Question

The main features of fish.  How can fish be described according to examples of representative species, basic morphology, skin, respiration, circulation, nitrogen waste, thermal control and types of reproduction?

Answer 1

Fishes are classified into two main classess.1.Osteichthyes 2.Chondricthyes

Representatives species are :

Chondrichthyes-shark,rays,

Osteichthyes-sardines,tuna,salmon

Basic morphology	hydrodynamic body, chondrichthyes-cartilaginous skeleton,mouth on ventral side of the head. osteichthyes-bony skeleton,mouth on terminal end of the head.
Skin	osteichthyes-cycloid and ctenoid scales and glandular epidermis chondricthes-placoid scales
Respiration	through gills,branchial respiration
Circulation	closed,incomplete,two chambered heart
Nitrogen waste	Chondrichthyes-Urea Osteichthyes-Ammonia
Thermal control	Heterothermic
Types of reproduction	Sexual Chondrichthyes-internal and Osteichthyes-external