Evolution of Penguins

Penguins have evolved in a complex and distinguishably different manner than most birds. This style of evolution raises uncertainty about their future. Unlike most birds, which have flexible elbow joints and wings for flight, penguins have evolved with virtually inflexible elbow joints and flippers with a hydrofoil shape, which allows them to propel underwater. Furthermore, penguins have short stalky legs and broad anklebones, which allow them to maneuver in water and have an energy efficient waddle on land. Also, penguins have dense waterproof feathers and a thick layer of subcutaneous fat to conserve body heat, a necessity in an aquatic environment where the rate of heat loss is 30% faster than in air. Penguin’s tuxedo is a camouflage that protects them from avian and aquatic predators. The white reduces their visibility at the waters surface and the black makes them resemble the oceans bottom. Penguin’s large body allows them to stay in the water longer with minimized heat loss due to their lower surface area to volume ratio. These are only some of the many unique characteristics of penguins.

The wing humerus arterial plexus (HAP), currently found in all living penguins, is a braided network of blood vessels that lie in the grooves of the humeral arterial sulcus. These vessels act as a counter-current heat exchange (CCHE), which is essential for penguins because their flippers only have a thin layer of subcutaneous fat and lose heat rapidly when exposed to the frigid water. Heat is transferred from warm arterial blood to the cold venous blood, which cools the outbound blood to the flipper and warms incoming blood to the body, which minimizes heat loss because the flipper has a larger surface area, less insulating fat and is completely exposed to frigid water therefore if the warm blood went to the flipper it would be lost to the surrounding environment. Overall, the CCHE conserves heat loss to the aquatic environment and maintains body