Question

The excretory structure in Amoeba is
(A)Food vacuole
(B)Contractile vacuole
(C)Gas vacuole
(D)None of these

Answer 1

Hint: The excretory structure in Amoeba is a specialized type of vacuole which helps in regulating the amount or quantity of water which should be present there in the cell. Like other vacuoles, it is also oval in shape.

Complete answer:
The contractile vacuole is essentially a water bubble within the endoplasm of A. proteus. Its function is to manage the water content of the cell. It's also a way of excreting its waste from the cell (out through the cell membrane) via diffusion. Even if the contractile vacuole is absent, the amoeba may burst.

Additional Information: An amoeba is also called an amoeboid, which is a type of cell or unicellular organism which has the ability to change its shape, primarily by extending and retracting pseudopods.
As osmotic pressure is to be maintained, to regulate osmotic pressure in amoeba's, most freshwater amoebae have a contractile vacuole that expels excess water from the cell. The freshwater has a lower concentration of solutes such as salt than the amoeba's own internal fluids (cytosol).
Without a contractile vacuole, the cell would fill with excess water and, eventually, burst, because the surrounding water is hypotonic with respect to the contents of the cell, water is transferred across the amoeba's cell membrane by osmosis.
The food on which the amoeba feed mostly varies. Some amoebae are predatory and can survive by consuming bacteria and some other protists. Some are detritivores and eat only the dead organic material.
So, the correct answer is ‘Contractile vacuole’.

Note: Contractile Vacuole is not present in every amoeba. The contractile vacuole is absent in the case of the marine amoebae because the solute concentrations inside the cell are in balance with the concentration of the surrounding water.