Question

In which one of the following option excretory organs are correctly stated against the given organism?
A. Human – Kidneys, sebaceous glands and tear glands
B. Earthworm – Pharyngeal, integumentary and septal nephridia
C. Cockroach – Malpighian tubules and enteric caeca
D. Frog – Kidneys, skin and buccal epithelium

Answer 1

Hint: The body of an organism can have multiple organs that are used for the excretion of different waste products. The waste product can be in the form of uric acid, ammonia, urea, amino acids, gaseous matter, etc. The excretory organs of an organism may be found in most of the segments of their body.

Complete answer:
Nephridia are the excretory organs of an earthworm. They are tube-like porous structures that are present in almost all the segments of the earthworm’s body.

Based on their position in the body, they can be of three types – septal, pharyngeal, and integumentary.
> Septal Nephridia
They are the largest nephridia in an earthworm. They are arranged in two rows and each septum contains around 80-100 such nephridia.
These nephridia help in discharging waste into the lumen of the intestine.

> Pharyngeal Nephridia
Pharyngeal nephridia are present on the 4th, 5th, and 6th segment of an earthworm. They discharge the waste into the pharynx and the buccal cavity. The waste is then passed out from the anus.

> Integumentary Nephridia
The integumentary nephridia are present in the 7th to the last segment of an earthworm. They facilitate the discharge of nitrogenous waste outside the body.

Hence, the correct answer is option (B).

Note: Nephridia are present in all the segments of an earthworm except for the first three. The nephridia are supplied with capillaries and glandular cells from which the nitrogenous waste and water are extracted. Urea forms the major component of the total nitrogenous waste of earthworms. This means that they are ureotelic organisms.