Question

Contractile vacuole in protozoa Amoeba is meant for
A) Respiration
B) Excretion
C) Locomotion
D) Osmoregulation

Answer 1

Hint:Contractile vacuole is defined as an organelle which helps in expelling and removing the excess water from the cell and protects the cell from excessive expansion. Contractile vacuoles are mainly present in protozoans and other aquatic animals like sponges.

Complete answer:
These protozoans are organisms mainly living in freshwater, so the concentration inside the cell is more than surrounding, so the water flows from the external environment to inside of the cell where the process is called osmosis. The excessive entry of water that occurs inside the cell may result in expansion so contractile vacuoles expels entry of excess water by contracting the cell.

Now let us collect answer from given options:
A) Respiration : There is no specialised structure in protozoa for respiration , these occur through general body surfaces.
B) Excretion : The process of excreting nitrogenous waste occurs through the general body surface.
C) Locomotion : Locomotion that is movement takes place with the help of cilia and flagella. With the help of these they move from one place to another.
D) Osmoregulation : when protozoa excrete it also helps to maintain ionic balance that is osmoregulation. along with water other amounts of substances such as ammonia which are soluble in water are also extracted or expelled out of the cell. The function of contractile vacuole occurs in a periodic cycle by collecting water

Thus the correct answer is option ‘D’ i.e, osmoregulation.

Note:One should not confuse vacuole with contractile vacuoles. Where vacuoles perform function is the storage of food or water. Contractile vacuoles are also called as pulsatile vacuoles where their function is to maintain osmoregulation