LABORATORY

9

Invertebrate diversity: How are they different? How are they the same?

As we look back on what we’ve discovered so far in the lab we may want to review the details of how animal diversity became so amazing. Differences in cell types and functions (Labs 1,2,3,4) lead to the very tissues that determine the way we will study animals in this lab. Recall our study of the inheritance of DNA through meiosis and the maintenance of life through mitosis as well as our study of the hierarchy of characteristics that are used to describe each phylum (Labs 5, 6, 7). As we examine the differences between each group, notice how much our understanding of the whole organism and its evolution rest upon our knowledge and experience of the evolutionary past of the organism (Labs 8, 9). Traditionally, the study of animals in a general biology class is driven by the complexity of structures and tissues (similar cells that have similar functions). We begin with the simplest of animals, the sponges, and work our way to animals with more and more specialized structure that work together to result in successful adaptation to their environment. By having different structural adaptations the diversity in animals translates into a world where animals can live almost everywhere. Let’s put together these differences in the context of the evolution of the structures that made each group different and imagine how these adaptations have resulted in a world where animals are well adapted to live in saltwater, freshwater, soil, forests, mountaintops and city parks. Some of the organisms we will study are also well adapted to live in your body as parasites. In this lab we will: • • • •

Learn how to observe and describe the distinguishing features of various types of invertebrates Locate and identify some external and internal structures of the representative animals from each phylum Compare and contrast the differences in the anatomical structures among the phyla Understand evolutionary adaptations in terms of the ecology of these animals

THE CLASSIFICATION OF ANIMALS Thanks to recent discoveries in the cellular development of animals, biologists have created a classification system of two major groups. Those animals that develop mouth first (the 9-1

Protostomes) and those whose mouth develops second, after the anus develops (the Deuterostomes). Prior to this developmental research, animals were grouped according to whether they were Invertebrates (those without backbones) or Vertebrates. We will use both of these classifications to organize our study. The Invertebrates The greatest number of organisms on the planet are invertebrates; the largest group being the insects. The present invertebrate fauna is the result of many “hopeful monsters” making it through the Cambrian explosion. As we will see, the winners are those heterotrophs with structures that allow them to obtain food and avoid predation. Let’s see who the winners are. To organize our investigation, recall from the taxonomy lab how classification works. Here we will be studying the Kingdom Animalia and within that kingdom several Phyla. Within some of the phyla we will further identify less inclusive groups known as Classes. Orders, Families, Genera, and Species which link animals with ever increasing similarities. The following criteria are used to designate the similarities among invertebrates. These distinctions are directly related to the overall body plan and then complexities in the digestive, nervous and skeletal systems. Use your textbook (page _____) to identify the following criteria used in classifying invetebrates. Symmetry: Germ layers: Coelom:

radial or bilateral Endoderm, ectoderm and/or mesoderm 2 layer (no coelom), 3 layer (no coelom), 3 layer (pseudocoelom), 3 layer (coelom) Gut: Tubular, gastrovascular cavity Segmentation: yes/no Studying the invertebrates also gives us a chance to see which group the development of organs and special tissues found in our bodies began to evolve such as: Nervous tissue - ganglia Circulatory - heart and blood vessels Digestion - specialized cells Urinary - nephrons Muscule tissue Use your textbook and laboratory examples to see the what features distinguish each group. It will then be your task to organize your specimens into their appropriate groups. Finally, complete the table under each phylum that summarizes the features.

9-2

Phylum Porifera: the sponges a. Using your text draw a sponge, label the specialized cells (flagellated, amebocyte, etc.) and show the flow of water

b. How do sponges reproduce?_______________________________ c. What does hermaphroditic mean? ___________________________ d. Complete Table 10-1 for Porifera.

Phylum Cnidaria: jellyfish, anemones, hydras, corals, Portuguese man-of-war a. Draw a polyp body plan

b. Draw a medusa body plan

Using the three major groups of Cnideria, which animals go with which plan? (polyp vs medusa) Cniderian Group

Body plan

Scyphozoans Anthozoans Hydrozoans

What are the two stages of the Cnidarian life cycle? __________________________________________________________________________ Which stage is sexual and which is asexual? ________________________________________

c. What specialized cells do Cnidarians have to capture their prey? ______________________ d. Complete Table 10-1 for Cnidaria 9-3

THE PROTOSTOMES-DEVELOPING MOUTH FIRST Phylum Platyhelminthes flatworms: planaria, tapeworms and liver flukes a. Look at the life cycle of various parasites…how can you avoid them? _____________________ __________________________________________________________________________ b. Look at tapeworms in your book. What structures are used to make the most of their host? __________________________________________________________________________ c. What new features are found in the platyhelminthes that are not found in the previous phyla?

d. Complete Table 10-1 for Platyhelminthes

Phylum Nematoda: roundworms (Ascaris, Pinworms, Heartworms) a. These animals lack a true coelom. What do they have instead? Besides distributing nutrients, gases and wastes, what other function does this have? Although this group often plays an important role in aerating soils and digesting sewage, they also are known as agricultural pests destroying crop plants and inhabiting other animals as parasites. b. Complete the table for Nematodes

Phylum Mollusca (Molluska): slugs, snails, clams, oysters, squid, octopus a. Describe the function of some special features Molluscs have: Foot Mantle Radula Operculum

9-4

b. What organs do we see representing the following systems for the first time in Molluscs: Circulatory system Nervous system Excretory system Respiratory system c. All molluscs have soft bodies, not all have shells Class Nudibranch are Molluscs without shells (slugs), that are terrestrial and aquatic. They must have other protection-what could it be?

d. The three other classes of Molluscs we will observe are: Class Gastropoda Characteristic Features: Examples: Class Bivalvia Characteristic Features: Examples: Class Cephalopoda: Characteristic Features: They have a highly reduced and lacks which feature found in the previous classes? _____________________________________ What modified feature do they have instead? ____________________________ Examples: c. Complete Table 10-1 for Molluscs Phylum Annelida segmented worms: earthworms, polychaete worms, leeches a. What does segmentation specifically allow for? b. Describe each group: 9-5

Earthworms: Polychaetes: Leeches: d. Complete the table for Annelids

Phylum Arthropoda the segmented animals: insects, crustaceans, millipedes, centipedes, ticks, horseshoe crabs, spiders a. What different types of body segments are found members of this group?

b. How do these animals grow?

c. How are these animals classified into more specific taxa (such as class)?

Describe 3 major groups of Arthropods in your own way: 1)Group criteria: Examples: 2) Group criteria: Examples 3)Group criteria: Examples:

e. Describe 3 important impacts this phylum has on humans. 1.

2.

3. 9-6

THE DUETEROSTOMES-DEVELOPING ANUS FIRST Phylum Echinodermata: sea urchins, starfish, sand dollars, sea cucumbers 1. What distinguishing features does this group have? a. b. c. 2. Complete Table 10-1 for Echinoderms

Table 10-1 Features of animal phyla Phylum

Germ layers

Symmetry Gut type

Porifera

Cnidaria

Playhelminthes

Nematoda

Mollusca

Annelida

Arthropoda

Echinodermata

9-7

Coelom Segmentation Examples

Sorting the phyla: You will be given animals to sort into their correct phyla. Use your lecture notes, these lab observations and your textbook to decide which animals go into which phyla. First, someone at your table will need to cut out the phylum names found at the end of this lab and put them in order. Under those names you should also cut out the special features and sort them out under the proper phylum names as well.

9-8

Phyla

Echinodermata

Porifera

Nematoda

Cnidaria

Platyhelminthes

Arthropoda

Mollusca

Annelida

9-9

9-10

Special Features Pseudocoelem

parapodia

1st ganglia

scolex

mantle

pneumatocytes

exoskeleton

hermaphroditic

jointed appendages

falgellated collar cells

water vascular system

Medusa

spiney skin

operculum

wings

9-11

9-12