Whales

Whales are related to both dolphins and porpoises. Sometimes, a species of the dolphin or porpoise family may have the term 'whale' in the name (ex. Pilot whale), but are not in the whale family. Whales are descendents from land-living mammals (same as dolphins and porpoises) and entered into the water about 50 million years ago. Like all mammals, whales breathe through lungs, are warm blooded, feed thier young milk from mammary glands and have a small amount of hair.
In 1911, a young scientist determined that whales were descendents from land living animals and have since fully adapted to a full aquatic life. This was not widely accepted within the scientific community, but later on it was prived to be correct.
A whales is considered to have what is known as a fusiform body shape, one which resembles a fish. The forelimbs on a whale are called flippers and are paddle-shaped. The end of a whales tail holds the fluke, a.k.a. 'tail fins', which provide the animals with propulsion, or verticle movement. Most whales contain a fin on their backs, a dorsal fin and very few contain hind limbs, some with feet and even digits. whales contain blowholes, which are located on the top of the head and they allow the animal to stay submerged under the water. Beneath the skin is a layer of fat, or blubber, which acts as an energy reservoir. they also have four-chambered hearts. Whales do not have much flexibility because the neck vertebrate are fused together, which allow the whale to have stability.
Whales are considered to be a predator and their food ranges from microscopic plankton to very large fish. A male whale is called a bull, female is called a cow and the young are called calves. A whale is known as a 'conscious breather' meaning that they choose when they breathe due to the harsh environments they live in. A whale needs to be conscious to breathe, so they are unable to fall into an unconscious state of sleep, so they do not sleep for long periods of time. It is believed that only one hemispere of the whales brain sleeps at a time, so in fact the whale is never truly asleep, but they do get around 8 hrs a day, so they get enough rest. Whales communicate through lyrical sounds. Since they are so large and powerful, these sounds are very loud and can be herd for miles. A female gives birth to a single calf and the nursing time is generally long. This associates a strong bond between mother and offspring. Reproductive maturity usually occurs late, around 7-10 yrs. This stratgy yields few offspring but allows for a higher rate of servival out in the wild.
Some species of whales are endangered due to the activitie, whaling, of humans during the nineteenth and twentieth centuries. They have been hunted for oil, meat, baleen and ambergris. In the twentieth century, some populations were severly depleted. Like humans, whales are threatened by global warming and climate change. As the Atlantic ocean warms, some populations of krill, a main food source of the whale, reduces dramatically and are replaced by things such as jellyfish and salps.

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~http://en.wikipedia.org/wiki/Whale
~http://dkd.net/whales/