Annelids

Segmented worms.Albert Gordon

Jacob Cole

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Types Oligochaeta: Earthworms

and other terrestrial worms; chaetae (chitin bristles), no parapodia

Polychaeta: Marine worms that are free or tube living; parapodia

Hirudinea: Leeches and other flat annelids with no chaetae

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Body Formation Annelids are

Coelmates which means that they have a fluid filled cavity completely surrounded by tissue

In mature form, annelids are long with ridged segments in their skin.

Range from 1mm to 3m in length

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Body Formation (cont) Bilateral Symmetry Hydrostatic skeleton; supported by septa

between segments

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Nervous System Cerebral Ganglia That’s it. They’re not exactly intellectuals…

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Digestive & Excretory Has mouth and anus; a digestive

tract extends along length of worm. Metanephridia (same neph as in

nephron of the kidneys in humans) parallel to worm’s digestive tract filter blood and coelomic fluid. Waste secreted through exterior pores

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Circulatory Closed circulatory system Many hearts Blood vessels wrap around the digestive tract

in loops

Albert Gordon

Reproductive System Cross-fertilizing hermaphrodites Secrete mucous cocoon in which embryos

develop Some can also reproduce asexually via

fragmentation

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More Facts Earthworms are beneficial to

farmers because castings (egested materials) are valuable as a fertilizer and help recycle soil.

Hirudinea or leeches are still used in medicine today to neatly drain blood from wounds

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Quiz Questions1. Annelids are:

a. pseudocoelomatesb. coelomatesc. acoelomates

2. Annelids live in all of the following environments EXCEPT:

a) seawaterb) freshwaterc) damp soild) inside the human body

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Quiz Questions Continued3. Which of the following do NOT have a closed circulatory

system (select all that apply):a. Nematodab. Annelidac. Cephalopodsd. Arthropods

4. Annelids can reproduce by which of the following processes?

a) Self-fertilizationb) Cross-fertilizationc) Fragmentationd) All of the above

Jacob Cole

Citations All information from Chapters 32 and 33 of

Textbook (Biology 7th Edition, Campbell, Reese)

The End

Yay!