years to evolve. The mantle of a mollusc usually attaches to the visceral mass and covers most of the body. In molluscs that possess a hard shell, the shell is secreted by the mantle. Between the 61

S ECTION 1

Class Gastropoda - Mollucs with One Shell

The class Gastropoda contains over 35,000 living species. It is the largest molluscan class and contains species that are marine, freshwater and terrestrial. Most humans encounter gastropods at some point in their life. You may see them on a menu at a restaurant, in a fish tank, or in your garden. The class Gastropoda includes slugs, snails, and limpets. How do Gastropods Work? Respiration

L EARNING O BJECTIVES 1. Understand how the gastropod shell is formed. 2. Analyze the advantages of torsion. 3. Understand the structure and functioning of the open circulatory system. 4. Understand the ecological impact of gastropods.

Gas exchange in mollucs involves the mantle cavity. Some molluscs have one gill that is used to extract oxygen from water. Other molluscs, which live on land, rely on diffusion to obtain oxygen. Certain species of snails are terrestrial and rely on diffusion for respiration. Gastropods that burrow possess a siphon that extends from the body and above the surface of the substrate to bring water in and pass it over the gill. Because of these modes of respiration, molluscs must remain moist at all times. Brainstorm: Think about how you kill a slug. Why does this work? Circulation Gastropods have an open circulatory system. All molluscs contain blood and that blood must circulate throughout the body. In an open circulatory system, a heart is present and pumps the blood, but the blood spends some time outside of the vessels. In order to bathe the necessary organs and tis62

sues in blood and supply them with oxygen, the blood collects in sinuses.

G ALLERY 4.2 Class Gastropoda

Structure of a common snail.

63

Brainstorm: What do you think of when you hear the word “sinus”? Describe your thoughts. Feeding Most gastropods feed by scraping algae or other small, attached organisms from their substrate using their radula. Others are herbivores that feed on larger plants, scavengers, parasites or predators.

M OVIE 4.1 Class Gastropoda

Nervous Function Gastropods have a nervous system that contains ganglia in the anterior region. These ganglia are responsible for coordinating movement, as well as controlling the senses. Gastropods have welldeveloped sense organs. Eyes are located on the head, sometimes on tentacles. The eyes may be simple photoreceptors, or they may be more complex and form images. Statocysts are located on the foot and help the gastropods to sense gravity, especially in water. Gastropods also have chemoreceptors known as osphradia that help them to sense chemicals in water or air. The osphradia are used to help detect prey.

The anterior portion of the digestive tract may be modified into a proboscis, which can be extended from Reproduction the mouth. The probosThe conch is a gastropod that is valued for its meat and Gastropods can be monoecious or cis contains the radula. shell. The one seen here is moving and feeding using its dioecious. Most marine snails are dioeSome snails use the pro- proboscis. cious. Gametes are discharged into the boscis and radula to exwater for external fertilization. tract food from hard to reach places. Food is moved through the digestive system and into the stomach. A digestive gland, Snails that are monoecious fertilize internally. Somelocated in the visceral mass, near the stomach secretes the entimes the fertilization results in the exchange of sperm bezymes that are responsible for digestion. Waste, in the form tween two snails. Eggs are then laid and hatch to release of feces, is excreted through the anus.

64

larva. The eggs of gastropods must hatch in an environment that allows the larva to remain moist during its development.

G ALLERY 4.3 Class Gastropoda

Other Gastropods have some features that make them different from the rest of the molluscs. Most gastropods have one shell and their body must be twisted in a way that allows them to fit into that shell. The shell of a mollusc is part of its body and grows along with the animal. In order to remove a snail from its shell, it must be killed. The twisting of the body is referred to as torsion. The shell of many snails has only one opening, so that opening must be used for intake of materials and excretion of materials. Torsion is a 180 degree counterclockwise twisting of the visceral mass, mantle and mantle cavity. Torsion positions the gill, anus and openings from the excretory and reproductive systems just behind the head. This positioning of the body also allows the gastropod to retract completely into its shell for protection. Some snails have an operculum, which covers the opening of the shell when the snail is retracted. This allows the snail to withstand drying conditions. The foot of the gastropod extends out of the shell for movement. The foot is often ciliated or covered with gland cells. The muscular foot secretes mucous as it moves across the substrate. Gastropods such as abalones and limpets have a foot that is modified for clinging.

The body of a snail twisting the gastropod develops. Torsion is completed in the adult.

What are the Different Types of Gastropods? Subclass Prosobranchia The largest group of gastropods includes marine snails as well as some freshwater and marine species. There are approximately 20,000 species in the subclass Prosobranchia. Most members of this subclass are herbivores, but some are carnivorous. The carnivores of the subclass Prosobranchia inject venom into their prey using a radula that is modified into 65

a hollow, harpoonlike structure. This class includes several species of sea snails and land snails. Subclass Opisthobranchia The subclass Opisthobranchia includes approximately 2,000 species of molluscs. This subclass is made up of sea hares, sea slugs and their relatives. In most of these species, the shell, mantle cavity and gills are reduced or lost. Members of the subclass Opisthobranchia often prey on cnidarians. When these animals consume a cnidarian, like a jellyfish, they are able to acquire the unused nematocysts and use them for their own protection.

G ALLERY 4.4 Class Gastropoda

Brainstor: Why would it be beneficial for sea slugs to acquire nematocysts from their prey? Subclass Pulmonata There are approximately 17,000 species of molluscs that are classified in the subclass Pulmonata. This subclass includes mainly freshwater and terrestrial species. The snails in this subclass are herbivores and possess a long radula for scraping plant material. The mantle cavity of the terrestrial snails is modified to act as a lung, allowing them to survive on land.

Calliostoma annulatum. A member of the subclass Prosobranchia.

Find it! What is the largest species of land snail? Where is it found?

66

Gastropods and Humans

R EVIEW 4.1 Class Gastropoda Question 1 of 5 How many shells do gastropods have?

A. one or none B. one or two

With your group, answer the following questions. These are short answer questions and you should support your answers with what you have learned in this section.

1. How do gastropods benefit humans? 2. How do gastropods harm humans? 3. List and describe 5 animals that would be effected if gastropods disappeared from Earth. 4. Describe a way that gastropods have effected you or may effect you sometime in the future.

C. two or three D. three or more

Check Answer

67

S ECTION 2

Class Bivalvia - Molluscs with Two Shells

The second largest molluscan class, Bivalvia, consists of nearly 30,000 species of molluscs. This group includes clams, oysters, scallops and mussels. The defining characteristic of this class is that they have a shell that consists of two valves, or halves. Many members of this class are edible and some form pearls. They are also very important in filtering bacteria from polluted water.

G ALLERY 4.5 Class Bivalvia

L EARNING O BJECTIVES 1. Compare members of the class Bivalvia to the other molluscs. 2. Analyze the adaptations that bivalves have developed in order to live a sedentary life. 3. Understand the impact of bivalves on humans and other animals. Internal structure of a bivalve.

The structure of a bivalve shell is what gives them their bilateral symmetry. The two parts of the shell, or valves, grow 68

with the mollusc and are permanently attached to the visceral mass. The oldest part of the shell is the umbo. The inner layer of the shell is the nacre. The nacre protects the visceral mass and is sometimes known as mother of pearl. When pearls are formed, it is the nacre that is responsible for that. One of the main functions of the bivalve shell is protection. In order to protect itself, the bivalve molluc has strong adductor muscles to hold the shell closed. The adductor muscles are extremely strong and help protect the bivalves from predators, such as sea stars.

is the inhalant region and the cavity dorsal to the gills is the exhalant region. Bivalves that spend their lives buried in sediment are adapted to obtain oxygen through a siphon. The siphon is an extension of the mantle that extends above the surface of the sediment and allows them to feed and exchange G ALLERY 4.6 Lorem Ipsum dolor amet, consectetur gases. Circulation Bivalves possess an open circulatory system. Blood flows from the heart to the tissue sinuses, nephridia, gills and back to the heart. Because bivalves move extremely slowly, or do not move at all, an open circulatory system works for them.

Find it! What are the different colors of pearls?

Feeding

How do Bivalves Work? Respiration

Giant clam siphon.

Bivalves are adapted for a sedentary life. These molluscs live in water and must obtain oxygen without moving from place to place. In order to do this, they have evolved cilia-covered gills. The purpose of the cilia is to keep water moving over the gills, allowing the bivalves to obtain oxygen. The mantle cavity ventral to the gills

Bivalves are filter feeders. In order for this to happen, water must continuously move through the animals shell. When water enters the siphon and passes over the gills, particles are filtered from the water. Food is trapped by the gills and moved along food grooves on the gills. The grooves move the food toward the mouth, which leads to the esophagus. The esophagus leads to the stomach, which then leads to 69

the intestine. A digestive gland is present, which secretes the enzymes necessary for digestion. Any waste exits through the anus at the end of the digestive tract. Nervous Function The nervous system of bivalves consists of three pairs of ganglia. The margin of the mantle is the primary sense organ of bivalves. It always has sensory cells, and it may have sensory tentacles with photoreceptors. The photoreceptors can be simple structures that sense light, or they can be more com-

plex structures that are able to form simple images. Bivalves also rely on statocysts to detect gravity. Reproduction Most bivalves are dioecious. Gonads are in the visceral mass. Gonads produce the gametes and release those gametes into the mantle cavity. The gametes are released into the surrounding water and external fertilization takes place. The eggs that hatch produce larvae. The larvae settle into the substrate and develop into the adult bivalves. Other

M OVIE 4.2 Class Bivalvia

Most bivalves to not move, but some species are able to move by opening and closing their shell. Although they do not move quickly, it is an effective way to escape predators such as sea stars, which move very slowly. Some bivalves are able to produce a substance that allows them to attach permanently to a substrate. Find it! Find a bivalve that has had a negative impact on Illinois and describe that impact.

Common mussel feeding. 70

M OVIE 4.3 Class Bivalvia R EVIEW 4.2 Class Bivalvia Question 1 of 5 What structure(s) is used by bivalves for respiration?

A. Lungs B. Gills Giant Clam.

C. Skin D. All of the above

Bivalves and Humans 1. How do bivalves benefit humans? 2. How do bivalves harm humans? 3. List and describe 3 animals that would be effected if bivalves disappeared from Earth. 4. Describe a way that bivalves have effected you or may effect you sometime in the future.

Check Answer

71

S ECTION 3

Class Cephalopoda - Softbodied, Fast-moving Molluscs

L EARNING O BJECTIVES

Find it! What does the word Cephalopod mean? The class Cephalopoda includes some of the most fascinating and most puzzling animals on Earth. Because many of these animals spend their entire lives in the depths of the ocean, they are proving difficult for humans to study. This class includes octopi, squid, cuttlefish and nautiluses. These animals have adapted to be very quick and agile predators, therefore most of them have evolved to live their lives without a shell. The exception is the nautilus, which is a very ancient animal that humans rarely encounter.

G ALLERY 4.7 Class Cephalopoda

1. Understand the many functions of the mantle cavity of cephalopods. 2. Compare the members of the class Cephalopoda to other members of the phylum Mollusca. 3. Analyze the cephalopod nervous system and compare it to those of more advanced animals. 4. Understand the complex behaviors of cephalopods. Caribbean Reef Squid

72

How do Cephalopods Work? Unlike most of the invertebrates studied so far, cephalopods are able to move quickly through their environment. This movement requires many adaptations to the animal. The foot of cephalopods is divided into arms or tentacles. The number of arms or tentacles varies from species to species.

G ALLERY 4.8 Class Cephalopoda

Brainstorm: What happens to your body when you run quickly? What body systems are involved in this?

Respiration and Circulation Cephalopods possess gills that allow them to acquire oxygen from the water. The gills of the cephalopod are directly connected to a closed circulatory system so that the oxygen that is obtained can be quickly distributed throughout the body. Cephalopods use a structure referred to as a siphon to bring water into the mantle cavity and run it over the gills. The closed circulatory system of cephalopods keeps blood contained in vessels, arteries and veins. Keeping the blood moving is a 3-chambered heart. The heart consists of two auricles and one ventricle. In addition to the heart, the circulatory system has contractile arteries and branchial hearts. These additional structure help to keep the blood moving. Blood flow is very important to the cephalopod because an active lifestyle requires higher metabolic rates. The circulatory system is also very closely associated with the nephridia, allowing the cephalopod to quickly expel wastes that would kill the animal if they stayed in the body too long.

Simple anatomy of an octopus.

Feeding Most cephalopods locate their prey using sight and capture the prey using tentacles with adhesive cups. All cephalopods have jaws and a radula. The jaws are powerful struc73

tures for tearing the food while the radula is used to force the food into the mouth.

M OVIE 4.4 Class Cephalopoda

Common Octopus shown swimming and feeding. Cephalopods are predators and feed on everything from small invertebrates on the ocean floor to larger fishes. The digestive tract of cephalopods is one way, with a mouth and and anus. Most digestion occurs in the stomach. Digestive waste leaves by way of the anus and is carried out of the body with water that is being exhaled.

Nervous Function Cephalopod brains are the most complex of any invertebrates. Their brains are formed by the fusion of many ganglia, as found in other invertebrates. The evolution of the large brain found in cephalopods is directly related to their predatory habits and the coordination of their tentacles. Research shows that cephalopods are also capable of learning and memory functions. The eyes of octopi, cuttlefish and squid are similar to the structure of our own eyes. Cephalopod eyes can form images, distinguish shapes and colors. The ability to distinguish colors aids cephalopods in blending in with their surroundings. When people think of animals that can change color, most think of the chameleon. Cephalopods are much better at camouflage than the chameleon. Chromatophores are pigment cells that cover the skin of the cephalopod. By expanding and contracting the cells, the skin changes color, allowing cephalopods to communicate and blend in with their surroundings. The complex nervous system of the cephalopods allows them to not only communicate with each other, but also to learn. Octopi and squid have a larger brain relative to body weight than any other invertebrate, fish or amphibian. The evolution of intelligence, for example in primate animals, is usually associated with long lives and social interactions. However, cephalopods live one to four years and are mostly solitary animals. Therefore, the intelligence that has evolved

74

in cephalopods is believed to be connected to hunting and avoiding being hunted as prey themselves. Reproduction Cephalopods are dioecious. The male reproductive tract consists of testes and structures for encasing sperm in packets called spermatophores. The female reproductive tract produces large, yolky eggs and is modified with glands that secrete gel-like cases around the eggs. Brainstorm: What is the purpose of egg yolks and shells?

Find it! What happens to the female octopus after she lays eggs?

When the eggs hatch, they are in the form of miniature adults. The adults provide no care for their G ALLERY 4.9 Class Cephalopoda young. Cephalopods lay a large number of eggs because many of these young do not survive to mature and reproduce. Find it! How many eggs does an octopus lay?

Locomotion One tentacle of a male cephalopod is modified to transfer the spermatoFast moving cephalophore to the female. The male deposits pods use a jetthe spermatophore into the mantle cavpropulsion system. ity of the female. As the eggs are reWhen a mollusc, such as Young octopi hatching from eggs. leased by the female, they are fertilized a squid, expands its manby the sperm. Because the eggs are fertle cavity, it fills with watilized inside the mantle cavity, but not ter. The squid then coninside the reproductive system of the female, this is still contracts the mantle cavity, forcing the water out and propelling sidered external fertilization. The female attaches the eggs to the animal forward. All cephalopods have the ability to prosubstrate, sometimes inside of a den. As the eggs develop, the duce ink. When escaping a predator, many cephalopods expel female cleans the eggs with her arms squirts of water. ink along with the water in order to create a distraction and make the escape easier. 75

Find it! List 3 animals that feed on cephalopods.

M OVIE 4.5 Class Cephalopoda

Other Cephalopods raise many curiosities in humans. They are often beautiful animals that appear friendly or playful. However, certain species can be dangerous. The powerful jaws of an octopus or squid can pose a threat to divers. Not only are those jaws strong enough to bite off a finger, some octopi are armed with a very deadly venom that is delivered when it bites. It can sometimes be easy for divers or swimmers to encounter octopi because the animals are often curious about humans. This can turn into a dangerous situation. Large octopi are stronger than humans and can pull a diver into the depths or pull off a person’s scuba gear. Find it! What is the most deadly species of cephalopod? Where is it found? How does it harm humans?

Cuttlefish swimming and signaling to one another. The exception to the fast moving cephalopods is the nautilus. The nautilus is the only cephalopod that has maintained a shell. These molluscs are normally found very deep in the ocean. Their shell is of interest because it is chambered and the animal is able to control the amount of fluid in the shell in order to control its depth in the ocean. Humans have used the design when building submarines, allowing them to control the depth of the submarine.

One of the largest mysteries in the ocean is the giant squid. This illusive animal raises many questions. Because they live so deep in the ocean, giant squid are difficult for humans to study. Brainstorm: Why can’t researchers bring a giant squid up from the depths to study it?

76

M OVIE 4.6 Class Cephalopoda R EVIEW 4.3 Class Gastropoda Question 1 of 5 Which of the following correctly describes the cephalopod eye?

A. Simple, detects only light and dark B. Complex, able to see images and shapes, no color Two Humboldt Squid fighting and inking. Cephalopods and Humans

1. How do cephalopods benefit humans? 2. How do cephalopods harm humans? 3. List and describe 3 animals that would be effected if cephalopods disappeared from Earth. 4. Describe a way that cephalopods have effected you or may effect you sometime in the future.

C. Simple, detects shadows and movements D. Complex, able to see images, shapes and color

Check Answer

77

Chapter 4 Vocabulary head-foot visceral mass mantle open circulatory system radula mantle cavity osphradia torsion umbo nacre adductor muscles food grooves gonads siphon chromatophores spermatophores

Chapter 4 Summary ★ Molluscs are characterized by a head-foot, visceral mass, mantle and mantle cavity. ★ All molluscs have a radula. ★ Members of the class Gastropoda have one or no shell. ★ Members of the class Gastropoda are characterized by torsion, which allows them to live in a coiled shell. ★ Members of the class Bivalvia have two shells. ★ Bivalves are filter feeders that play a role in cleaning ecosystems. ★ Members of the class Cephalopoda have a foot that has been divided into arms or tentacles. ★ Cephalopods have a very complex nervous system. ★ Cephalopods are fast moving with a closed circulatory system.

78

C HAPTER 5

Arthropods What animal species has the greatest number of individuals? The best answer can only be an educated guess; however, most zoologists believe that it is most likely a species of small crustacean. Small crustaceans, known as copepods, are found in lakes, streams and open oceans. Copepods are food for fish, whales and many other aquatic animals. Many food chains would collapse without copepods. These tiny animals are just one of many groups of animals that belong to the phylum Arthropoda. Zoologists have described about 1 million species of arthropods and have estimated that there are 30 to 50 million that have yet to be described. Arthropods are found in nearly every environment on earth and are considered to be the most successful of all animals.

Characteristics of the Phylum Arthropoda: As you will learn, arthropods come in many forms and live many lifestyles. These remarkable animals are adapted to live in many different habitats and feed on many different foods. All arthropods share the following characteristics: 1. Metamerism with body regions modified for specific functions. 2. Chitinous exoskeleton that provides support and protection and is modified to form sensory structures. 3. Paired, jointed appendages. 4. Growth accompanied by ecdysis or molting.

metamerism in arthropods is that it allows for the different body segments to be specialized for different functions. For example, the anterior segment of a wasp is specialized for sensing and feeding, while the posterior segment is specialized for stinging. The central segment is the place of attachment for the legs and wings. The Exoskeleton The exoskeleton, which encloses arthropods, is often cited as the major reason for arthropod success. The exoskeleton provides structural support, protection and helps prevent water loss. Like your endoskeleton, the exoskeleton also provides a place for the muscles of the arthropod to attach.

Metamerism

The exoskeleton covers all body surfaces of the arthropod and is secreted by a single layer of epidermal cells. The exoskeleton is non-living and does not grow with the animal. The exoskeleton has two layers. The outer layer is impermeable to water, microorganisms and pesticides. The inner layer is composed of chitin. Hardening of this inner layer provides the arthropod with armor-like protection. The segmentation of the exoskeleton allows for flexibility.

Several aspects of the arthropod body have contributed to their success. Metamerism is one of these aspects. The metamerism of arthropods can often be seen externally. Many arthropod bodies are composed of a series of similar segments, each having a pair of appendages. Unlike annelids, arthropods are not segmented internally. The advantage of

The exoskeleton does not grow, therefore it must be shed for the exoskeleton to grow. During the process of ecdysis, or molting, the exoskeleton splits open, allowing the arthropod to emerge. During this time, the arthropod’s new exoskeleton is not completely hardened, therefore making it vulnerable to predators.

5. Ventral nervous system. 6. Open circulatory system. 7. Complete digestive tract. 8. Metamorphosis is often present.

80

Metamorphosis Metamorphosis is a series of changes in the arthropod body that help to reduce competition between adults and immature stages of arthropods. When arthropods hatch from the egg, they are referred to as larva. The larva feed on different food than the adults, therefore reducing competition between the two. For example, a caterpillar, which is a butterfly larva, feeds on leaves while the adult butterfly feeds on the nectar of flowers.

G ALLERY 5.1 Phylum Arthropoda

There are two types of metamorphosis, complete and incomplete. We will learn more about these as we cover the different classes of arthropods. Find it! What is a trilobite? Where can they be found? Arthropod Classification Phylum Arthropoda Subphylum Chelicerata Class Merostomata Class Arachnida Subphylum Crustacea Class Remipedia Class Cephalocarida Class Branchiopoda Class Malacostraca Class Maxillopoda Subphylum Hexapoda Subphylum Myriapoda

Class Merostomata

81

S ECTION 1

Subphylum Chelicerata

L EARNING O BJECTIVES 1. Identify the characteristics of the subphylum Chelicerata. 2. Understand the classes that belong to the subphylum Chelicerata. 3. Analyze the feeding methods of arachnids. 4. Compare and contrast chelicerates with other arthropods. 5. Understand the function of chelicerae and pedipalps. 6. Understand the impact of chelicerates on the environment and on humans.

The subphylum Chelicerata includes arthropods that many of us encounter daily. These animals include spiders, mites, ticks, horseshoe crabs and sea spiders. The animals in this subphylum are characterized by two segments, a cephalopthorax and an abdomen. The cephalothorax usually has eyes, but unlike other arthropods, there are never antennae present. The appendages of chelicerate attach to the cephalothorax. The first pair of appendages are called chelicerae. The chelicerae are specialized for feeding. In some arthropods, the chelicerae are small pincers, in other, they are hollow fangs. The second pair of appendages are pedipalps. The pedipalps are usually specialized for sensory functions, but can also be used in feeding, locomotion or reproduction. Posterior to the pedipalps are paired walking legs. Class Merostomata The class Merostomata includes some of the lesser known chelicerates. The only living members of this class are four species of horseshoe crabs. Found in the Atlantic Ocean and Gulf of Mexico, horseshoe crabs do not look like normal crabs. They are large and heavy and scavenge in the sand and mud for annelids, small molluscs and other invertebrates. Horseshoe crabs have remained unchanged for nearly 200 million years. Find it! What are three states in the US in which horseshoe crabs can be found? A hard, horseshoe-shaped carapace covers the cephalothorax of the crab. The chelicerae, pedipalps, and first three 82

pairs of walking legs are used for walking and feeding. The last pair of appendages is specialized for locomotion and digging. The abdomen has a long, unsegmented telson. If the waves and water manage to flip the horseshoe crab onto its back, the telson is used to right the animal.

G ALLERY 5.2 Class Merostomata

In the abdomen, the first pair of appendages covers the genital pores. The remaining five pairs are book gills. As blood circulates through the gills, oxygen is exchanged between the water and blood. Horseshoe crabs have an open circulatory system, so the blood flows freely around the gills. Horseshoe crabs are dioecious. During reproduction, males and females gather to Horseshoe crab on the beach. fertilize eggs. As a female digs a shallow hole in the sand and deposits her eggs, a male releases sperm into the same hole and the eggs are fertilized. The eggs are then buried and develop without the care of an adult. Find it! When do horseshoe crabs lay their eggs?

Class Arachnida The members of the class Arachnida are animals that raise severe fears in many people. Although small, mostly harmless, and extremely helpful to humans, many people fear the arachnids. Brainstorm: Is there anything that you genuinely fear? What happens to you when you encounter the things that you fear? The class Arachnida includes spiders, ticks, mites and scorpions. The earliest arachnid fossils date back almost 425 million years. One adaptation that has helped the arachnids survive is water conservation. Like many other animal groups, early arachnids were aquatic. As these arthropods evolved and begin to move into terrestrial habitats, it was necessary for them to adapt a way to conserve water. Without water conservation, the animals would dry out quickly and die. These adaptations are found in the exoskeleton and excretory system. Find it! How long can a human survive without water? 83

In addition to conserving water, the terrestrial arachnids also had to evolve new ways to exchange gasses and move about. All invertebrates studied so far have lived in moist environments, allowing them to obtain oxygen from water. Arachnids, such as scorpions, live in environments where water is very scarce. Therefore, they have adapted ways to obtain oxygen from the air around them. The appendages of these terrestrial arachnids must also be able to carry the animal across the land. The arachnids are members of the subphylum Chelicerata and share many characteristics with the horseshoe crab, but are also very different. Unlike the slow, heavy horseshoe crab, arachnids are lightweight and very nimble.

made of tubes called tracheae, which open to the outside of the body through holes called spiracles. Air enters through the spiracles and travels through the tracheae to the body tissues, delivering oxygen.

A defining characteristic of arachnids is that they have eight legs. The eight legs are used for walking, while other appendages are used for feeding and capturing prey. In addition to the eight walking legs, arachnids have a pair of chelicerae and a pair of pedipalps.

Most arachnids are carnivores. Arachnids hold their prey with their chelicerae while enzymes from the gut pour over the prey. These enzymes begin digestion and then the partially digested food is taken into the mouth. Other arachnids, such as spiders inject the enzymes, referred to as venom, into the prey and then suck out the partially digested animal tissue.

Respiration and Circulation Most arachnids breathe using structures called book lungs. They are believed to be a modification of the book gills found in the horseshoe crab. The book lungs were given their name because they are made of a series of folded membranes that make them look like a book. Because of the open circulatory system, blood is flowing amongst the lungs and oxygen diffuses from the air into the blood. Arachnids that do not have book lungs have a tubule system that delivers oxygen directly to the tissues. The system is

The circulatory system of arachnids is open with a heart that keeps the blood moving throughout the tissues. Blood bathes the tissues, providing oxygen, and then returns to the heart and enters through openings called ostia. Find it! What color is the blood of arachnids? Feeding

Find it! What is the most poisonous spider in the world? Where is it found? The digestive system of arachnids is divided into three regions, the foregut, midgut and hindgut. The foregut is often modified into a pumping stomach. From the foregut, the food moves to the midgut where nutrients are absorbed. From the midgut, food moves to the hindgut, where any remaining water is absorbed. 84

G ALLERY 5.3 Class Arachnida

into the gut for excretion. The major excretory product of arachnids is uric acid. Find it! What is the advantage of excreting uric acid? Nervous Function The nervous system of arachnids contains ganglia that work as a brain. The nervous system coordinates many sensory structures. There are mechanoreceptors and chemoreceptors that allow the arachnids to sense their surroundings. Mechanoreceptors function in sensing vibration and movement. These structures are very important to spiders that rely on a web to capture their prey. A spider’s mechanoreceptors allow them to determine the size of the prey and its position in the web.

Wood tick

In order to absorb all the available nutrients and water, yet remove the wastes from the body, arachnids have two structures as a part of their excretory system. These structures are coxal glands and Malpighian tubules. Some arachnids use one of these structures, others use both. Coxal glands are similar to nephridia and remove nitrogenous wastes from the blood. The wastes are then excreted through pores at the base of posterior appendages. Arachnids that are adapted to live in dry environments use Malpighian tubules to absorb waste material from the blood and empty it

The chemoreceptors allow the arachnids to sense chemicals and function similarly to the sense of smell and taste of vertebrates. Arachnids also possess one or more pair of eyes. The primary function of the eyes is to sense light and movement. However, the eyes of hunting spiders are probably able to form images. Find it! How many eyes does a tarantula have? Reproduction Arachnids are dioecious. The genital openings are on the ventral side of the second segment. Sperm transfer is usually indirect. The male often packages the sperm in a spermatophore, which is transferred to the female. Courtship rituals ex85

ist in some species. The male will attract the female and position her for transfer of the spermatophore. Many spiders tend to the eggs and when the eggs hatch, miniature adults emerge. It is not uncommon for the adult to then care for the young. Brainstorm: Why do spiders that care for their young lay less eggs than other species? Find it! How many eggs do spiders usually lay? Order Scorpionida Scorpions are found in tropical and warm climates. Scorpions are nocturnal animals that spend their days hiding under logs and stones. The cephalothorax of scorpions is fused to form a strong, shield-like exoskeleton. Located on the cephalothorax is a pair of very small chelicera and a pair of pedipalps. The pedipalps are generally large and are in the form of pincers. Behind the pedipalps are the four pairs of walking legs.

male body and hatch before the your emerge. It appears as though the mother is giving live birth, but she is not. The young are still nourished by a yolk as they develop. Animals that are viviparous give live birth and the young are nourished by the mother as they develop. Scorpions produce 20 to 40 young at a time and they may take 1.5 years to develop before hatching or being born. The exoskeleton of the young scorpions is soft, making them vulnerable to predators. The young crawl onto the back of the mother and may remain there for up to a month.

M OVIE 5.1 Order Scorpionida

The abdomen of scorpions is often referred to as the tail. The abdomen is jointed, making it flexible. At the end of the tail is a stinger. The stinger contains venom glands and has a sharp, hollow point. The scorpion holds its prey with the claws and then uses its tail to inject venom. Find it! List two scorpions that are toxic to humans. Where can they be found? Scorpions can be ovoviviparous or viviparous. When the scorpion is ovoviviparous, the eggs develop inside the fe-

Scorpion young being born and then riding on the mother.

86

Order Araneae The order Araneae is made up of nearly 34,000 species, making it the largest order in the class Arachnida. The order Araneae is made up of the spiders. The cephalothorax of spiders is generally much smaller than the abdomen. Attached to G ALLERY 5.4 Class Arachnida the anterior segment are two chelicera, armed with venom glands and fangs. There is also a pair of pedipalps, which are used for feeding and reproductive purposes. Posterior to the pedipalps are four pairs of walking legs. Also on the cephalothorax are three to four pairs of eyes. The abdomen has openings for the reproductive and respiratory systems. Also on the abdomen are the spinnerets, which are connected to multiple silk glands.

ders from falling. When spiders lay their eggs, they often wrap them in silk to protect them during development. Find it! What type of spider builds the strongest web? Most spiders feed on insects or other arthropods, however there are some species that are large enough to feed on small birds. Imagine how strong a web must be in order catch a bird! All spiders produce venom, however, most species produce a venom that is not toxic to humans. A couple of exemptions are the black widow and the brown recluse. Both of these species are found in the central United States and are toxic to humans.

Order Araneae. Wonderful parachute spider.

Spider silk is extremely versatile and strong. Different species of spiders produce different kinds of silk, with different functions. Some strands form the border of the web, while a different type of thread makes up the inside. Silk is also used as a safety line to keep the spi-

Brainstorm: How would your life be different if spiders did not exist? Order Opiliones

Members of the order Opiliones include harvestmen and daddy longlegs. These arachnids appear to be made of one segment, but are in fact made of two. Because the joint between the cephalopthorax and abdomen is so wide, it is hard 87

to see the two separate segments without closely inspecting the animal. Unlike the spiders, harvestmen are generally omnivores, feeding on both plant and animal material. Members of this order generally lay eggs in a damp location, which is why you often see daddy longlegs in the bathtub. Find it! Are daddy long legs actually poisonous? Order Acarina The members of the order Acarina are generally small, but can be a nuisance to humans. This order includes ticks and mites, many of which are ectoparasites of humans or domestic animals. Of all of the arachnids, the members of this order have the greatest impact on human health and welfare. Mites are 1mm or less in length. The two segments of the body are fused and covered by the exoskeleton. Like all arachnids, mites have 4 pairs of walking legs. The mouthparts are modified depending on the lifestyle. Some have evolved to pierce, bite, suck or anchor to the host. The mites that do not attach to a host can cause problems by damaging crops and other plants. Brainstorm: Other than itching and inflammation, how do you think these arachnids can cause problems for humans. Parasitic mites do not permanently attach to their hosts. One of the most commonly encountered mites is the chigger, which feeds for a few hours a day and then drops from the host. The larval stage of the chigger generally causes the most

trouble. The larva will attach to the host and secrete enzymes that break down the host’s skin, causing inflammation and itching. Look around you, do you think anyone near you is currently hosting a parasite? Will chances are, yes, many students in the classroom are probably host to a common, but harmless mite, Demodex folliculorum. This mite is very common and is found in the hair follicles of humans. Once these mites find a host, they attach permanently and feed on dead skin cells or oils secreted by the host. Also members of the order Acarina, ticks are ectoparasites for their entire life. Ticks are similar to mites, but slightly larger. They feed on the blood of their hosts and can sometimes transmit disease. Ticks commonly drop out of trees onto their hosts, humans or dogs, in the forest. When a tick is finished feeding, it drops to the ground. Find it! How should you remove a tick? Table 5.1 Subphylum Chelicerata CLASS

DESCRIPTION

Merostomata

Marine, with book gills. Horseshoe crabs

Arachnida

Mostly terrestrial, book lungs, tracheae or both. 4 pairs of walking legs. Spiders, scorpions, ticks, mites.

88

Chelicerates and Humans

R EVIEW 5.1 Subphylum Chelicerata 1. How do chelicerates benefit humans? 2. How do chelicerates harm humans? 3. List and describe 3 animals that would be effected if chelicerates disappeared from Earth. 4. Describe a way that chelicerates have effected you or may effect you sometime in the future.

Question 1 of 10 Which of the following is a characteristic of arachnids?

A. 6 legs B. 8 legs C. 2 pairs of wings D. 3 body segments

Check Answer

89

S ECTION 2

Subphylum Crustacea

Have you ever eaten seafood? Not fish....but an actual creature that you had to remove from its shell? If so, you consumed an invertebrate member of either the class Bivalvia or the subphylum Crustacea. Recall that bivalves are animals with two shells. So, if you ate clams, scallops, or oysters, you consumed a bivalve mollusc. If you dined on crab, lobster or shrimp, you ate an arthropod of the subphylum Crustacea. The most visible difference between crustaceans and all other arthropods is that they have two pairs of antennae. Other arthropods have one pair of antennae or no antennae at all. In total, there are five classes of crustaceans, in this section we will cover the three that are most common.

L EARNING O BJECTIVES

Class Malacostraca

1. Understand the characteristics of crustaceans.

3. Compare crustaceans to other arthropods.

The largest class in the subphylum Crustacea is Malacostraca. This class includes the most common crustaceans, found on restaurant menus everywhere. In addition to the crabs, lobsters and shrimp that people often eat, there are also krill, isopods and amphipods.

4. Analyze the the impact of crustaceans on the ecosystem and humans.

Brainstorm: Do you eat crustaceans? If so, what is your favorite crustacean dish?

2. Analyze the modifications of the different species of crustaceans.

The most commonly studied crustacean is the crayfish. The crayfish is abundant, easy to study, and a good representative of the crustacean group. The body of a crayfish is divided into two regions, the cephalothorax and abdomen. The abdomen is what is most commonly referred to as the “tail.” Both of the body regions have appendages attached. On the cepha90

lothorax are antennae, chelipeds and walking legs. On the abdomen are swimmeretes. Appendages Around the mouth of the crayfish are mandibles and maxillae. These are appendages that have been modified for chewing and grinding. Crayfish feed on other invertebrates, as well as plant matter and dead and dying animals. When feeding, they use the chelipeds to hold the food as the mandibles and maxillae chew and bring the food into the mouth.

G ALLERY 5.5 Crayfish Anatomy

Find it! What type of crab has the strongest claws? The tail of a crayfish is made of 5 pieces. The different pieces of the tail can be expanded and contracted like a fan. The center part of the tail is the telson. The outer four parts of the tail are the uropods, which are involved in swimming. The telson consists of two parts on each side of the telson. This can be seen in gallery 5.5. The exoskeleton of crustaceans gives room for muscles to attach. The chelipeds of many crustaceans are very strong and can crack the shells of other invertebrates that they feed upon. The four pairs of walking legs are attached to the cephalothorax and are the main mode of movement. The swimmeretes are attached to the abdomen and are involved in swimming and reproduction. In male crayfish, the anterior pair of swimmeretes is larger and used when mating with a female crayfish. Respiration and Circulation

Crayfish anatomy. Dorsal on the right and ventral on the left. Maxilliped and maxillae = mouthparts.

Crayfish respiration involves the use of gills. The gills are located under the cephalothorax, and because crayfish are aquatic, oxygen diffuses from the water to the blood, by way of the gills. Once oxygen has entered the blood, it is circulated around the body to the tissues. Like all arthropods, crayfish have an open circulatory system. A heart keeps the blood moving. The heart is a small, dorsal structure with ostia that allow blood into the heart so that it can be pumped again.

91

In order to get rid of metabolic wastes, crustaceans have structures referred to as green glands. The green glands play a part in the filtration of blood. The main excretory products are ammonia and excess water. The green glands function similarly to the coxal glands of arthropods. Nervous Function Crayfish have multiple ganglia that control the nervous system. These ganglia work as small brains and control the senses, muscles and reflexes. The antennae on the head of a crayfish are sensory appendages. The two pairs of antennae are able to sense movement, chemicals, pheromones and touch.

Reproduction Crayfish are dioecious. In fact, all crustaceans are dioecious, with the exception of barnacles. In the crayfish, the gonads are located in the dorsal part of the thorax. Mating occurs just after the female has molted. During mating, the male fertilizes the eggs as the female releases them. The eggs then attach to the ventral part of the abdomen and the female carries them until they hatch. When the crayfish eggs hatch, a miniature adult emerges. Many other crustaceans emerge from the eggs as larva, which spend the first part of their life as plankton.

M OVIE 5.2 Subphylum Crustacea

In addition to the antennae, crayfish also have eyes, statocysts and setae. There are two types of eyes found on a crayfish, compound eyes and simple eyes. The compound eyes are located on movable stalks on the head. The eyes have 25 to 14,000 individual receptors, so they function similarly to insect eyes. The simple eyes, referred to as ocelli, help to detect light. This is important for crayfish larva because it helps lead them to the surface waters, where they feed on the plankton. Crayfish have statocysts located at the bases of the first antennae. The main function of the statocysts is to sense gravity and vibrations. Statocysts also aid the crayfish in balance and positioning. It is important for the animals to be positioned correctly in the water so they are not vulnerable. Brainstorm: What parts of your body help you balance?

Freshwater crayfish moving across the substrate. Pay attention to the movement of the antennae. 92

Order Euphausiacea

M OVIE 5.3 Subphylum Crustacea

The order Euphausiacea includes krill. You may have never heard of krill, but if you have, chances are it is because they are part of many food chains. Some of the largest animals in the ocean are able to survive on eating only these very small creatures. Krill migrate vertically in the ocean. They spend the daytime in the depths of the ocean and migrate vertically to the surface during the day. Many krill are bioluminescent. Krill are also used as an ingredient in many fish foods used in home aquariums. Find it! Find 5 ocean animals that feed on krill. Find it! List 3 animals that are bioluminescent. Order Isopoda Members of the order Isopoda are often fascinating to children. You can find them in your yard, under rocks and in your plants. They do not bite you and are quite amusing. We call them roly polys, but they are actually knowns as pillbugs. Most people believe that roly polys are insects, but in fact, they are more closely related to a lobster than an ant. Pillbugs feed on decaying plant and animal material. As a defense mechanism, they are able to roll into a ball, which led to the nickname roly poly. Find it! How many legs does a pillbug have?

Krill feeding. They have specialized appendages to feed on particles floating underneath the ice.

Class Branchiopoda Members of the class Branchiopoda life primarily in freshwater. These animals include fairy shrimp, brine shrimp and water fleas. These animals do not often have a direct impact on humans, but are important parts of aquatic food chains. The members of the class Branchiopoda often feed on dead and decaying material, allowing those nutrients to be recycled through the ecosystem. 93

Class Maxillopoda The class Maxillopoda include barnacles, which are exclusively marine and include about 1,000 species. Most barnacles are monoecious and the larval stage is spent as plankton. As an adult, barnacles are sessile and appear to have shells. In fact, they are not shells, but the exoskeleton is formed in

G ALLERY 5.6 Class Branchiopoda and Maxillopoda

Barnacles attach to a variety of substrates, including rocks, ships, whales and other animals. Some barnacles are evolving to be ectoparasites to feed off of the animal they are living on. This evolution is logical because the barnacles already live on the animals. Find it! How can barnacles cause problems for ships? Crustaceans and Humans

1. How do crustaceans benefit humans? 2. How do crustaceans harm humans? 3. List and describe 3 animals that would be effected if crustaceans disappeared from Earth. 4. Describe a way that crustaceans have effected you or may effect you sometime in the future.

Fairy shrimp

two halves, which serves as protection to the rest of the body. 94

R EVIEW 5.2 Subphylum Crustacea Question 1 of 5 How many antennae do crustaceans have?

A. 1 B. 2 C. 3 D. 4

Check Answer

95

S ECTION 3

Subphylum Myriapoda

The subphylum Myriapoda consists of terrestrial arthropods that are known for their high numbers of legs. Although there are four classes of myriapods, we will focus on the two that are most commonly encountered by humans, the diplopods and chilopods.

G ALLERY 5.7 Subphylum Myriapoda

L EARNING O BJECTIVES 1. Compare and contrast millipedes and centipedes. 2. Analyze the advantages and disadvantages of having numerous appendages. 3. Understand the impact of myriapods on the ecosystem and humans.

Common centipede

Class Diplopoda The class Diplopoda contains the millipedes. Millipedes have been rumored to have a million legs, however, this is not true. Millipedes have two pairs of legs per segment. The num96

ber of segments varies from species to species, it can be anywhere from 11 to 100 segments. Most millipedes have a round, tube-shaped body, although a few species are flattened. Millipedes are found worldwide, but are always found under leaf litter or decaying logs. The exoskeleton of millipedes does not contain a waxy cuticle, therefore millipedes must choose a habitat that will keep them moist. Millipedes use the strength of their many legs to bulldoze through the substrate. When threatened, millipedes roll into a ball. Millipedes are dioecious and males transfer spermatophores to the females. When the young hatch, they are small, but they acquire a new segment and legs with each molt.

consists of small arthropods, earthworms and snails. However, some centipedes are able to feed on frogs and small mammals, such as mice. Most centipedes produce venom that is not toxic to humans, although it can cause pain. The bite of a common centipede has been compared to the sting of a wasp. Brainstorm: Can you think of 5 arthropods that you have encountered this semester? (The ones we look at in class don’t count!)

M OVIE 5.4 Subphylum Myriapoda

Class Chilopoda Members of the class Chilopoda include the centipedes. The easiest way to tell the difference between a centipede and a millipede is to look at the number of legs. As in millipedes, centipedes do not have a set number of legs. However, unlike millipedes, centipedes only have one pair of legs per segment, not two. Centipedes have 15 or more body segments, with the appendages on the last segment being modified as sensory appendages. Another visible difference between centipedes and millipedes is that centipedes have a flattened body. If you encounter a centipede, it is best to avoid the animal. Unlike their close relatives that feed on decaying material, centipedes are fast-moving predators. Centipedes have poisonous claws that poison or kill their prey. Prey usually

Amazonian giant centipede feeding on bats in a cave.

97

R EVIEW 5.3 Lorem Ipsum dolor amet, consectetur Myriapods and Humans

1. How do myriapods benefit humans? 2. How do myriapods harm humans? 3. List and describe 3 animals that would be effected if myriapods disappeared from Earth. 4. Describe a way that myriapods have effected you or may effect you sometime in the future.

Question 1 of 5 How many legs does a millipede have?

A. 1 million B. 100 C. 1 pair per segment D. 2 pairs per segment

Check Answer

98

Chapter 5 Vocabulary exoskeleton appendages ecdysis molting chitin cephalothorax abdomen chelicerae pedipalps book gills book lungs tracheae spiracles coxal glands Malpighian tubules oviparous viviparous bioluminescent

Chapter 5 Summary ★ Arthropods are metameric, which has resulted in the specialization of the body for specific functions. ★The exoskeleton covers the entire body surface and provides structural support, as well as protection and water conservation. ★Arthropods must periodically shed the exoskeleton in order to grow. ★Metamorphosis has contributed to arthropod success by reducing competition between immature and adult arthropods. ★Chelicerates have two body segments and specialized mouthparts for feeding. ★Arachnids have 4 pairs of walking appendages and are adapted to feed in a variety of ways. ★Crustaceans are characterized by two pairs of antennae and are primarily aquatic. ★Centipedes and millipedes are different in the number of legs per segment, body shape and feeding method.

99

C HAPTER 6

Subphylum Hexapoda What are the most successful animals on Earth? Humans? You may think so because of everything we have built and all that we are able to do to survive, but you would be wrong. The answer is: members of the subphylum Hexapoda, or insects. Think about it...we build houses, we mow our lawns, we plant gardens...but who can ruin it all? Insects. They may be a nuisance, but we also could not live without these marvelous creatures.

The subphylum Hexapoda is divided into two classes, Entognatha and Insecta. In this chapter, we will focus on the class Insecta. Insects are members of the phylum Arthropoda. They are closely related to the crustaceans and arachnids and share all of the characteristics that make an animal an arthropod. Find it! What are 5 characteristics of an arthropod? You can tell an insect from all other arthropods by looking for a few characteristics: 1.

3 body segments: head, thorax, abdomen

2.

5 pairs of head appendages

3.

3 pairs of legs, located on the thorax

The class Insecta includes over 20 orders of insects. Some of the most common are listed in table 6.1. Find it! How can you tell the difference between a butterfly and a moth?

ORDER

DESCRIPTION

Odonata

Long, thin wings; long, slender abdomen; large, compound eyes. Dragonflies

Mantodea

Long legs with spines for grasping; predators. Praying mantis

Blattaria

Oval, flattened body; head protected by shieldextension of exoskeleton. Cockroach

Isoptera

Workers white and wingless; social structure with workers, reproductives and soldiers. Termites

Orthoptera

First wing long, narrow and leathery, hind wing broad, do not fly. Crickets

Phasmida

Long, stick-like body; wings reduced or absent. Walking sticks

Phthiraptera

Small, wingless ectoparasites; white. Lice

Hemiptera

Piercing-sucking mouthparts; membranous wings. Cicada

Coleoptera

Forewings hardened to form covers over the abdomen; chewing mouthparts; largest insect order. Beetles

Lepidoptera

Wings borad and ocvered with scales; mouthparts formed into a sucking tube. Butterflies

Diptera

Well developed wings for very nimble flight; variously modified mouthparts. Flies

Hymenoptera

Wings membranous; sometimes possess a stinger; mouthparts modified for biting and lapping; often social. Bees 101

S ECTION 1

Insect Form and Function

Insects didn’t become the most abundant and successful animals on Earth by chance. The remarkable creatures have evolved to live in nearly every habitat and feed on nearly every food available. There are approximately 900,000 species of insects that have been identified. Zoologists believe that we have not even found half of the insects that exist. Let’s take a look at how insects work and think about how this has made them such a successful group of animals. Respiration and Circulation

L EARNING O BJECTIVES 1. Analyze the adaptations of insects and how it has led to their success. 2. Compare insects to other arthropods. 3. Understand the feeding adaptations of insects. 4. Understand the structure and function of the nervous system of insects.

Insects use tracheae and spiracles in order to exchange gasses. Recall that spiracles are openings that allow air into the tracheae, which then deliver oxygen to the tissues. Because insects are very active, often in flight, they require larger amounts of oxygen. Some insects solve this problem by using the flight muscles to force more air into the tracheae. Brainstorm: Do you think humans could survive with spiracles and tracheae instead of lungs? Why or why not? Like all other arthropods, insects have an open circulatory system. Insects have a heart (it’s really just a blood vessel that contracts), which keeps the blood moving around the tissues. The blood of insects distributes nutrients, hormones, and wastes. However, due to the tracheae, which deliver oxygen directly to the tissues, blood is not important in gas exchange. For the first time in arthropods, we are seeing an importance in body temperature. Insects are some of the first ani102

mals that have a need for thermoregulation. Think of your and maintain the temperature. If the temperature inside the own muscles. How do they work when they are warm? How hive becomes too warm, bees will gather at the entrance of the do they work when they are cold? There is a reason that we hive and fan their wings to bring cooler air in. As we learn warm up before we exercise, muscles work better when they more about honeybees, we will see the remarkable efforts that are warm. Thermoregulation is they put forth in order to keep especially important for flying their society functioning. G ALLERY 6.1 Subphylum Hexapoda insects. Virtually all insects Brainstorm: What do you do warm themselves by resting on to cool yourself off? What do warm surfaces. Like all other inyou do to warm yourself up? vertebrates, insects rely on an external source for their body Feeding heat and are therefore considInsect feeding is highly specialered ectotherms. If an insect ized and highly varied. The must create their own body mouthparts of insects are heat, they do so by rapidly conadapted to collect food from the tracting the flight muscles. This various sources. Insects can be process is similar to you shiveromnivores, carnivores, herbiing when you are cold. Insects vores or scavengers. The varithat rely on both the external enety of feeding styles has, in part, vironment and their own musled to the success of insects. cles to generate heat are referred to as heterotherms.

Mandibles of a bull ant.

Honeybees have evolved to regulate their own body temperature and the temperature of their hive. Honeybees need an internal body temperature of 35 degrees Celsius for flight, wax production and larval development. Inside the hive, bees will form clusters and contract muscles in order to generate

Find it! What does a housefly eat? How is its mouth adapted for this? The digestive tract of insects is long and straight. As with other arthropods, it consists of a foregut, midgut and hindgut. In some sucking insects, the foregut is modified into a pharynx, which sucks liquids into the digestive tract. Be103

hind the pharynx is the crop, which stores food. After leaving the crop, the food moves to the gizzard for grinding. The midgut functions in digestion and absorption. The hindgut is the site where any remaining water is absorbed. Brainstorm: Can you think of 2 insects that impact you by the way that they feed? Nervous Function Have you ever tried to swat a fly? It’s a difficult task due to their well developed nervous system and sensory organs. In addition to their well developed nervous and sensory system, research shows that insects are capable of learning and have a memory. This does not mean that you can teach an insect to do tricks, but they may be capable of remembering bad experiences and learning from them, for example, a fly swatter. If you look closely at a fly, it will appear to have hair. Those are not hairs, but setae, which are sensory structures. Much like the whiskers of a dog or cat, these small structures can sense movement and vibration. When you attempt to swat a fly, you move the air around the fly, which triggers the setae, causing the fly to move. Insects can not hear you, but when you make noise, you create air movement and vibration. This also is sensed by the setae, causing the insect to react. The setae of some insects are associated with tympanal organs, which function similarly to ears. These organs are so specialized that they can not only detect sound, but detect which direction the sound is coming from.

The tympanal organs of a noctuid moth are so advanced that they can detect the ultrasonic frequencies emitted by bats during echolocation. When the bats use echolocation to find insects to prey upon, the moths can sense this, determining where the bat is and therefore avoiding being eaten. Sensing smell and chemicals is very important for insects. When choosing a food source, smell is more important to an insect than shape or color. When choosing a mate or egg-laying site, insects often use chemoreception. These

M OVIE 6.1 Insect Form and Function

Common Housefly

104

senses also play a vital role in the social organization of certain species of insects. Compound eyes are present in most adults. Compound eyes have many lenses to form images and are very sensitive to movement. In addition to forming images, insect eyes are also capable of detecting light. Light can be very important to insects because some of them use it for navigation, orientation, feeding and other functions. Brainstorm: Where is the sun located at 9 am? Where is the sun located at 6 pm? The complexity of the insect nervous system can lead you to believe that they are making conscious decisions to fly one way or the other. This however, does not appear to be true. The insect nervous system is very advanced and their movements are made in response to their surroundings without them being aware of it. Their movements could be compared to reflexes.

Flight is a very complicated process. Not only does it require large amounts of energy to lift the body from the ground, but the angle of the wings helps control the movement of the insect once they are in the air. As discussed earlier, thermoregulation is very important and vital for the flight of insects. In addition to flying, insects can also walk, run and jump. When an insect walks, it has three or more legs on the ground at all times, creating a very stable stance. A running insect may have fewer legs in contact with the ground, but will have a much greater speed. Jumping insects, such as grasshoppers, usually have long, enlarged hind legs that propel them off of the ground. We often associate crickets and grasshoppers with the ability to jump, but they are far from the best jumpers in the insect family. Find it! Which insect can jump the farthest (relative to body size)? How far can it jump?

Locomotion Insects move in many ways, but flight is the most important method of locomotion. Insects were the first animals to fly. Most insects have two pairs of wings. Although both pairs of wings are used in flight, some have evolved to serve other purposes as well. For example, when not in flight, the forewings of a beetle cover the abdomen, protecting the body.

105

R EVIEW 6.1 Insect Form and Function Question 1 of 5 How many wings do most insects have?

A. 2 B. 4 C. 6 D. 8

Check Answer

106

S ECTION 2

Social Behavior and Reproduction

Brainstorm: Describe three things that you rely on other people for. Another insect characteristic that has contributed to their success is their behavior. Just as it would be difficult for you to live completely on your own, some insects can not survive without the help of others. These are referred to as the social insects. Find it! List 5 species of social insects.

L EARNING O BJECTIVES 1. Understand the social structure of insect societies. 2. Analyze the advantages and disadvantages of social structure. 3.

Understand the functions of the different pheromones.

4. Compare and contrast the different types of metamorphosis. 5. Understand the purpose of metamorphosis. 6. Analyze how behavior of insects has contributed to their success.

Social Behavior Many social insects live in colonies. Usually, within the colonies, different members are specialized, often structurally and behaviorally, for performing specific tasks. Social behavior is most evolved in ants, wasps, bees and termites. Within the colonies are castes. The castes are the different roles within the colony, generally there are three or four. There is usually a reproductive female, referred to as the queen. Workers are sterile males or females that support and protect the colony. The reproductive organs of the workers are generally non-functional. There are also reproductive males, whose role is to fertilize the eggs of the queen. These reproductive males are generally referred to as drones. The soldiers are the insects that protect the colony using large mandibles. Honeybees Honeybees have three castes in their colonies. A single queen lays all of the eggs. The hive is constructed by the work107

ers, which are all females. The hive is constructed out of wax that the female workers produce. The workers also gather nectar and pollen to feed the queen and drones. In addition to all of this, the workers must care for the larva and protect the

G ALLERY 6.2 Social Insects

Brainstorm: Why would the younger workers be assigned jobs within the hive? Brainstorm: Why would a drone leave the hive to mate with a queen from another hive? Unlike humans, bees do not know their place in the society. Pheromones that are released by the queen control many things within the society. One particular pheromone keeps the worker bees from raising new queens. When the queen dies, this pheromone decreases and the workers begin to feed female larva with food for the queens, also known as “royal jelly.” As these larva develop and become queens, they eliminate each other until there is only one queen remaining. That queen will maintain the colony for several years. Brainstorm: Describe a place in human society that has “castes”. Reproduction

Honeybees working together to build the hive.

hive. A worker’s job is determined by their age. The younger workers are given jobs around the hive, while the older workers leave the hive to find food. The drones develop from unfertilized eggs and are fed by the workers. Once fully grown, the drones leave the hive to attempt to make with a queen.

Insects reproduce very quickly and produce high numbers of offspring. Insect reproduction is dependent on many factors. Pheromones play a role in determining when an insect is sexually mature. Other factors that affect mating are usually environmental conditions, including how much food is available. For example, a female mosquito is not able to lay eggs until she has a blood meal. The amount of blood ingested also determines the number of eggs laid. Recall that reproduction in animals is an instinct and they will not produce more offspring than they can handle. The reproductive pat108

terns of insects vary by species, but the goal of them all is to produce eggs that will withstand the current environmental conditions. Find it! Is fertilization of eggs in insects internal or external?

PHEROMONE

FUNCTION

Sex pheromones

Excite or attract members of the opposite sex; accelerate or slow down sexual maturation. Example: Female moths produce and release pheromones that attract males.

Caste-regulating pheromones

Used by social insects to control the development of individuals in a colony. Example: The amount of “royal jelly” fed to a female bee larva determines whether the larva will become a worker or a queen.

Alarm pheromones

Released to warn other individuals of danger; may signal for insects to join in an attack. Example: A sting from one bee alarms other bees in the area, who are likely to attack.

Trailing Pheromones

Laid down by insects that are seeking food to help other members of a colony identify the location and quantity of food found by one member of the colony. Example: Ants often leave a pheromone trail from a food source. The more ants that travel the path, the stronger the pheromones become, making the path easier to follow.

Find it! Where do mosquitoes lay their eggs? Development and Metamorphosis As mentioned before, insects undergo metamorphosis, which reduces the competition between adults and immature insects. Insects spend most of their lives in the immature stages of metamorphosis. During this time they are accumulating energy and preparing to transition into adulthood. Once they reach the adult stage, they begin to reproduce and disperse eggs. Find it! How long does a mosquito live? There are two types of metamorphosis, complete and incomplete. Complete metamorphosis involves four stages. The stages of complete metamorphosis are egg, larva, pupa and adult. Complete metamorphosis generally involves a larva that is very different from the adult. The larva eat almost constantly and grow very rapidly. As the larva grows, it molts. After a specific number of molts, which varies by species, the last molt results in a pupa. Find it! What are three different types of pupa? Although the pupa stage appears to be inactive, it is actually a time of very rapid cellular change. Inside the pupa, all of the changes necessary to form the adult are taking place. Once fully developed, the adult emerges from the pupa.

109

M OVIE 6.2 Insect Development

Find it! List 5 insects that undergo incomplete metamorphosis.

R EVIEW 6.2 Social Behavior and Reproduction Question 1 of 5 Which of the following correctly lists the stages of complete metamorphosis in order?

A. pupa,egg, larva, nymph Wasp emerging from pupa. Find it! List 5 insects that undergo complete metamorphosis. The most obvious difference between complete and incomplete metamorphosis is that incomplete metamorphosis has no pupal stage. When the egg hatches, an immature adult emerges. These immature insects are referred to as nymphs. They appear as a smaller version of the adult, but are not sexually mature. After a certain number of molts, which is dependent on the species, the nymph becomes and adult and is able to reproduce.

B. egg, nymph, pupa, adult C. pupa, larva, nymph, adult D. egg, larva, pupa, adult

Check Answer

110

S ECTION 3

Insect Orders - The Big 4

Covering all 30 insect orders would require an entire textbook. There are four orders which are considered the most important. Their importance is based on their interactions with humans and the number of species that they contain. These orders are Coleoptera (the beetles), Lepidoptera (the moths and butterflies), Diptera (the flies), and Hymenoptera (the ants, bees and wasps). Order Coleoptera

L EARNING O BJECTIVES 1. Identify the four most important orders of insects. 2. Understand the adaptations that have made the four orders so successful. 3. Analyze the impact of the four orders of insects on humans.

Forty percent of all insects on Earth are beetles. There are approximately 350,000 species of beetles that have been identified. Zoologists believe that there are millions more species of beetles that have yet to be identified. Beetles are found in every natural habitat on Earth, except for polar ecosystems. Some beetles have even evolved to live in marine environments. Beetles undergo complete metamorphosis during their development. Adult beetles have a very hard exoskeleton and their forewings usually cover the dorsal part of the thorax when the insect is not in flight. When the insect begins to fly, the forewings are raised and the hindwings expand and power the flight. Both adult beetles and larva consume a variety of living and dead plant and animal material. June beetle larva feed on the roots of grasses and adults feed on leaves and trees and shrubs. Most rove beetles are predators of other insects and invertebrates as both larvae and adults. Larvae are voracious feeders and eventually pupate, usually within the larval habi111

tat. Adults and larvae employ a variety of defensive strategies, Brainstorm: When insects damage crops, how do you think including camouflage, mimicry, toxicity, and more active dethis effects YOU? fense. Bombardier beetles expel chemicals from glands in Although some beetles cause great amounts of damage, their abdomen. Two separate glands release chemicals, hydrooverall beetles are very beneficial quinone and hydrogen peroxto ecosystems. Beetles that feed ide, and the mixing of the two G ALLERY 6.3 The Four Major Insect Classes on dead and decaying material creates a reaction that results speed up the decomposition procin boiling, foul-smelling liquid ess and allow nutrients to be recyand a popping sound. cled faster. Beetles also feed on Brainstorm: Think of the other insects, helping control Bombardier beetle and the detheir population. fense described above. Why Find it! What do ladybird beedo you think it has evolved tles feed on? Why is this benefithis way? Why do you think cial? there are two separate glands involved? Order Lepidoptera Some beetles are known The order Lepidoptera includes for damaging agricultural the moths and butterflies. There crops. For example, the Coloare approximately 180,000 derado potato beetle can comscribed species. These insects go Cardinal Beetle. Order Coleoptera. pletely strip potato plants of through complete metamorphotheir leaves, causing millions sis, with the larval stage being a of dollars worth of damage. caterpillar. Caterpillars have Humans are continuously putting forth effort to fight these inchewing mouthparts and feed on plants. In order to obtain sects, but they are constantly adapting and building resistance the energy to fuel metamorphosis, caterpillars feed almost conto our pesticides. Boll weevils cause great damage to cotton stantly. crops, which has resulted in billions of dollars lost by cotton farmers. 112

At the end of the larval stage, a pupa is formed. While inside the pupa, the caterpillar undergoes a complete physical change and emerges as the adult butterfly or moth. Find it! What is a butterfly pupa called? Find it! What is a moth pupa called? Adults in the order Lepidoptera usually have scalecovered wings and mouthparts adapted for sucking nectar. Many people have a difficult time telling the difference between a moth and a butterfly. They have many things in common, three body segments, six legs, four wings, but there are differences. The structural differences are very minor, so what sets butterflies apart from moths is mostly behavioral. Find it! List four differences between butterflies and moths. Moths and butterflies use several defensive strategies to avoid predators. One of the most common defenses is tasting bad. Just like you, most predators do not want to feed on something that tastes bad. Lepidopterans ingest chemicals as larva, which are stored in the tissues and result in a horrible taste. The monarch butterfly employs this strategy. Monarch caterpillars feed on milkweed, which results in them tasting bad and being poisonous, protecting them from bird predators. Find it! What type of bird feeds on monarchs? How does it avoid the bad taste?

These defensive strategies have led to mimicry by other butterflies. For example, the viceroy is a butterfly that looks almost identical to the Monarch. As mentioned, the Monarch is a foul-tasting, and poisonous. The viceroy is harmless, but because it looks so much like the Monarch, most birds avoid it. Caterpillars use a strategy called cryptic coloration. Cryptic coloration is when the caterpillars resemble leaves or twigs on which they feed or crawl. This simply makes it harder for predators to find and eat the caterpillars. Members of the order Lepidoptera have fascinated many people over the years. Photographers, painters, collectors and researchers have been inspired by butterflies for year. Butterflies and moths are also very important for the pollination of plants. Moths can also be pests. For example, the larva of the codling moth is a serious pest of apples, pears, walnuts and other fruit. The codling moth was accidentally brought to the United States from Europe and is now a serious pest in hardwood forests. Find it! What is an invasive species? Order Diptera Chances are, everyone in the classroom has had an encounter with a member of the order Diptera. In fact, it wouldn’t be surprising if there was an insect of the order Diptera in the classroom right now. There are approximately 120,000 described species of flies, which belong to the order Diptera. Flies live in almost every habitat, including some extremes, like hot springs, saline lakes and tundra ponds. 113

Flies have extremely sharp senses and are extremely agile in flight, which is why they are so difficult to swat. True flies (which does NOT include mayfies, caddisflies and dragonflies) only have one pair of wings. This is different from other arthropods. The wings are located on the thorax, as are structures called halteres. The halteres provide increased stability during flight, helping them avoid danger.

M OVIE 6.3 Order Diptera

Brainstorm: When you think of maggots, what do you think of? Have you ever encountered maggots? Flies are herbivores, detritivores, predators and parasites. Many of the flies are beneficial, serving as predators and parasites of other insects and pollinators of plants. However, flies have also had many detrimental effects on human society. Imagine life without a refrigerator and imagine how many flies would make their way to your food. Flies also carry many diseases and spread them from person to person. Mosquitoes are members of the order Diptera. Due to the disease that they carry, mosquitoes have killed more humans than any other organism on Earth. Brainstorm: How do you feel when you see a fly on your food? Explain. Find it! List 5 diseases spread by mosquitoes. Order Hymenoptera

Housefly feeding. The mouthparts of adult flies are modified for a liquid diet. Flies feed by sucking or sponging up plant and animal fluids. The larva of flies are most commonly known as maggots.

Members of the order Hymenoptera are ants, wasps and bees. There are approximately 115,000 species that have been identified. These insects are found on every continent except Antarctica. Hymenopterans are characterized by two pairs of wings and the mouthparts are usually adapted for chewing. However, some have evolved to feed on nectar. As described earlier, bees are social insects. Ants also have highly evolved social structures. This has led to their suc-

114

cess. There are approximately 12,000 species of ants, most of which are tropical. Ants, bees and wasps can be pests to humans, but they are also very important. Bees are responsible for the pollination of many of the flowers on Earth. These insects are also at the bottom of many food chains and many animals depend on them as their main source of nutrients.

R EVIEW 6.3 Insect Orders - The Big 4 Question 1 of 5 Which of the following insects belongs to the order Lepidoptera?

Find it! Which species of bee has the most painful sting?

Insects and Humans

1. How do insects benefit humans? 2. How do insects harm humans? 3. List and describe 3 animals that would be effected if insects disappeared from Earth. 4. Describe a way that insects have effected you or may effect you sometime in the future.

A. Flies B. Butterflies C. Beetle D. Wasp

Check Answer

115

Chapter 6 Vocabulary thermoregulation ectotherms heterotherms crop gizzard tympanal organs echolocation castes mimicry cryptic coloration halteres

Chapter 6 Summary ★ Animals in the subphylum Hexapoda are characterized by 3 body segments, 5 pairs of head appendages, 3 pairs of legs and 2 pairs of wings. ★ Insects develop by way of complete metamorphosis or incomplete metamorphosis. ★ Insect mouthparts are highly adapted for the type of food that they eat. ★ Gas exchange in insects involves spiracles and tracheae. ★ Insects secrete pheromones, which have many different functions. ★ Social insects have a specific caste in the society. ★ Social insects work together to insure the success of the species. ★ Most insects on Earth are beneficial to humans.

116

C HAPTER 7

Echinoderms The last group of invertebrates is a successful group of marine animals. The phylum Echinodermata includes sea stars, sea cucumbers and sea urchins. Most people refer to sea stars as “starfish,” however, they are not fish and should actually be referred to as sea stars.

The members of the phylum Echinodermata are not well known by most people, but are very abundant in marine environments. Echinoderms have something that no invertebrate we have studied has, an endoskeleton. Characteristics of the Phylum Echinodermata 1. Calcarious endoskeleton 2. Radial symmetry in adults 3. Water-vascular system 4. Nervous system with nerve net, nerve ring and radial nerves

118

S ECTION 1

Echinoderm Form and Function

L EARNING O BJECTIVES 1. Understand the function of the water vascular system. 2.

Analyze the advantages of regeneration.

3. Compare the structure of echinoderms to other invertebrates.

There are approximate 7,000 species of living echinoderms. These animals are exclusively marine and live at all depths of the ocean. Adult echinoderms show radial symmetry, with the body parts arranged around a central disc. The body parts are arranged in fives or multiples of fives. For example, the common sea star has five arms, but some have ten or fifteen arms. Radial symmetry is an adaptation for slowmoving or sedentary animals. Having the body parts arranged in a circle around the body allows the animal to sense in nearly all directions at the same time. The echinoderm skeleton consists of a series of calcium carbonate plates called ossicles. These plates are held in place by connective tissues and covered by the epidermis. The Water Vascular System The most important part of an echinoderm’s body is its water vascular system. Like many other invertebrates, echinoderms are strictly aquatic and rely on water to carry out many functions. The water vascular system is essentially a series of tubes that run throughout the body. In the center of the body is a ring canal that brings the entire water vascular system together. The water vascular system is involved in gas exchange, feeding, sensory reception and locomotion. There is generally one opening to the water vascular system located on the aboral side of the animal. That opening is known as the madreporite. From the ring canal, the water vascular system branches off and runs down each arm of the echinoderm. 119

These branches of the water vascular system are referred to as radial canals.

outstretched arms to catch passing particles. Other echinoderms feed by scraping algae off of rocks with specialized mouthparts that have evolved in animals such as sea urchins.

The water vascular system is involved in movement by being connected to the tube feet. The tube feet emerge from Sea stars are either detritivores or carnivores. Recall openings in the skeletal ossicles. that detritivores feed on dead G ALLERY 7.1 Phylum Echinodermata Inside of the body, they end in and decaying organic material. bulblike ampullae (think of an The preferred food of most echieye dropper). The end of the noderms is bivalve molluscs, tube foot that extends outside of which they must open using the body often has a suction their tube feet. To feed on an cup, which aids in movement animal such as a clam, a sea star and attachment to the substrate. moves over the animal and Sea stars can have thousands of pries the shell open. When a tube feet, which must work tosmall gap is formed, the sea star gether for the animal to move. expels its stomach from its The suction created by the ammouth and into the shell. The pullae is very strong. This aids stomach secretes digestive enthe animal in staying attached zymes and slowly liquifies the to substrate when a predator body parts of the mollusc. tries to pry it away. The tube When digestion of the mollusc feet can also aid in feeding when Basic structure of the sea star. is complete, the sea star retracts the echinoderm attempts to eat its stomach, with the meal ina mollusc and must pry the shell side of it. This same method open. can be used to feed on sponges, sea anemones and coral. Feeding and Digestion Feeding methods among echinoderms vary widely. Some are filter feeders or suspension feeders, using their 120

G ALLERY 7.2 Echinoderm Regeneration

Brainstorm: Why would an echinoderm need to know how deep the water is? Reproduction and Regeneration Sea stars are well known for their powers of regeneration. They can regenerate any part of a broken arm. In some species, an entire sea star can be regenerated from an arm as long as that arm has part of the central disk attached to it. Regeneration is a slow process and involved in the reproduction

M OVIE 7.1 Phylum Echinodermata

Sea star. The white spot int he center is the madreporite.

Nervous Function The nervous system of sea stars consists of a nerve ring that surrounds the mouth and radial nerves that extend the length of each arm.The nerves coordinate the functions of the tube feet, as well as collect sensory information. Most sensory receptors are distributed over the surface of the body and tube feet. Sea stars respond to light, chemicals, and various other stimuli. Many sea stars have specialized receptors on the ends of their arms. These receptors are generally used to detect light, helping the animal determine the depth of the water that it is in.

Sea Star moving.

121

of some echinoderms. Some species are able to divide in half and regenerate, resulting in two complete new animals. Most sea stars are dioecious. There are two gonads in each arm. The eggs and sperm are typically released into open water, where fertilization takes place. In some species, the release of sperm and egg is synchronized, depending on the lunar cycle. Other species aggregate during the reproductive season to increase the probability that their eggs will be fertilized. When an echinoderm egg hatches, a bilateral larva emerges. The larva are often ciliated and become part of the plankton in the ocean. Regeneration can be used as a mode of reproduction, but most often it is a way to escape predators. Many echinoderms are able to discharge an arm or other appendage when threatened by a predator. This allows them to escape without the major part of the body being damaged. Over the course of a year, the echinoderm will then grow back the body part that was sacrificed.

R EVIEW 7.1 Echinoderm Form and Function Question 1 of 5 Which body system of echinoderms is responsible for gas exchange and movement?

A. Respiratory system B. Muscular system C. Water vascular system D. Nephridic system

Check Answer

122

S ECTION 2

Echinoderm Classes

The phylum Echinodermata is divided into five classes. They are the classes Asteroidea, Ophiuroidea, Echinoidea, Holothuroidea and Crinoidea. The animals in each of these classes share the characteristics of the phylum but have characteristics that set them apart from the others. Class Asteroidea

L EARNING O BJECTIVES 1. Compare the five classes the phylum Echinodermata. 2. Compare and contrast the life styles of the five classes. 3. Analyze how the five classes have adapted to live their different lifestyles. 4. Understand the impact of Echinoderms on ecosystems and humans.

The sea stars make up the class Asteroidea, which is approximately 1,500 species. Members of this class often live on hard substrates in marine environments, although some have adapted to live in sandy or muddy substrates. The most common of all sea stars is Asterias, which is an orange sea star that is commonly found on the Atlantic coast of North America. The sea star body plan usually consists of a central disk and five arms surrounding it. However, there are species that have more than five arms. Located on the ventral, or oral, side of the disk is usually the mouth. The mouth is usually facing downward and surrounded by movable spines. Sea star anatomy is relative simple, but extremely effective. The body plan is no mistake, these animals have evolved to live and thrive in their environment. Find it! What is the highest number of arms that a sea star can have? Recall that echinoderms have an endoskeleton. Sea stars are no exception. They have an interior support system that runs down each arm. Also in each arm is two pyloric ceca 123

and two gonads. The pyloric ceca are linked to the stomach, which is located in the disk, and aid in digestion. The gonads are part of the reproductive system, produced sperm or egg. Also associated with each arm are the ampullae and tube feet, which allow the animal to move and feed. The movement of the tube feet is coordinated by the nervous system, allowing the animal to walk. The tube feet also serve as suction cups which help the animal stay on the substrate during strong wave action in the ocean.

G ALLERY 7.3 Class Asteroidea

Find it! What is the largest species of sea star? Sea stars feed on snails, bivalves, crustaceans and a variety of other foods. The stomach is often expelled from the mouth, digesting the food externally and then bringing it into the body. Some of the sea stars digest the prey whole, outside of the body. This is most effective when the sea star is consuming a bivalve and must eat the soft part of the body from inside the shell. Any digestive waste is expelled through the mouth. Sea stars do not have a circulatory system or respiratory system. Because they live in water, they are able to rely on diffusion for gas exchange and circulation. The nervous system consists of a nerve ring that surrounds the mouth and radial nerves that extend into each arm. Sensory receptors are distributed on the body and tube feet, including photoreceptors generally found on the end of each arm. Sea stars respond to light, chemicals and other stimuli, such as touch. Sea stars are well known for their powers of regeneration. They can regenerate any part of a broken arm. Most sea stars are dioecious, but there is no way to tell a male from a female by simply looking at them. When reproduction is taking place, gametes are released into the water and external fertilization takes place. Sea star embryos are planktonic, swimming among the other microscopic organisms in the sea.

Crown of thorns starfish.

Brainstorm! How could the ability to regenerate be beneficial to humans? 124

Class Ophiuroidea With over 2,ooo species, the class Ophiuroidea include the basket stars and brittle stars. These echinoderms are more numerous than the sea stars, but are not as well known because of their small size and their tendency to stay hidden in cracks and crevices.

members of this class have a fission line across their central disk and are able to split in half, forming two new organisms.

G ALLERY 7.4 Class Ophiuroidea

Unlike the sea stars, the arms of these echinoderms are long and slender and are sharply set off from the central disk. Ophiuroids do not rely on the water vascular system for movement. Instead, the skeleton has been modified and muscles associated with the tube feet cause the animal to move. The tube feet do not have suction cups like the sea stars, which may explain why these animals tend to hide in cracks and crevices. Find it! What kinds of animals feed on brittle stars? Members of the class Ophiuroidea are predators or scavengers. They use their arms and tube feet in sweeping motions to collect prey and particles, which are then transferred to the mouth. The mouth is located on the ventral side of the central disk and is surrounded by jaws that allow them to chew. The mouth leads to a saclike stomach and the digestive system is completely contained in the central disk. The members of the class Ophiuroidea can regenerate lost arms. If a brittle star is grasped by an arm, the animal is able to contract muscles and release the arm. The process of releasing a body part is knowns as autotomy. Some of the

Common brittle star.

When not reproducing asexually, Ophiuroids are dioecious. Class Echinoidea Sea urchins and sand dollars make up the class Echinoidea. There are nearly 1,000 species and they are found in nearly all marine environments. Sea urchins are specialized for living on hard substrates, often wedging themselves into 125

crevices or holes of rocks and coral. Sand dollars burrow in sand or mud and use tube feet to catch organic material around them.

Class Holothuroidea The class Holothuroidea contains approximately 1,500 species of echinoderms. The members of this class are commonly called sea cucumbers, which are found at all depths of the ocean. Sea cucumbers have their name because they resemble the food of the same name. Sea cucumbers have no arms and crawl over hard substrate and burrow through softer substrate.

Sea urchins are rounded and have a skeleton that is referred to as a test. The tests are composed of plates, which have openings for tube feet. The spines of sea urchins are sharp and can contain venom. Sea urchins can feed on plankton, or can use their venom in order to feed animals such as sea G ALLERY 7.5 Classes Echinoidea, Holothuroidea and Crinoidea stars. The water vascular system is similar to that of other echinoderms. The tube feet possess ampullae and suction cups. Echinoids use their spines for pushing against the substrate and tube feet for pulling. Sand dollars use their spines to burrow into the sand. Echinoids are dioecious. During the breeding season, gametes are shed into the water and fertilization is external. The larva are planktonic and after metamorphosis become and adult. Find it! Some humans eat sea urchin. Find 3 dishes that include sea urchin.

Purple sea urchin

Find it! Are there any human uses for sea cucumbers? Like other echinoderms, the sea cucumbers have tube feet. The tube feet around the mouth are elongated and function similarly to tentacles. Most sea cucumbers ingest small particles using their tentacles. Mucus covering the tentacles traps food as the tentacles sweep across the substrate or are held out in seawater. Unlike most other echinoderms, sea cucumbers have a complete digestive tract, with a mouth an an anus. In order to deter predators, many sea cucumbers pro126

duce toxins in their body wall. Most sea cucumbers are dioecious. Fertilization is usually external and embryos are planktonic. Before settling to the substrate, the larva undergo metamorphosis and become adults. Find it! What kinds of animals prey upon sea cucumbers? Class Crinoidea Members of the class Crinoidea include sea lilies and feather stars. They are the most primitive of all echinoderms and there are approximately 630 living species. The fossil record indicates that members of the class Crinoidea have been around for 200 to 600 million years. Sea lilies are named such because they resemble flowers. These animals attach permanently to their substrate by a stalk. The end of a stalk has a flattened disk that attaches to the substrate. Sea lilies and feather stars have five or more arms. The arms of the animal face upward, like the petals of a flower and are used in gathering food. The food is trapped by tube feet and is then moved by cilia to the mouth. Like other echinoderms, most crinoids are dioecious. Fertilization is external and larva are often released into the water. Some species actually brood the larva among the arms before releasing them to the water for metamorphosis. Once the animal has completed metamorphosis, it attaches to the substrate to carry out its adult life.

R EVIEW 7.2 Lorem Ipsum dolor amet, consectetur Question 1 of 5 Which of the following correctly describes the class Asteroidea?

A. Stalk attached to substrate B. Usually 5 arms C. Tube-shaped body D. Long, cylindrical arms

Check Answer

127

Chapter 7 Vocabulary

Chapter 7 Summary

endoskeleton

★ Echinoderms show radial symmetry, have an endoskeleton and an water vascular system.

ossicles ring canal madreporite radial canals tube feet

★ The water vascular system of echinoderms has many functions, including feeding, respiration and locomotion. ★ The phylum Echinodermata is divided into 5 classes. ★ Sea stars usually five arms arranged around a central disk.

ampullae

★ The largest Echinoderm class is Ophiuroidea, which includes the brittle stars.

suspension feeders

★ The class Echinoidea includes sea urchins and sand dollars.

pyloric ceca

★ Echinoderms feed in a variety of ways and on a variety of foods.

128

Credits Cover (Anne Weller)

Page 12: Black Swan (Dave Watts), Black Swan Family (Peter Reese), Jewel Sea Anemone (Sue Daly), Hydra (Lutra) Page 15: Aardvark (Anthony Bannister), Arctic Fur Seal (Suzi Eszterhas), Asian Vine Snake (Andrea and Antonella Ferrari), Arctic Fox (J.L. Klein and M.L. Hubert)

Table of Contents (Anne Weller) Chapter 1: Introduction to Zoology Page 3: Standard Poodle (Anne Weller), Cat (Hayden Oake), Humpback Whale(Sue Flood), Chimpanzee (Clive Bromhall), Tex Page 4: Orchid (Mauro Rosim), Aristotle (Wikipedia Public Domain)

Page 16: Charles Darwin (Wikipedia Public Domain), Large Cactus-Finch (Bill Coster), Medium Tree Finch (Bill Coster), Warbler Finch (Tui De Roy), Cocos Finch (Peter R. Grant) Page 20: Boulder Brain Coral (Viola’s Photo Visions, Inc.) Page 21: Pink Sponge (Brandon Cole), Blue Sponge (www.bioweb.uwlax.edu), Yellow Sponge (www.goodnews.ws)

Page 5: Cheetah (Tony Heald) Page 8: Coral (Alasdair Harris), Mushroom (Tom Bruns), Fried-egg Jellyfis (Ken Lucas), Common Mussel (gettyimages), Barnacles (Inigo Everson), Carrion Flower (Martin Heigan Page 10: Giraffe (Anup Shah), Lion (David Tipling), Brown Bear (Eric Baccega), Earthworm (gettyimages), Peacock Worm (gettyimages) Page 11: Hawksbill Sea Turtle (Tom Zuraw), Leopard Shark (Doug Perrine), Weller’s Salamander (Nathan Haislip), Common Jellyfish (Graham Eaton)

Page 24: Yellow Tube Sponges (Shutterstock), Blue Sponge and Fish (Scientific American), Dried Sponge (Wikipedia Public Domain), Manmade Sponges (Wikipedia Public Domain) Page 27: African Pillow Coral (Josh Jensen), Compass Jellyfish (Sue Scott), Beadlet Anemone (gettyimages), Nematocysts (Wikipedia Public Domain) Page 29: Lion’s Mane Jellyfish (Herb Segars), Hydra (gettyimages), Page 29: Common Jellyfish Video (Wildscreen)

Page 30: Obelia (Corbisimages), Gonionemus (airows.com), Brown Hydra (Willem Kolvoort) Page 31: Class Staurozoa (Wikipedia Public Domain), Aurelia polyp (gettyimages), Polyps feeding (Nature Production), Aurelia (Christian Reier), Tentacle (Jean Lacomte), Sea Nettle (Nancy Barnett), Box Jellyfish (Wikipedia Public Domain) Page 32: Duncan Coral (Sabine Pennison), Beadlet Anemone (gettyimages), Beadlet Anemone mouth (Sue Daly) Page 33: Portuguese man-of-war (Justin Gilligan) Page 36: Giant tube worm (Peter Batson)

Page 55: Nematode (nematode.uml.edu) Page 58: Ascaris (ascarislumbricoides.org), New World Hookworm (SPL), Filarial Infection (Wikipedia Public Domain), Pinworm (emedicine.com) Page 61: Curled octopus (Espen Rekdal), Common mussels (Sue Daly), Cowrie (Roy Anderson) Page 63: Snail anatomy ( Original by Al2, English captions and other edits by Jeff Dahl) Page 65: Torsion (McGraw Hill)

Page 38: Phylum Platyhelminthes (Wikipedia Public Domain)

Page 66: Gastropod (Aaron Baldwin), Slugs (Wikipedia Public Domain)

Page 39: Turbellarian Anatomy (Wikipedia Public Domain)

Page 68: Bivalve shells (Wikipedia Common Domain)

Page 40: Freshwater Turbellarian (mit.edu)

Page 69: Banded wedge (Heather Angel), Common cockell (Sue Scott), Peppery furrow (Rodger Jackman)

Page 44: Tapeworm Scolex (sciencephoto.net), Human tapeworm (Wikipedia Public Domain), Dog tapeworm (pitbullregristry.com), Human brain (nutritionfacts.org) Page 48: Peacock worms (Sue Daly), Earthworm (gettyimages), Leech (Roger Key), Christmas Tree Worm (Nick Hobgood) Page 51: Earthworm gallery (gettyimages) Page 52: Medicinal Leech (Brian Brevan), Leech Habitat (Roger Key)

Page 73: Octopus Anatomy (colorado.edu) Page 72: Caribbean Reef Squid (Howard Hall), Common Cuttlefish (David Fleetham), Common Octopus (Jean MicheleMille) Page 75: Octopus Eggs (Fred Bavendam), Octopus eye and siphon (Mark Deeble & Victoria Stone) Page 79: Megachile leaf-cutter bee (Nigel Cattlin)

cxxx

Page 81: Horseshoe Crab (Wikipedia Public Domain), Spider (Wikipedia Public Domain, Kilarin), Sea Spider (Steve Childs), Remipedia (Joris van der Ham, Fairy Shrimp (Hans Hillewaert), Lobster (Wikipedia Public Domain), Barnacles (MichaelMaggs), Butterfly (Didier Descouens), millipede (Marshman) Page 83: Horseshoe crab on beach (Rick Price), Horseshoe crab swimming (David Cayless), Horseshoe crab mating (Ingo Arndt), Page 85: Crab Spider (Dave Cozens), Emperor scorpion molting (gettyimages), Two harvestmen (Steve Hopkin), Kangaroo Tick (Fred and Jean Hort)

Page 108: Honeybees (Gabriel Meilhac), Wasp (Paulo De Oliveira), Ants (Pascal Goetgheluck) Page 112: Cardinal Beetle (Hippocampus Bildarch), Comma Butterfly (John Mason), Housefly (gettyimages), Asian Dwarf Honeybee (Mohammed Baarman) Page 117: Common Sea Star (Andrey Nekrasov) Page 120: Sea star structure (Marine Biology by P. Castro) Page 121: Sea Star (Jonathan Bird), Oral view of sea star (Sinclair Stammers), Sea star with stomach expelled (Rodger Jackman), Sea star regenerating (Jim Greenfield Page 124: Crown of thorns starfish (Kurt Amsler), Sand star (Kare Telmes), Sunflower star (David Fleetham)

Page 87: Wonderful parachute spider (Rick C. West), Mite and chigger (Wikipedia Public Domain)

Page 125: Common brittle star (Paul Kay)

Page 91: Crayfish (Wikipedia Public Domain)

Page 126: Sea urchin (John Mason), Sea cucumber and sea lily (Wikipedia Public Domain)

Page 94: Fairy shrimp (Richard Manuel), Water fleas (naturepl.com), Acorn barnacles (gettyimages), Goose barnacle (naturepl.com) Page 95: Common centipede and flat-backed millipede (Hippocampus Bildarch) Page 100: Painted lady (Stephen Dalton) Page 103: Insect mouthparts (Wikipedia Public Domain) cxxxi

Abdomen In arthropods, the segment that contains the digestive, reproductive, respiratory and excretory organs.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 5 - Subphylum Chelicerata

Aboral The end of the body opposite of the mouth.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 2 - Soft-Bodied Animals: Phylum Cnidaria

Acoelomate An animal that does not have a body cavity.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 3 - Phylum Platyhelminthes - Flatworms

Adductor muscles Strong muscles, located anteriorly and posteriorly in a bivalve shell that keep the shell closed.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 4 - Class Bivalvia - Molluscs with Two Shells

Alternation of generations The regular alternation of body forms or of mode of reproduction in organisms.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 2 - Soft-Bodied Animals: Phylum Cnidaria

Amoeboid Cell Cell that does not have a defined shape. Is capable of changing shape in order to perform a specific function.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 2 - Phylum Porifera - Sponges Chapter 2 - Soft-Bodied Animals: Phylum Cnidaria

Ampullae The round, muscular structure on a tube foot that aids in movement.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 7 - Echinoderm Form and Function

Appendages External structure, outgrowth from the body. For example, legs or arms.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 5 - Arthropods

Asexual Reproduction Reproduction of an organism without fusion of gametes. Requires only one individual. Results in offspring that are genetically identical to the parent.

Related Glossary Terms Sexual Reproduction

Index

Find Term

Chapter 1 - What is an Animal?

Auricles Sensory lobes that project from the side of the head in Turbellarians. Detect touch, currents and chemical in the surroundings.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 3 - Phylum Platyhelminthes - Flatworms

Autotomy The self-amputation of an appendage

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 7 - Echinoderm Classes

Bilateral symmetry A body plan that can be divided into two equal halves. The two halves are mirror images of each other.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 3 - Phylum Platyhelminthes - Flatworms

Binomial Nomenclature A system for naming in which each organism is given a two part name. The two parts consist of the genus and species. The = two

Nomen = name

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 1 - What is Zoology?

Calare = to call (Latin)

Biology The Study of living things. Bio = life Ology = the study of (Greek)

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 1 - What is Zoology?

Bioluminescent Describes a living organism that is able to produce its own light. Includes jellyfish, krill and some fish. The animals appear to glow in the dark.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 5 - Subphylum Crustacea

Book gills Modifications of a horseshoe crab’s exoskeleton into a series of leaflike plates that are a surface for gas exchange between the arthropod and the water.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 5 - Subphylum Chelicerata

Book lungs Structure found in arthropods that provides a surface for gas exchange between blood and air. Found in spiders.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 5 - Subphylum Chelicerata

Botany The study of plants. Botane = pasture, grass (Greek)

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 1 - What is Zoology?

Carnivore Animal that consumes only other animals.

Related Glossary Terms Drag related terms here

Index

Find Term

Castes Distinct kinds of individuals in a colony of social insects (queens, drones, workers, etc)

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 6 - Social Behavior and Reproduction

Cephalization Describes an animal that has a head.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 3 - Phylum Platyhelminthes - Flatworms

Cephalopthorax A segment, usually in arthropods, that is formed by a fusion of the head and the thorax.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 5 - Subphylum Chelicerata

Chelicerae The first pair of appendages of chelicerates. Specialized for feeding, these appendages can be pincers or fangs.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 5 - Subphylum Chelicerata

Chitin The polysaccharide in the exoskeleton of arthropods.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 5 - Arthropods

Choanocyte Cells of sponges that create water movement and filter food. Also known as collar cells.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 2 - Phylum Porifera - Sponges

Chromatophores Cells containing pigment that, through contraction and expansion, produce temporary color changes.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 4 - Class Cephalopoda - Soft-bodied, Fast-moving

Molluscs

Clitellum Region of an annelid responsible for secreting mucus around two worms during reproduction and secreting a cocoon to protect the fertilized eggs.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 3 - Phylum Annelida - Segmented Worms

Cloaca Body opening that allows reproductive matter and waste to leave the body. Found in many invertebrates and lower vertebrates.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 3 - Phylum Nematoda - Roundworms

Closed circulatory system Circulatory system in which the blood is contained to veins, arteries and vessels. Usually includes a heart or hearts, which keeps the blood moving throughout the body.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 3 - Phylum Annelida - Segmented Worms

Cnidocytes The cells that produce and discharge the stinging structures of animals such as jellyfish.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 2 - Soft-Bodied Animals: Phylum Cnidaria

Coelom Body cavity of animals.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 3 - Phylum Annelida - Segmented Worms

Coxal glands An organ of excretion in some arthropods (spiders) that empties through a pore near the posterior appendages.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 5 - Subphylum Chelicerata

Crop A part of the digestive system of many animals. Functions in the storage of food before it moves to the gizzard.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 6 - Insect Form and Function

Cryptic coloration Protective coloration. Coloration that conceals an organism.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 6 - Insect Orders - The Big 4

Detritivore Animal that feeds on dead or decaying plant and animal material (detritus).

Related Glossary Terms Scavenger

Index

Find Term

Development to go through a process of natural growth, differentiation, or evolution by successive changes

Related Glossary Terms Metamorphosis

Index

Find Term

Chapter 1 - What is Zoology?

Diffusion The movement of particles from an area of high concentration to an area of lower concentration.

Related Glossary Terms Respiration

Index

Find Term

Chapter 1 - What is an Animal?

Dioecious Describes animals that have the male and female reproductive organisms in separate animals. Separate sexes.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 2 - Soft-Bodied Animals: Phylum Cnidaria

Ecdysis 1. The shedding of the arthropod exoskeleton to accommodate increased body size or a change in morphology. 2. The shedding of the epidermal layers of the skin of a reptile.

Related Glossary Terms Molting

Index

Find Term

Chapter 5 - Arthropods

Echolocation A method of locating objects by determining the time required for an echo to return and the direction from which the echo returns.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 6 - Insect Form and Function

Ectotherms Animal that relies on an external heat source to raise their body temperature. Often referred to as cold-blooded.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 6 - Insect Form and Function

Elephantiasis A chronic filarial disease most commonly occurring in the tropics due to infection of the lymphatic vessels by nematodes.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 3 - Phylum Nematoda - Roundworms

Endoskeleton A skeleton on the inside of the body.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 7 - Echinoderms

Epidermis Outer body layer. In some animals, it is the skin.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 2 - Soft-Bodied Animals: Phylum Cnidaria

Ethology The study of animal behavior. Ethos = Character Ology = The study of (Greek)

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 1 - What is Zoology?

Evolution Change over time.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 1 - What is Zoology?

Exoskeleton A skeleton located on the outside of the body.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 5 - Arthropods

Extinct No longer in existence.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 1 - How do Animals Change?

Filter Feeder Animal that strains suspended matter or food particles from water.

Related Glossary Terms Drag related terms here

Index

Find Term

Fission A method of asexual reproduction in which the animal splits in half and grows into two separate animals, genetically identical

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 3 - Phylum Platyhelminthes - Flatworms

Flagella Long, tail-like structures that protrude from a cell. Able to move in order to create water movement or move the cell itself.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 2 - Phylum Porifera - Sponges

Flame cells Hollow excretory or osmoregulatory structures located at the end fine tubules. Help to excrete metabolic wastes and excess water.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 3 - Phylum Platyhelminthes - Flatworms

Food grooves Ciliated tracts along the gills of bivalve molluscs. These tracts transport food filtered by the gills toward the mouth.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 4 - Class Bivalvia - Molluscs with Two Shells

Food Vacuole A cell organelle that functions in digestion.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 2 - Phylum Porifera - Sponges

Ganglia Cluster of nerve cells that serves as a primitive brain.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 3 - Phylum Platyhelminthes - Flatworms

Gastrodermis Lining of the gastrovascular cavity in cnidarians.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 2 - Soft-Bodied Animals: Phylum Cnidaria

Gizzard Part of the digestive system of some animals, functions in grinding the food. Located posterior to the crop.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 6 - Insect Form and Function

Gonads A gamete producing structure. Ovary or testis.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 4 - Class Bivalvia - Molluscs with Two Shells

Growth An increase in biological mass over time.

Related Glossary Terms Metamorphosis

Index

Find Term

Chapter 1 - What is an Animal?

Halteres Small, knoblike structures, located on the thorax of flies. Believed to modified from the hindwings, these provide stability during flight.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 6 - Insect Orders - The Big 4

Head-foot The body region of a mollusc that contains the head and is responsible for locomotion as well as retracting the visceral mass into the shell.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 4 - Mollucs

Heartworm disease A parasitic infection in dogs caused by a nematode.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 3 - Phylum Nematoda - Roundworms

Herbivore Animal that consumes only plant material.

Related Glossary Terms Drag related terms here

Index

Find Term

Hermaphrodites Describes organisms that have both male and female reproductive organs.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 3 - Phylum Annelida - Segmented Worms

Heterotherms Describes an animal that relies on the external environment and its own body to generate heat and control its body temperature.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 6 - Insect Form and Function

Instinct Inherent behavior of an organism toward a particular behavior.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 1 - What is an Animal?

Invertebrate Animal without a backbone.

Related Glossary Terms Drag related terms here

Index

Find Term

Larva An immature form of an animal.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 2 - Phylum Porifera - Sponges

Madreporite Opening on the aboral side of echinoderms. Functions in filtering water before letting it into the water vascular system.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 7 - Echinoderm Form and Function

Malpighian tubules Excretory and osmoregulatory tubes that join the midgut of insects and other arthropods. Secrete waste products and form urine.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 5 - Subphylum Chelicerata

Mantle The outer fleshy tissue of molluscs that secretes the shell. The mantle of cephalopods may be modified for locomotion.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 4 - Mollucs

Mantle cavity The space between the mantle and the visceral mass of molluscs.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 4 - Mollucs

Medusa Usually the sexual stage in the life cycle of cnidarians. The jellyfish body form.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 2 - Soft-Bodied Animals: Phylum Cnidaria

Mesenchyme Cell Cells found in the mesohyl of a sponge. Amoeboid cells specialized for reproduction, forming skeletal elements, and transporting and storing food.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 2 - Phylum Porifera - Sponges

Mesoglea A jelly-like layer between the epidermis and gastrodermis of cnidarians.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 2 - Soft-Bodied Animals: Phylum Cnidaria

Mesohyl Jelly-like layer between the outer (pinacocyte) and inner (choanocyte) layers of a sponge. Contains the mesenchyme cells.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 2 - Phylum Porifera - Sponges

Metameric Longitudinal segmentation. Found in some worms and crustaceans.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 3 - Phylum Annelida - Segmented Worms

Metamorphosis Change of shape or structure, particularly a transition from one developmental stage to another, as from larva to adult form.

Related Glossary Terms Development, Growth

Index

Find Term

Chapter 1 - What is an Animal?

Metanephridia Excretory organ in many invertebrates. Consists of a tubules that has one end opening to the outside of the body and the other end leading into the body cavity. Helps get rid of excess water and liquid waste.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 3 - Phylum Annelida - Segmented Worms

Microvilli Microscopic protrusions of the cell membrane.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 2 - Phylum Porifera - Sponges

Mimicry A type of defense. A harmless animal develops to look similarly to a harmful animal.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 6 - Insect Orders - The Big 4

Molting The periodic renewal of feathers of birds by shedding and replacement. In arthropods and other invertebrates, the shedding of an exoskeleton or other body covering.

Related Glossary Terms Ecdysis

Index

Find Term

Chapter 5 - Arthropods

Monoecious Both sexes occur in the same individual. Able to produce both sperm and egg.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 2 - Phylum Porifera - Sponges

Motile Able to move from place to place. Motility

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 1 - What is an Animal?

Mutation A change in an organism, sometimes viewed as a mistake.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 1 - How do Animals Change?

Mutualism A symbiotic relationship in which both species benefit.

Related Glossary Terms Symbiotic relationship

Index

Find Term

Chapter 2 - Soft-Bodied Animals: Phylum Cnidaria

Natural Selection the idea that some individuals in a population possess variations that make them less able to survive and/or reproduce. These organisms die or fail to reproduce. Also known as survival of the fittest.

Related Glossary Terms Survival of the Fittest

Index

Find Term

Chapter 1 - How do Animals Change?

Naturalist One who studies the natural world, usually focused on biology or botany.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 1 - How do Animals Change?

Nematocysts A structure discharged by the cnidocytes of jellyfish. Has barbs or spikes containing venom.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 2 - Soft-Bodied Animals: Phylum Cnidaria

Nerve Net The simplest of all nervous systems. A network of neurons found in cnidarians.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 2 - Soft-Bodied Animals: Phylum Cnidaria

Ocelli A simple eye or eyespot in many invertebrates. A small cluster of photoreceptors that detect light.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 3 - Phylum Platyhelminthes - Flatworms

Omnivore Animal that consumes both plant and animal material.

Related Glossary Terms Drag related terms here

Index

Find Term

Open circulatory system A circulatory system found in insects and some other invertebrates in which blood is not confined to vessels in part of its circuit. Blood bathes tissues in blood sinuses.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 4 - Mollucs

Operculum A cover. 1. the cover of a gill chamber of a bony fish. 2. The cover of the genital pore of a horseshoe crab. 3. The cover of the aperture of a snail shell.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 4 - Class Gastropoda - Mollucs with One Shell

Organ A structure consisting of a group of specialized tissues that performs a specialized function.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 1 - What is an Animal?

Organ System A set of interconnected or interdependent parts (organs) that function together in a common purpose.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 1 - What is an Animal?

Osculum Large opening at the top of a sponge through which the water exits. Sponges may have one or more osculum, depending on the species.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 2 - Phylum Porifera - Sponges

Osphradia Chemoreceptors in the anterior wall of the mantle cavity of gastropods that detect chemicals in water or air.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 4 - Class Gastropoda - Mollucs with One Shell

Ossicles The term ossicles means “tiny bones.” In invertebrates it refers to the endoskeleton of an echinoderm.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 7 - Echinoderm Form and Function

Ostia Small openings on the side of the sponge through which water enters.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 2 - Phylum Porifera - Sponges

Ovoviviparous Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 5 - Subphylum Chelicerata

Parapodia Fleshy, paired appendages of annelids used for locomotion and respiration.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 3 - Phylum Annelida - Segmented Worms

Parasites Animals that have a symbiotic relationship with another animal, while harming them. The parasite benefits from the relationship while the other animal (often referred to as the host) is harmed. Example: mosquito and human.

Related Glossary Terms Symbiotic relationship

Index

Find Term

Chapter 3 - Phylum Platyhelminthes - Flatworms

Pedipalps The second pair of appendages in chelicerates. Usually sensory, but can also be used for feeding, locomotion or reproduction.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 5 - Subphylum Chelicerata

Pharynx In flatworms, the ingestive organ, or tube that extends from the mouth to take in food.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 3 - Phylum Platyhelminthes - Flatworms

Pheromone A chemical that is synthesized and secreted to the outside of the body by one organism and that is perceived (by smell) by a second organism of the same species, releasing a specific behavior in the recipient.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 5 - Subphylum Crustacea

Phylogenetic Tree a branching diagram showing the inferred evolutionary relationships among various species Phylo = kind

Genesis = beginning (Latin)

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 1 - What is Zoology?

Pinacocyte Thin, flat cells covering the outer surface of a sponge.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 2 - Phylum Porifera - Sponges

Polyp The attached, usually asexual, form of a cnidarian. The coral body form.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 2 - Soft-Bodied Animals: Phylum Cnidaria

Porocyte Tube-shaped cells in the body wall of a sponge that allow water to flow to the inner chamber(s) of the sponge.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 2 - Phylum Porifera - Sponges

Proboscis A slender, tubular, sucking and feeding structure found in some invertebrates.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 3 - Phylum Annelida - Segmented Worms

Proglottids Segments of a tapeworm. Each segment contains a set of reproductive organs and detaches to pass out of the host.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 3 - Phylum Platyhelminthes - Flatworms

Protonephridia Primitive kidneys. These organs work in simpler animals to get rid of metabolic waste and to get rid of excess water.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 3 - Phylum Platyhelminthes - Flatworms

Pyloric ceca Part of the digestive system, secretes digestive enzymes and provides increased surface area for the intestine.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 7 - Echinoderm Classes

Radial canals A structure in echinoderms which runs the length of each arm and takes water out to arm from the ring canal.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 7 - Echinoderm Form and Function

Radial symmetry A form of symmetry in which an organism can be divided in multiple ways into two equal halves. Similar to the spokes of a bicycle wheel.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 2 - Soft-Bodied Animals: Phylum Cnidaria

Radula The rasping, tonguelike structure of most molluscs that is used for scraping food.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 4 - Mollucs

Regeneration A process of renewal, restoration and growth. Allows organisms to regrow lost parts or grown a new organism from pieces that are broken off.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 2 - Phylum Porifera - Sponges

Respiration The process that allows animals to take in oxygen and give off carbon dioxide.

Related Glossary Terms Diffusion

Index

Find Term

Chapter 1 - What is an Animal?

Response A reaction to a specific stimulus

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 1 - What is an Animal?

Ring canal A circular canal near the mouth that carries water from the madreporite to the radial canals of the water vascular system.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 7 - Echinoderm Form and Function

Scavenger Animal that feeds on dead or decaying plant and animal material (detritus).

Related Glossary Terms Detritivore

Index

Find Term

Scolex The “head” of the tapeworm. Attaches to the intestinal wall of the host.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 3 - Phylum Platyhelminthes - Flatworms

Sessile Not able to move from place to place.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 1 - What is an Animal?

Setae Hairlike bristles used for locomotion by many annelids.

Hairlike modifications of an arthropod’s exoskeleton, helps sense movement around them.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 3 - Phylum Annelida - Segmented Worms

Sexual Reproduction The generation of a new organism by the fusion of two gametes (sperm and egg). The new organism receives half of its genetic information from each parent.

Related Glossary Terms Asexual Reproduction

Index

Find Term

Chapter 1 - What is an Animal?

Siphon A tubular structure through which fluid flows. Siphons of some mulluscs allow water to enter an leave the mantle cavity.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 4 - Class Cephalopoda - Soft-bodied, Fast-moving

Molluscs

Spermatophores Encapsulated sperm that a male can deposit on a substrate for a female to pick up or that a male can pass directly to a female.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 4 - Class Cephalopoda - Soft-bodied, Fast-moving

Molluscs

Spicule Skeletal elements of a sponge. Created by mesenchyme cells, made of either calcium carbonate or silica.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 2 - Phylum Porifera - Sponges

Spiracles An opening for ventilation. The openings of the tracheal system of an arthropod. Or an opening posterior to the eye of a shark, skate or ray.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 5 - Subphylum Chelicerata

Spongin A fibrous protein that makes up the supportive framework of some sponges.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 2 - Phylum Porifera - Sponges

Statocysts Sensory structures that help aquatic species detect the direction of gravity.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 2 - Soft-Bodied Animals: Phylum Cnidaria

Stimulus Anything that causes a reaction.

Plural: stimuli

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 1 - What is an Animal?

Survival of the Fittest The idea that the organism that is best suited to its environment will survive, reproduce and pass those characteristics on to the next generation.

Related Glossary Terms Natural Selection

Index

Find Term

Chapter 1 - How do Animals Change?

Suspension feeders A sub-group of filter feeder that feed by straining suspended matter and food partilcels from the water passing by.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 7 - Echinoderm Form and Function

Symbiotic relationship A close, permanent relationship between two living organisms.

Related Glossary Terms Mutualism, Parasites

Index

Find Term

Chapter 2 - Soft-Bodied Animals: Phylum Cnidaria

Taxonomy the description of species and the classification of organisms into groups that reflect evolutionary relationships Taxis = arrangement

Related Glossary Terms Drag related terms here

Index

Find Term

Nomia = method (Greek)

Thermoregulation Regulation of the body temperature. Usually an attempt to keep the temperature steady or at a specific level.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 6 - Insect Form and Function

Tissue A group of similar cells that performs a specified function.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 1 - What is an Animal?

Torsion Twisting of the visceral mass of gastropods that results in an anterior opening of the mantle cavity and a twisting of nerve cords and the digestive tract.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 4 - Class Gastropoda - Mollucs with One Shell

Trachea Small tubes that carry air from spiracles through the body cavity of an arthropod.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 5 - Subphylum Chelicerata

Trichinosis A disease resulting from infection by Trichinosis spiralis larvae from eating undercooked meat. Symptoms include muscular pain, fever and other symptoms.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 3 - Phylum Nematoda - Roundworms

Tube feet Muscular projections from the water-vascular system of echinoderms that are used in locomotion, gas exchange, feeding and attachment.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 7 - Echinoderm Form and Function

Tympanal organs Sensory organs of insects that detect sound vibrations. Primitive ears.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 6 - Insect Form and Function

Umbo The rounded part of the mollusc shell, closest to the hinge. It is the oldest part of the shell.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 4 - Class Bivalvia - Molluscs with Two Shells

Vector Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 3 - Phylum Nematoda - Roundworms

Vertebrate Animal with a backbone.

Related Glossary Terms Drag related terms here

Index

Find Term

Visceral mass The region of a mollusc’s body that contains visceral organs.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 4 - Mollucs

Viviparous Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 5 - Subphylum Chelicerata

Zoology Zoology - The study of animals Zoo = Animal

Ology = The study of (Greek)

Related Glossary Terms Drag related terms here

Index

Find Term

Chapter 1 - What is Zoology?