Question

Earthworms possess hearts
A. 6 pairs
B. 4 pairs
C. 2 pairs
D. 1 pair

Answer 1

Hint: Earthworm belongs to kingdom Animalia and phylum Annelida. The earthworm is an invertebrate. They are monoecious or hermaphrodite. Hermaphrodite means both male and female organs are present on the same individual. They possess tubular hearts.

Complete answer: In earthworm, the blood vascular system is of closed type in which the blood passes to the heart and blood vessels. An earthworm has four pairs of tubular hearts. These hearts are thick-walled, enlarged and have valves. In the 7th and 9th segments, two pairs of the heart are present on the anterior side and are known as lateral hearts. These lateral hearts connect the dorsal blood vessel with the ventral blood vessel. In the 12th and 13th segments, two pairs of hearts are present on the posterior side, they are called as latero-esophageal hearts. Latero-esophageal hearts are muscular, thick and have rhythmically contractile vessels. In each of the 10th and 11th segments, there is a pair of non-pulsatile, thin-walled, loop-like broad vessels that are present and are known as anterior loops. These vessels are without valves. Along the body of an earthworm, the blood flows in well-organized vessels. There are few prominent blood vessels such as dorsal blood vessels and ventral blood vessels. The dorsal blood vessel is the largest blood vessel running along the mid-dorsal above the alimentary canal. It has the presence of valves which prevents the backflow of the blood. The dorsal blood vessel receives blood from various body parts. The ventral blood vessel extends from one end of the body to the other end. This blood vessel doesn’t possess any valves. This blood vessel distributes blood to all body parts, it is the main disturbing blood vessel.
Hence, the correct answer is option B.

Note: The blood of earthworm consists of fluid plasma and colourless blood corpuscles (only leukocytes are present). The human blood consists of coloured respiratory pigment i.e. haemoglobin, which gives a red colour to the blood and also helps in the transportation of oxygen.