fish, amphibians, and reptile

FISH, AMPHIBIANS, AND REPTILES

Nearly all big animals are vertebrates, or backbone animals. They are a very succesfull group. Their body chemistry works fast. Many are very active. They have developed body shapes and limbs to move in water, on land, and in the air. They have the biggest brains an include the most intelligent animals. Fish, amphibians, and reptiles are “cold-blooded”. Bird and mammals maintain their own body temperature.

Vertebrates first evolved in the water. Later they colonized the land. Over hundreds of millions of years they have developed efficient boddies, brains, and method of reproduction, putting them in a position of dominance over all other life on the planet.

1.             Fish

They are two main groups of fish. The cartilaginous fish include the sharks and rays.  They have rough skins with scales like little sharp teeth. In many ways they seem to be “ old –fashioned” fish, and some have hardly changed for millions of years. But there still over 600 species, among them the biggest fish of all, the plankton-eating whale shark.

  

2.             Amphibians

Amphibians  include frogs, toads, newts, and salamanders.

They are mosthly land animals, but their lives are tied to the water. They lay their eggs in the water and these developed into tadpoles, which swim and have gills to breathe. Later the tadpoles developed legs, lose their gills, and developed lungs. At this stage, as tiny frogs or newts, they move to the land. Even then, they mostlyinhabit damp places, because their smooth, slimy skins are not waterproof. The advantage of these skins is that they ca be used for breathing, which means they are able to help out the simple lungs.  

3.             Reptile

Turtles, crocodiles, snakes, and lizards are all reptiles. Reptiles evolved from amphibians and in several ways are better at the job of living on land. Among other things their legs are generally longer and stronger, and their lungs are more efficient. But perhaps the two most important improvements reptiles have made are in their skins and in their skins and in their breeding. Reptile skins are dry, scaly, and quite waterproof. Reptiles do not need damp place. Many live in deserts. They do not need water to breed either. Unlike the soft amphibian egg thet has to developed in water, a reptile egg has a hard or leathery shell, and is laid on land. From this hatches out the young, which is a small replica of its parents. 

(encyclopedia of science-plants and animals)