Question

Assertion: Most fish when out of the water die of suffocation.
Reason: Atmospheric air contains far less oxygen content than the dissolved oxygen in the water.
A. Both the assertion and the reason are true and the reason is a correct explanation of the assertion.
B. Both the assertion and reason are true but the reason is not a correct explanation of the assertion.
C. Assertion is true but the reason is false.
D. Assertion is false but the reason is true.

Answer 1

Fishes are aquatic animals. They respire through gills by inhaling dissolved oxygen in water. Amount of air is higher in air than in water but gills of the fishes collapse when they come out of water. This reduces surface area for absorption and causes death of the fish.

Complete answer:
Atmospheric air contains more oxygen than water. There is 21 percent of oxygen present in air while water contains 0.5-0.9 percent of oxygen. Volume of oxygen depends on the temperatures. Fishes respire through gills. It gets oxygen from water through tiny blood vessels spread over the surface area of its gill. When the fishes come out of the water gills stick together and blood vessels are no longer exposed to air. Due to this surface area for exchange of gases reduced. Due to this less oxygen enters into the fish body and causes suffocation. From the above information we have found that the assertion given in the question is true but the reason is false.
So, the correct answer is option C.

Note: Some fishes can respire on land taking oxygen from air. Mangrove Rivulus can live out of water and remain active for a long time. Species of fishes found on earth is more than mammals, birds, amphibians, and reptiles. There are more than 32000 types of fishes in the world. If there is not enough oxygen present in water fishes can drown too.