Animals are divided into invertebrates and vertebrates The

• Animals are divided into invertebrates and vertebrates. • The invertebrates are the animals that do not posses a backbone or vertebral column while the vertebrates do. • Vertebrates are usually larger than the invertebrates and have a more complex body organization and structure. • It includes mainly five classes: amphibian, fishes, reptiles, birds and mammals.

Amphibians • They have a smooth, scales-less and moist skin and legs • When they are larvae, they live in water and use gills to breathe. • When they become adults, they will live on land have lungs and moist skin for breathing. • They carry out external fertilisation. • They are cold-blooded that their body temperatures changes with the surrounding.

Fishes • They live in water and their bodies are covered with wet scales. • They have gills for breathing and fins for swimming that can maintain balance. • They carry out external fertilisation. • They are cold-blooded.

Reptiles • • They have a hard, dry scaly skin. They use lungs for breathing. They carry out internal fertilisation. The females lay eggs on land which enclosed in hard shells. • They are cold-blooded.

Birds • Their bodies and legs are covered with feathers and dry scales respectively. • They have lungs for breathing. • They have a beak but no teeth. • Their forelimbs are modified to wings. • They carry out internal fertilisation and their eggs are enclosed in chalky shells. • They are warm-blooded that their body temperatures are constant and are independent of the surrounding temperature.

Mammals • • They have hair on their skin. They use lungs for breathing. They have a diaphragm. They carry out internal fertilisation and the young are born alive. -Babies are developed inside the body of the mother with the embryo. -Young are fed on milk with their mothers’ mammary glands. • They are warm-blooded.

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Ichthyosaurus were a kind of animals that living in the sea which belonged to reptiles. They looked like dolphins and their bodies were well-designed that suitable for them to swim. Their speed was so high even though they weighted about 3 tonnes. Most of the Ichthyosaurus were used to catch fishes with their sharp teeth and long mouth. They can produce fertile offspring by borning the babies alive in the sea.