Question

Give the characteristic features of the following citing one example of each
a. Chondrichthyes and Osteichthyes
b. Urochordata and Cephalochordata

Answer 1

a.

Chondrichthyes	Osteichthyes
A class of cartilaginous fishes found in marine habitats.	All the bony fishes found in both freshwater and marine habitats.
Endoskeleton is made up of cartilage.	Endoskeleton is made up of bone.
Do not have operculum.	Have operculum.
Mouth is ventral.	Mouth is terminal.
Air bladder in absent.	Air bladder is present.
Have placoid scales.	Have cycloid/ ctenoid scales.
Undergo internal fertilisation.	Undergo external fertilisation.
Many of them are viviparous.	Mostly oviparous.
Example: Scoliodon.	Example: Exocoetus.

b.

Urochordata	Cephalochordata
Notochord is only present in the tail of the larva.	Notochord extends from head to tail region.
Have open circulatory system.	Have a closed circulatory system.
Adults are sedentary.	Adults are motile.
Larva undergo retrogressive metamorphosis.	Larvae undergoes progressive metamorphosis
Example: Ascidia.	Example: Branchiostoma.