Worms

1. Worms 27-1, 27-2,27-3 BIO 1004

2. Flatworms • Softand flattened • Have tissues and internal organ systems • Known as “acoelomates” – means without coelom • Coelom – fluid filled body cavity • Contain “flukes” which are parasitic and tapeworms

3. Characteristics of Flatworms • Carnivores/decomposers/parasites • Single opening through which food and waste pass (like cnidarians) • Most have NO circulatory system – rely on diffusion to move materials • Have “flame cells” that help remove excess water from the body

4. Cont. Flatworms • No true brain, but a connection of ganglia cells • Nerve cells • Have an eyespot • Most are hermaphrodites • Usually two worms will deliver sperm to each other and eggs are laid and hatch a few weeks later • Also can reproduce by fission

5. Roundworms (27-2) • Un-segmented with tapering ends • Contain “pseudocoeloms” – false coelom • Have two openings – mouth and anus • No circulatory/respiration system – diffusion • Sexual reproduction – internal fertilization • Ex: hookworms, filarial worms,etc.

6. Annelids (27-3) • Derived from the latin word “annellus” – means little ring • Body divided into segments called “septa” • Segments can carry specialized features such as eyes, antennas, sense organs, etc. • Have a true coelum • Mouth and anus

7. Cont. annelids • Closed circulatory system • Possess a crop and gizzard • Aquatic annelids have gills and terrestrial annelids exchange gases through their skin • Sexual reproduction • Clitellum secretes a mucus in which the sperm and eggs are released into

8. Groups of Annelids • Oligochaetes – earthworms – few setae • Leeches • Polychaetes – blood worms and sand worms