Vertebrate animals

1. Fish are cold-blooded animals, since their body temperature varies according to the temperature of the environment.
2. Some fish have bodies which are covered with scales which overlap towards the tail.
3. Fish have fins which help them to swim and change direction.
4. Fish use gills to get oxygen from water. Gills are covered by a hard cover called an operculum.
5. The body of fish is streamlined in order to help them to move smoothly in water.
6. Most fish breed by laying eggs.
7. The body of a fish is covered by some mucus material which reduces resistance when it is swimming.

Most of the animals in this group live in water at the early stages of their development. Examples of the animals found in this group are frogs and toads. Frogs live in water and toads live on land but lay eggs in water. Most frogs lay eggs in fresh water. Eggs hatch into larvae. A larva is also called a tadpole, which lives in water and breathes by using gills. When the tadpole grows in size, legs and lungs develop. At this stage, the frog can live on dry land.

1. Amphibians have soft and moist skin which is used for gaseous exchange.
2. Amphibians have tympanic membranes on each side of the head just behind the eyes. These are used for hearing.
3. Amphibians have gills during their early stage. Gills help them to breathe. At maturity, they use lungs and skin to breathe.
4. Amphibians are cold-blooded. Their body temperature changes according to the temperature of the environment. This condition is termed as poikilothermic.
5. Amphibians have four limbs. The fore limbs are shorter than the hind limbs.
6. Each limb has five digits which are joined together by webs.
7. Most amphibians lay eggs in water, but some amphibians give birth to young ones. An example of an amphibian that gives birth to young ones is the Kihansi toad.
8. Amphibians have a wide mouth which helps them to swallow food very fast and easily.

Most of the members of this group of animals live on dry land and very few live in water. Examples of the reptiles that live on dry land are lizards, snakes, tortoises and chameleons. Examples of the reptiles that live both in water and on land are crocodiles, turtles, some snakes and monitor lizards. Some of the animals in this group such as lizards and monitor lizards have legs. However, some reptiles such as snakes do not have legs and they move by crawling. Most reptiles live and lay their eggs on land. Others such as turtles live in water but lay their eggs on land.

1. The skin of reptiles is dry and it is covered with scales.
2. Many reptiles have streamlined bodies from the head towards the tail.
3. Their tails are long and thin.
4. Some reptiles, for example snakes, do not have limbs. They move by crawling.
5. Some reptiles have limbs with five clawed digits which help them to move.
6. The mouths of reptiles are wide and elongated.
7. Most reptiles lay eggs.
8. The body temperature of reptiles changes with that of the environment. Therefore, they are cold-blooded animals.
9. Reptiles use lungs to breathe.

Birds are animals with a vertebral column and feathers. Some are domestic birds while others are wild birds. Examples of domestic birds are chickens, ducks, pigeons, guinea fowls and parrots. Examples of wild birds include kites, owls, eagles, pigeons, crows and ostriches. Most birds live on land, but some spend most of their time in water.

1. Birds have a streamlined body shape which helps them to fly with minimum resistance. The middle part of the body is broader than the head and the tail.
2. The body of a bird is covered by feathers which help in insulating the body. The feathers also prevent water from reaching the skin.
3. Birds have wings with long feathers which help them to fly. However, there are birds which do not fly. Examples of birds which do not fly include penguins, ostriches and kiwis.
4. A bird's beak is tough and elongated. Some birds such as flamingos and hornbills have very long beaks, while others such as ducks and doves have very short beaks with sharp ends.
5. All birds have two legs which have scales and each leg has four digits with tough claws.
6. The temperature of the bird's body does not change with that of the environment. This means birds have constant body temperature; thus, they are called warm-blooded animals. This condition is termed as homoeothermic. The average bird's body temperature is 40°C.
7. Birds reproduce by laying eggs.

Mammals constitute one of the groups of animals which have a vertebral column. Most of them reproduce by giving birth to young ones. Their bodies are covered by hairy skin. However, the amount of hair varies, depending on the type of mammal. Most mammals live on land. They use two or four legs to move. Some mammals such as bats can fly. Some mammals such as whales live in water. Examples of mammals are human beings, bats, whales, rats, elephants, dogs, donkeys, lions, horses, zebra, leopards, kangaroos, cows, goats, baboons and sheep.

1. Mammals feed their young with milk from their mammary glands.
2. Mammals have ears which are visible externally. The ears are large because they are used to pick up sound waves.
3. Their bodies are covered with hairs which conserve heat and maintain body temperature.
4. The skin of the mammals that live on land has sweat glands, which are responsible for producing sweat. The skin of whales does not have sweat glands because this animal lives in water.
5. Most mammals give birth to alive young ones. A few mammals such as echidnas and duck-billed platypuses lay eggs. Others such as kangaroos give birth to immature young which are reared in a special pouch found on their bodies.
6. Except for human beings that move by using two legs, mammals move by using four legs.
7. Most mammals live on land but a few live in water. Examples of mammals which live in water are whales and porpoises.
8. The temperature of the mammalian body does not change with that of the environment. Mammals can maintain a constant body temperature. This is a homoeothermic condition. This condition enables mammals to live in environments with different temperatures.
9. Mammals use lungs to breathe.