Vol 5 World of Reptiles ... Introduction ... How reptiles are related to other animals
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Introduction

How reptiles are related to other animals

Reptiles are more advanced than amphibians, like frogs, but are less advanced than birds and mammals.
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The animal world is made up of lower animals (usually classed as animals without backbones) and higher animals. This second group of animals ranges in complexity from primitive types of fish up to primates like gorillas and humankind.

The most primitive higher animals live in water, and the transition from water to land is seen in the amphibians, a group of moist-skinned animals which still depend on water, especially for nuturing their eggs. Biologists consider the reptiles slightly more advanced than amphibians because they do not depend on water to reproduce. The reptiles successfully made the complete transition from water to land and are found in some of the driest places on earth. Some reptiles do choose to live in water, but these groups have probably evolved in turn from land-dwelling ancestors.

Reptiles are considered less advanced than the birds and mammals which evolved from them: this is because birds and mammals are both warm blooded and have a more efficient circulatory system. Although dinosaurs were a group of reptiles, they may have been warm blooded, and may have been the direct ancestors of the birds.