AP Biology help please? Thank you!

Compare and contrast the circulatory systems in endotherms and ectotherms.

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In fish the heart is called single circuit heart because it has one atrium and one ventricle, and there are gills as respiratory organ for gas exchange.
In amphibians, there are two atria, and one ventricle, and the circulation is double circuit, because of lungs.
In reptiles, ventricle is incompletely divided except in crocodiles where ventricle too has become completely divided. Circulation is double circuit.
In birds and mammals, heart is completely four chambered, and circulation is double circuit.