AP BIOLOGY

Detailed explanation-1: -A four-chambered heart separates oxygenated blood coming from the lungs from the partially deoxygenated blood that heading back to the lungs to be re-oxygenated. This ensures that mammalian tissues only receive oxygen-rich blood, allowing for more sustained physical activity with fewer intervals of rest.

Detailed explanation-2: -The characteristics that make a mammal a mammal include pres-ence of hair or fur, warm-blooded, young born alive, mammary glands and complex brain.

Detailed explanation-3: -As mammals, we have four main parts to the heart, a left and a right atrium and a left and a right ventricle. This is called a four-chambered heart. Other mammals and birds all have four-chambered hearts.

Detailed explanation-4: -Mammals, like birds, possess a four-chambered heart. Mammals also have a specialized group of cardiac fibers located in the walls of their right atrium called the sinoatrial node, or pacemaker, which determines the rate at which the heart beats.