AP BIOLOGY

Detailed explanation-1: -Reason: Bats and whales have a four-chambered heart.

Detailed explanation-2: -Crocodiles, birds and mammals have complete, four-chambered hearts.

Detailed explanation-3: -An eel-shaped, slimy fish, the hagfish is the only known extant animal to possess a skull but no vertebral column. Its strange, alienlike appearance likely contributed to its less-than-flattering name. In addition, it also contains four hearts, one more than the octopus or squid.

Detailed explanation-4: -In the four-chambered heart, the left half is completely separated from right half by septa. This prevents oxygenated and deoxygenated blood from mixing. This allows a highly efficient supply of oxygenated blood to all parts of the body. This is useful in animals that have high energy needs, such as birds and mammals.

Detailed explanation-5: -The four-chambered heart provides an efficient solution by keeping oxygenated and non-oxygenated blood separate. The supply of oxygen to the body can also be improved by increasing how often the heart contracts.