Previous Year Question
With reference to ‘earthworms’, which of the following statements is/are correct?
Earthworms improves soil fertility and are known as farmer's friends.
Earthworm has two pair of hearts.
Select the correct answer from the code given below:
Only 2
Neither 1 nor 2
Both 1 and 2
Only 1
Correct Answer: D
Detailed Solution
Statement 1 is correct. Earthworms make burrows in the soil and increase its porosity and aeration. This improves the movement of air and water through the soil and creates favourable conditions for root development. They consume and decompose dead organic matter, while their casts help increase available nutrients and organic matter in the soil. Because of this beneficial role, earthworms are known as ‘Farmer's Friends’.
Earthworms are also used in vermicomposting, in which organic waste is converted into nutrient-rich organic manure. This can improve soil structure, microbial activity and nutrient availability.
Statement 2 is incorrect. In Pheretima, the earthworm commonly studied in Indian zoology, there are not two but four pairs of pulsatile hearts. Two pairs of lateral hearts occur in the 7th and 9th segments, while two pairs of lateral oesophageal hearts occur in the 12th and 13th segments. These assist the movement of blood between the dorsal and ventral blood vessels.