Amphibians are creatures which spend part of their life in water and part of their life on dry land. Frogs, toads and newts all start their lives as eggs. They hatch out astadpoles which breath through gills. As they grow, they develop lungs and legs, and are able to leave the water and walk on land.
Amphibians consist of three groups of vertebrates: frogs, salamandersand caecilians (found in the tropics only). Amphibians have smooth, scaleless skin which is permeable to water. Water can evaporate easily from the skin, and an amphibian can dry up and die in a fewhours if it does not have access to water. Thus amphibians tend to be active at times when evaporation is minimized: at night and when it rains.
However, this same skin permeability makes it possiblefor amphibians to obtain moisture from sources besides pools of water. This means that amphibians can live in very dry climates, like deserts, and when the dry season arrives, they just burrowunderground and pull in moisture from the surrounding soil. Despite this, the amphibian's tie to water remains: their eggs must be laid in water in order to survive.
What is a fish?
A fishis any aquatic vertebrate animal that is typically ectothermic (or cold-blooded), covered with scales, and equipped with two sets of paired fins and several unpaired fins. Fish are abundant in the seaand in fresh water, with species being known from mountain streams (e.g., char and gudgeon) as well as in the deepest depths of the ocean (e.g., gulpers and anglerfish).
Food prepared from fish isalso called fish, and it is an important food source for humans. They are harvested either from wild fisheries (see fishing) or farmed in much the same way as cattle or chickens (see aquaculture). Theyare also exploited by recreational fishers and fishkeepers, and are exhibited in public aquaria. Fish have had a role in many cultures through the ages, ranging from deities and religious symbols...