Animal
Animals live everywhere. They roam the land. They burrow in the ground. They swim in the sea. They fly through the air. They creep, they leap, they soar, and they dive. A very few—including corals and barnacles—stay in one place.
Animals come in all sizes. The biggest animals are whales, which can be 100 feet (30 meters) long. The smallest animals can only be seen through a microscope.
Zoologists (scientists who study animals) have found more than 2 million species (kinds) of animals. They think they have discovered only a small portion of all animals on Earth.
Several things make animals different from other living things. Unlike plants, animals cannot make their own food. Animals eat other living things—plants and other animals—to get energy. Animal bodies are made up of more than one cell, unlike bacteria and other life forms with only one cell. Cells are the building blocks of living things. Animals also have senses, such as eyes or ears, that tell them what is going on around them.
WHAT KINDS OF ANIMALS ARE THERE?
Zoologists divide animals into about 30 groups. First, they divide them by whether they have a backbone. Animals that have a backbone are called vertebrates. Animals that do not have a backbone are called invertebrates.
The biggest and best-known animals are vertebrates. Mammals, birds, reptiles, amphibians, and fish are vertebrates. You are a vertebrate. Your backbone is also called your spine. There are about 40,000 species of vertebrates.
There are far more species of invertebrates. Even though you can probably think of many vertebrates, the many kinds of invertebrates greatly outnumber vertebrates. Almost all invertebrates are small animals. Insects, spiders, mollusks, and worms are all invertebrates. The biggest invertebrate is the giant squid. It can be up to 60 feet (18 meters) long.
COLD-BLOODED AND WARM-BLOODED ANIMALS
Zoologists divide vertebrates into two types, cold-blooded and warm-blooded animals. The body of a cold-blooded animal is the same temperature as the air or water around it. A cold-blooded animal has to stay in the sun to get warm. It must find shade to cool off. Reptiles, amphibians, and fish are cold-blooded.
The body of a warm-blooded animal stays about the same temperature all the time. Warm-blooded animals use food energy to stay warm. Some warm-blooded animals can sweat to cool off. Birds and mammals are warm-blooded.
You are warm-blooded. The normal temperature of your body stays at about 98.6° Fahrenheit (37.0° Celsius). When it is hot outside, you feel hot. You might sweat or look for an air-conditioned place. But your body temperature does not change. When it is cold outside, you feel cold. You might put on a coat or go indoors. But your body temperature does not change much.
PLANT EATERS AND MEAT EATERS
All animals eat plants, other animals, or the remains of dead animals. Animals that only eat plants are called herbivores. They eat seeds, nuts, grasses, stems, or flowers. Some mammals, such as cows, are plant eaters. Some insects, such as termites, only eat plants. Bees, moths, and butterflies suck nectar from flowers.
Animals that only eat meat are called carnivores. The meat can be from other living animals or animals that have died. Many meat eaters hunt the animals that they eat. Sharks go after smaller fish. Lions and wolves hunt deer and other mammals. Owls swoop down on rabbits, squirrels, rats, and mice. Some frogs and lizards zap insects with their sticky tongues. Hyenas and vultures mainly eat animals that are already dead.
Animals that commonly eat both animals and plants are called omnivores. Bears and opossums are omnivores. Humans are omnivores. They eat fruit, vegetables, fish, chicken, and steak.
HOW ANIMALS BREATHE
All animals must breathe oxygen to stay alive. They must breathe out a waste gas called carbon dioxide.
Some animals breathe through lungs. Lungs take oxygen out of air. Cattle, dogs, cats, whales, people, and other mammals breathe through lungs. Birds and reptiles also breathe air through lungs.
Lungs cannot take air from water. Seals, whales, dolphins, and other mammals that live in water breathe through lungs. They can stay underwater a long time because they can hold their breath for a long time.
Sharks and other fish breathe through gills. Gills take oxygen out of water. Snails, slugs, clams, squids, octopuses, and other mollusks breathe through gills. Crabs, crayfishes, lobsters, and shrimp have gills. Gills cannot take oxygen out of air.
Some animals breathe through their skin. Insects have small holes in their bodies called spiracles. Air comes in through the holes. Oxygen from the air goes through tubes to all parts of an insect’s body.
Amphibians, animals that live on land and in water, can also breathe through their skin. Amphibians also may have lungs or gills or both.
Lion
What if you could yell to a friend who lived several miles away—and your friend could hear you? That is how loud a lion can roar! No wonder this mighty animal is called the king of beasts.
Lions are big cats. Along with tigers, lions are the world’s biggest and strongest cats. There are two kinds of lions, African and Asian lions. Lions live on grassy plains, savannas, and dry woodlands in Africa and India. They do not like to live in jungles and thick forests.
MASSIVE BODIES
Lions have huge shoulders, strong front legs, and powerful jaws. Their paws have long, sharp claws. To keep its claws sharp, a lion draws them in when not in use.
Male lions are large and powerful. They weigh from 330 to 550 pounds (150 to 250 kilograms) and stand about 4 feet (about 1.2 meters) tall at the shoulder. Female lions are smaller than males.
FUR AND MANE
The fur of grown-up lions can be light tan to reddish-brown. Lions have darker fur on the backs of their ears. Their tails have a tuft of darker fur on the end.
Male lions grow a kind of fur collar called a mane. The mane grows around their head, neck, and shoulders. The mane becomes darker and fuller as the lion gets older. It makes a lion appear larger and fiercer to opponents.
Cubs, or baby lions, have fur dotted with many spots. The spots help them hide from enemies in brush and clumps of grass. The spots fade as the cubs grow up.
WHAT IS A PRIDE?
Lions live in groups called prides. There are as many as 35 males, females, and cubs in a pride. All the females in a pride are related. The females in the pride hunt together and care for cubs together.
The males in a pride are not always related. Males join a female pride to mate and produce cubs. Males do not help care for cubs. Males patrol their territory. They try to keep rival males away from their pride.
When female cubs grow up they stay with the pride. Males must leave the pride.
HUNTING AND EATING
Female lions do most of the hunting. Lions like to hunt at night. They hunt alone or in groups. A lion alone often hunts smaller prey such as hares or warthogs. The lion slowly and silently stalks the animal. If the prey sees the lion and runs, the lion usually gives up. When the lion gets close enough, it suddenly runs for the prey. It grabs the animal with its teeth and claws, pulls it to the ground, and kills it.
Groups of lions hunt large prey, such as buffalo, zebras, and even giraffes. A group of lions may surround an animal to trap it. Some lions may drive the animal toward waiting lions. Two or more lions grab and bring down the animal. Lions also steal prey killed by other animals, such as hyenas.
The pride eats together. Males eat first. Then the females eat. Cubs eat last.
A HARD LIFE
Lions do not have an easy life in the wild. They starve when they cannot find food. They get injured or killed while hunting or fighting with each other. They suffer from diseases.
Males have bloody fights. Younger males challenge older males for leadership of a pride. Sometimes they drive the older males away.
Females fight with the new males. The new males try to kill cubs that were fathered by the other males. Females are too small to fight male lions one on one. But the pride females may join together to save their cubs.
Male lions only live about 10 years in the wild. Females live a little longer. In zoos where they are cared for and cannot fight, lions may live as long as 25 years.
THREATS TO LIONS
Lions once roamed all over Europe, Africa, the Middle East, and Asia. People have hunted and killed lions since ancient times. They have also hunted the animals lions need for food. In many places, people have destroyed the areas where lions lived by building towns, roads, and farms.
There are about 100,000 lions left in the world. Only a few hundred Asian lions live in India. Most lions live on game reserves in Africa. Thousands of lions also live in zoos and circuses around the world.