How to classify annelids and linear animals?

It can be distinguished by the following points:

1, body type

Linear animals are slender and cylindrical, with tapering ends and no division.

Annelida has a slender body, which consists of many similar ring-shaped parts.

2. Body shape and structure

The body wall of linear animal phylum is composed of three layers of germ layers, with protocytoma, and the digestive tract is not curved, with the front end being the mouth and the back end being the anus;

The body wall of annelids consists of three layers of germ layers and has a true cavity. Colonoma is a cavity surrounded by the lumen layer in the body wall and the lumen layer in the intestinal wall.

3. Excretion system

Linear animals have excretory organs-anus. Starting from linear animals, anus appears in the digestive tract, which has two openings: mouth and anus. Food passes through the mouth, pharynx, intestine and rectum, and then is discharged from the anus, so that the digested and absorbed food is no longer mixed with the newly entered food, which is more perfect and more differentiated than the incomplete digestive system, which is of great significance in evolution.

The excretory organ of annelids is the posterior renal duct, and the typical posterior renal duct is a tortuous tube, one end of which opens in the anterior body cavity and is called the renal foramen, with a ciliated funnel, and the other end of which opens on the body surface of the body segment as the renal foramen, so that excreta can directly enter the tube from the renal foramen, with high efficiency.

4. Ordinary animals

Common linear animals such as vinegar nematodes, hookworms, pinworms, roundworms, filariasis, trichuris, Trichinella spiralis, etc.

Common annelids, such as earthworms, leeches and nereis.

References:

Baidu Encyclopedia-Linear Animal Gate?

Baidu encyclopedia-annelids