Question

Which of the following statements is correct about the respiration of frog? (i) In frog, cutaneous and pulmonary respiration are found. (ii) A pair of elongated pink hollow lungs are found in thorax. (iii) During aestivation and hibernation, gaseous exchange takes place through skin. (a) (i), (ii) and (iii) (b) (i) and (iii) (c) (ii) and (iii) (d) (i) and (ii)

Short answer

(a) (i), (ii) and (iii)

Step-by-step solution

Identify the Correct Statements

Evaluate each statement given for its correctness based on biological knowledge of the respiration in frogs.

Statement (i) Analysis

Frogs perform cutaneous respiration through their skin and pulmonary respiration through their lungs. Since both types are mentioned, statement (i) is correct.

Statement (ii) Analysis

Frogs do have lungs which are elongated, hollow, and found in the thorax; therefore, statement (ii) is also correct.

Statement (iii) Analysis

During aestivation (summer sleep) and hibernation (winter sleep), frogs respire mainly through their skin because they are less active and their metabolism is slower, making statement (iii) correct.

Combining the Valid Statements

As all statements (i), (ii), and (iii) are correct about the respiration in frogs, the combined answer is option (a).

Key concepts

Cutaneous Respiration

Frogs have a unique way of breathing known as cutaneous respiration, where they utilize their skin to exchange gases with the environment. This process is possible due to the thin, moist skin that they possess, allowing oxygen to diffuse directly into their bloodstream and carbon dioxide to diffuse out.

During this mode of respiration, the skin must stay moist to enable the proper transfer of gases. This is especially important when frogs are in environments where lung breathing is not efficient, such as underwater or during periods of dormancy like aestivation and hibernation.

Pulmonary Respiration

In addition to cutaneous respiration, frogs also have the ability to breathe using their lungs, called pulmonary respiration. The lungs in frogs are relatively simple structures, elongated and pink, located in the thoracic cavity. They are not as complex as mammalian lungs but serve the essential function of enabling the frog to take in oxygen from the air and expel carbon dioxide.

Frogs depend on their lungs when they are active, particularly when outside of water. The combination of cutaneous and pulmonary respiration allows them to adapt to various environments and activities.

Aestivation

Frogs experience periods of inactivity during hot and dry seasons in a state called aestivation. It's a survival mechanism to conserve energy and moisture in unfavorable conditions. During aestivation, a frog's metabolic rate slows down significantly, and it seeks shelter in cool, moist places.

Throughout this time, the reliance on cutaneous respiration increases because the reduced activity level means a decreased need for oxygen. Frogs will bury themselves in mud or hide in other moist locations to maintain the necessary moisture for skin respiration and to protect themselves from the heat.

Hibernation

Hibernation is similar to aestivation, but it occurs during the cold winter months. This is a time when frogs enter a dormant state to survive the freezing temperatures and food scarcity. Just like during aestivation, a frog's metabolic processes slow, and cutaneous respiration becomes the primary mode of breathing.

Different from aestivation, hibernation often involves frogs being submerged in water or burrowed in soil below the frost line. Their ability to breathe through their skin is indispensable during these times as it allows for a low yet sufficient rate of oxygen intake without using their lungs, which are not functional in such low-temperature conditions.