Living things change

Life Sciences
Standards
Preview
Standard Set 3. Life Sciences
3. Adaptations in physical structure or
behavior may improve an organism’s
chance for survival. As a basis for
understanding this concept:
3.c. Students know living things cause
changes in the environment in which
they live: some of these changes are
detrimental to the organism or other
organisms, and some are beneficial.

3.d. Students know when the
environment changes, some plants and
animals survive and reproduce; others
die or move to new locations.
3.e. Students know that some kinds
of organisms that once lived on Earth
have completely disappeared and that
some of those resembled others that
are alive today.

by Kim Fields

Genre

Nonfiction

Comprehension Skill

Make Inferences

Text Features

• Captions
• Glossary

Science Content

Changing
Environments

Scott Foresman Science 3.5

ISBN 0-328-23531-8

ì<(sk$m)=cdfdbf< +^-Ä-U-Ä-U


Vocabulary
competition
extinct
fossil
habitat

by Kim Fields

Picture Credits
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 copyright of Dorling Kindersley, a division of Pearson.
Photo locators denoted as follows: Top (T), Center (C), Bottom (B), Left (L), Right (R), Background (Bkgd).
Opener: U.S. Geological Survey, Corbis, AP/Wide World Photos, Visuals Unlimited; 1 (C) Douglas Faulkner/Corbis;
2 (B) Corbis; 4 (C) Animals Animals/Earth Scenes; 6 (B) AP/Wide World Photos; 7 (T) Animals Animals/Earth Scenes;
8 (B) ©Jeff Foott/Nature Picture Library; 10 (C) U.S. Geological Survey; 11 (BR) AP/Wide World Photos; 12 (C) Corbis;
13 (B) Douglas Faulkner/Corbis; 14 (C) Corbis; 15 (C) The Image Works, Inc.; 16 (B) Visuals Unlimited, (C) James L.
Amos/Photo Researchers, Inc.; 17 (B) Visuals Unlimited, (C) Photo Researchers, Inc.; 18 (C) Getty Images; 19 (C) Photo
Researchers, Inc.

ISBN: 0-328-23531-8
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 permission(s), write to
Permissions Department, Scott Foresman, 1900 East Lake Avenue, Glenview, Illinois 60025.
1 2 3 4 5 6 7 8 9 10 V010 13 12 11 10 09 08 07 06


Living Things Change
The Environment
A habitat is a place where a living thing makes its
home. A habitat provides the resources a living thing
needs to survive and grow.
Think of a habitat as a balance. One side of a habitat
has the resources a habitat supplies. The other side
has the things that live there. If the habitat has enough
resources to help support life, the balance is level.

2

Change often shifts the balance. When two or
more living things need the same things, they are in
competition. The gray seal and the harbor seal live in
Canada. If there are too many seals or too little food,
the same kind of seals are in competition. Some seals
may die.

Too many seals or too little
food leads to competition.

3


Changes Caused by Animals
Some animals change their habitats when they make
homes. Beavers, for instance, need deep water. If the
stream where they live is too shallow, they build a pond.
Beavers use their sharp teeth to cut down trees. Beavers
then put together dams from these trees. A dam creates
a pond.
Beavers change the
environment when they
build dams.

This change helps plants and animals that need still
water. Dragonflies can live in this new environment.
Also, the trees the beavers cut down no longer shade the
ground below. Small plants and shrubs that benefit from
direct sunlight grow in their place.

The change harms plants and animals that live in
the moving waters of a river or stream. Some plants and
animals no longer have a place to live. This change can
affect fish. The pond harms plants and animals whose
homes are flooded. Trees needed to make the dam are
also lost.

TK

4

5


This picture shows kudzu
invading the living space
of other plants. No animals
eat kudzu. Nothing stops
it from growing more. It
covers other plants and
gets all the sunlight.

Changes Caused by People
All living things need shelter to stay alive. People need
shelter just like other living things. Humans change the
environment when they build homes. To make room for
houses, people may plow grasslands. They may cut down
trees. Each of these changes affects the environment.
Sometimes animals and humans are in competition for
space. People move to places where animals live. Then

they might see coyotes in their backyards!

Helpful and Harmful Change

TK

Changes can help some living things and hurt others.
Kudzu is a plant brought to the United States that many
people use to decorate their yards. It can help keep the
soil from washing away.
Kudzu also causes many problems. It is hard to get rid
of. No animals eat the plant. Kudzu grows fast and thick.
It stops a forest from getting the light it needs to grow.
Kudzu breaks other plants with its weight.

Cycles of Change
Some changes happen in a cycle. Scientists believe a
change in the weather affects small fish called sardines.
The overall weather around Monterey Bay changes in a
fifty-year cycle. In the 1930s, there were many sardines in
the bay. By the 1950s, most of the sardines disappeared.
By 1999, there were many sardines in the bay again.

6

7


Changes in The
Environment Affect

Living Things
Too Little Water
Humans can change environments by taking too
much water from streams and lakes. Plants and animals
that need the water can die.
Dry weather can also change environments. It may be
too dry for plants to survive and reproduce. Animals die or
move somewhere else.

Over thousands of years, many places have become
drier. In these places, grasses and shrubs that need
less water have replaced trees that need a lot of water.
Animals that use trees for food and homes are replaced
by animals that use grasses and shrubs for food and
homes.

Too Much Water
Too much water at the same time can change an
environment. Storms can cause flooding. Floods can
wash away people’s homes. Floods can also wash away
plants and soil. Animals, including snakes, can lose their
homes to flooding. Floods carry thick blankets of mud to
different places.
Flooding in Linda, California

A dry season in Imperial
Valley, California

8

9


Volcanic Eruption

After the Eruption

In the spring of 1980, a huge volcano erupted in
Washington State. Hot rock and gases from Mt. St.
Helens melted ice and snow. The water caused a flood.
One side of the mountain broke apart and slid away. The
volcano blew a cloud of ash into the air. Even though it
was daytime, the sky grew dark. Wind carried the ash all
over the world.
The eruption changed the environment. Many forests
were destroyed. Mud covered whole areas. Ash was piled
up a meter high in some places.

Some shrubs and plant roots covered by snow
survived the eruption. Seeds carried by the wind sprouted
and grew. As plants grew, more animals could find food.
Animals that lived underground also lived through
the eruption. Gophers, mice, spiders, and ants were safe
from the eruption. Voles, shrews, and mice came to live
on the mountain. Birds came to live in the dead trees that
were left. Large elk, hawks, and eagles also came to live
on the mountain.
The environment won’t be like it was for a long time.
But there are many living things on the mountain. Each
new change on the mountain allows different types of

animals and plants to live there.

Elk came to live on the
mountain as plants grew back.

In 1980, Mt. St. Helens
erupted.

10

11


Wildfire

After a Fire

A wildfire brings a huge change to a forest. When
lightning strikes a tree in the forest, it can set the forest on
fire. Then the fire rushes through the forest. Small plants
and dead brush burn. Trees with thick bark live through
the wildfire. Other trees may burn down. This creates
open spaces in the forest.

Animals that hunt go back into the burnt forest. The
animals they hunt do not have many places to hide.
Animals and wind carry in new seeds to the forest.
Shrubs, flowers, and grasses that can live with a lot of
sunlight grow. The changes these plants bring help the
next group of plants. Then new trees can grow in the

forest. After a while, the forest grows back.
Fire causes harmful and helpful changes. Fire destroys
animals’ homes. Many living things die. Wildfires are also
helpful for many plants and animals. They clear out the
forest floor. New trees and plants have more space to live.
The ash makes the soil healthy, helping plants to grow.

The temperature of a wildfire
can reach 800°C.

Young trees grow with plenty
of living space and sunlight.

12

13


Comparing Living
Things to Those Of
Long Ago
Fossils
An environment can change. Some kinds of animals
and plants may not adapt to this change. The change
may cause some animals and plants to become extinct.
Extinct means no longer living on Earth.
During Earth’s history, many plants and animals have
become extinct. We cannot see these plants and animals
because they no longer live on Earth. We can, however,
study the fossils left by extinct plants and animals. A fossil is

the remains or mark of a living thing from long ago.

What Fossils Tell Us
Fossils tell us things about extinct animals and plants
and where they lived. We can tell how extinct animals
and plants are like those alive today. We can also tell
how they are different. The fossil of a giant wombat, for
instance, was found in Australia. It was the size of a small
car! It lived at a time when many giant creatures were
on Earth.
We can also find out how the environments of these
plants and animals changed. Fossils of animals with teeth
for eating plants might be found in a desert. This shows
that the area may have once been a swamp.
An Australian wombat

This is a fossil of a giant
wombat’s jawbone.

14

15


Plants Change over Time
The first plants did not have cones or flowers.
Actually, many of them looked like the ferns and
horsetails we have today. We can tell this by looking at
plant fossils. Horsetails live in moist environments and
can be found across the United States.

As Earth changed over time, many plants also
changed. Trees with cones appeared. Then plants that
had flowers followed. Many of these kinds of plants no
longer exist.
Horsetail fossil

16

Like horsetails, magnolias are a kind of plant that still
exists today. The first magnolias kept their leaves yearround. They lived in a warm, wet world.
Some magnolias changed as environments changed.
Many places where magnolias live have cold winters.
Magnolias that live there lose their leaves in fall. Still, the
flowers and leaves of the magnolias are like those that
lived a long time ago. The flower of the magnolia has
stayed nearly the same for 100 million years.

Magnolia leaf fossil

17


Animals Change over Time
Fossils of extinct dinosaurs show how those dinosaurs
are like animals of today. Animals have teeth that are
adapted to eat certain types of food. Animals that eat
plants have grinding teeth. Animals that eat meat have
teeth that tear and cut. You can look at the teeth of
extinct animals to find out what they ate.
Scientists in England

assembled an 84-foot-long
dinosaur skeleton.

Some dinosaurs used their sharp teeth to tear off meat
from other animals. Velociraptors were small dinosaurs,
but they had sharp teeth! Velociraptors could attack and
eat larger animals.
Other dinosaurs had teeth that could grind up food.
Diplodocus had small teeth for grinding up plants.
Fossils can show us how Earth has changed over time.
When scientists find fossils of animals that ate plants,
they know that the area had many plants. But today the
same area may not have very many plants!

Velociraptor skull

18

19


Glossary
competition

when two or more living things need
the same resources

What did you learn?
1. How can beavers harm the environment when they
build dams?

2. How can dry weather affect animals?

extinct

no longer lives on Earth

fossil

the remains or mark of a living thing
from long ago

habitat

20

3. How did some plants survive the eruption of
Mt. St. Helens?
4.

Suppose that you discovered
a fossil. Where did you find it? What does it look like?
What does it feel like? Is it a plant or an animal? Write a
paragraph to answer these questions about your fossil.

5.

Make Inferences If a fossil shows an animal with
teeth that were not sharp, what do you think that
animal ate?

the place where a living thing makes
its home