1. Annelids
Section 29.2

2. Segmented worms Coelomates 2/3rds are marine
Each segment contains digestive, excretory, circulatory and locomotor organs and is separated from other segments by septa
Some segments also contain areas responsible for specific functions such as reproduction, feeding or sensation
A primitive brain – the cerebral ganglion – is located at the anterior end, with a nerve cord that runs the length of the body

3. Key Characteristics Coelom – located inside the mesoderm
Organ systems – including a closed circulatory system and a one-way gut with specialized organs
Bristles – stiff, external setae which provide traction for crawling; some also have fleshy legs called parapodia

4. Marine Worms The largest group of annelids Have parapodia for movement
Many are burrowing; some secrete a glue-like material that sticks grains of sand together to make a tube
Some are free-swimming predators

5. Marine Tube Worms glue grains of sand together to make their tubes

6. Marine Feather Duster Tube Worms

7. Marine bristle worm with parapodia

8. Earthworms No parapodia Only a few seta on each segment
No eyes, but they do have light and touch sensitive areas on each end of their bodies
Highly specialized scavengers
Body shape is maintained by a hydrostatic skeleton
They are hermaphrodites

9. Earthworms are hermaphrodites but don’t fertilize their own eggs

10. Leeches Have suckers at each end Most are predators or scavengers
Some are parasites of vertebrates or crustaceans
No seta or parapodia
No internal segments

11. Leeches can be useful medicinally