1. In Phylum Porifera organisms possess a water transport system or canal system where water enters through minute pores called ostia lining the body wall through which the water enters into a central cavity (spongocoel) and goes out through the osculum.
2. This water transport system is helpful in food gathering, circulation, respiration and removal of waste.

Phylum: Ctenophora
(G. Ktenos -comb; phoros -bearing)
Ctenophora are exclusively marine, radially symmetrical, diploblastic animals with tissue level of organisation. Though they are diploblastic, their mesoglea is different from that of cnidaria. It contains amoebocytes and smooth muscle cells. They have eight external rows of ciliated comb plates (comb jellies) which help in locomotion, hence commonly called comb jellies for Sea Walnuts.

(i) Cartilaginous fishes live in marine
(ii) Notochord is persistant
(iii) Placoid scales cover the skin
(iv) Caudal/tail fish in hetero cercal (asymmetrical both externally and internally)
(v) Modified teeth from placoid scales in the mouth ventrally founed directed backwards
(vi) Jaws are powerful and are predaceous animals
(vii) Lamelli form gills without operculum perform respiration
(viii) Heart is two chambered
(ix) Kidneys are mesonephric and ureotelic
(x) Blood retains urea to maintain the osmotic concentration of the body fluids
(xi) Animals are poikilothermic, viviparous and unisexual
(xii) Pelvic fins serve as claspers to aid in copulation and fertilization is internal
Eg: Scoliodon (Shark, dog fish) Trygon (sting ray) and Pristis (saw fish).

1. The vertebrates have notochord during embryonic stage. In adult, it is replaced by vertebral column.
2. They have paired appendages.
3. The skin is covered by protective skeleton like scales, feathers, hairs, claws, nails etc.
4. Respiration is by gills, skin, buccopharyngeal cavity and lungs.
5. They have a ventral heart with two, or three or four chambers.

1. They are marine, sessile, pelagic or free swimming.
2. Body is unsegmented and covered by a test or tunic.
3. Adult forms are sac like.
4. Coelom is absent.
5. Notochord is present only in the tail region of the larval stage.
6. Heart is ventral and tubular.
7. Nerve cord is present only in the larval stage.
8. They are hermaphrodites and development is indirect with a free swimming tadpole larva.
9. Retrogressive metamorphosis is seen e.g:Ascidian