Temperature is the most ecologically relevant environmental factor. The average temperature on land varies seasonally, decreases progressively from the equator towards the poles and from plains to the mountain tops. It ranges from sub-zero levels in polar areas and high altitudes to more than 50°C in tropical deserts in summer. These variations in temperature affect the distribution of animals on the Earth. Some animals can tolerate a wide range of temperature, such animals are termed as eurythermal animals. While others which can tolerate a narrow range of temperature are termed stenothermal animals.
Animals also shows various adaptations to suit their natural habitats. For example, animals found in colder areas have shorter ears and limbs that prevent the loss of heat from their body. This rule is known as allen’s rule. Animals found in Polar regions or cold conditions have thick layers of fat below their skin and thick coats of fur to prevent the loss of heat. These all adaptations help the organism to survive in the adverse conditions of their habitat.
Organisms exhibit different behavioural changes to adapt to their natural habitat. The changes in the behaviour of an organism that help it to escape environmental stresses are called behavioural adaptations. For example, desert lizards are termed as ectotherms as they cannot regulate their body temperature. So, they show various behavioural changes to escape temperature variations. For example, . Desert lizards and snakes bask in the sun during early morning and burrow themselves in the sand during afternoons to escape the heat of the day. Certain endothermic animals (warm-blooded animals) such as birds and mammals escape cold and hot weather conditions by hibernating during winters and aestivating during summers respectively.
Water is an important component and scarcity of water forces an animal to undergo various adaptation methods. Animals found in deserts such as desert kangaroo rats, lizards, snakes, etc. are well adapted to stay in their habitat. The kangaroo rat stays in burrows during the day to avoid water loss through evaporation. They conserve water by excreting highly concentrated urine. Reptiles like the Texas horned lizard have thick and tough integument that doesn't let water out. Desert mammals have fewer sweat glands than their counterparts in less extreme environments. Such adaptations can be seen to prevent the loss of water.
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