Phylum- Annelida

http://kentsimmons.uwinnipeg.ca/16cm05/16labman05/lb6pg2_files/earthworm2.bmp

Phylum Annelida• This phylum consists of the segmented worms• The members of this phylum live in three

different environments:– Freshwater– Saltwater– On land

• This phylum consists of three classes:– Class Oligochaeta– Class Polychaeta– Class Hirudinea

Term “Annelid”

• The term annelid means little rings• This is referring to the many body segments

found in members of this phylum

All (approximately 15,000) members of this phyla have:

1) Bilateral Symmetry2) A true coelom3) Segmentation4) All three germ layers

a) Endodermb) Ectodermc) Mesoderm

Coelom and the 3 Germ Layers:

Coelom: a fluid filled cavity within the mesoderm

Evolutionary more advanced

• The presence of a true coelom, three germ layers and all organ systems makes the annelids the most advanced of all the worm phyla

• Setae or parapodia:– These structures are found on the outside of each

body segment– The presence or absence of parapodia groups the

annelids into 3 classes; also, the number of setae per segment is used for this function