Annelida

Annelida, commonly known as segmented worms, is a phylum of invertebrate animals including earthworms, leeches, and marine polychaetes. They are characterized by their long, cylindrical bodies divided into segments, which facilitate movement and flexibility. Annelids have a distinct body plan featuring a coelom (a fluid-filled body cavity), a closed circulatory system, and a centralized nervous system. They play important roles in ecosystems, such as enriching soil and recycling nutrients. Some species can also be found in aquatic environments, contributing to the biodiversity of habitats. Their unique body structure and adaptations make them an important study in biology.