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Having realized that the a biotic conditions of many habitats may vary
drastically in time, we now ask–how do the organisms living in such
habitats cope or manage with stressful conditions? But before attempting to
answer this question, we should perhaps ask first why a highly variable
external environment should bother organisms after all. One would expect
that during the course of millions of years of their existence, many species
would have evolved a relatively constant internal (within the body)
environment that permits all biochemical reactions and physiological
functions to proceed with maximal efficiency and thus, enhance the overall
„fitness‟ of the species.
This constancy, for example, could be in terms of optimal
temperature and osmotic concentration of body fluids. Ideally then, the
organism should try to maintain the constancy of its internal environment (a
process called homeostasis) despite varying external environmental
conditions that tend to upset its homeostasis. Let us take an analogy to
clarify this important concept.
Suppose a person is able to perform his/ her best when the temperature is
250C and wishes to maintain it so, even when it is sportingly hot or
feelingly cold outside.
It could be achieved at home, in the car while travelling, and at
workplace by using an air conditioner in summer and heater in winter. Then
his/ her performance would be always maximal regardless of the weather
around him/her. Here the person‟s homeostasis is accomplished, not
through physiological, but artificial means. How do other living organisms
cope with the situation? Let us look at various possibilities. Mammals from
colder climates generally have shorter ears.