1. Earthworms and Leeches
Phylum Annelida
Earthworms and Leeches

2. About 9,000 species!

3. Segmentation Segmentation is also called metamerism.
Segments each contain elements of such body systems as circulatory, nervous, and excretory tracts.

4. Setae…
                      
All annelids except leeches also have chitonous hair-like structures, called setae, projecting from their cuticle.

5. Metamerism
Metamerism increases the efficiency of body movement by allowing the effect of muscle contraction to be extremely localized.

6. More Characteristics Internal organs are well developed
Digestive system is a complete tube with mouth and anus
Gases are exchanged through the skin
Some have fairly well developed eyes
Found throughout the world, in marine, freshwater, and terrestrial environments

8. Earthworms… Oligochaetes feed primarily on detritus and algae.
Earthworms cycle huge quantities of soil through their guts, a process that speeds the turnover of nutrients in soil and increases productivity.
They also help to aerate soil.

10. Leeches Class Hirudinea
Most are free-living and eat small invertebrates, feeding on their blood
Most live in freshwater environments, although a few can live in terrestrial environments

11. LEECHES!
Small sucker in the anterior end and a larger one in the posterior end

12. Hirudin
Leeches secrete chemicals that prevent the formation of blood clots into the host's blood
One of these chemicals, hirudin, is the most powerful anticoagulant (substance that prevents blood clots) known.