In this article we will discuss about:- 1. Origin of Cyclostomes 2. General Characters of Cyclostomes 3. Classification 4. Representative Types 5. Affinities. Origin of Cyclostomes: The Cyclostomata (Gr., cyklos = circular + stoma = mouth) are the living agnathans, they are primitive in many respects, but specialised in others. They are a modified and degenerate offshoot of the primitive [...]
In this article we will discuss about the external features of lamprey with the help of suitable diagrams. Also learn about its habit and habitat. Shape and Size: The body of adult Petromyzon is elongated, cylindrical and eel-like. Petromyzon marinus (sea-lamprey) attains a length of a metre, Lampetra fluviatilis (Lampern or common freshwater lamprey) reaches a length of about 90 [...]
The birds have an efficient circulation, a high rate of metabolism and a high and constant temperature. The birds and mammals are the only vertebrates that have a complete separation of the respiratory and systemic circulations, making possible a high arteriolar pressure, which allows materials to reach the tissues rapidly. The circulatory system of pigeon includes heart, arteries, veins, the [...]