A. Nearly all then plants and about 99% of animals cannot maintain a constant internal environment. Their body temperature is changes with the change in the surrounding not constant. Such organisms are conformers, for examples fishes lizards, frogs etc.
Organisms which are able to maintain constant internal environment (homeostasis) by physiological and behavioural means. They maintain constant body temperature by thermoregulation and osmoregulation. These organisms are regulators, for examples birds and mammals including humans.
B. Regulation of body temperature is a function of surface area. Since conformers have a larger surface area relative to their volume, they tend to lose body heat very fast when it is cold outside. They have to expend much energy to generate body heat through metabolism. This is the main reason why there more conformers than regulators in the animal world.
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