Question: Circulatory systems in organisms can be quite different, although they have similar functions. One difference is in the number of chambers in the heart of an organism. Discuss other differences and give examples of organisms that have different numbers of chambers in the heart.

Two chambers - fishes (atrium and ventricle)

three chambers - amphibians (two atria and ventricle)

also reptiles have three chambers with incomplete separation in ventricle

crocodiles, birds and mammals have four chambers - two atria and two ventricles (complete separation)

other differences: arthropods and many other groups of invertebrates have an open circulatory system which means that vessels are open and blood/other fluid circulates partially in body cavity