Question

Pheretima Posthuma (earthworm) is highly useful as
(a) Their burrows make the soil lose
(b) They make the soil porous, leave their castings and take organic debris in the soil
(c) They are used as fish meal
(d) They kill the birds due to the biomagnification of chlorinated hydrocarbons

Answer 1

Hint: Earthworm is an invertebrate which is terrestrial. It belongs to Opisthopora and consists of a tube within a tube body plane with segmented internal segmentation and setae on all the segments. They are commonly found in the soil and eat a variety of organic matter which includes plant matter, protozoa nematodes, bacteria, fungi, rotifers, and other microorganisms.

Complete answer:
Pheretima Posthuma is highly useful in making the soil porous, and they leave their casting and take organic debris in the soil. They are considered as the friend of farmers as they form burrows in the soil and penetrate the roots of the developing plants. They increase the fertility of the soil through the process of vermicomposting and feed on the dead organic matter present in the soil.
Earthworm excretes carbon dioxide and nitrogen is waste as their main waste materials and the carbon dioxide is excreted from the body through its moist skin which is known as diffusion. The nitrogenous waste is excreted from the body by special excretory organs which are known as nephridia. It is a tubular coiled structure which is a rounded funnel-shaped nephrostome. Nephrostome is opened in a coiled tube known as the nephridial tubule which is lined with cilia. It opens outside the body. The highest percentage of nitrogenous waste is excreted out from the body and the remaining fluid through the nephridiopore with movements of cilia.

So, the correct answer to this question is option (b) They make the soil porous, leave their castings and take organic debris in the soil.

Note:
There are over 6,000 species of earthworm worldwide and more than 180 species of earthworm are found in the US and Canada of which 60 are invasive species. They do not consist of lungs or other specialized respiratory organs and breathe through their skins which exude a lubricating fluid that helps in movement under burrows.