Question

Blood vessels in pheretima, which have valves, are
a. Dorsal
b. Ventral
c. Supra-Oesophageal
d. Lateral Oesophageal

Answer 1

Hint: The earthworm is a terrestrial invertebrate that inhabits the upper layer of the moist soil. The common Indian earthworms are Pharethima and Lumbricus. Pherethima exhibits a closed type of vascular system. Blood is circulating to the heart and blood vessels.

Complete answer:
> Option A: Dorsal-
The earthworm is metamerically segmented nocturnal animals, live in burrows made in the soft, moist soil of lawns, gardens, forest, pastures, and the soil rich in decaying organic matter. They are rarely found in dry, sandy. They usually lie in the upper layers of soils.

Its body is elongated, 100-200 segmented cylindrical, and pointed at both ends. It measures about 150mm in length and about 3 to 5 mm in diameter. The first segment is called peristomium with an extension of fleshy lobe, prostomium, segments 14-16 are covered by clitellum.
> Option B: Ventral-
During the copulation, two earthworms are closely attached with each other by their ventral surfaces in such a way that the head region of one is opposite the tail region of the other

> Option C: Supra-oesophageal-
The cockroach brain (supra-oesophageal ganglia) sends out nerves to the compound eyes and antennae. The suboesophageal ganglion similarly supplies nerves to many of the mouthparts.

> Option D: Lateral oesophageal-
The mouth of the earthworm is situated on the ventral side of the first segment. It opens into the buccal cavity which lies in the first 3 segments. This opens into the pharynx situated in the fourth segment. From the 5th to 7th segment is the esophagus followed by a highly muscular structure known as gizzard situated in the 8th segment. From the 9th to 14th segments lies the stomach (12th and 13th segment called lateral oesophageal vessel). From the 15th segment until the last segment is the intestine.

Hence, the correct answer is option (A).

Note: Pheretima shows a closed type of blood vascular system, consisting of blood vessels, capillaries, and heart. Due to the closed circulatory system, blood is confined to the heart and blood vessels. Contraction keeps blood circulating in one direction. The earthworm moves by muscular contraction and expansion of the body aided by chitinous setae present in the body wall.