Phylum Annelida Phylum Annelida p. 594-600

Characteristics Segmented worms Cylindrical Less than ½ mm  3 metres 3 germ layers, bilateral, coelomate Vary in colour, patterning, & other superficial features Many segments are separated by internal walls (septa) Includes: C. Polychaeta – sandworms, bloodworms C. Oligochaeta – Earthworms C. Hirudinea - Leeches

Body Systems Digestive System: Herbivores, carnivores, & detritus feeders Two openings More complex For example - Earthworm: Mouth  pharynx  esophagus  crop  gizzard  intestine  anus

Mobility: Respiration: 2 muscle groups: longitudinal muscles & muscles that circle the body Respiration: Some aquatic use gills Some respire through their skin using diffusion Note: Terrestrial annelids require moist skin so secrete a cuticle.

Internal Transport: Closed circulatory system Blood moves to head through dorsal blood vessel Blood moves to tail through ventral blood vessel Blood moves through body by one of two methods: Muscle contractions “hearts” (larger ring vessels) that pump

Excretion: Response: Solid wastes via anus Liquid wastes (metabolic wastes) by nephridia Response: Well developed nervous system 2 large nerves connected to a brain by a pair of ganglia From ganglia, ventral nerve cord runs the length of the body Variety of sense organs

Reproduction: Most sexual Few asexual (budding) Separate sexes & external fertilization Hermaphroditic & internal fertilization Few asexual (budding)

Ecological Role Human parasites (leech) Leeches in medicine Bloodletting Reattachment & skin grafts As a food source To condition & aerate the soil (ex. Earthworms)