Knowra Annelid Annelid Annelids are segmented worms in the phylum Annelida, including earthworms, leeches, and polychaetes. Their bodies are typically divided into repeated segments.
Metamerism : The division of an animal’s body into a series of repeated segments. Annelid segmentation repeats muscles, nerves, and other structures along the body.
Earthworm : A terrestrial oligochaete annelid that feeds on soil and decaying organic matter. Earthworms mix soil and create channels that affect its structure and drainage.
Nematode : A roundworm belonging to the phylum Nematoda, with an unsegmented body and a tough outer cuticle. Nematodes resemble annelids in overall shape but lack their repeated body segments.
Lophotrochozoa : A major animal clade that includes annelids, mollusks, and several other invertebrate groups. Annelids belong to this broader branch of protostome animals.
Jean-Baptiste Lamarck : A French naturalist who developed an early theory of biological evolution and contributed to animal classification. Lamarck established the name Annelida for the group of segmented worms.
Coelom : A fluid-filled body cavity completely lined by mesoderm. In many annelids, the coelom forms compartments within successive segments.
Leech : A segmented annelid, often blood-feeding, with anterior and posterior suckers. Some leeches feed on vertebrate blood, while others prey on small invertebrates.
Platyhelminth : A flatworm in the phylum Platyhelminthes, typically with a flattened, unsegmented body. Flatworms are another familiar worm group, but their body plan lacks annelid segmentation.
Trochophore : A distinctive, often free-swimming larval form with a band of cilia around its body. Many marine annelids develop through trochophore larvae, linking their life cycles to other lophotrochozoans.
Charles Darwin : An English naturalist whose theory of evolution by natural selection transformed biology. Darwin studied earthworm behavior and documented its effects on soil formation.
Show all 26