Question

Which is correct about earthworms?
A. It can crawl on the smooth surface easily.
B. It secretes cocoon around unfertilized eggs.
C. It has a brain but no head.
D. It has no locomotory organs.

Answer 1

Earthworm is a terrestrial invertebrate that lives in the upper layer of moist soil.
It is reddish-brown in colour. They have long cylindrical bodies which are divided into hundreds of small segments that are similar to each other.

Complete answer: Earthworms have long cylindrical bodies. Its body is divided into more than hundreds of small segments which are similar to each other. The dorsal surface of the body is marked by a dark median mid-dorsal line along the longitudinal axis of the body. The ventral surface is differentiated by the presence of genital openings or pores. The anterior end of the earthworm body consists of the mouth and the prostomium, a lobe which serves as a covering for the mouth and as a wedge to force open cracks in the soil which the earthworm may crawl. The very first segment of the body is known as peristomium which consists of the mouth. Earthworms have a brain that connects with the nerves from their skin and muscles but does not have a distinct head. The setae help in the locomotion in the earthworm. They secrete cocoons around the fertilized egg.
Hence, the correct answer is option C.

Note: Other morphological features includes:
i. Four pairs of spermathecal apertures are placed on the ventral-lateral sides of the intersegmental grooves.
ii. A single female genital pore is present in the midventral line of 14 segments.
iii. A pair of genital pores are present on the ventral-lateral sides of the 18 segment.
iv. Setae are S-shaped and are present in the body segments except for the first, last and clitellum.