Before we get started  Anterior: head-end  Posterior: tail-end  Dorsal: top-side  Ventral: bottom-side

Phylum Annelida  many marine, freshwater, and terrestrial worms  Ex) leeches and earthworms  “segmented worms” –division of rings or segments  septa/septum (walls) separate segments  setae: small, bristle-like appendages

Earthworm

Giant Gippsland Earthworm of Australia

External Anatomy

Internal Anatomy

Digestive System  obtain food by eating through and taking nutrients from soil

 Mouth  Pharynx  Esophagus  Crop: storage compartment.  Crop: storage compartment.  Gizzard: soil ground up and churned  Intestine: digestion and absorption occur  Anus: Undigested material is voided

Earthworm Digestion Animation  m/Overview.html m/Overview.html m/Overview.html

Respiratory System  All annelids live in moist environments –most are aquatic. –most are aquatic.  earthworm can survive only in damp soil.  earthworm can survive only in damp soil. –Gas exchange occurs at body surface through diffusion –No lungs!

Circulatory System  closed system  five pairs of pseudohearts surround esophagus and pump blood  blood travels to dorsal vessel

Nervous System  Cerebral ganglia acts as “brain”  Prostomium: tongue-like lobe above mouth, allows earthworms to “feel” through soil

Reproductive System  Earthworms are hermaphrodites –male and female reproductive organs present in each individual –cross fertilize  mate by attaching at clitella, exchanging sperm, then seperating – sperm stored while clitellum secrete a mucous cocoon –cocoon slides along worm to collecting sperm and also eggs –slips off worm's head –embryos develop in cocoon.