Practice question

Earthworms belong to Class Oligochaeta within Phylum Annelida meaning few bristles, characterized by reduced setae per segment typically four pairs, lack parapodia and head appendages, absence eyes, hermaphroditic system with clitellum secreting cocoon, primarily terrestrial and freshwater habitats with direct development lacking free larval stage. Exemplar Lumbricus terrestris shows over 100 metameric segments, closed circulation with five aortic arches as hearts, metanephridial excretion, cutaneous respiration, typhlosole. Oligochaeta contrasts markedly with Polychaeta bearing numerous chaetae parapodia separate sexes for marine life, and Hirudinea leeches lacking setae possessing suckers and fixed segment number throughout body.