Question

Give reasons for the following.
Aquatic animals are more comfortable in cold water than in warm water.

Answer 1

Hint: Consider the difference in the solubility of dissolved oxygen in cold water and in warm water. Aquatic animals also need oxygen for survival. But aquatic animals cannot simply breath the oxygen from air, through lungs as, along with oxygen, water will also enter the lungs. Aquatic animals have gills, through which oxygen dissolved in water, enters the blood.

Complete answer:
Aquatic animals are more comfortable in cold water than in warm water. This is because the solubility of oxygen in water increases with decrease in temperature. The amount of dissolved oxygen per unit volume is more for cold water than for warm water. Thus, in cold water, aquatic animals can breathe easily whereas in warm water, breathing for aquatic animals is difficult.
Thus, aquatic animals can breathe easily in cold water containing more amount of dissolved oxygen than in hot water containing less amount of dissolved oxygen.

Additional Information: Generally Aquatic animals cannot breathe through lungs. They need gills for breathing. If aquatic elements had lungs, then they would become useless in the first breath itself as water would enter the lungs.

Note: Almost all the Aquatic animals have gills that are made from several thin filaments. Gills contain blood vessels. These gills help aquatic animals to breath. When water containing dissolved oxygen reaches gills, the oxygen is transferred to blood present in the blood vessels in the gills.