Question

Describe the evolutionary changes in the pattern of heart among the vertebrates​

Answer 1

Answer :

The number of heart chamber and complexity increases with evolution.

(i) Two-chambered heart :

$\bigstar$ In fishes, the heart is two chambered, with an atrium and a ventricle. The heart pumps out only deoxygenated blood to the gills for oxygenation, i.e., there is single circulation.

(ii) Three-chambered heart :

$\bigstar$ In amphibians and reptiles (except crocodile), the heart is three-chambered, with two atria and a ventricle.

$\bigstar$ The left atrium receives oxygenated blood from lungs and the right atrium receives deoxygen-ated blood from all parts of the body. But in the single ventricle, the oxygenated and deoxygenated blood get mixed up and that is pumped to all parts of the body, i.e., incomplete double circulation.

(iii) Four-chambered heart :

$\bigstar$ In mammals and birds heart is four chambered with two atria and two ventricles. There is complete partitioning of deoxy-genated and oxygenated blood.

$\bigstar$ Two circulatory pathways, pulmonary circulation and systemic circulation, operate, i.e. there is double circulation

Answer 2

☯️ $\sf\underline\orange{ Evolution ~~of~~Vertebrate~~heart}$ :-

1. Heart is modified blood vessel.
2. It is clearly evident in the developmental stages.
3. In fishes these is a two chambered heart having an atrium and ventricle.The blood is sent to gills for oxygenation.As the blood passes through it is venous blood it is also called venous heart. The circulation is single circulation.
4. Amphibians have three chambered heart with two atria and one ventricle. It is the beginning of double circulation.
5. Reptiles also have three chambered heart but the ventricle is incompletely divided.
6. Crocodiles,birds and mammals have four chambered heart with double circulation i.e., having a seperate pulmonary and systemic circulations.

☃️$\huge\sf\fcolorbox{red}{turquoise}{Frozen~♡~}$☃️