by Patricia Fitzhugh

Scott Foresman Science 5.5

Genre Comprehension Skill Text Features Science Content

Nonfi ction Predict • Labels

• Captions

• Diagrams

• Glossary

Interactions in Ecosystems

ISBN 0-328-13928-9

ì

Illustration Title Page, 20, 21, 22 Adam Benton Photographs: Every 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. Unless otherwise acknowledged, all photographs are the property of Scott Foresman, a division of Pearson Education. Photo locators denoted as follows: Top (T), Center (C), Bottom (B), Left (L), Right (R) Background (Bkgd) Opener: ©Claus Meyer/Minden Pictures 2 (CC) ©D. Robert & Lorri Franz/Corbis, (Bkgd) ©Larry Michael/Nature Picture Library, (BL) ©Joe McDonald/Animals Animals/Earth Scenes 5 ©Galen Rowell/Corbis 6 (CL) ©DK Images, (R) ©Michael Fogden/OSF/Animals Animals/Earth Scenes 7 (BR) ©Tom Brakefield /Corbis, (L) ©Carr Clifton/Minden Pictures 8 (BL) ©W. Perry Conway/Corbis, (R) ©Phil Schermeister/Corbis 9 (L) ©W. Wayne Lockwood, M.D./Corbis, (BR) ©Ron Sanford/Corbis 10 (R) ©Diego Lezama Orezzoli/Corbis, (BR) Jerry Young/©DK Images 11 (BL) ©Ron Sanford/Corbis, (BL) ©Roy Corral/Corbis 12 (R) ©David Muench/Corbis, (BC) ©Jim Zuckerman/Corbis 13 (L) ©David Muench/Corbis, (BC) ©Frank Greenaway/©DK Images 14 (TC) ©Frank Greenaway/©DK Images, (BL) ©Stuart Westmorland/Corbis, (R) ©Stephen Frink/Corbis 15 (L, BR) ©Ralph White/Corbis 16 ©Bill Kamin/Visuals Unlimited 17 ©Stephen Frink/Corbis 18 (BL) ©Michael Sewell/Peter Arnold, Inc., (BL) ©DK Images, (BC) ©Daniel Cox/Getty Images, (BC) ©Michael Quinton/Minden Pictures, (BC) ©John Shaw/Tom Stack & Associates, Inc., (BC, BL) Neil Fletcher and Matthew Ward/©DK Images, (BR) Getty Images, (BL) Matthew Ward/©DK Images 19 (CL) ©Michael Sewell/Peter Arnold, Inc., (CL) ©Michael Quinton/Minden Pictures, (BL, BC) Neil Fletcher and Matthew Ward/©DK Images

ISBN: 0-328-13928-9

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 any prohibited reproduction, storage in a retrieval system, or transmission in any form by any means, electronic, mechanical, photocopying, recording, or likewise. For information regarding permissions, write to: Permissions 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

Vocabularycommunity

cycle

ecosystem

energy pyramid

habitat

niche

population

What did you learn?1. What are some living and nonliving parts of an ecosystem?

2. In what group of ecosystems do rivers, wetlands, coral reefs, and the deep sea belong? What group is made up of forests, grasslands, deserts, and tundra?

3. Explain what a cycle in an ecosystem is. Give at least one example.

4. Organisms have special behaviors that help them meet their needs. On your own paper, write to explain how behaviors help organisms live in a biome where it is very hot or very cold. Include details from the book to support your answer.

5. Predict Describe what might happen to a rainforest ecosystem if its yearly rainfall decreased a great deal.

13928_CVR_FSD Sec1:213928_CVR_FSD Sec1:2 5/27/05 10:33:29 AM5/27/05 10:33:29 AM

Interactions in Ecosystemsby Patricia Fitzhugh

13928_01-24_FSD 113928_01-24_FSD 1 5/27/05 11:24:10 AM5/27/05 11:24:10 AM

A community is a bigger part of an ecosystem. A community is all the populations in an area. Members of a community depend on each other for food and shelter.

The nonliving parts of an ecosystem include air, water, soil, sunlight, and temperature. These things often control what kinds of organisms—and how many—can live in an ecosystem.

If a population’s needs are not met in an ecosystem, that population will get smaller. Its members may not survive.

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What is an ecosystem?Living and Nonliving Parts

Wherever there are living things, there are ecosystems. An ecosystem is all the living and nonliving things in an area.

Living and nonliving things work together in ecosystems. A population is all the organisms of one species living in an area at the same time. This may be all the oak trees. It may be all the red ants.

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BiomesA biome is a large ecosystem. Biomes are so large

that a single one may cover many countries. The climate and organisms are generally the same in all parts of the biome.

There are several kinds of biomes. One kind is a rainforest. A rainforest biome has large amounts of rain and thick plant growth.

The United States has a rainforest biome in the state of Washington. This rainforest is a temperate rainforest. It receives a lot of rain, but can be quite cool.

Each living thing in an ecosystem has a niche. A niche is an organism’s role in an ecosystem. For example, the spotted owl has a niche in the temperate rainforest. It is a hunter. The owl hunts and eats small animals, such as mice.

Each living thing also has a habitat. A habitat is where an organism lives. The spotted owl’s habitats are the trees and land where it lives.

All the relationships in an ecosystem keep it balanced. For example, the populations of mice and spotted owls balance each other. It works like this:

If the number of mice drops, the owls will have less food. So, the number of owls will drop, too. With fewer owls hunting, fewer mice will be eaten. So, the population of mice will grow. Then owls will have more mice to hunt. So, the population of owls will grow again.

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What are land biomes?Tropical Rainforest Biomes

Ecosystems near the equator are always warm. Some of them get a lot of rain—more than three meters each year. In these places plant populations grow large. A tropical rainforest results.

Tropical rainforests have more different kinds of life than any other biome. There may be dozens of different species living in a single tree.

Deciduous Forest BiomesDeciduous forests grow in cooler

areas. They cover much of the eastern United States. Oak, elm, and maple trees grow in these biomes. These are deciduous trees. That means that they lose their leaves when it gets cold. This helps them save food and water.

Some other organisms also change in colder seasons. Bears sleep through much of the winter. Snakes and frogs stay underground. Some rabbits’ fur becomes snowy white. This helps the rabbits blend in with the snow. They can easily hide from animals that hunt them.

Organisms have structures that help them survive. The kinkajou’s long tongue can get honey and insects. Its tail can grab onto branches.

Grassland BiomesGrasslands are biomes with many

types of grasses. Grasslands do not get much rain. So few trees can grow in these biomes.

Grasslands once covered huge areas of the midwestern United States. Then settlers came. Over many years, settlers turned most of the grasslands into farms.

Bison, antelope, and prairie dogs live on the grasslands. The changing of this habitat into farms has affected animal populations. For example, gray wolves once hunted prairie dogs. Farming reduced the prairie dog population, so the wolves had less to eat. People also hunted the wolves. These changes caused the gray wolf population to fall very low.

Taiga BiomesA taiga is a kind of forest biome.

Tiagas are found in areas that are cold and fairly dry. They cover much of Canada and Russia.

Most trees that grow in the taiga have very thin leaves called needles. Needles help trees live where it is cold, dry, or both. They stay on the tree all year long so they are ready to make food as soon as warm weather arrives. They have a waxy coating that helps the tree hold water.

Large animals such as bear, elk, and moose live in the taiga. Smaller animals such as porcupines and mice live there as well. All these animals have fur. It keeps them warm. Ducks, owls, and woodpeckers also live in the taiga. These animals have feathers to help keep them warm.

Gray wolves once lived over most of North America. Now wolves live in only a small part of this area.

The moose is a very large animal found in the taiga.

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Desert BiomesDeserts are areas that get less than

25 cm of rain or snow each year. All deserts have low rainfall. Many deserts are very hot, but others are cold most of the time. Some deserts have sand dunes and others are very rocky. Large deserts are found in Africa, Asia, and Australia.

Desert animals may include rattlesnakes, lizards, jackrabbits, and beetles. Plants may include bushes, grasses, and cactuses.

Desert plants have special parts that help them live without much water. Some have large root systems close to the surface of Earth. These roots can take in rainwater quickly.

Desert animals have special behaviors that help them survive. Many animals rest during the hot day. Some animals dig into the ground to keep cool. They look for food at night, when it is cooler.

Tundra BiomesThe tundra is a very cold biome. It

gets little rain. Tundras lie in the far northern parts of the world. Rodents, rabbits, and caribou live on the tundra. Tundra animals may also include weasels, owls, and foxes.

In any ecosystem, a population can only grow so large. The number of organisms that can live in a place is the carrying capacity. If a population grows larger than the carrying capacity, there won’t be enough food, water, space, or shelter.

Populations will have to move to another area to survive.

On the tundra, cold weather makes it hard for plants to grow. The small plants that do grow cannot provide enough food and shetler for animals. This keeps the carrying capacity low.

Emus are found in many areas of Australia, including deserts.

When snow covers the tundra, caribou often move to warmer areas to find food.

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What are water ecosystems?Rivers

Many different animals live in rivers. They include fish, ducks, turtles, and insects. Some animals live only in rivers that flow slowly.

River ecosystems also include animals that spend much of their time on land. The river otter, for example, does well in both environments. In the water, its sleek body lets it swim fast to catch fish. While swimming, it can close its nose and ears. On land, it can run to catch frogs and small mammals.

Organisms that live in rivers usually do not also live in oceans. The ocean water is too salty for their cells.

WetlandsThere are many kinds of wetlands.

All are partly covered with water or flooded at least part of each year. Florida’s Everglades is a wetland. It has huge areas of sawgrass that grows more than 3 meters tall. Alligators, fish, deer, and snakes live in the Everglades.

A swamp is a wetland with many trees and bushes. Deer, otters, turtles, snakes, and wild pigs may live in swamps.

Some wetlands are parts of estuaries. These are places where rivers flow into the ocean. Grassy wetlands called salt marshes are found in estuaries.

Wetlands are helpful in many ways. The plants, soils, and tiny organisms of wetlands often act as filters. They clean water that flows through the wetland.

The river otter can live easily on the land or in the water.

Crayfish are often found in swamp ecosystems.

Coral ReefsCoral reefs are

home to many types of organisms. These include sharks, clams, crabs, clownfish, eels, and many other animals.

Corals are animals. They have a special relationship with algae. Some algae need sunlight, so they only grow in shallow water. These algae grow inside the coral. Other algea help the coral make a hard outside coating. Over time, many corals grow and die. Their hard outside coatings pile up to make a coral reef. Many kinds of plants and animals live in the reef.

Corals grow well in warm water with few nutrients and little oxygen. They are found near Florida, Australia, and many other places. Coral reefs help to protect the shore from storms. They also provide us with food and new types of medicine.

The Deep SeaSome very strange animals live in

deeper areas of the ocean. They must deal with cold, darkness, and very high water pressure. These animals are well-suited to the pressure. Some will die if they come to the surface, where water pressure is lower.

Sunlight cannot reach these deep areas. So, no plants can grow. Many animals in the deep sea eat dead plants and animals that sink down.

Clams, crabs, and tubeworms live around vents in the deep sea. Bacteria live there, too. They make food from chemicals in the water. The bacteria themselves are food for larger animals.

Jellyfish belong to the same phylum as coral.

Tubeworms don’t have mouths or stomachs. Bacteria live inside the tubeworms and make food that they share.

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How do organisms interact?Competition

Organisms often compete for things they need. They may compete over space, food, or water. Sometimes they compete for their lives.

Animals of the same species compete. You may have heard cats screeching outside as they fight for territory. Animals of different species also compete. For example, rabbits and mice in a desert community compete. They compete to find plants for food.

Plants may compete for sunlight or for water. The kudzu plant is very successful at competing for light. It covers other plants, keeping them from getting any sunlight. Plants with larger root systems will take in water faster than other plants.

SymbiosisSymbiosis is a long–term relationship between different

species. One of the species is always helped. The other might be helped, harmed, or not affected.

The buffalo and the cattle egret have one kind of symbiosis. As the buffalo moves through the grass, it scares up insects. The egret can catch the insects easily. This helps the bird, but it doesn’t affect the buffalo.

In another kind of symbiosis, very small organisms are fed as they help the buffalo digest its food. Both species are helped.

The buffalo and worms show a third kind of symbiosis. The worms live inside the buffalo. They get food, but the buffalo may become weak or sick. Organisms that feed on other organisms in this way are called parasites.

In a fourth kind of symbiosis, one organism can’t survive without another. Lichen is a fungus and an algae living together. The algae makes food from sunlight. The fungus could not survive without the food that the algae produces.

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Plants may compete for sunlight. Kudzu, shown here, often covers other plants in this competition.

The relationship between the buffalo and the cattle egret is an example of symbiosis.

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How does energy move in ecosystems?Food Chains and Webs

All living things need energy to live. They get energy from food. The organism that is eaten gives food energy to the one that eats it. Producers are organisms such as plants, which make their own food. They get energy from sunlight or chemicals in nature. Consumers are organisms that cannot make their own food. They must eat other organisms. All animals are consumers.

When food is eaten, the energy in the food moves from one organism to another. Food energy moves in chains such as this:

sun ➝ plants ➝ snowshoe hare ➝ spotted owl ➝ bacteria

The diagram below shows many food chains combined in one food web. You can see an ecosystem more fully in a web than in a chain. That’s because consumers usually eat many kinds of other organisms.

Energy PyramidsAn energy pyramid is a diagram of a food chain. It shows

the flow of energy from one level to the next. The energy pyramid is widest at the base. That’s because producers are shown at the base. They have the greatest amount of energy in an ecosystem.

Look higher on the energy pyramid. Notice that it gets narrower as it rises. This shows that less energy flows through higher levels.

An energy pyramid has more energy at its base than at its top. This is because some energy is given off as heat by each organism in the pyramid.

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What cycles occur in ecosystems?Recycling Matter

Some substances go through an ecosystem again and again. They go in cycles. A cycle is a repeating flow of materials through a system. There is a constant cycle of minerals and some nutrients through ecosystems.

Decomposers play a key role in this cycle. Decomposers are organisms that eat waste and dead matter. They break it into smaller pieces and return it to the soil. In this way, decomposers recycle waste and dead material. They make minerals and nutrients that were in their food available to living plants. The plants will then be food for other organisms.

Nitrogen CyclePlants and animals need nitrogen to live. The air around us

is almost 810 nitrogen gas, but most living things cannot use this form of nitrogen. Nitrogen is made into useable compounds by lightning, and brought to the ground by rain. Compounds are also made by bacteria. Plants take these compounds from the soil.

Some animals get nitrogen by eating plants. Others get it by eating plant eaters. Nitrogen returns to the soil when animals die and decay. It is also put into the soil in fertilizers used by farmers. Plants use this nitrogen and the cycle begins again.

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Slugs, flies, and fungi are decomposers. Whenever you see something rotting, decomposers are at work.

Only a part of the nitrogen cycle is shown here.

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Carbon Dioxide and OxygenCarbon dioxide and oxygen gases are always being made

and used. Recall that plants take in carbon dioxide. They give off oxygen. Animals take in oxygen. They give off carbon dioxide. Look at the diagram below. As it shows, oxygen and carbon dioxide take many paths through an ecosystem.

Oxygen can enter the atmosphere during photosynthesis. Carbon dioxide can enter the atmosphere in many ways. Two major ways are respiration and combustion.

Respiration is a process that cells use to get energy. They combine oxygen with food. Plants and animals live by respiration. The results are carbon dioxide and water.

Combustion is the burning of a material. It takes place naturally, as in forest fires. It also happens in machines, such as cars and furnaces.

Photosynthesis in plants gives off oxygen. Volcanoes release

carbon dioxide.

Carbon dioxide is released when materials are decomposed.

Combustion from cars, factories, and machines gives off carbon dioxide.

Forest fires give off carbon dioxide.

Plankton in the ocean give off oxygen.

Animals use oxygen and give off carbon dioxide.

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Glossarycommunity the group of all the populations in

an area

cycle a repeating process or repeating flow of materials through a system

ecosystem all the living and nonliving things in an area

energy pyramid a diagram that shows the flow of energy through a food chain

habitat the place in an ecosystem in which an organism lives

niche the job that an organism has in an ecosystem

population a group of organisms of one species that live in an area at the same time

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Illustration Title Page, 20, 21, 22 Adam Benton Photographs: Every 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. Unless otherwise acknowledged, all photographs are the property of Scott Foresman, a division of Pearson Education. Photo locators denoted as follows: Top (T), Center (C), Bottom (B), Left (L), Right (R) Background (Bkgd) Opener: ©Claus Meyer/Minden Pictures 2 (CC) ©D. Robert & Lorri Franz/Corbis, (Bkgd) ©Larry Michael/Nature Picture Library, (BL) ©Joe McDonald/Animals Animals/Earth Scenes 5 ©Galen Rowell/Corbis 6 (CL) ©DK Images, (R) ©Michael Fogden/OSF/Animals Animals/Earth Scenes 7 (BR) ©Tom Brakefield /Corbis, (L) ©Carr Clifton/Minden Pictures 8 (BL) ©W. Perry Conway/Corbis, (R) ©Phil Schermeister/Corbis 9 (L) ©W. Wayne Lockwood, M.D./Corbis, (BR) ©Ron Sanford/Corbis 10 (R) ©Diego Lezama Orezzoli/Corbis, (BR) Jerry Young/©DK Images 11 (BL) ©Ron Sanford/Corbis, (BL) ©Roy Corral/Corbis 12 (R) ©David Muench/Corbis, (BC) ©Jim Zuckerman/Corbis 13 (L) ©David Muench/Corbis, (BC) ©Frank Greenaway/©DK Images 14 (TC) ©Frank Greenaway/©DK Images, (BL) ©Stuart Westmorland/Corbis, (R) ©Stephen Frink/Corbis 15 (L, BR) ©Ralph White/Corbis 16 ©Bill Kamin/Visuals Unlimited 17 ©Stephen Frink/Corbis 18 (BL) ©Michael Sewell/Peter Arnold, Inc., (BL) ©DK Images, (BC) ©Daniel Cox/Getty Images, (BC) ©Michael Quinton/Minden Pictures, (BC) ©John Shaw/Tom Stack & Associates, Inc., (BC, BL) Neil Fletcher and Matthew Ward/©DK Images, (BR) Getty Images, (BL) Matthew Ward/©DK Images 19 (CL) ©Michael Sewell/Peter Arnold, Inc., (CL) ©Michael Quinton/Minden Pictures, (BL, BC) Neil Fletcher and Matthew Ward/©DK Images

ISBN: 0-328-13928-9

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 any prohibited reproduction, storage in a retrieval system, or transmission in any form by any means, electronic, mechanical, photocopying, recording, or likewise. For information regarding permissions, write to: Permissions 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

Vocabularycommunity

cycle

ecosystem

energy pyramid

habitat

niche

population

What did you learn?1. What are some living and nonliving parts of an ecosystem?

2. In what group of ecosystems do rivers, wetlands, coral reefs, and the deep sea belong? What group is made up of forests, grasslands, deserts, and tundra?

3. Explain what a cycle in an ecosystem is. Give at least one example.

4. Organisms have special behaviors that help them meet their needs. On your own paper, write to explain how behaviors help organisms live in a biome where it is very hot or very cold. Include details from the book to support your answer.

5. Predict Describe what might happen to a rainforest ecosystem if its yearly rainfall decreased a great deal.

13928_CVR_FSD Sec1:213928_CVR_FSD Sec1:2 5/27/05 10:33:29 AM5/27/05 10:33:29 AM

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