Jeff Wheeler, age 12, of Pocatello, Idaho, for his question:
HOW LARGE IS THE LARGEST WHALE?
The largest animal that has ever lived is the whale. Whales are bigger than elephants. Even the prehistoric dinosaurs weren't as large as whales. Largest of all is the blue whale, which can grow to be 100 feet in length and weigh up to 150 tons.
Thre are two main types of whales: whales that have teeth and whales that do not have teeth. There are 76 known species in the family that includes whales, dolphins and porpoises. All live in the oceans and look much like fish. But they aren't fish. They are mammals and they must breathe air.
Most smaller whales, plus all the dolphins and porpoites, belong to the suborder Odontoceti, the toothed whales. Those more than 16 feet long are generally referred to as whales, while the smaller species are known as dolphins or porpoises.
One toothed whale, the sperm whale, is quite large. The male grows to a length of about 60 feet. The female gets to be 40 feet long.
Baleen whales have no teeth . They belong to a suborder called Mysticeti. They have horny plates in their mouths that strain out their food from the water. These plates are called baleen or whalebone. The baleen hangs in two rows, like curtains, one on each side of the whales jaw. The inner edges of the plates have a fringe of bristles that strain out food.
The largest whale of ail, the blue whale, is a baleen whale.
Another giant baleen whale is the finback. This monster mammal grows to be 82 feet long and weighs about 100 tons.
The humpback whale, also a toothless baleen, will grow to be 50 feet long and weighs about 50 tons. Also about this same size is the gray baleen whale.
When feeding, a baleen whale swims with its mouth open in order to engulf plankton and seawater by the ton. There are between 160 to 360 plates on each side of the whales mouth.
After the mouth is full of seawater, the whale shuts its cavernous mouth and presses its tongue against the back of the baleen bristles. The whale then forces the water out of its mouth, trapping the plankton on a mat of overlapping baleen.
Whales, like other mammals, have lungs. They breathe air through a single nostril, or pair of nostrils, on top of the head. But contrary to a popular image, they do not spout water when they exhale. The visible "spout" is simply water vapor in the lungs and a small amount of water present in the depression around the blowhole, which is blown into the air as the whale exhales.
A number of physiological adaptations enable whales to perform deep dives. First, they have a larger blood volume than land animals of comparable size and weight, and they also have a greatly increased capacity to store oxygen in their blood and muscle tissue.
Second, each breath provides an 80 to 90 percent renewal of air in a whale's lung, compared with only 10 to 20 percent in most land animals.
Third, whales have a resistance to the metabolic by product carbon dioxide. They can hold their breath up to 50 minutes when diving. The sperm whale can hold for 75 minutes.