1. Phylum Annelida

2. Eating and pooping (Digestive System)
Annelids have a 1 way digestive system. This means they have a mouth, and a separate anus.
Earthworms: eat dirt though its mouth, stores it in its crop, then grinds it around in its gizzard to break down organic material. This organic matter is then absorbed in its intestine after which it poops the dirt from its anus.
Leeches: use suckers at both ends of their bodies to hold onto their prey, then sharp mouth “blades” to slice open its skin and drink its blood.
Bristly marine worms have a variety of eating styles depending on their food of choice. Some are predators and carnivores, some filter feed, while others grave on plant matter.

3. Breathing (Respiratory System)
Annelids usually breathe through their skin (though some aquatic examples have simplified gills)
For a surface to be good for respiration it must be moist (like the inside lining of out lungs) so even terrestrial annelids are a bit wet to the touch.
Gills
Pompeii Worm

4. Moving stuff around (Circulatory System)
Annelids have a closed circulatory system
The heart of an annelid is actually a long series of connected tubes that spans across a few body segments at the anterior (head) end of the worm.

5. Peeing (Excretory System)
Annelids collect the waste from their cells in a series of tubes called nephridia (which is the same thing molluscs use)
Each body segment has it’s own nephridia, and the waste then empties out of the tube through the skin (like sweat! Worms are covered in pee-sweat ALL THE TIME)

6. Thinking & Sensing (Nervous System)
Annelids have teeny weeny clusters of nerves that we call a brain near their anterior end.
Some have specialized tentacles, antennae, eyespots or chemical receptors to sense the world around them (this varies species to species)
Antennae
A species of bristly marine worm

7. Sex (Reproductive System)
Most annelids perform some sort of internal fertilization
Earthworms: Usually hermaphrodites. Store sperm of other worm in mucus filled clitellum. This slips off to form cocoon
Leeches: Usually hermaphrodites
Bristly marine worms: Usually have separate sexes
Clitellum
Two earthworms fertilizing each other