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Solve this: * a 2:49 a) In birds and mammals the heart is divided into four chambers compared to fishes and amphibia. Justify. b) Draw a sectional view of human heart and label the following parts. (l ) Chamber which receives the oxygenated blood. (2) Chamber which pumps deoxygenated blood to lungs. (3) The blood vessel which carries oxygenated blood to heart. (4)The vessel which carries oxygenated blood to different parts ofthe body.

Vertebrates include Pisces, Amphibians, Reptiles, Aves, Mammals. The design of the heart varies with the complexity of the organism. The two types of circulation are single circulation and double circulation.
Pisces (Fish heart): It is a two-chambered heart comprising one atrium and one ventricle. Gills help in purifying the deoxygenated blood.
Amphibian/Reptilian heart: It is a three-chambered heart which includes two atria and one ventricle. Here both oxygenated and deoxygenated blood gets mixed up with each other. Double circulation is seen in the organisms possessing this type of heart. Lungs are involved in purifying the blood.
Avian heart: Bird’s heart is a four-chambered heart and complex in its evolution. It pumps more blood than mammalian heart as birds require a lot of energy to fly high in the air
Mammalian heart: It is made up of four chambers which include two atria and two ventricles. The organisms with this type of heart exhibit double circulation. The deoxygenated blood is completely separated from the oxygenated blood completely. The atria and ventricles are separated by many types of valves which prevent the mixing up of pure blood from that of impure blood.
  
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