I learnt in biology that the annelids were the first animals on earth that developed segmentation. By that, we mean that an organism can develop different parts of the body to have different functions. For example, sensory organs can develop in the front segment. Organs that help with gathering food can develop around the mouth.
Annelida in animal evolution to a higher stage of development is the beginning of higher invertebrates. About 9,000 species. Vitro secretion of epidermal cells from the cuticle, body wall muscle and a one outer longitudinal muscle layer within. Worldwide distribution, found in various habitats, especially in the ocean, in fresh water or wet soil.