Question

Skin is an accessory organ of respiration in
A) Humans
B) Frogs
C) Rabbits
D) Lizards

Answer 1

The skin has several roles to play. First of all, it forms an impermeable protective layer against pathogenic organisms, dehydration, and even to some extent, against predators. In some animals, however, it may have functions like respiration.

Complete answer:
Depending on the kind of organism, the respiratory organs will differ. Tiny animals like insects have small openings known as spiracles that connect to a network of tubes which carry the oxygen through their bodies. As animals increase in size and complexity, such passive methods fall short, and more complex respiratory systems are required. Fish, for instance, carry out the exchange of gases in gills, which are richly supplied with blood vessels to absorb oxygen from the water.

Humans depend on lungs for their respiration. Air is inhaled and passes down through the upper and mid respiratory tract till it reaches the lungs. Within the lungs, there is an exchange of gases in structures called alveoli. Oxygen is taken up, and carbon dioxide is released from the bloodstream, and exhaled out to the atmosphere. All air-breathing vertebrates have lungs. Option A is incorrect.

Frogs, like other vertebrates, use their lungs to breathe when they are on land. The process is similar to that of humans and other animals. However, when they are submerged, their skin functions as a respiratory organ. Being richly supplied with blood vessels, and permeable to gases, this how the frog can breathe and stay underwater or hibernate for long periods of time. Option B is the correct answer.
Just like humans, rabbits are mammals and have a very similar respiratory system.Option C is incorrect.

Lizards are air-breathing reptiles. Some species of lizards and related animals like iguana are able to hold their breath for long periods of time, but they have to come to the surface to breathe using their lungs. Option D is incorrect.

Hence the correct answer is option ‘B’.

Note: Lower animals have different systems of respiration, which may not involve even gills or spiracles. Sponges, for example, absorb the oxygenated water directly through their ostia and into the cells.