Question

This is the figure of a typical annelid earthworm. Identify and label the parts A to H

Answer 1

Pheritima is an invertebrate which belongs to the Annelida. The body is externally segmented and has a tube within a tube form. The segments are called setae. It feeds on organic plants and microbes. It feeds through its mouth and excretes through the anus.

Complete answer:
The earthworm is a terrestrial organism and is found in soil. It respires through the moist skin and has its digestive system located throughout the body. It has a closed circulatory system and the transport system is made up of coelomic fluid. There are several chemoreceptors around the mouth.

The major parts of the earthworm as shown in the question are-
A) Mouth- It is the part through which the food enters the body.
B) The central nervous system comprises two ganglia that is one above the mouth and the other on either side of the segment.
C) Nerve rings-These are present in the 3 and 4 segments around the pharynx. They are ring-like spherical in shape.
D) Pharynx- It is the portion behind the mouth where food is swallowed.
E) Aortic arch- It is called the heart. It is the organ for circulation.
F) Blood vessels- They help in the transport of blood. There are three vessels- The aortic arch, dorsal blood vessel and ventral blood vessel.
G) Crop- It is the storehouse of the food. The food passes through the oesophagus and stored in a crop.
H) Gizzard- It is the digestive organ in the earthworm. It exhibits strong contractions which help in grinding the food with the help of mineral particles taken along with the food.

The detailed diagram of the earthworm is shown below.

Note: The excretory system consists of nephridia which are present in every segment except the first and the last. The gaseous exchange is carried out with the help of moist skin. The blood contains haemoglobin where the oxygen dissolves and is transported. Earthworms are hermaphrodites.