Biology · Chapter 8
Study notes aligned to the official NEB syllabus.
The earthworm Pheretima posthuma is a common annelid studied as a representative invertebrate. Its new name is Metaphire posthuma.
The earthworm is cosmopolitan in distribution. It is very common in the moist soil of gardens and irrigated farms that are rich in decaying organic matter. It is cold-blooded and nocturnal. Its process of burrowing is peculiar.
It is a bilaterally symmetrical animal, cylindrical and elongated. A mature worm measures about 150 mm in length and 3 to 5 mm in width. The dorsal surface of the body is recognised by its darker colour and a mid-dorsal line.