Many people like the gigantic whales. Human sympathy 【C1】______ whales is only natural of all the creatures in the sea. 【C2】______ are closer relatives to us than these warm-blooded mammals. And how they got into the sea is one of the most fascinating stories of 【C3】______ . Most authorities believe that 60 million years ago ancestors of modern whales were four-legged, wolf-size animals living on the sea shores, 【C4】______ an abundance of fish and shrimp tempted them to try wading. Over 10 to 15 million years, their bodies grew, forelegs shrank into flippers used for 【C5】______ and steering and hind legs disappeared. As a result of some amazing transformations, they arc now helpless on land. If stranded on a beach, they can barely breathe.
With abundant 【C6】______ of food, whales grew into the largest creatures that lived, 【C7】______ larger than dinosaurs. A blue whale can grow to 100 feet. Its tongue is ten feet thick and heavier than an elephant. Some arteries are big enough for a child to swim 【C8】______ . The half-ton heart has walls two feet thick and pumps eight tons of blood. 【C9】______ its size comes awesome strength. A blue whale swimming 【C10】______ 15 knots generates 1000 horsepower. 【C11】______ their size, these giants move at a good speed. An 18-ton whale can even 【C12】______ 12 m. p. h., over short distances. A whale can 【C13】______ up to 9000 pounds of food a day. The world's biggest creature 【C14】______ itself almost entirely on shrimp-like krill, smaller than a person's thumb.
Maternal instincts are also highly 【C15】______ . Because a calf is born underwater, the mother must get it to the surface before it 【C16】______ . Often another whale will help. The mother pushes it gently 【C17】______ the baby is confident with its swimming usually after about 30 minutes. If the calf is born 【C18】______ , she may support it on her back until it gradually rots away. Like all mammals, whale babies feed 【C19】______ mother's milk. And the milk is more than 30-percent fat, over 10-percent protein, and the babies grow extremely fast. A blue whale calf lengthens 【C20】______ two inches a day and gains an average seven pounds per hour.
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