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Life Sciences Standards Preview 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. Genre Comprehension Skill Text Features Science Content Nonfiction State the Purpose • Captions Animal Life Cycles • Labels • Glossary Scott Foresman Science 2.4 ì<(sk$m)=cdfadc<ISBN 0-328-23503-2 +^-Ä-U-Ä-U by Nancy Day
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Vocabulary amphibian insect larva life cycle mammal pupa tadpole Picture Credits by Nancy Day 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. 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 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
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What is Animals look different at each stage. a life cycle? All animals change size. Many animals change shape. Some animals change color. 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. Living things change size. 2 3
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Growing and Changing in An amphibian is an animal. Different Ways It lives in water for part of its life. A mammal is an animal. Young amphibians do not look Young mammals look like their parents. like their parents. They change size as they grow. They change size, shape, and color, too. An insect is an animal. An adult toad It has three body parts and six legs. It changes size, color, and shape as it grows. Bears are mammals. This is a young toad. Toads are amphibians. 4 5
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What is the life The tadpole grows and changes. cycle of a frog? It grows back legs first. Later come the front legs. The tadpole’s legs get stronger. A frog is an amphibian. Its tail gets smaller. It begins life as an egg. Some frog eggs float in the water. This tadpole is A tadpole hatches from the egg. nine weeks old. It swims out. A tadpole is a very young frog. A frog egg is tiny. This frog is A tadpole twelve weeks old. has a tail. 6 7
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From Young Frog to Adult Frog The adult frog may lay eggs in The frog is no longer a tadpole. the water. It is no longer a young frog. Those eggs might become tadpoles. Now it is an adult. Then the life cycle starts over again. A young tadpole An egg An older tadpole An adult frog 8 9
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What is the life The mouse grows. cycle of a mouse? It looks more like its parents. At last, the mouse is an adult. It can have baby mice. Mice are mammals. Then the life cycle starts over. A baby mouse is called a mouse. It looks like its parents. But it is much smaller. Two-week It does not have hair. old mice Newborn mice Adult mice 10 11
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What is the A hard case grows around the life cycle of a caterpillar. It is now a pupa. butterfly? Out of the pupa comes an adult butterfly. A butterfly is an insect. It looks nothing like a caterpillar! It starts life as an egg. Next, a caterpillar hatches. A caterpillar is a larva. A larva is a young insect. egg pupa adult larva 12 13
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What is the The nymph has six legs. life cycle of a It does not have wings. The nymph grows into an adult. grasshopper? The adult grasshopper has two pairs of wings. A grasshopper is an insect. It starts as an egg. The egg hatches. Out comes a young grasshopper. It is a nymph. eggs nymph adult 14 15
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What did you learn? Glossary 1. Go back to what you read about young amphibian an animal that lives part of its insects, mammals, and amphibians. Which life in water and part on land look like their parents? Which do not? insect an animal that has three body 2. What are the four stages of the butterfl y’s parts and six legs life cycle? 3. Have you seen a cat or larva a young insect dog grow from a newborn kitten or puppy to an adult? How did they look after they life cycle the way a living thing grows were born? When did they start to play? and changes Who or what did they play with? What did they eat? mammal an animal that usually has hair or fur on its body 4. State the Purpose Go back to the pictures on pages 8 and 9. What is their purpose for being there? pupa the stage after the larva in some insects’ life cycles tadpole the second stage of a frog’s life cycle 16
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