Orthodox sections and their significance? The one that is the same and the different is more primiti

Annelid. Except for the first two segments and the last segment, the rest of the segments are basically the same in morphology, which is called the isorhythm segment.

This is a relatively primitive segmentation phenomenon. The number of segments in annelids varies from species to species, ranging from a few segments to hundreds of segments. The segmentation of the animal's body is distinguished not only from the external morphology, but also from the internal to the arrangement of the internal organs.

Excretory system, nervous system of annelids.

The circulatory system, etc., is arranged repeatedly according to the links. The emergence of somites makes the movement of the animal body more flexible, and the functional division of the somites in different parts will appear, which is very necessary for the formation of the head, chest, abdomen and appendages related to the joints in the evolution of animals.

Which school? Do you want to take zoology?

The same rhythm is more primitive.

Homorhythmic segmentation begins with annelids, and except for the first two segments and the last segment, the rest of the somites are basically the same in morphology, which is called homorhythmic segmentation.

Heterorhythmic segmentation begins in the phylum Arthropod, and the somites are further differentiated, and the morphological structure of each somite is significantly different, the somites of different parts of the body complete different functions, and the internal organs are also concentrated in a certain somite, which is called heterorhythmic segmentation.

Orthorhythmic segmentation has certain limitations, such as.

1. It is not conducive to the transportation of substances in the body cavity.

2. It restricts the development of organs and the space for movement.

3. It reflects the low function of head regulation.

As for the heterorhythmic segmentation, it is developed on the basis of the homorhythmic segmentation of annelids.

In other words, the morphological differentiation and functional division of different parts of the body segment form the body regions (tagma), such as the head, thorax and abdomen. The segmentation phenomenon is conducive to the enhancement of motor ability, which not only makes the overall movement flexible, but also can move locally or independently for each segment.

Isorhythmic subsections: annelids.

Except for the first two segments and the last segment, the rest of the segments are basically the same in morphology.

Heterorhythmic segmentation: The somites are further differentiated, the morphological structure of each somite is significantly different, the somites of different parts of the body complete different functions, and the internal organs are also concentrated in a certain somite.

The body segments of different parts of the heterorhythmic segmentation showed morphological differentiation and functional division of labor, forming body regions. The segmentation phenomenon is conducive to the enhancement of motor ability, which not only makes the overall movement flexible, but also can move locally or independently for each segment, and enhances the ability to exercise and avoid the environment.

Therefore, the isorhythm segmentation is a further evolution of the isorhythm section, which is higher than the isorhythm section.

Encyclopedia: Dividing the same law.

Heterorhythmic segmentation.

The phenomenon of somites refers to the phenomenon of dividing the body of an animal into a certain number or an indefinite number of somites.

When each segment has approximately the same structure (e.g., primitive ring worms), it is called a homorhythmic somite. The structure of multiple somites in the head, thorax and abdomen of tube-dwelling polychaetes is significantly different from each other, that is, the somites are differentiated from each other, which is called heterorhythmic somite.