To survive and propagate further in any environment, organisms show one of the four possible ways, viz. regulate, conform, migrate and suspend.
(1) Regulate : In this method, organisms maintain homeostasis by physiological and behavioural changes. Due to homeostatic regulation, they can perform thermoregulation or osmoregulation.
E.g. All birds and mammals show constant body temperature and osmotic concentration irrespective of external temperature.
(2) Conform : Most of the animals and plants are unable to maintain a constant internal environment. Their body parameters change according to outside environment.
E.g. Poikilothermic animals cannot maintain body temperature but they are simple conformers. In few aquatic animals, the osmotic concentration of the body fluids changes according to surrounding osmotic concentration. Few conformers can regulate the parameters in limited range.
(3) Migrate : When organism is unable to cope up with surrounding temperatures, they migrate temporarily from such stressful habitat to a more favourable habitat. After the stressful period is over, they return back. Birds show long-distance migrations during severe winter.
(4) Suspend : Suspending the life activities for particular period is one of the methods to cope up with stressful conditions. Seeds of plants remain dormant over unfavourable period and once favourable conditions are resumed they start growing. This state is called dormancy during which metabolic activities are suspended. Hibernation and aestivation seen in some animals is also for escaping severe winter or summer respectively.
E.g. Polar bear shows hibernation while snails and fish show aestivation. These are also suspension measures.
