Transcript Phylum Annelida

Phylum Annelida
Earthworms and Leeches
About 9,000 species!
Segmentation
 Segmentation is also called metamerism.
 Segments each contain elements of such
body systems as circulatory, nervous, and
excretory tracts.
Setae…
 All annelids except leeches also have
chitonous hair-like structures, called
setae, projecting from their cuticle.
Metamerism
 Metamerism increases the efficiency of
body movement by allowing the effect of
muscle contraction to be extremely
localized.
More Characteristics
 Internal organs are well developed
 Digestive system is a complete tube with
mouth and anus
 Gases are exchanged through the skin
 Some have fairly well developed eyes
 Found throughout the world, in marine,
freshwater, and terrestrial environments
Earthworms…
 Oligochaetes feed primarily on detritus
and algae.
 Earthworms cycle huge quantities of soil
through their guts, a process that speeds
the turnover of nutrients in soil and
increases productivity.
 They also help to aerate soil.
Leeches
 Class Hirudinea
 Most are free-living and eat small
invertebrates, feeding on their blood
 Most live in freshwater environments,
although a few can live in terrestrial
environments
LEECHES!
 Small sucker in the anterior end and a
larger one in the posterior end
Hirudin
 Leeches secrete chemicals that prevent
the formation of blood clots into the
host's blood
 One of these chemicals, hirudin, is the
most powerful anticoagulant (substance
that prevents blood clots) known.