Question

Which of the following layers will you find in the body wall of the earthworm (from the outside to the inside)?
A) Non-cellular cuticle, epidermis, circular muscles, longitudinal muscles, coelomic epithelium
B) Cuticle, epidermis, longitudinal muscles, circular muscles, coelomic epithelium
C) Non-cellular cuticle, epidermis, coelomic epithelium, circular muscles, longitudinal muscles
D) Cuticle, epidermis, peritoneal muscles

Answer 1

Hint: Earthworms are segmented annelid worms, belonging to the class Oligochaeta. AS such, they do have a true coelomic cavity, and have an outer covering to protect them from drying in the soil.

Complete answer:
The correct answer is option (A). From outside to inside, the earthworm’s body wall consists of a cuticle, under which is the epidermis, then the two bands of muscle – circular and longitudinal, and finally the coelomic epithelium.
Option B is incorrect because even though the basic order appears to be the same, the positions of the circular and longitudinal muscles have been interchanged.
Option C is incorrect. The coelomic cavity has to be on the absolute inside of the earthworms’ body, and not the muscles. Coelom stands for the body cavity. It has to be lined by coelomic epithelium.
Option D is incorrect. The presence of the coelom has been completely ignored, and peritoneal muscles have been added when the earthworm does not have a peritoneum. That is found in higher animals.
Though the earthworm has a cuticle to provide protection against rough material and drying up, it still needs a fairly wet environment in order to survive. They are also essential for aerating and fertilising the soil.

Hence the correct answer is OPTION(A)

Note: The longitudinal and circular muscles help in locomotion of the earthworm. AS one type of muscle contracts, the earthworm’s body becomes shorter and fatter, to push against soil surrounding it. Then when the circular muscles contract, the earthworm elongates and pushes forward through the soil in front of it.