Annelids are segmented worms that can be found in marine, freshwater and terrestrial habitats.
Structurally, annelids are quite advanced despite their simple appearance.
They have a closed circulatory system, highly developed internal organs, a complete digestive system and
nervous system, and some species even have highly developed eyes.
They achieve locomotion by alternating the contraction of circular and longitudinal muscles.
These contractions are also responsible for the odd wriggling movements of worms when crossing sidewalks.
Annelids range from being filter feeders to predators.