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Scott Foresman Science 4.1

Genre Comprehension Skill Text Features Science Content

Nonfi ction Compare and Contrast

• Labels

• Captions

• Diagrams

• Glossary

Classifying Plants and Animals

ISBN 0-328-13860-6

ì

1. Describe how organisms are built from cells.

2. What are the fi ve groups of vertebrates?

3. What are adaptations? Give an exampleof one.

4. Plants can be vascular or nonvascular. Describe on your own paper how they differ. Include details from the book to support your answer.

5. Compare and Contrast Think about crocodiles and alligators. How are they similar? How are they different?

What did you learn?Vocabularycellchloroplastcytoplasmgenusinvertebrates nucleusspeciesvertebrates

Picture CreditsEvery effort has been made to secure permission and provide appropriate credit for photographic material. The publisher deeply regrets any omission and pledges to correct errors called to its attention in subsequent editions.

Photo locators denoted as follows: Top (T), Center (C), Bottom (B), Left (L), Right (R), Background (Bkgd).

Opener: (B) Bryan F. Peterson/Corbis, (C) Frans Lanting /Minden Pictures; 4 (BR) Science Photo Library/Photo Researchers, Inc.; 8 (CR) Mary Ann McDonald/Corbis (CB, CRB) ”Jerry Young/DK Images;9 (CL, CR, C, C1) Mary Ann McDonald/Corbis, (CLB, CBL, CBR, CRB) ”Jerry Young/DK Images, (CA, CAR, CRA) ”Barry Watts/ DK Images; 13 (CR) Bryan F. Peterson/Corbis, (BR) Frans Lanting /Minden Pictures; 18 (BR) Fred Bavendam /Minden Pictures; 19 (T) Ken Lucas/Ardea, (BC) Fred Bavendam/Minden Pictures; 22 Kennan Ward/Corbis.

Unless otherwise acknowledged, all photographs are the copyright © of Dorling Kindersley, a division of Pearson.

ISBN: 0-328-13860-6

Copyright © Pearson Education, Inc. All Rights Reserved. Printed in the United States of America. This publication is protected by Copyright, and permission should be obtained from the publisher prior to anyprohibited reproduction, storage in a retrieval system, or transmission in any form by any means, electronic,mechanical, photocopying, recording, or likewise. For information regarding permission(s), write toPermissions Department, Scott Foresman, 1900 East Lake Avenue, Glenview, Illinois 60025.

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13860_01-04_CVR_FSD.indd Cover213860_01-04_CVR_FSD.indd Cover2 5/12/05 6:15:36 PM5/12/05 6:15:36 PM

by Laura Johnson

13860_05-28_FSD.indd 113860_05-28_FSD.indd 1 5/12/05 6:16:04 PM5/12/05 6:16:04 PM

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The Building Blocks of Living Things

Think about the building blocks you played with when you were younger. You started with just one block. If you put a few blocks together, you could build a house. If you put many blocks together, you could build something complicated, like a castle with towers. All living things—plants and animals—are made of cells. A cell is the smallest unit of a living thing. You can

think of cells as building blocks. Some living things are made of just one block, or cell. Most plants and animals are made by putting thousands, millions, or even billions of cells together.

Cells can have many jobs. Some cells help a living thing to be healthy. Other cells help

it to adapt to its environment.Microscopes make objects appear

larger than they really are. By looking at cells under a microscope,

scientists can see inside them and learn how they work.

blood cell


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The Parts of a CellCells have different parts, and each part has a

specifi c job to do. The nucleus is like the “brain” of the cell. The instructions for the cell’s job are stored in the nucleus.

The cell membrane is a thin covering all around the cell. It has two jobs. It separates the cell from things around it. It also acts as a guard that decides what can come into and go out of the cell.

Cytoplasm holds everything a cell needs to carry out its life processes. It is a material similar to jelly that fi lls the cell. The nucleus fl oats in the cytoplasm.

Plant cells have the same parts as animal cells—plus some extras. The cell wall is outside of the cell membrane. The walls of all the cells help hold up a plant. Chloroplasts are the parts of a cell that trap energy from sunlight so a plant can make its own food.

cell wall

plant cellanimal cell

membrane

cytoplasm

chloroplasts

nucleusnucleus


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From Cells to OrganismsCells have different shapes, depending on the kinds

of jobs they do. For example, nerve cells are very thin. They act like wires that send messages through the body. Nerve cells can be as long as your arm or as short as the period at the end of this sentence.

Cells that look alike and have the same shape do the same job. These cells combine to build tissue. For example, nerve tissue is made of nerve cells.

Tissues of the same type combine to form organs. For example, the brain is an organ that is made of nerve tissue.

nerve cell nerve tissue


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Organs that work together form an organ system. Two organs—the brain and the spinal cord—build the central nervous system in your body. An organism is the complete living thing that is made when all the parts are combined.

An organism is made of many cells. Unlike an organism, a virus is a very tiny particle with similarities to both living and nonliving things. It uses plant and animal cells to make more viruses.

brain

central nervous system


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Sorting Living Things Into Groups

There are more than a million organisms. Who keeps track of them all? Biologists! In order to identify, compare, and study all these organisms, biologists use a classifi cation system. Using this system, they place every kind of organism into a group. All the organisms in a group have common characteristics.

Biologists would ask questions like these to help them decide if a shark and a dolphin belong in the same group.

Do sharks and dolphins have one cell or many cells? They have many cells. That is a common characteristic, so they belong in the same group.

Where do sharks and dolphins live? They live in the ocean. That is another common characteristic, so they still belong in the same group.

How do sharks and dolphins get oxygen? Sharks get oxygen from the water. Dolphins get oxygen from the air. That is a different characteristic, so they belong in different groups.


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Kingdoms—The Largest GroupKingdoms are the largest groups in the

classifi cation system. Many scientists divide organisms into six kingdoms. The kingdom that an organism belongs to depends mostly on how many cells it has, what cell parts it has, where it lives, and how it gets its food.

Kingdom Number of Cells Cell Parts Habitat Food Source

Ancient one cell no separate land or water make their Bacteria nucleus own food

True Bacteria one cell no separate land or water some kinds get nucleus food; some make their own food

Protists usually one cell have a nucleus water and damp many get food; and other cell places on land some make parts their own

Fungi usually many cells have a nucleus land get food and other cell parts

Plants many cells have a nucleus land and water make their and cell wall own food

Animals many cells have tissues, land and water get food organs, systems

The Six Kingdoms of Living Things


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Dividing the KingdomsSorting living things into six kingdoms is only the

beginning! Next, scientists divide the members of each kingdom into smaller and smaller groups. They use organisms’ features to decide which organisms are in each group. After kingdoms, the groups are divisions, classes, orders, and families. The last two groups are genus and species. Scientists use these last groups to name animals. A genus is a group of animals that are similar in many ways. For example, a dog and a wolf are members of the same genus. Their genus is Canis. The genus group is divided one more time into groups of species. A species is a group of animals whose members can reproduce. The species name often describes where the animal lives or what color it is.

The fi rst part of an animal’s scientifi c name is the genus. The second part is the species. So, although you might name your pet dog Max, his scientifi c name would be Canis familiaris.

FAMILYGENUSSPECIES


9

KINGDOMDIVISIONCLASSORDER

How Living Things Are Classifi ed At the right of the chart is the kingdom, the largest group to which your family dog belongs. The groups get smaller and smaller, and more and more specifi c, until the fi nal two groups, which form the animal’s scientifi c name.


10

How Scientists Classify Plants

To sort plants into groups, scientists look at two main characteristics. One is the way that a plant transports water and nutrients. The other is how a plant reproduces.

Moving Water and FoodSome plants, called vascular plants, have parts that

look like tubes. Water and nutrients from the soil move up and down these tubes to the roots, stems, and leaves. Vascular plants are all around you. You may have stepped on some this morning, if you walked on grass. If you had celery with your lunch, you ate one! The tissue that makes up the tubes supports a plant’s stems and leaves. Because of this, vascular plants can grow to be very tall.

moss


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ReproductionThe second way that scientists

classify plants is by how they reproduce, or make new plants. One group reproduces by making seeds. A seed is a structure with a protective covering. Inside the seed is a young plant. In plants with fl owers, the seeds are in the fl owers.

Conifers are plants that make seeds but do not have fl owers. In conifers, the seeds are in the cones.

Some plants have no seeds at all. They use spores to reproduce. A spore is a single cell surrounded by a cell wall. It can grow into a new plant if it falls on a place where it can get the water and food it needs. Ferns and mosses have spores.

Plants without these tubes are called nonvascular plants. These plants pass water and nutrients through cell walls, from one cell to the next. This process is very slow, so nonvascular plants usually grow close to the ground. That way, water and nutrients do not have to travel so far. Some nonvascular plants are mosses, lichen, and algae.

seed


12

How Scientists Classify Animals

The animal kingdom is divided into two main groups. One group is vertebrates, or animals with a backbone. The other group is invertebrates, or animals without a backbone.

VertebratesScientists have divided vertebrates into fi ve smaller

groups. This chart shows the characteristics that are true for most of the vertebrates in each group.

Vertebrate Covering Breathing Birth

mammals hair or fur lungs live birth

birds feathers lungs hatch from eggs

reptiles scales lungs live birth or hatch from eggs

amphibians wet skin lungs or gills hatch from eggs

fi sh scales gills most hatch from eggs


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ReptilesLet’s take a closer look at one group of vertebrates—

reptiles. Reptiles include lizards, snakes, turtles, crocodiles, and alligators. These animals live in the water and on land. As you can see from the chart, reptiles breathe air with their lungs. Many people are very surprised when they touch a reptile for the fi rst time. They expect them to be wet and slimy, but they have dry skin covered with scales.

People often confuse crocodiles and alligators because the bodies of these reptiles are similar in many ways. An easy way to tell them apart is to look at their mouths. You can see a crocodile’s teeth when its mouth is shut, but you cannot see an alligator’s teeth in that position.

alligator

crocodile


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The Life Cycle of a ReptileSea turtles spend most of their time underwater,

where they swim, sleep, and eat. Like all reptiles, they have to come to the surface to breathe air with their lungs. If they are swimming, they need to come up for air about every fi ve or ten minutes. However, if they are asleep, they can stay underwater for hours. Male sea turtles rarely come on land, but female sea turtles come on land about six times each nesting year to lay their eggs.

A female sea turtle lays her eggs on land.

Baby turtles hatch from the eggs between forty-fi ve and seventy days later, and they make their way to water.


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Scientists are not sure how old female sea turtles are when they nest for the fi rst time. But they do know that they swim back to the same area where they were hatched as babies—even if that place is miles and miles away.

The turtles grow to be adults who will reproduce.


16

Animals Without A Backbone

Animals without a backbone are called invertebrates. You might be surprised to learn that most animals in the world are invertebrates.

Arthropods are the largest group of invertebrates. This group includes ticks, spiders, bees, shrimp, scorpions, and centipedes. At fi rst, these animals seem very different because some swim, some fl y, and some crawl. However, they have two common characteristics that cause scientists to group them together. The fi rst characteristic is that all arthropods have legs

and a body that are divided into sections. The second is that all arthropods are covered with

a lightweight, hard skin that protects them. This hard skin is called an exoskeleton.

centipede

bee


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The second largest group of invertebrates are mollusks. This group includes scallops, oysters, squid, and snails. Mollusks have soft bodies. Some have a hard shell and some don’t. Most mollusks live in water, but some live on land in damp places. Most mollusks are only a few inches long, but a few kinds are huge! Giant clams, for example, can grow to more than four feet long and weigh more than fi ve hundred pounds!

scallop

squid


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The Life Cycle Of a Mollusk

When octopuses are ready to mate, the male fertilizes the female’s eggs. The female attaches the fertilized eggs to a rock or places them in a hole. Over the course of several days, a female may lay more than 100,000 eggs! If the female has laid her eggs in a hole, she will often seal up the hole to protect the eggs and ensure that they are not harmed.

Females guard the eggs constantly. Depending on temperature, the eggs hatch anytime between four weeks and seven months later. A short time after the baby octopuses emerge from their eggs, the female octopus dies.

When the baby octopuses emerge from their eggs, they fl oat to the top of the water. They stay there until they grow larger and can return to the bottom of their water habitat.

eggs


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baby octopus

adult octopus


20

Animal AdaptationsAdaptations are physical features or behaviors

passed on from parents. Adaptations help animals get food, protect themselves, move, and reproduce. Animals with the best adaptations have a better chance at getting the resources they need, so they have a better chance of reproducing.

Adaptations That Help and Protect

Many animals have physical adaptations that help them move. Did you know that birds have hollow bones to make them lighter? Did you know that fi sh have bags of air in them that help them fl oat? Or that fl amingoes have long necks so they can submerge their heads in water and fi nd food in the muddy bottom? What about snails? They have a fl at foot that oozes a sticky liquid. They move by sliding along paths of their own slime.

Shapes and colors can provide protection by making animals nearly invisible. When the long, thin razor fi sh holds itself straight up and down in the water,

it looks like a piece of fl oating grass. Features such as claws, tusks, and horns protect some animals.


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Chemicals are another kind of adaptation. Some chemicals give animals a nasty smell or taste so other animals won’t eat them. Others poison their victims. An octopus can use its sharp teeth to drill a hole in a clamshell. It then injects poison through the hole. After the clam is poisoned, its shell can be opened easily.

sharp teeth


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Animal InstinctsInstincts are behaviors that are inherited from

parents. These natural behaviors tell young animals how to move, how to hide, and how to catch food. They will remember these things all their life. Remember the baby turtles that fi nd their way to the sea? That is an instinct.

Migration and HibernationMigration is an instinct. Many animals migrate

to fi nd food as seasons change. Arctic terns leave the Arctic Ocean in the fall, when the ocean begins to freeze and fi sh are scarce. They fl y to Antarctica, where fi sh are plentiful. In the spring, when the ice in the Arctic Ocean begins to melt, the terns fl y home to nest.


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Another natural behavior that does not need to be learned is hibernation. Some kinds of mammals, reptiles, and amphibians hibernate, or become inactive, when the weather is very cold and food is hard to fi nd.

Chipmunks, for example, eat a lot in the fall. The food is stored as body fat that gives them energy during winter, when they hibernate. They don’t sleep straight through the winter but wake for short periods to move around and snack on saved food.

hibernating frog

Animals LearnNot all animal behaviors are

instincts. Many animals learn behavior from their parents. Mother bears teach their cubs to fi sh. And wolves have a way of teaching their young to avoid traps!

All living things, from the smallest cell to the largest organism, can be classifi ed. Knowing the classifi cation of living things gives us information about what they are made of and how they adapt.


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Glossary

cell the smallest unit of a living thing

chloroplast the part of a plant cell that traps energy from sunlight so the plant can make its own food

cytoplasm the substance in a cell that contains what the cell needs to carry out its life processes

genus a group of closely related animals

invertebrates animals without a backbone

nucleus the control center of a cell

species a group of animals whose members can mate

vertebrates animals with a backbone


1. Describe how organisms are built from cells.

2. What are the fi ve groups of vertebrates?

3. What are adaptations? Give an exampleof one.

4. Plants can be vascular or nonvascular. Describe on your own paper how they differ. Include details from the book to support your answer.

5. Compare and Contrast Think about crocodiles and alligators. How are they similar? How are they different?

What did you learn?Vocabularycellchloroplastcytoplasmgenusinvertebrates nucleusspeciesvertebrates

Picture CreditsEvery effort has been made to secure permission and provide appropriate credit for photographic material. The publisher deeply regrets any omission and pledges to correct errors called to its attention in subsequent editions.

Photo locators denoted as follows: Top (T), Center (C), Bottom (B), Left (L), Right (R), Background (Bkgd).

Opener: (B) Bryan F. Peterson/Corbis, (C) Frans Lanting /Minden Pictures; 4 (BR) Science Photo Library/Photo Researchers, Inc.; 8 (CR) Mary Ann McDonald/Corbis (CB, CRB) ”Jerry Young/DK Images;9 (CL, CR, C, C1) Mary Ann McDonald/Corbis, (CLB, CBL, CBR, CRB) ”Jerry Young/DK Images, (CA, CAR, CRA) ”Barry Watts/ DK Images; 13 (CR) Bryan F. Peterson/Corbis, (BR) Frans Lanting /Minden Pictures; 18 (BR) Fred Bavendam /Minden Pictures; 19 (T) Ken Lucas/Ardea, (BC) Fred Bavendam/Minden Pictures; 22 Kennan Ward/Corbis.

Unless otherwise acknowledged, all photographs are the copyright © of Dorling Kindersley, a division of Pearson.

ISBN: 0-328-13860-6

Copyright © Pearson Education, Inc. All Rights Reserved. Printed in the United States of America. This publication is protected by Copyright, and permission should be obtained from the publisher prior to anyprohibited reproduction, storage in a retrieval system, or transmission in any form by any means, electronic,mechanical, photocopying, recording, or likewise. For information regarding permission(s), write toPermissions Department, Scott Foresman, 1900 East Lake Avenue, Glenview, Illinois 60025.

3 4 5 6 7 8 9 10 V010 13 12 11 10 09 08 07 06 05

13860_01-04_CVR_FSD.indd Cover213860_01-04_CVR_FSD.indd Cover2 5/12/05 6:15:36 PM5/12/05 6:15:36 PM

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