Acid Rain
People generally think that the largest animals ever to live on earth were the dinosaurs, but even those giants were not as huge as the blue whalethat is still alive today. Named for its blue-gray color, this huge cetacean may grow to be roughly 30.5 m (100 ft) long and weigh more that 108,000 kg (120 tons). Its close relatives include the smaller fin, humpback, sei, Bryde's, and minke whales.
The blue whale and its relatives are called baleen whales because they have a feeding structure known as baleen that takes the place of teeth. Baleen is made of a flexible material containing a protein called keratin, which is also found in your fingernails and in the hooves of horses and cows. Baleen plates hang down from the roof of the whale's mouth in rows, somewhat like the teeth of a comb. The inner edges of the baleen plates are fringed and look hairy.
A large part of the whale's diet is made up of small shrimp-like animals called krill, which the animal strains with its plates of baleen. In order to get enough of these small creatures to eat, a blue whale has to filter large amounts of water. Folds of skin on its throat expand like an accordion to allow the whale to gulp in as much as 64,600 liters (17,000 gal) of water at one time. The whale then pushes its tongue (which can be as large as a Volkswagen) to the roof of its mouth in order to force out the water. Food is caught in the hairs of the baleen and swallowed. A blue whale weighing 75 to 80 tons eats about 4 tons of krill per day during the feeding season.
As summer approaches, blue whales migrate to feeding grounds near the north or south poles. Concentrations of krill are greatest in these areas during the summer, and it is then that the whales eat huge amounts of food. Groups of blue whales can be seen at this time, especially around Antarctica. In the fall, after feeding for half a year, the whales begin to swim toward warmer water to mate and to give birth to their...
Please login to view the full essay...