Describe the characteristics of phylum porifera,phylum …

Characteristics of Porifera:

(i) They are sessile, sedentary, and marine except one group that lives in fresh water. These are non-motile animals attached to some solid support.

(ii) Simplest multicellular, diploblastic animals.

(iii) The body design involves minimal differentiation and division into tissues.

(iv) Asymmetrical or radically symmetrical.

Example: Sponges and Sycon.

Characteristics of Annelida:

(i) Body triploblastic, bilaterally symmetrical, soft, elongated, vermiform and cylindrical or dorsoventrally flattened.

(ii) Exoskeleton absent; body is covered by a thin cuticle.

(iii) Alimentary canal is tube-like, complete and extends straight from mouth to ****.

(iv) Reproduction is by sexual means. Sexes may be united (hermaphroditic) or separate.

(v) True coelomate animals with closed blood vascular system. Coelom allows true organs to be packaged in the body structure.

(vi) They live in a variety of habitats. Mostly aquatic, marine or fresh water. Some are terrestrial, burrowing in tubes, some free-living forms.

Example: Nereis (sand worm) and Hirudinaria (leech).

• Echinodermata:

Characteristics of Echinodermata:

(i) Simple animals may be a star like, spherical or elongate.

(ii) Body triploblastic, coelomate, unsegmented and radially symmetrical.

(iii) Body lacks head but has oral and aboral surfaces. Oral surface of the body has five radial areas called ambulacra.

(iv) Body wall is covered with spiny hard calcareous (calcium carbonate) plates (ossicles) that forms a rigid or flexible endoskeleton.

Example: Echinus (sea urchin) and Asterias (star fish).