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Before we get started

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

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Before we get started

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

  2. 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

  3. Earthworm

  4. Giant Gippsland Earthworm of Australia

  5. External Anatomy

  6. Internal Anatomy

  7. Musculature • *Cuticle-  thin external layer. • *Epidermis- outer cellular layer • Circular muscle layer • Longitudinal muscle layer

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

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

  10. Earthworm Digestion Animation • http://www.ncsu.edu/scivis/lessons/earthworm/Overview.html

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

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

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

  14. 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.

  15. What happens when an earthworm is cut in half? • Can it form two separate worms? • most organs are in anterior • can regenerate a new posterior • posterior end can not regenerate a new posterior • so, no you don't get two new worms.

  16. Photographs, Images and text adapted from • http://images.google.ca/imgres?imgurl=http://kentsimmons.uwinnipeg.ca/16cm05/16labman05/lb6pg2_files/earthworm2.bmp&imgrefurl=http://kentsimmons.uwinnipeg.ca/16cm05/16labman05/lb6pg2.htm&h=480&w=640&sz=901&hl=en&start=4&tbnid=Rvj5IZLbr72DvM:&tbnh=103&tbnw=137&prev=/images%3Fq%3Dearth%2Bworm%26gbv%3D2%26svnum%3D10%26hl%3Den%26sa%3DG

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