Write examples of phylum Echinodermata.

Explanation

The general characters of phylum eclinodermata are as follows:
(i) The body has various shapes-star like, cylindrical, disc like or flower like.
(ii) The symmetry is radial in the adults and bilateral in the larvae.
(iii) The echinoderms are triploblastic animals and have organ system level of organisation.
(iv) Head is absent in echinoderms.
(v) Locomotion occurs with the help of tube feet (podia).
(vi) A true coelom is present. It contains a fluid with amoeboid cells. These cells are called coelomocytes.
(vii) In echinoderms, the digestive tract is complete except class ophiuroidea.
(viii)Respiration occurs by gills, called dermal branchiae in starfish, by peristomial.gills in sea urchins and by tube-feet in all.
(ix) The circulatory system is greatly reduced and open type. It is called haemal system. Respiratory pigment is absent in blood.
(x) Ammonia is the nitrogenous waste in echinoderms.
(xi) The nervous system includes a nerve ring and radial nerve cords. Brain is absent.
(xii) Sexes are separate but sexual dimorphism is absent. Fertilization is generally external. Some forms reproduce asexually by self-division.