Genre
Nonfiction
Comprehension Sk Skill
Sequence
Text Fe Features
• Labels • Diagram
Science Co Content
Animals
• Glossary
Scott Foresman Science 3.2
ISBN 0-328-13812-6
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Vocabulary
adaptation hibernate inherited larva migrate pupa trait vertebrate
by Erika Alexander
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.
Photo locators denoted as follows: Top (T), Center (C), Bottom (B), Left (L), Right (R), Background (Bkgd). 2 (L) Terry Andrewartha /Nature Picture Library, (CL) ”Jerry Young/DK Images; 4 (TL) ”Philip Dowell/DK Images; 6 David Wrobel/Visuals Unlimited; 15 (CR) Steve & Dave Maslowski/Photo Researchers, Inc.; 16 (BR) Samuel R. Maglione/Photo Researchers, Inc.; 18 Steve Bloom/Alamy Images; 22 (BL) ”Jerry Young/DK Images; 23 (CR) ”Jerry Young/DK Images. Scott Foresman/Dorling Kindersley would also like to thank: 10 Jerry Young/DK Images; 12 Jerry Young/DK Images; 19 (T) Natural History Museum/DK Images; 20 (T) Senckenberg Nature Museum, Frankfurt/DK Images. Unless otherwise acknowledged, all photographs are the copyright © of Dorling Kindersley, a division of Pearson.
ISBN: 0-328-13812-6 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 f orm 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. 3 4 5 6 7 8 9 10 V010 13 12 11 10 09 08 07 06 05
What All Animals Need
Animal Groups
All animals need food, water, oxygen, and shelter. Animals need food and water for their systems to work. Oxygen is a gas that animals breathe. They need oxygen to stay alive. Animals that live on land use their lungs to breathe. Animals that live in the water use their gills. Shelter provides animals with a safe spot to rest or to hide from other animals.
There are lots of different animals in the world. When animals are grouped together, we can see the things they have in common. You can learn many different things about animals when you group them. This is because animals can be grouped in so many different ways.
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Ways of Grouping Animals The way you group animals should depend on what you want to learn about them. If you want to learn about animals’ environments, group them by where they live. If you want to learn if animals are herbivores or carnivores, then group them by what they eat. Animals can also be grouped by the traits they share. A trait is a feature that is passed on to a living thing from its parents. Webbed feet or fins are traits that are passed from parents to their young.
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Animals with a Backbone A vertebrate is an animal with a backbone. Reptiles, amphibians, fish, birds, and mammals are all vertebrates. Reptiles have lungs. Their skin can be dry and scaly. Amphibians spend time in the water and on land. They have gills when they are young. When they get older, they usually grow lungs. Fish have gills, never lungs. They live only in the water. Mammals have hair during some part of their lives. All mammals breathe through lungs. Birds have lungs too. They also have wings, beaks, feathers, and light bones.
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Animals Grow and Change
Animals Without a Backbone
As animals grow and change, they go through life cycles. Every animal’s life cycle has a set order. Animals grow and change in a certain order. Certain life cycles take a long time. Other life cycles are very short.
Most animals in the world do not have a backbone. Sea jellies, worms, mollusks, and arthropods are all animals without a backbone. Insects and spiders do not have backbones. Animals without a backbone usually do not grow very big. Think about how small most insects and spiders are when compared to a mammal. Some animals have a shell or outside skeleton instead of a backbone. A shell or outside skeleton can give the animal support.
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Life Cycles All animals come from eggs. Sometimes the egg grows inside the animal’s mother. The mother then gives birth to the animal. Other times, the mother lays the egg. The animal then hatches from the egg. The first stage of an animal’s life cycle is birth. An animal grows bigger during its growth stage. Then it develops into an adult. Adults give birth to young animals through reproduction. An animal’s life comes to an end with death.
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A Butterfly’s Life Cycle A butterfly is an insect. It goes through many changes during its lifetime. First an adult butterfly lays a very small egg on a plant. A caterpillar hatches from that egg. It does not have wings. Next the caterpillar eats and grows. It sheds its skin many times. During this stage the caterpillar is called a larva. Then a hard shell, or chrysalis, forms around the caterpillar. The caterpillar becomes a pupa. Inside the chrysalis, the caterpillar keeps changing. Finally a butterfly comes out of the chrysalis. Now the butterfly is an adult. After it lays eggs, the butterfly completes its life cycle.
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Mammals go through smaller changes during their life cycles. They give birth to their young. Young mammals grow inside their mother’s body. When mammals are born, they usually have fur or hair. Young mammals get milk from their mother’s body. Some mammals grow up quickly.
Other Life Cycles Snakes are a kind of reptile. Some snakes live on the land and in the water. When a female snake is ready, she lays her eggs in a warm, damp, and dark place. A young snake uses its egg tooth to cut through its eggshell. The egg tooth will fall off later. Snakes can grow very fast. After a baby snake has grown enough, it sheds its old skin and grows a new skin. Most snakes become adults by the time they are two to four years old. Once a female snake becomes an adult, she is ready to lay eggs on her own. The snake life cycle starts again.
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Adaptations Help Animals You have learned that animals need food, water, oxygen, and shelter to stay alive. Animals also have special features that help them survive in their environment. Every environment is different, so each animal has adapted to the environment where it lives.
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Adaptations An adaptation is a special trait that helps animals survive where they live. The camel’s long thick eyelashes are an adaptation for the desert. They protect the camel’s eyes and keep out blowing sand. A male lion has a very thick mane around its neck for protection. These body part adaptations are inherited. Things that are inherited get passed from adults to their young.
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Adaptations For Protection
Adaptations For Getting Food All animals need food to survive. Sometimes they develop adaptations that make catching or eating their food easier. An animal may be adapted to run very quickly, like a cheetah. Cheetahs need to chase their food to catch it. An animal may have very good eyesight and hearing. Owls use both of these senses to hunt at night. Giraffes have very long necks so they can eat leaves that grow in tall trees.
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Many animals have developed adaptations to protect themselves. Skunks are small animals that release a strong-smelling spray when they are scared. Other animals use camouflage to hide from their enemies. Polar bears are adapted to use camouflage in their snowy environment. It is very difficult to see a polar bear because the color of its coat blends in well with snow.
Skunk
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Behaviors That Help Animals
Instincts
Animals behave in many different ways. A behavior is something that a living thing does. Animals are born knowing some behaviors, but animals must learn other behaviors. A baby bird is born with wings, but that does not mean the bird can fly right away. The bird must learn to fly.
An instinct is a behavior that does not have to be learned. Animals have instincts. When the weather changes, some animals have an instinct to migrate, or move. Snow geese migrate in large groups during the winter. They fly from areas that get very cold to areas that are warmer. Other animals hibernate or rest for long periods of time. When animals hibernate, they go a long time without waking up, eating, or drinking. Black bears hibernate during the winter. They hibernate because the food they eat is harder to find in the winter.
Baby birds
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Learning Animals are able to learn different ways to survive in their environment too. Sometimes an animal will learn a behavior from its parents. Young wolves learn how to hunt by watching adult wolves. In the same way, young beavers learn how to build beaver dams and homes by watching their parents cut and move branches and logs.
Fossilized reptile
Animals Then And Now Sometimes looking at the past can help explain the present. By learning about animals from the past, you can also learn about the animals of today. Today’s animals are alive because they were able to adapt. Animals from the past provide clues about the changes to animals over time.
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Fossilized pterodactyl
Ancient Insects
Animals That Lived Long Ago We learn about animals from long ago by looking at fossils. Fossils are signs of past life. Fossils can be whole skeletons or a single bone. Sometimes an impression of a skeleton or bone is found in a rock. By looking at fossils, fossil molds, and casts, scientists can tell how big an animal was. Scientists may also be able to tell whether an animal ate plants or meat, just by looking at fossils.
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Sometimes scientists will find more than just fossil bones. Whole animals, such as small insects, get caught in tree sap. Over time, the sap turns into a hard yellow or brownish substance called amber. Because we can see through amber, scientists have been able to Spider in amber look at insects from long ago.
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How Today’s Animals Compare With Those of Long Ago
Fossilized plants
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Scientists like to study both plant and animal fossils. From fossils, scientists can often figure out what the weather was like. Using all of the clues that fossils give, scientists are often able to figure out how today’s animals adapted to the Earth’s changes.
Grouping animals helps you learn more about them. There are many ways to group animals. By grouping animals, you can learn about how animals are the same and how they are different.
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What did you learn?
Glossary
1. What are the vertebrates that live in your area? What do they look like?
adaptation a trait that helps a living thing meet its needs in the place it lives
2. What are the different stages of an animal’s life cycle?
hibernate
to rest during the winter or for a long period of time
inherited
passed on from a parent to its young
larva
a stage in the life of an insect when it hatches from an egg and does not have wings
migrate
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Animals can be grouped in different ways. Using your own paper, describe some of the ways animals can be grouped. Use details from the book to support your answer.
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Sequence Describe the life stages of a butterfly in order. Use the words first, next, then, and finally in your answer.
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