Question

Why do fishes die when taken out of water?
A) Fishes respire with the help of gills
B) Gills are richly supplied with blood capillaries and can readily absorb oxygen dissolved in water
C) Both A and B
D) Fishes cannot tolerate the atmospheric air pressure

Answer 1

Hint: A fish's respiratory system allows it to spend its entire life in water. Fishes does not require to come to the surface of water frequently to breathe air. It gets the necessary required amount of oxygen from water through tiny blood vessels spread over the surface area of its gills and not from air.

Complete Answer:
To the concerned question,
1) Option A is fish respire with the help of gills and we all know this very well. It is the structure of gills that helps fish respire inside water. It cannot breathe through the atmospheric oxygen and hence the fishes die when taken out of the water.
2) Option B is gills are richly supplied with blood capillaries and can readily absorb dissolved Oxygen in water. This option is also correct in reference to the structure of gills. As earlier mentioned, structures of gills are responsible to help survive a fish underwater but it cannot help fish to sustain living out of the water.
3) Option C is both a and b and this will be the correct answer
4) Option D is fish cannot tolerate atmospheric air pressure. But this is not actually the case. Fishes die due to the cut off of oxygen supply.

Let us see how the structure of gills is to understand the answer properly: Gills, as we know are the organs that allow fishes to breathe underwater. Most fishes exchange gases like oxygen and carbon dioxide using gills that are protected under gill covers on both sides of the pharynx (throat).
Gills are tissues that are like the short threads, generally protein structures called filaments. These filaments have many functions including the transfer of ions and water, as well as the exchange of oxygen, carbon dioxide, acids and ammonia.
Each filament contains a capillary network that provides a large surface area for exchanging oxygen and carbon dioxide. Fish exchange gases by pulling oxygen-rich water through their mouths and pumping it over their gills.
When taken out of the water, gills (the respiratory organs of fishes) collapse due to which the fishes will not get oxygen further and later on this is the reason for why they die when taken out of the water.

Hence option ‘C’ is the correct answer.

Note: Gills are the respiratory organs for fishes. Without respiration and oxygen an organism cannot live for more than a minute and when a fish is taken out of the water, its supply of oxygen is cut off which leads to the death of fishes in just a few minutes after taking them out from the water.