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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
4
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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
Duplicating any part of this book is prohibited by law.
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:
■
■
■
12
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
13
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.
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15
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?
17
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.