Problem: Read the characteristics of each animal described below. Then decide whether the animal should be classified as an ectotherm or an endotherm.
Penguins have thick feathers that trap heat against their skin. Even though most penguins have bare legs and feet, countercurrent heat exchangers in their legs allow heat to be transferred from warm arterial blood to cool venous blood. This arrangement returns heat back to the trunk of the body, while allowing cool blood to flow to the feet. This also keeps them from losing body heat as they stand on ice.