Read the passage carefully. Attempt the questions.

An overwhelming majority (99 per cent) of animals and nearly all plants cannot maintain a constant internal environment. Their body temperature changes with the ambient temperature. In aquatic animals, the osmotic concentration of the body fluids change with that of the ambient air and water osmotic concentration. These animals and plants are simply conformers. Considering the benefits of a constant internal environment to the organism, we must ask why these conformers had not evolved to become regulators. Recall the human analogy we used above; much as they like, how many people can really afford an air conditioner? Many simply 'sweat it out' and resign themselves to suboptimal performance in hot summer months. Very small animals are rarely found in polar regions. During the course of evolution, the costs and benefits of maintain in a constant internal environment are taken into consideration. Some species have evolved the ability to regulate, but only over a limited range of environmental conditions, beyond which they simply conform.

If the stressful external conditions are localised or remain only for a short duration, the organism has five other alternatives for survival.

Identify the animal which is NOT a conformer.

Polar Bear

The correct answer is Option (3) → Polar Bear

Some organisms are able to maintain homeostasis by physiological (sometimes behavioural also) means which ensures constant body temperature, constant osmotic concentration, etc. All birds and mammals, and a very few lower vertebrate and invertebrate species are indeed capable of such regulation (thermoregulation and osmoregulation).

Polar bears, are regulators. They maintain a constant internal environment (homeostasis) regardless of external conditions, through mechanisms such as thermoregulation. As mammals, they are endothermic (warm-blooded) and actively regulate their body temperature

Conformers are organisms whose internal conditions vary with external environmental conditions. They do not actively regulate their internal environment and adapt to the external changes. Examples include lizards and most ectotherms (cold-blooded animals).

Hummingbirds and shrews are conformers and are not able to maintain a constant internal environment. This is because, since small animals have a larger surface area relative to their volume, they tend to lose body heat very fast when it is cold outside; then they have to expend much energy to generate body heat through metabolism. This is the main reason why very small animals are rarely found in polar regions

Lizards are conformers, as their body temperature depends on the external environment.