The term 'WHALE's food-filtering system' refers to BALEEN, a type of filter-feeding system found in certain species of whales. BALEEN is made up of keratin, the same material that makes up human fingernails and hair, and is used by whales to strain small prey from the water. BALEEN is found in the upper jaw of the WHALE and consists of a series of plates that act as a sieve, allowing the WHALE to feed on small organisms such as krill and plankton.