Question

Assertion: Pila has dual mode of respiration.
Reason : Pila leads an amphibious life.
A. Both Assertion and reason are correct and Reason is the correct explanation for assertion.
B. Both Assertion and reason are correct but Reason is not the correct explanation for Assertion.
C. Assertion is correct but Reason is incorrect.
D. Assertion is incorrect but Reason is correct.

Answer 1

Hint: Pila is an aquatic gastropod commonly known as apple snail or pond snail. They live in lakes and ponds but can also live well on land.

Complete Answer:
Let’s analyse the question to find the correct answer.
- Pila is an amphibious animal. Pila performs aquatic respiration by gills. They have a single ctenidium situated on the right chamber of the mantle cavity or branchial chamber.
- The gill consists of numerous branchial lamellas which are composed of two layers of epithelia.
- When in water, the current of water which contains dissolved Oxygen is drawn into the mantle cavity of the Pila with the help of left siphon. This water flows through the gills which leads to the gas exchange between the water and the blood vessels of the gill.The water then gets expelled through the right siphon.
- When the oxygen concentration of water decreases,Pila comes to land and on the land they respire with the help of pulmonary sac.
- The pulmonary sac is a closed cavity with an opening called pneumostome. It’s a hanging structure from the left chamber of the mantle cavity.The dorsal wall of the pulmonary sac is highly vascular and helps in gaseous exchange.
- Pila respire through pulmonary sac in two ways; from land as well as from water by coming to the water surface to inhale atmospheric air.
- In conclusion, Pila have dual mode of respiration because they are amphibious animals.
Thus, both Assertion and reason are correct and Reason is the correct explanation for Assertion.

Hence the correct answer is option A.

Note: Siphons are tube-like structures present in molluscs in which water flows into. Apart from respiration, this water flow facilitates locomotion and feeding as well. Pila senses the oxygen levels of water with the help of osphradium, a comb like sensory organ.