Question

How many hearts are present in the blood vascular system of Pheretime Posthuma?
A. 6 pairs
B. 2 pairs
C. 1 pair
D. 4 pairs

Answer 1

Hint: Earthworms are organisms belonging t the phylum Annelida and their body is divided into segments that show metamerism, in the blood vascular system vessels are found which have hearts, intestines, and other organs. They are divided into 2 regions which are the region before the 13th segment and the region after the 13th segment.

Complete answer: In earthworm or Pheretime posthuma, a closed circulatory system is found in which the blood travels to the whole body in vessels.
Three types of vessels that are found in earthworms are the aortic arches, dorsal blood vessel, and ventral blood vessels.
The haemoglobin in earthworm does not travel via blood corpuscles and are dissolved in the blood plasma, this gives a distinctive red-colored appearance to the blood of earthworms.
The blood vessels are collecting and distributing types based on the function they perform. Hearts in the case of earthworm are present in the region lying before the 13th segment and they are found in 4 pairs.
In the segment after the 13th segment, the intestinal region is found.

Hence, the correct option is (D), 4 pairs.

Note: Unlike vertebrates only one heart is not resent in case of organisms like an earthworm, they have a blood vascular system of more than one heart as seen in the case of earthworm it has 4 pairs of heart. The blood travels via vessels and hence it is a closed system.