Earthworms are tube-shaped, segmented worms that are commonly found in soils. They are one of the most important species in the food chain for both small and medium-sized animals such as fish, birds, and raccoons. They also help in the aeration and breaking down of soil while obtaining food from smaller organisms.

Snails' excretion organs originally were derived from the segmented worms' (Annelida) metanephridia. While water snails excrete a very much diluted primary urine, terrestrial pulmonate snails have developed the ability to resorb most of the water.