Photo Credits: Cover: Kennan Ward/Corbis; 2 Gerlach Nature Photography/Animals Animals; 3 ABPL/Wayne Griffiths/Animals Animals - Earth Scenes; 4 Kevin and Suzette Hanley/Animals Animals - Earth Scenes; 5 Juergen & Christine Sohns/Animals Animals - Earth Scenes; 6 John Daniels/Ardea; 8 Joe McDonald/Corbis; 9 (r) Russell Illig/Photodisc/Getty Images, (l) CMCD/Photodisc/Getty Images; 10 Gerard Lacz/Animals Animals - Earth Scenes; 11 PhotoLink/Photodisc/Getty Images; 12 Frans Lanting/ Corbis; 13 Lee Snyder/Photo Researchers, Inc.; 14 Comstock/Getty Images; 15 Stan Osolinski/Animals Animals - Earth Scenes; 16 Momatiuk-Eastcott/Corbis; 17 Joe Tucciarone/Photo Researchers, Inc.; 18 Mark A. Schneider/Photo Researchers, Inc.; 19 Darren Bennett/Animals Animals - Earth Scenes.

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Animals and plants need certain things in order to survive. These are called basic needs. Animals need food, water, air, and shelter. Animals need plants and other animals for food.

Animals get their food in a variety of ways. Some animals hunt their food and catch it. Lions hunt and catch their food. Other animals, such as vultures, eat the leftovers after another animal has killed its prey.

Humans grow and raise their own food. Humans grow farm crops for food. They also raise animals for food. Sometimes humans hunt or catch food such as fi sh or deer.

Animals fi nd water from their environment in ponds, lakes, and rivers. Other animals get their water from the plants they eat. Tortoises that live in the desert get water from plants.

Every animal needs a certain amount of air to live. Animals find air wherever they are. It is all around them in the environment.

Animals also need shelter. They find shelter in many different places. Shelter can be a rock, a log, the ground, or a tree. Humans build their homes as shelters.

Living things know when something is needed. Animals feel hunger and thirst, and they feel warmth and cold. Animals know how to meet their basic needs.

A living thing must meet its basic needs to survive. Some plants and animals have adaptations to help them. An adaptation is a body part or a behavior that helps an organism survive.

The coloring of an animal can help it survive. Tigers have stripes that look like light colors and shadows. They can easily hide in the tall grass where they live. Toads have bumps that look like rocks.

Some animals have sharp spines to protect them from predators. Porcupines have spines. Other animals have scales that protect them from disease and injury. Fish and snakes have scales.

Adaptations are not just for protection. Adult dolphins have no hair on their bodies. With so little hair they can swim easily to get food. Frogs and lizards have long tongues that help them catch their food.

Birds have a variety of interesting adaptations. Eagles have claws for grabbing food. Owls have large eyes so they can see well at night. Feathers and hollow bones allow birds to fl y. Birds that cannot fl y, like ostriches, have long legs for running. Penguins have feet that allow them to glide in the water.

You have learned about genes and how they determine traits in living things. And you know Variations, or differences, can show up in offspring.

Those changes affect the offspring of two parents. But are there changes that can affect an entire species?

Yes! The different traits that offspring inherit from their parents can help those offspring survive better. If the trait helps enough, the organisms with that trait will survive and reproduce, passing the trait on to their own offspring.

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For example, what if a plant had roots that went deeper than the plants around it? It would be better able to absorb the water and nutrients that it needed to survive. If this plant’s offspring also had roots that grew deeper, then those offspring would survive better than other plants. After a while, there would be more plants with roots that went deeper.

The organisms that are best adapted for survival are better able to live and reproduce. The process by which organisms with the right traits for the environment are better able to live and reproduce is called natural selection.

Plants and animals all have life cycles. They can start as fertilized eggs or even as clones. Each organism, according to its life cycle, grows into an adult. Then they reproduce and the cycle starts over for the offspring.

While some organisms are growing into adulthood, other organisms have reached the end of their life cycle and are dying and decaying. This is part of an organism’s life cycle as well.

There are many organisms that help to decay, or decompose, dead organisms. For example, fungi, insects, bacteria, and other plants all take nutrients from dead organisms. Other nutrients are returned to the soil. This replaces nutrients that living organisms need to survive.

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Plants grow on the fallen tree. It might take a very long time, but eventually the plants and other organisms that are feeding on the nutrients in the fallen tree will consume the trunk and it will be gone. New plants can grow in its place.

Most animals, including humans, already know some things when they are born. No one teaches this information to the animals. These actions are instincts. Instincts are behaviors animals begin life with that help them meet their needs. Instincts help animals protect themselves and get what they need to survive.

You already know animals have certain basic needs. These needs are for food, water, air, and shelter. Animals are born with instincts that help them get food. Babies know to cry when they are hungry. Young animals and humans are born with the ability to suck. That’s how they take in the food and liquid they need.

Animals also know how to get air. Babies will gasp for breath if they do not have enough air. They are not taught to seek air. They know how to do it.

Some animals are born knowing how to provide the shelter they need. Look at trees during the winter. You will see a variety of birds’ nests. Birds are born knowing how to build a nest. They know which twigs and grasses will make a good nest.

Animals are born with the instinct to protect themselves too! They know how to avoid predators. For example, cows travel in herds for protection.

Animals use their instincts to protect themselves when their environment changes. When the seasons change, animals are adapted so they can survive.

Some animals go into hibernation. They become very inactive. Their heart rates slow down. Their breathing almost stops. Even their body temperature becomes lower. The animals are not dead. They are just saving energy. Bats, frogs, squirrels, and turtles hibernate.

A ground squirrel hibernates. It moves to a nest it built under the ground. The squirrel drops its body temperature to 59°F. It slows its breathing. The squirrel only takes about four breaths each minute!

Animals prepare to hibernate. They eat a lot of food before the cold season starts. This adds fat to keep their bodies warm. Then they fi nd shelters.

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Some animals migrate when the seasons change. To migrate means to move from one place to another. Some animals migrate long distances for several months. Gray whales migrate about 9600 kilometers (5970 mi) every year. Other animals such as salmon migrate for years. They travel to the sea for years. Then, they return to the streams to lay eggs.

Animals migrate for different reasons. Gray whales migrate to give birth. They also migrate to find food easily. Many birds migrate to warmer places where they can survive.

Animals begin their lives with instincts about how to survive. Instincts are not all they need as they grow. They also need learned behaviors. Older animals have more experience in life. They can teach younger animals many important things. Learned behaviors are behaviors that an organism doesn’t begin life with.

Think of what you knew how to do when you were born. Those things are instincts. During your life, you pick up other information that helps you survive. This is behavior that you learn. Knowing how to feed yourself is a learned behavior. It is something the older people in your family taught you. You can survive on your own once you can feed yourself.

Like other mammals, humans help their children grow and become adults. Humans and other mammals teach their children how to fi nd food. Parents also teach their children how to protect themselves.

Tigers teach their cubs to hunt. The cubs study their mothers as they hunt. They also practice hunting skills when they play with other cubs.

Chimpanzees also learn from the adults in their animal group. They learn how to build nests for sleeping. They also learn to use stones to break open nuts. Chimpanzees learn that different sounds have different meanings. They watch and learn from the adults around them.

Plants and animals often leave behind information after they die. This information is found in a fossil. A fossil is evidence of a plant or an animal that lived long ago.

Fossils are made before dead plants and animals completely decay. Minerals combine with the plant or animal parts. This forms the shape of the fossil.

Fossils are found in sand or mud that has hardened into rock. Sometimes whole animals were buried in the sand or mud. Other large animals were trapped in ice glaciers thousands of years ago. Their fossils were found years later.

Often the footprint of an animal is left behind. You can tell how large the animal was. You can get information about its movement too!

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Plants leave fossils that show their shape. Have you ever seen an imprint of a leaf on a rock? It was probably a plant fossil. The imprint was created when the leaf landed in mud. Later, the mud hardened into rock.

Another example of a plant fossil is petrifi ed wood. Part of a tree is buried in mud before it decays. Minerals take the place of the wood, and it becomes as hard as a rock.

Some plants and animals lived long ago but no longer exist. They are extinct. Extinction means that all the members of a certain group of organisms have died.

Extinction happens for different reasons. Sometimes the environment becomes too cold or too warm. Animals and plants die off before they can fi nd better places. For example, wooly mammoths and dinosaurs no longer exist today. This is because of changes in the climate.

Humans can also cause animal extinction. Polluting the water, air, and soil can change the habitats of animals. Some animals have nowhere else to go, and they die off.

Predators and limited food supplies also cause extinction. Some scientists believe many living things became extinct about 65 million years ago. They think the environment and the food supply changed. These changes were too much for many animals and plants to survive.

All living things have basic needs. They need food, water, air, and shelter. Animals have instincts from birth. They learn more behaviors from adults. Animals also adapt to survive and protect themselves. Scientists get information about animals that lived long ago from fossils. Some of these animals could not adapt to changes around them. They no longer exist.

adaptation (ad uhp TAY shuhn) A body part or behavior that helps an organism survive (4, 5)

extinction (ek STINGK shuhn) The death of all the members of a certain group of organisms (14, 15)

fossil (FAHS uhl) The remains or traces of a plant or animal that lived long ago (12, 13, 15)

instinct (IN stinkt) A behavior that an animal begins life with (6, 7, 8, 10, 15)

learned behavior (LERND bee HAYV yer) A behavior that an organism doesn’t begin life with (10, 15)

natural selection (NACH uhr uhl suh LEK shuhn) A process in which the healthiest organisms in an ecosystem are able to survive and reproduce (7)

What are some ways animals adapt to changes in their environment?

What parts of the body have birds adapted in order to survive?

How are the instincts of humans and other animals alike?

Pretend you are writing a speech to raise money for a project. The project will support the survival of animals. Tell your audience what humans can learn from animals.

With a friend or an adult, walk around the outside of your home or school. See if you can find any footprints or tracks in mud or cement. Try to guess where they came from. Now, think of a way to make your own handprint or footprint.

Look in your neighborhood for animal habitats. Can you find shelters for dogs, birds, or other animals? Make a list and talk to family members. Ask them to help you think of other shelters.

ISBN 978-0-15-362225-0ISBN 0-15-362225-3

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