Developed in Consultation with Texas Educators

Table of Contents Texas Essential Knowledge and Skills Correlation Chart. . . . . . 6 TEKS

Chapter 1 Cells. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Lesson 1 Cell Structures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

2C, 2E, 2F, 3F, 4A, 4B

Lesson 2

Homeostasis and Cell Transport . . . . . . . . . . . . . . . . . 19

4B

Lesson 3

Photosynthesis and Cell Respiration. . . . . . . . . . . . . . 24

4B, 9B

Lesson 4

The Cell Cycle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

5A, 5C, 5D

Lesson 5

Organic Macromolecules. . . . . . . . . . . . . . . . . . . . . . . 33

4B, 9A

Lesson 6

Enzymes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

3B, 9C

Lesson 7

Viruses and Disease . . . . . . . . . . . . . . . . . . . . . . . . . . 44

2E, 4C

Chapter 1 Review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 Chapter 2 Organisms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55 Lesson 8 Levels of Organization . . . . . . . . . . . . . . . . . . . . . . . . . 56

5B, 10A, 10C

Lesson 9

The Endocrine System. . . . . . . . . . . . . . . . . . . . . . . . . 61

5B, 10A, 10C, 11A, 11B

Lesson 10

The Nervous System . . . . . . . . . . . . . . . . . . . . . . . . . . 65

5B, 10A, 10C, 11A, 11B

Lesson 11

The Digestive System . . . . . . . . . . . . . . . . . . . . . . . . . 69

2H, 5B, 9C, 10A, 10C

Lesson 12

Human Reproduction. . . . . . . . . . . . . . . . . . . . . . . . . . 74

5B, 5C, 10A, 10C

Lesson 13

How the Body Defends Itself. . . . . . . . . . . . . . . . . . . . 81

5B, 10A, 10C, 11C

Lesson 14

Plant Organs and Tissues . . . . . . . . . . . . . . . . . . . . . . 88

5B, 10B, 10C

Lesson 15

Plant Responses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93

1A, 2E, 5B, 10B

Chapter 3 Genes and Heredity . . . . . . . . . . . . . . . . . . . . . . . . . 105 Lesson 16 The Structure and Role of DNA. . . . . . . . . . . . . . . . . 106

6A, 6B, 6D, 7G

Lesson 17

The Structure and Role of RNA . . . . . . . . . . . . . . . . . 113

4B, 6C

Lesson 18

Genetics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118

3F, 6F

Lesson 19

Meiosis and Genetic Variation . . . . . . . . . . . . . . . . . . 126

6G

Lesson 20

Mutations and Genetic Variation . . . . . . . . . . . . . . . . 131

6E

Lesson 21

Studying the Genome . . . . . . . . . . . . . . . . . . . . . . . . 136

3C, 3D, 3F, 6H

Chapter 3 Review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142

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Chapter 2 Review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98

TEKS

Chapter 4 Evolution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149 Lesson 22 The Origin of Life on Earth. . . . . . . . . . . . . . . . . . . . . 150

3F, 9D*

Lesson 23

Darwin and Evolutionary Theory . . . . . . . . . . . . . . . . 154

2C, 3F, 7A

Lesson 24

Patterns, Processes, and Rates of Evolution . . . . . . 159

2A, 2B, 2C, 2D, 3F, 7B, 7F

Lesson 25

Evidence for Evolution . . . . . . . . . . . . . . . . . . . . . . . . 164

7A

Lesson 26

Natural Selection and Changes in Organisms. . . . . . 170

7C, 7D, 7E, 7F

Lesson 27

Classification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 174

3A, 3B, 8A, 8B, 8C

Chapter 4 Review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 182 Chapter 5 Interdependence . . . . . . . . . . . . . . . . . . . . . . . . . . . 191 Lesson 28 Relationships among Organisms. . . . . . . . . . . . . . . . 192

2G, 12A

Lesson 29

Microorganisms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 197

11C, 12A

Lesson 30

Adaptations to Different Environments . . . . . . . . . . . 201

11B, 12B

Lesson 31

Ecological Succession. . . . . . . . . . . . . . . . . . . . . . . . 207

11D, 12B, 12D

Lesson 32

Energy Flow and Trophic Levels . . . . . . . . . . . . . . . . 211

3E, 12C

Lesson 33

The Carbon and Nitrogen Cycles . . . . . . . . . . . . . . . 217

12E

Lesson 34

How Human Activities Affect Ecosystems . . . . . . . . 221

11B, 12D, 12F

Chapter 5 Review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 227 Investigations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 235 Investigation 1 Investigating Osmosis 235

1A, 1B, 2B, 2C, 2E, 2F, 2H, 3A, 4B

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Investigation 2 Investigating Tropisms . . . . . . . . . . . . . . . . . . . . 245

1A, 2B, 2C, 2E, 2F, 2H, 3A, 10B

Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 255 Comprehensive Review. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 267 Safety Guidelines for Investigations . . . . . . . . . . . . . . . . . . . . . . 289

*Not directly assessed on the STAAR™. 5

Chapter 1 • Lesson 1

TEKS: 2C, 2E, 2F, 3F, 4A, 4B

Cell Structures Key Words • cell • organelle • eukaryote • prokaryote • cytoplasm • nucleus • nuclear membrane • chromosome • cell membrane • ribosome • endoplasmic reticulum • Golgi body • mitochondria • lysosome • cell wall • chloroplast • vacuole

Getting the Idea All organisms share a common feature—the cell. The cell is the basic unit of structure and function in all organisms. This fact is not obvious, because cells are too small to be seen with the unaided eye. The discovery of the cell, its structure, and its function came about through the work of many different scientists over many years of study.

Development of the Cell Theory In 1665, British scientist Robert Hooke used a microscope that he designed to study a thin slice of cork. The cork appeared to be made of tiny, empty chambers. They reminded Hooke of rooms in a monastery known as cells, so he called the structures in the cork cells. Around the same time, Anton van Leeuwenhoek of Holland looked at pond water through a microscope. He saw tiny, single-celled organisms he named animalcules (meaning tiny animals) moving in the water. Leeuwenhoek was the first person to observe living cells.

Schleiden and Schwann’s work led to a basic understanding of cells and that they make up both plants and animals. However, the idea that cells come only from other cells was not formulated until the 1850s. Until then, many people had thought that living things could grow spontaneously from nonliving matter. The German physician Rudolf Virchow proposed the theory that every cell comes from another living cell. He based this idea partly on work by other scientists. The discoveries made by these and other scientists are summarized in the modern cell theory. A theory is a reliable and well-established explanation of a physical or natural occurrence. The cell theory states: ■ ■ ■

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All living things are made up of cells. Cells are the basic units of structure and function in living things. New cells are produced only from existing cells.

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In 1838, German botanist Matthias Schleiden studied plants using a microscope. He was the first person to state the theory that all plants are made of cells. He proposed that cells are the basic units of life in plants and that plants grow by making new cells. The next year, German biologist Theodor Schwann reached the same conclusions about animals.

Eukaryotic and Prokaryotic Cells A cell is the smallest unit that can carry out all the functions of life. There are two basic types of cells: eukaryotic cells and prokaryotic cells. Both types of cells perform similar functions in the same ways. Both are enclosed by a membrane, are filled with cytoplasm, and contain structures called ribosomes (which you will learn about later in this lesson). Both types of cells have DNA, which controls the functions of the cell and carries the hereditary information that is passed on to future generations. Also, the genetic code of prokaryotic cells is the same as that in eukaryotic cells. How, then, do prokaryotic cells differ from eukaryotic cells? You can observe some of the differences by examining the diagrams below.

Eukaryote

Prokaryote Cell membrane

Nucleus

Mitochondria

Cell wall

Ribosomes

Capsule

Cytoplasm

Flagellum

An obvious difference is that the eukaryotic cell is more complex than the prokaryotic cell. It is also larger. Other differences involve the internal structures of the two kinds of cells. The eukaryotic cell has a distinct nucleus and other cell structures, called organelles, which are enclosed within membranes. Organisms whose cells have a distinct nucleus and membranebound organelles are called eukaryotes. In eukaryotes, the organelles carry out the processes needed to sustain life. Plants, animals, protists, and fungi are all eukaryotes.

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A prokaryotic cell does not have a nucleus or membrane-bound organelles. Organisms whose cells lack a nucleus and organelles are called prokaryotes. In prokaryotes, most of the processes of life occur in the cytoplasm. The cytoplasm is the fluid that occupies most of the space within a cell. All bacteria are prokaryotes. The table shows some components of prokaryote cells and of different kinds of eukaryote cells. Cell component

Prokaryotes

Protists

Animals

Plants

Fungi

Cell membrane

Yes

Yes

Yes

Yes

Yes

Cytoplasm

Yes

Yes

Yes

Yes

Yes

Cell wall

Yes

Sometimes

No

Yes

Yes

Nucleus

No

Yes

Yes

Yes

Yes

Mitochondria

No

Yes

Yes

Yes

Yes

Chloroplasts

No

Sometimes

No

Yes

No

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The Nucleus The most visible structure inside most eukaryotic cells is the nucleus. The nucleus directs and controls most cell activities. It is enclosed by a two-layered structure called the nuclear membrane. Openings, or pores, in the membrane act as pathways through which materials can flow between the nucleus and the rest of the cell. In most cells, the nucleus contains the DNA and much of the RNA. These nucleic acid molecules control protein production and cell activity. DNA also stores the genetic information that is passed from parent to offspring during reproduction. Eukaryotic DNA is organized into structures called chromosomes. The chromosomes contain genetic information. Prokaryotic cells do not have a nucleus or other membrane-bound organelles. In these cells, most of the materials needed to sustain life are scattered throughout the cytoplasm. The cell’s genetic material also floats in the cytoplasm. Most prokaryotes have one circular molecule of DNA and a number of much smaller units of DNA called plasmids.

Structures Common to Most Eukaryotic Cells The organelles common to most eukaryotic cells, such as an animal cell, are shown in the diagram below.

Animal Cell Ribosomes

Endoplasmic reticulum

Chromosomes Nucleus

Cytoplasm Lysosome

Cell membrane Mitochondria

Golgi body

All cells have a cell membrane. The cell membrane is a thin structure that encloses the cell. The cell membrane gives the cell shape and support. It also controls what materials enter and leave the cell. You will learn more about how the cell membrane controls the movement of materials in the next lesson.

Ribosomes Ribosomes are the places where cells make new proteins. As you will read in Lesson 5, proteins are large molecules that are needed for proper cell structure and function. Cells synthesize proteins by combining amino acids. You will learn more about this process in Lesson 17. Unlike most organelles, ribosomes are not surrounded by membranes. Ribosomes are made up of proteins and RNA that are bound together. Most ribosomes are scattered throughout the cytoplasm. Others are attached to the surface of the cell’s endoplasmic reticulum (ER).

14 • Chapter 1: Cells

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The Cell Membrane

Lesson 1: Cell Structures

Endoplasmic Reticulum (ER) The endoplasmic reticulum (ER) is a system of membranes and sacs that act like a highway to transport molecules from one part of the cell to another. There are two types of endoplasmic reticulum. Rough endoplasmic reticulum, or rough ER, is dotted with ribosomes. Rough ER is common in cells that make large amounts of proteins. Smooth endoplasmic reticulum, or smooth ER, does not have ribosomes attached to its surface. Smooth ER is involved in regulating some cell processes. For example, it maintains muscle cells and breaks down toxic substances in liver cells.

Golgi Bodies Proteins move from the endoplasmic reticulum into Golgi bodies before they are transported to different parts of the cytoplasm. A Golgi body (also called the Golgi apparatus) is a system of membranes that modifies and refines proteins. Proteins are modified according to where in the cell they will be sent and their role in the cell. For example, proteins that will be sent to the nucleus are modified differently than those that will be sent to the cell membrane. You will learn more about how proteins are modified for their different roles in cells in Lesson 5.

Mitochondria Mitochondria (singular: mitochondrion) are the organelles that carry out cellular respiration. Cellular respiration is the process by which living things obtain energy from the chemical bonds in food molecules. Cellular respiration uses a series of chemical reactions to transfer energy from carbohydrates into adenosine triphosphate (ATP). When the bonds of ATP are broken, energy is released for the cell to use. Cells that need a lot of energy, such as muscle cells, have many more mitochondria than cells with lower energy requirements. You will learn more about cellular respiration in Lesson 3.

Lysosomes Lysosomes are small, spherical organelles that digest large molecules. The lysosomes break these molecules down into smaller molecules that can be used by the cell. Lysosomes also break down old organelles. Lysosomes use enzymes to digest organic molecules. You will learn more about enzymes and their roles in cells in Lesson 6. Lysosomes are common in the cells of animals and fungi. They are rare in plant cells. Duplicating any part of this book is prohibited by law.

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Structures Found in Some Eukaryotic Cells The organelles previously covered are common to almost all eukaryotic cells—animal, plant, protist, and fungus. Other organelles are found only in certain types of eukaryotic cells, particularly plant cells. You can observe some of these structures in the diagram of the plant cell below.

Plant Cell Cytoplasm Mitochondria Vacuole Chloroplast Golgi body

Endoplasmic reticulum Ribosomes Nucleus Cell wall Cell membrane

Cell Wall The plant cell shown is surrounded by a cell wall. A cell wall is a rigid structure that surrounds the cell membrane of some cells. The cell wall gives these cells additional shape and support. Cell walls are a characteristic of the cells of plants, bacteria, and fungi. Some protists also have cell walls.

Chloroplasts Plant cells contain chloroplasts. Chloroplasts are the organelles where photosynthesis occurs. They contain a green pigment called chlorophyll. This pigment traps the energy of sunlight and makes plants green. The chloroplasts use the trapped energy to make food molecules (sugars) through photosynthesis. Some protists, including algae that carry out photosynthesis, also have chloroplasts. In bacteria that carry out photosynthesis, the chlorophyll is scattered through the cytoplasm. Animal cells do not have chloroplasts. Plants cannot move to find water. They do not have bones or shells that give them support. To meet these needs, a plant cell has a large, central vacuole that stores water and dissolved materials. The pressure from the liquid-filled vacuole allows plants to support heavy structures such as leaves and flowers. Animal cells have small vacuoles, which help transport materials within the cell and through the cell membrane. The cells of some protists contain vacuoles that may serve as storage sites for needed materials or for wastes.

16 • Chapter 1: Cells

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Vacuoles

Lesson 1: Cell Structures

Focus on Inquiry You have used microscopes and hand lenses to study cells and other small objects. To study cells under a microscope, scientists and students first prepare slides. To examine a liquid, such as milk or seawater, you can use a dropper to place a drop of the liquid on a glass slide. Then, carefully lower a coverslip on top of the liquid. You can also make slides of solid objects. To make a slide of a plant, such as cork or celery, scientists cut thin sections of the plant. If you are making your own slides, your teacher may instruct you to use a scalpel or razor blade. Work carefully, and cut away from your body. After cutting a thin slice of the plant, cut a small piece that will fit on a slide. Place a drop of water on a slide, and then carefully put the plant slice on the drop of water. Lower a coverslip onto the sample you want to observe. You will also work with prepared slides. In the lab, your teacher may give you slides of plants, fungi, or animal cells. For this activity, your teacher will give you cork to study. You will be comparing what you see with what Robert Hooke described. Place the slide with the cork on the stage of a light microscope. Observe the cells under the lowpower objective and make a sketch of what you see. Then look at them using the high-power objective and sketch what you see using this objective. Compare your sketches to the diagrams in this lesson. Label the cell parts that you can identify in each of your sketches. What cell structures do you observe?

What structures of a living cell are not visible?

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What can you conclude about the cork cells based on these observations?

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Lesson Review 1.

On which of the following organelles are proteins assembled? A. mitochondria B. ribosomes C. chloroplasts D. lysosomes

2.

Which structure is the boundary between a cell and its environment? A. mitochondria B. cell membrane C. chloroplast D. nucleus

3.

How does a eukaryotic organism differ from a prokaryotic organism? A. A prokaryotic organism is not made up of cells. B. A prokaryotic organism does not contain genetic information. C. The cells of a prokaryotic organism do not contain chlorophyll. D. The cells of a prokaryotic organism do not have nuclei. Which of these statements is a principle of the cell theory that supports the idea that new cells will replace damaged cells in a scraped knee? A. All living things are composed of one or more cells. B. Cells are the basic units of structure and function in living things. C. All cells arise from previously existing cells. D. Most cells are too small to be viewed with the unaided eye.

18 • Chapter 1: Cells

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4.