annelids
biology project
what are annelids ?
annelids are a segmented worm of the phylum Annelida, such as an earthworm or leech.
polychaete
are a paraphyletic class of annelid worms, generally marine. Each body segment has a pair of fleshy protrusions called parapodia that bear many bristles, called chaetae, which are made of chitin.
oligochaeta
are a class of animals in the phylum Annelida, which is made up of many types of aquatic and terrestrial worms, and including all of the various earthworms.
echiura
The Echiura, or spoon worms, are a small group of marine animals. Once treated as a separate phylum, they are now universally considered to represent derived annelid worms, which have lost their segmentation.
polychaete
- The polychaetes are the largest and most primitive class of annelids, with more than 5300 described species, most of them marine.
- Although the majority are from 5 to 10 cm long, some are less than a millimeter, and others may be as long as 3 meters.
oligochaeta
- When oligochaetes mate, their anterior ends face in opposite directions. Their ventral surfaces touch. Sperm cells are released by both oligochaetes and held to each organism's body by a mucus cocoon. Egg cells are released into the mucus and fertilization occurs. The oligochaete sheds the mucous 'package' and new oligochaetes form.
echiura
the mouth can be bigger than the rest of the body
A digestive channel runs in full body length to the posterior end
characteristics
The fundamental characteristic of the phylum is the division of the body into a linear series of cylindrical segments, or metameres
they can be either herbivorous or carnivores
some physical are chaetae ( hairs made of chitin), segmentation, 3 cell layers, true coelom, head develops first ( protostomal)