Genre Comprehension Skill Text Features Science Content

Nonfi ction State the Purpose Captions

Labels

Glossary

Animal Life Cycles

Scott Foresman Science 2.4

StandardsPreview

Standard Set 2. Life Sciences

2. Plants and animals have predictable life cycles. As a basis for understanding this concept:

2.b. Students know the sequential stages of life cycles are different for different animals, such as butterflies, frogs, and mice.

ISBN 0-328-23503-2

Vocabulary

amphibianinsectlarvalife cyclemammalpupa tadpole

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.

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

ISBN: 0-328-23503-2

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.

1 2 3 4 5 6 7 8 9 10 V010 13 12 11 10 09 08 07 06

23503_CVR.indd Cover323503_CVR.indd Cover3 1/6/06 1:13:25 PM1/6/06 1:13:25 PM

by Nancy Day

23503_001-016.indd 123503_001-016.indd 1 1/6/06 2:17:02 PM1/6/06 2:17:02 PM

2What is a life cycle?Living things grow.Living things change.This growth and change is called a life cycle.Every life cycle has steps or stages.

Living things have life cycles.

23503_001-016.indd 223503_001-016.indd 2 1/6/06 2:17:10 PM1/6/06 2:17:10 PM

3

Animals look different at each stage.All animals change size.Many animals change shape.Some animals change color.

Living things change size.

23503_001-016.indd 323503_001-016.indd 3 1/6/06 2:17:17 PM1/6/06 2:17:17 PM

4Growing and Changing in Different Ways

A mammal is an animal. Young mammals look like their parents.They change size as they grow.

An insect is an animal. It has three body parts and six legs.It changes size, color, and shape as it grows.

Bears are mammals.

23503_001-016.indd 423503_001-016.indd 4 1/6/06 2:17:23 PM1/6/06 2:17:23 PM

5

An amphibian is an animal.It lives in water for part of its life.Young amphibians do not look like their parents.They change size, shape, and color, too.

This is a young toad. Toads are amphibians.

An adult toad

23503_001-016.indd 523503_001-016.indd 5 1/6/06 2:17:43 PM1/6/06 2:17:43 PM

6What is the life cycle of a frog?A frog is an amphibian.It begins life as an egg.Some frog eggs oat in the water.A tadpole hatches from the egg.It swims out.A tadpole is a very young frog.

A frog egg is tiny.

A tadpole has a tail.

23503_001-016.indd 623503_001-016.indd 6 1/6/06 2:17:47 PM1/6/06 2:17:47 PM

7

The tadpole grows and changes.It grows back legs rst.Later come the front legs.The tadpoles legs get stronger.Its tail gets smaller.

This tadpole is nine weeks old.

This frog is twelve weeks old.

23503_001-016.indd 723503_001-016.indd 7 1/6/06 2:17:57 PM1/6/06 2:17:57 PM

8From Young Frog to Adult Frog

The frog is no longer a tadpole.It is no longer a young frog.Now it is an adult.

An egg

A young tadpole

An older tadpole

23503_001-016.indd 823503_001-016.indd 8 1/6/06 2:18:02 PM1/6/06 2:18:02 PM

9

The adult frog may lay eggs in the water.Those eggs might become tadpoles.Then the life cycle starts over again.

An adult frog

23503_001-016.indd 923503_001-016.indd 9 1/6/06 2:18:08 PM1/6/06 2:18:08 PM

10

What is the life cycle of a mouse?Mice are mammals.A baby mouse is called a mouse.It looks like its parents.But it is much smaller.It does not have hair.

Newborn mice

23503_001-016.indd 1023503_001-016.indd 10 1/6/06 2:18:11 PM1/6/06 2:18:11 PM

11

The mouse grows.It looks more like its parents.At last, the mouse is an adult.It can have baby mice.Then the life cycle starts over.

Two-week old mice

Adult mice

23503_001-016.indd 1123503_001-016.indd 11 1/6/06 2:18:18 PM1/6/06 2:18:18 PM

12

What is the life cycle of a butterfl y?A butter y is an insect.It starts life as an egg.Next, a caterpillar hatches.A caterpillar is a larva. A larva is a young insect.

egg

larva

23503_001-016.indd 1223503_001-016.indd 12 1/6/06 2:18:25 PM1/6/06 2:18:25 PM

13

A hard case grows around the caterpillar.It is now a pupa.Out of the pupa comes an adult butter y.It looks nothing like a caterpillar!

pupa adult

23503_001-016.indd 1323503_001-016.indd 13 1/6/06 2:18:34 PM1/6/06 2:18:34 PM

14

What is the life cycle of a grasshopper?A grasshopper is an insect.It starts as an egg.The egg hatches. Out comes a young grasshopper.It is a nymph.

nymph

23503_001-016.indd 1423503_001-016.indd 14 1/6/06 2:18:45 PM1/6/06 2:18:45 PM

15

eggs

The nymph has six legs.It does not have wings.The nymph grows into an adult.The adult grasshopper has two pairs of wings.

adult

23503_001-016.indd 1523503_001-016.indd 15 1/6/06 2:18:47 PM1/6/06 2:18:47 PM

16

amphibian an animal that lives part of its life in water and part on land

insect an animal that has three body parts and six legs

larva a young insect

life cycle the way a living thing grows and changes

mammal an animal that usually has hair or fur on its body

pupa the stage after the larva in some insects life cycles

tadpole the second stage of a frogs life cycle

Glossary

23503_001-016.indd 1623503_001-016.indd 16 1/6/06 2:18:52 PM1/6/06 2:18:52 PM

What did you learn?1. Go back to what you read about young

insects, mammals, and amphibians. Which look like their parents? Which do not?

2. What are the four stages of the butterfl ys life cycle?

3. Have you seen a cat or

dog grow from a newborn kitten or puppy to an adult? How did they look after they were born? When did they start to play? Who or what did they play with? What did they eat?

4. State the Purpose Go back to the pictures on pages 8 and 9. What is their purpose for being there?

23503_CVR.indd Cover423503_CVR.indd Cover4 1/6/06 1:13:26 PM1/6/06 1:13:26 PM

previous:

next: