One very special feature in the earthworm $Pheretima$ is that
A
It has a long dorsal tubular heart
B
Fertilisation of eggs occurs inside the body
C
The typhlosole greatly increases the effective absorption area of the digested food in the intestine
D
The S-shaped setae embedded in the integument are the defensive weapons used against the enemies
The answer is C.
Solution
A characteristic feature of the intestine of the earthworm, after the 26th segment, is an internal median fold of the dorsal wall called the typhlosole. The typhlosole increases the effective area of absorption in the intestine. This statement is correct. The earthworm has a closed circulatory system with blood vessels and lateral hearts in segments; a long dorsal tubular heart is a feature of the cockroach. Fertilisation and development take place outside the body, within the cocoon deposited in the soil. The S-shaped setae help in locomotion, not in defence. Hence the special feature is the typhlosole that increases the absorptive area of the intestine.
ConceptTyphlosole
Earthworm in past papers
6 questions from this chapter have appeared across 4 exam years.
