California science grade 3 (8)

CHAPTER 3Environments Change How do changes to environments affect living things?. Some living things make small changes.. Living things can also change their environment in more noti

CHAPTER 3

Environments Change

How do changes to environments

affect living things?

126

3 LS 3 Adaptations in physical structure or behavior

may improve an organism’s chance for survival

127

underlying theme or author’s

message in fiction and

nonfiction text ELA W 3.1.1

Create a single paragraph:

a Develop a topic sentence

b Include simple supporting

facts and details.

128

Write About It

Response to Literature This book tells us that peregrine falcons almost died out What is the author trying to tell us about environmental

changes? Write a paragraph about environmental changes Include what we can do to protect

the environment

Peregrine falcons were quite common

in the United States until about 1950, but over the next 20 years they died out almost completely Most people blame DDT, a chemical used to kill harmful insects DDT was eaten by the insects, which were eaten by small birds, which were then eaten by the peregrine falcons The poison made falcon eggshells very thin and easy to break, so peregrines became unable to produce any young The falcons have been doing much better since DDT has

been banned .

Some peregrine falcons have

found ways to live with people

They have traded tall trees and

cliffs, where they usually build their

nests, for tall buildings in cities In

cities the falcons can find plenty of

pigeons and other birds to eat.

by David Dobson

from Can We Save Them?

- Journal Write about it online @ www.macmillanmh.com

129

Leaves fall from trees and cover the forest

floor In time, the leaves disappear Have

you ever wondered what happens to fallen

leaves? What makes them disappear?

130

ENGAGE

Put soil in the plastic container Then put

small stones and leaves on top of the soil

This models the forest floor

Place live worms on the “forest floor.”

Predict What will the worms do? Make

a short list of the things you might see the

worms do

Observe Check the worms, soil, leaves, and

stones every three to four days Keep the

tank moist How do the worms change their

environment? Record your observations

Draw Conclusions

How do worms change the environment in

which they live?

Explore More

How do other living things change their

environments? Make a plan to test your

ideas Then try your plan

Materials

stones

leaves moist soil

plastic container

3 IE 5.e Collect data in an investigation and analyze

those data to develop a logical conclusion.

131EXPLORE

How do living things change their environment?

Every living thing changes its environment

in some way Some living things make small changes A spider spins a web A bird builds

a nest A squirrel buries an acorn All these actions change the environment in small ways Living things can also change their

environment in more noticeable ways

Bacteria, worms, and fungi live in the soil They break down leaves and other dead plant material They help add nutrients back

to the soil These living things make big changes that help the environment.

struggle among living things for food, water, and other needs.

C Main Idea

Living things change

the environment in ways

that may be harmful

or helpful People

can improve some

of the harmful ways

that they change the

Grass and other small plants

sprout in warm, moist soil

They change this bare

environment as they grow

A Changing Environment

3 LS 3.c

132

EXPLAIN

As grass begins to grow, it takes in nutrients and

water from the soil It changes the environment as it

meets its needs In time, animals eat the grass for food

These animals change the environment as they meet

their needs When shrubs and trees begin to grow, they

compete for space, light, and water The trees block

sunlight from reaching the smaller plants The smaller

plants may die In this way environments change as

living things compete to meet their needs.

When shrubs take root, more

animals move to the environment

The plants and animals compete

to meet their needs

How does this environment change

over time?

Clue: Arrows help show a sequence

Watch how environments change

@ www.macmillanmh.com

Read a Diagram

133EXPLAIN

How does a beaver change its environment?

Beavers are master builders They cut down small trees and plants with their strong teeth Then they pile up these materials to build dams in streams

Dams block water from flowing through streams They cause deep pools of water

to form in which beavers can build lodges Lodges are shelters that are made from trees, shrubs, and mud Beavers use lodges for protection and to raise their young.

A Beavers cut down trees with

their strong front teeth

Beavers use branches to build dams and lodges in the water B

134

EXPLAIN

Quick Check

Predict If trees were not

available, would beavers still

build dams?

Critical Thinking Does a

beaver help or harm the

environment?

A Beaver’s Tools

Get several photos of beavers

Observe Look at the parts of the beaver’s body Which parts help it to swim, chew wood, and stay warm in cold water?

Communicate Make a chart to show how each body part helps

a beaver meet its needs

When beavers build lodges

and dams, they change the

environment in many ways

Sometimes they change large

areas of land and water Large

beaver dams can cause land to

flood Plants on flooded land can

die The homes of other plants

and animals can be washed

away Dams also harm plants

and animals that depend on

flowing water.

Changes that beavers make

can also help some living things

When beavers cut down trees,

they make space for smaller

plants to grow Their dams

can cause wetlands to form

Wetlands are home to many

plants and animals.

Body Part Purpose

sharp teeth flat tail webbed hind feet front paws fur

A beaver dam creates

a pool of deep water C

135EXPLAIN

in their daily lives Most Americans produce about 2.1 kilograms

(4.5 pounds) of trash each day Where does all this trash go? Many towns and cities put the trash they collect in landfills Landfills can cause pollution (puh•LEW•shuhn).

Pollution is what happens when harmful materials get into the air, water, or land

What can we do to protect the environment? One easy thing we

can do is practice the 3 Rs—reduce,

reuse, and recycle Reduce means

to use less of something Reuse

means to use something again

Recycle means to turn old things into new things When you practice

the 3 Rs, you produce less trash and

help the environment.

trash burned at combustion facilities

trash recycled or composted

Where does our trash go?

Clue: Each section of the pie

chart represents a fraction

Read a Chart

136

EXPLAIN

LR_TXT LR_TXT LR_TXT LR_TXT LR_TXT LR_TXT LR_TXT LR_TXT

LR_TXT LR_TXT LR_TXT LR_TXT LR_TXT LR_TXT LR_TXT LR_TXT

LR_TXT LR_TXT LR_TXT LR_TXT LR_TXT LR_TXT LR_TXT LR_TXT

Living things change

their environment

(pp 132–133)

Beavers change the

environment in both harmful and helpful ways (pp 134–135)

People can help the

environment by

practicing the 3 Rs

(p 136)

Think, Talk, and Write

Main Idea What are some ways in which plants and animals change their environment?

Vocabulary What is it called when living things struggle to get what they need?

Predict What might happen

if people keep polluting the environment?

- Review Summaries and quizzes online @www.macmillanmh.com

Make a Pie Chart

Keep track of the trash you throw

away Make a pie chart that

shows one week of trash from

your home Include paper, metal,

plastic, and food scraps

Make a Poster

Make a poster about the things people can do to help the environment Include things you learned from this lesson as well

as things you aleady knew

137EVALUATE

C Choose five students to survey in the

lunchroom

C Ask each student questions about how

many pieces of trash from lunch he or she

threw away today Ask about the containers

they used Will anything be reused?

Record Data

You read that most Americans change

their environment daily by producing

about 2 kg (4 lbs) of trash each! We can

never completely get rid of trash, so it is

up to everyone to cut down on trash

Do students in your school practice the

3 Rs? Find out the same way scientists

do: gather and record data

Learn It

When you record data, you write or

draw facts that have been collected through

measuring, counting, and experimenting

It is usually easier to study information if

you organize it on a chart or graph Often,

scientists gather and record data by asking

questions or by having people fill out surveys

You can do it, too

Try It

In this activity, you will gather and record

data about how much trash is thrown out by

students in your school You cannot survey the

whole school, but you can do a mini-survey

3 IE 5.e Collect data in an investigation and analyze those data to develop

a logical conclusion

138

EXTEND

Apply It

Now combine your data with those of your

classmates Record this larger data Then make

a bar graph to show the results

Do you predict these same students will

throw out more or less trash tomorrow? Plan

another survey to collect and record data

Compare those results to your first result just

as scientists do!

Student’s Name Reused Pieces Recycled Pieces Thrown Pieces

Away

Total Pieces of Trash

Now answer these questions:

C Did every student throw out some trash or

packaging material?

C Were you surprised by the data

you recorded?

C How many pieces of trash did these five

people create from just one lunch?

C Record each student’s data on a chart like

the one shown

139EXTEND

Lesson 2

Changes Affect

Living Things

Rain Rain More rain When it rains too

much, everything gets wet What happens

to living things when there is a flood?

3 LS 3.d Students know when the environment changes, some plants and animals survive and reproduce; others die or move to new locations.

140

ENGAGE

Step

3 identical plants

What happens to some plants

when there is a flood?

Make a Prediction

What happens to plants when they get too much

water? Write a prediction

Test Your Prediction

Label three plants A, B, and C Water plant

A once a week with 60 mL of water Water

plant B every day with 60 mL of water Water

plant C every day with 120 mL of water

Predict What will happen to the plants

after three weeks? Record your prediction

Record Data Observe your plants

every few days Measure how tall they

grow Record how they look with words

and pictures

Observe After three weeks, check the

plants carefully What do you observe?

Draw Conclusions

How do the plants look after three weeks?

Which plant looks the healthiest? Which

plant received the right amount of water?

Infer What happens to some plants when

there is a flood?

Explore More

Experiment Stop watering plant C for a week

How does the plant change?

Materials

graduated cylinder and water

ruler

3 IE 5.d Predict the outcome of a simple investigation

and compare the result with the prediction.

141EXPLORE

C Main Idea

Environments change

for many reasons Living

things have different

Cause and Effect

What are some ways environments change?

You know that living things change their environment Weather and other things can also change environments Lightning might start a grassland or forest fire Too much rain might cause flooding.

Some changes last a short time A summer drought can turn a green meadow brown Spring rain can make a desert bloom with flowers Other changes have long-lasting effects Earthquakes, storms, and volcanic eruptions can cause sudden changes in an environment The damage from such changes may last for years

D Desert marigolds are among the many flowers that bloom in deserts

1OcaS 3TTSQb

Wild flowers in Anza Borrego State Park, California, quickly bloom after a spring rain

C Technology

Explore how environments change with the Secret Agents.

3 LS 3.d

142

EXPLAIN

Some living things can recover from harmful changes

in their environment Grassland grasses have roots that

store food and moisture The grasses survive and grow

back quickly after a fire However, trees in a forest may

take hundreds of years to grow back after a fire

People often cause permanent changes When large

trees in old forests are cut down, those trees are gone

forever Rivers and lakes polluted by trash or chemicals

may not recover unless people clean them up.

In 1980 Mount St Helens, a volcano

in Washington, erupted The eruption knocked down or scorched trees in nearly 230 square miles of forest The environment is slowly changing as new living things start to grow again

Quick Check

Cause and Effect What are some things that can

cause sudden changes in an environment?

Critical Thinking Why do grasses survive a fire

better than trees?

143EXPLAIN

How do changes affect

plants and animals?

Plants and animals have adaptations

that help them survive in their

environments Zebras have flat teeth

for chewing grass Fish have gills that

help them get oxygen from water

What would happen to these living

things if their environment suddenly

changed? What would happen to a

zebra if its habitat became too dry

for a long time? A habitat is a living

thing’s home What would happen

to the living things in a pond if their

habitat dried up?

A Animals, such as this springbok, depend on watering holes

144

EXPLAIN

Quick Check

Cause and Effect What environmental changes might cause an animal to move

to another place?

Critical Thinking What might happen

to an elephant if its habitat suddenly becomes cold?

D Animals migrate, or move to another place, in search of food, water, and shelter as their habitat goes through seasonal changes

When an environment changes, the plants

and animals adapted to that environment can

be harmed If the changes last a long time,

some animals may move to a new habitat

Some plants and animals have adaptations

that help them survive change Other

plants and animals find a way to survive by

changing their behavior Living things that

are not able to travel or change might die.

When there is no rain for a long time in the

savanna, grasses can dry up Watering holes

can dry up, too Zebras and other animals

move to a new habitat where they can find

food and water Frogs burrow in the mud

They will come out when rain falls again

Grasses and most fish cannot move If their

habitat stays dry for too long, they may die.

A Many frogs are adapted

to burrow and survive underground when their environment becomes dry

145EXPLAIN

How do living things depend on

each other?

The living things in an environment depend on each

other to meet their needs Frogs depend on insects for

food Birds depend on plants for food and safety Living

things that depend on each other are part of an ecosystem

An ecosystem is all the living and nonliving things that

interact in an environment Ecosystems can be any size

They can be as small as a puddle or as large as an ocean.

Many populations of plants and animals live in an

ecosystem A population is all the members of a single

type of living thing in an ecosystem For example, all the

prairie dogs in a grassland make up a population Changes

to one population can affect the whole community

A community is all the different populations in an

ecosystem Grasses, prairie dogs, and eagles are all

part of a prairie community.

Other animals such

as mice and snakes visit

or live in the burrows

Eagles and coyotes depend on prairie animals for food

Prairie dogs build connected tunnels,

or burrows

A Prairie Community

146

EXPLAIN

In some prairie ecosystems,

prairie dogs build tunnels and

burrows Other prairie animals,

such as burrowing owls and mice,

also make their homes in these

burrows Eagles and black-footed

ferrets eat some of the animals

that live in the burrows When a

prairie dog population disappears,

their burrows collapse Many

kinds of animals lose a source of

food and shelter

Quick Check

Cause and Effect What might

happen to an ecosystem if a

population disappears?

Critical Thinking What changes

might harm an ecosystem?

If drought kills the grass,

prairie dogs lose their

source of food

Without prairie dogs, other prairie

populations such as eagles and

coyotes will lose a source of food

The whole prairie ecosystem can be

harmed by environmental change

What happens when prairie dogs leave

Paste the cards on a large sheet

What happens when new

living things move in?

Sometimes new living things enter an

ecosystem Seeds can be carried to an

ecosystem by wind Animals searching

for food and water may move in

People can also bring in new plants and

animals New plants and animals can

upset the balance in an ecosystem For

example, glassy-winged sharpshooters

moved to California from the southeastern

United States They eat California’s

grape plants and carry a disease that

makes grape leaves dry up The photos

show some ways new plants and animals

have affected California’s ecosystems

Quick Check

Cause and Effect What can

happen if a new animal moves

into an ecosystem?

Critical Thinking Why can it be

harmful to bring new plants into an

ecosystem?

A Eucalyptus trees were onceplanted to prevent soil erosion They grew quickly and crowded out native trees.They also burn easily, and help wildfires spread Now they are being removed and replaced with native trees

People once raised red foxes for their fur

When the fur trade stopped, these animals

were released into the wild They compete

with native animals for food and space C

D Glassy-winged sharpshooters

can destroy grape plants

148

EXPLAIN