Annelids Chapter 37

What are they? Annelids are round, worm-like animals that have long segmented bodies.

The classes Class Oligochaeta Class Polychaeta Class Hirudinea Earthworms Class Polychaeta Bristle worms Class Hirudinea Leeches

Feeding & Digestion They take in food by a pump-like organ (pharynx), which sucks in dirt and forces it into the intestines. They are a kind of detrivore animals that consume decomposing organic material

Respiration These organisms take in oxygen and give off carbon dioxide through their skin This process is called diffusion. Skin must be moist to exchange gas. They will die if their skin dries out.

Circulation Closed circulatory system Aortic arches (heart): Completely contained in blood vessels Transport oxygen, CO2, nutrients and waste through the body Aortic arches (heart): 5 pairs of muscular tubes

Annelid Diagrams

Response Cephalization Cerebral ganglia- chain of ganglia connected by a ventral nerve cord that respond to light, touch, temp., moisture. Etc. Sensory nerve in each segment of the body Send sensory signals to the cerebral ganglia (brain)

Movement Hydrostatic skeleton Two major muscle groups are used in movement. The longitudinal muscles run from front to rear and allow the animal to get longer or shorter. The circular muscles go around the body segments next to the epidermis and allow the organism to get skinnier and fatter.

Reproduction Earthworms are hermaphrodites. The clitellum secretes a cocoon for the eggs. A ciliated larva called a Trochopore larva.

Earthworms Mating

How do they benefit society? condition the soil burrow through the ground and aerate the soil grind and digest the decaying plants and animals help return nitrogen back to the soil

Excretion They excrete undigested food through their anus. The nephridium removes the nitrogen and H2O from the body.

Worm Anatomy