Give an account on phylum Annelida.

Explanation

(i) The animals in phylum annelida are segmented worms.
(ii) Example: Earth worms, Leeches and a group of marine worms.
(iii) Segmented body shows metamerism which means the property of having repeated homologous organs in each segment.
(iv) The animals possess body cavity called coelom.
(v) Some organisms show movable bristles called setae.
(vi) They have no legs and no hard skeleton.
(vii) The body is covered by moist outer cuticle.
(viii) A thick multi layered structure, outside the epidermis provides protection.
(ix) They have a central nervous system with a brain.
(x) Metabolic wastes are removed by Nephridia.