Although Ascaris sp. and Earthworms are both nematodes, they have different digestive system. An earthworm has pharynx, esophagus, crop, intestine and gizzard. While the ascaris has only mouth, pharynx, intestine and rectum. It is because of their diet, or the type of food they ingest. The earthworms eat on sediments while an Ascaris sp. is a parasite of the intestine in humans and other animals.