The tailless Amphibia belonging to family of the real frogs conduct both a land, and water way of life. The frogs living in water raise the head over a surface for breath. Ambient temperature and the need for food force to stick near a surface of a reservoir to them also.
Respiratory organs of Amphibia to which number frogs belong are lungs, skin and gills. Unlike tadpoles who lead a water life at adult frogs of a gill are absent. The oxygen dissolved in water comes to blood of these creations through skin. Such way of breath can provide an organism with necessary gas only if the frog is in a condition of hibernation. An exception is a number of species of tailless Amphibia which organism is supplied with oxygen only due to gas exchange in skin. The grass frog, typical for Europe, during the summer period can exist due to skin breath no more than eight days. Having put out the head from water and having inhaled air, it resupplies oxygen in blood.
To keep at a water surface of frogs can force the need for a certain ambient temperature. In the spring and in the summer when Amphibia are especially active, the top water layers get warm sunshine better. It does a surface of reservoirs of more comfortable for amphibians. It is known that grass frogs fall into hibernation when water temperature falls to six or ten degrees. Lake go to hibernation at decrease in average water temperature to eight degrees. For spawning of a frog also choose the warmed most up sites of reservoirs. Insects play a significant role in food of frogs. The amphibians leading an overland life get the main part of a forage on the land. Vida, chosen reservoirs as the habitat, hunt insects, having put out the head over a water surface. During reproduction which frogs carry out in water also the amphibians living on the land act this way. An exception are types which adhere to a so-called "marriage post" at this time and do not eat.