Question

Nephridia are excretory organ of
(A) Protozoan
(B) coelenterates
(C) Flatworms
(D) Annelids

Answer 1

Hint: A flame cell is a specialized excretory cell found in the simplest freshwater invertebrates, including flatworms, rotifers and nemerteans . Bundles of flame cells are called ‘Protonephridia’. Flame cell is the simplest excretory organ. Earthworms have slightly more evolved excretory structure, occurring in pairs having tubule and cilia.

Complete answer:
Nephridia is an organ of invertebrates. It is found in pairs and performs a similar function as kidney in vertebrates. Nephridia remove metabolic wastes from an animal’s body. The excretory organs which occur as segmentally arranged coiled tubules are called Nephridia. It helps in osmoregulation. There are 3 type of nephridia :-
(a). Septal nephridia
(b). Integumentary nephridia
(c). Pharyngeal nephridia
(A). Protozoans have no excretory organ.
(B). Coelenterates also lacks excretory organs.
(C). Flatworms (Platyhelminthes) have flame cells, which act as excretory organs.
(D). Annelids have nephridia as an excretory organ.

Thus, the correct answer here is (D) Annelids.

Additional Information :-
In earthworm, the nephridia are generally grouped in pairs throughout the segment of the worm’s body. They are present in many different invertebrate lines. Nephridia removes metabolic wastes from an animal’s body. Each septum has 40-50 septal nephridia, arranged in two rows and 200-250 integumentary nephridia are located throughout the earthworm’s body wall.

Note:
Annelids have nephridia as an excretory organ. As it is clear from the step by step solution, that protozoan does not have an excretory organ and coelenterates too lack an excretory organ. Flatworms have flame cells which act as their excretory organ. ‘Annelids’ have nephridia to remove their metabolic waste.