Intestinal roundworm (Ascaris sp.). Phylum Nematoda.
Roundworms are pseudocoelomates with organ-level organization. They exhibit a simple but complete digestive system and a large reproductive system. Both male and female anatomy are examined - roundworms are a nice example of animals that display sexual dimorphism.
This video was made by the teaching assistant (C. Ernst) for the students of Organisms II at McGill University, but is appropriate for any introductory-level zoology program.
Organisms II, 2012
