Abstract：Over the years， biologists have conducted experiments and researches on the fur of different animals in the biosphere. Different kinds of animals have different fur colors and different functions. General reptiles， deep sea fish fur color dull dark， and birds， some reptiles， fish colors more colorful. The function of fur is mainly not only used in camouflage， defense， heat preservation， heat dissipation， courtship， vibration perception but also status symbol and other aspects.

The main reason for this phenomenon is the result of natural selection. Another cause is genetic variation. By studying and learning more about animals， humans can better protect them by living peacefully with them and protecting the planet of our common home.

Keywords： color differenc， function difference ，natural selection ，genetic variation protection.

"Master camouflage" caterpillar

caterpillar is the food that many animals long for， so it has to develop its unique skills to protect itself from foreign aggression through the seamless disguise. When catching food， caterpillars， like a Japanese ninja， disguise themselves between the leaves and flowers and wait for their prey. The small villi nerve cells on its back are so sensitive that when it senses a prey passing by， it immediately picks it up with its pincer leg and can even snap at a fly that flies quickly past. So the caterpillar deserves to be a master of disguise.

The master of Color change--a Thunderbird is a global distribution of birds， is a typical boreal bird， the year-round residence in the cold north， from the Arctic tundra， until the forest and forest steppe， throughout the northern Eurasia and North America. Because of the long life in the ice and snow， a series of characteristics adapted to the cold environment， such as the thick and long legs of the hair is covered to the toe； there are many long Mao Yan around the toes that are warm and easy to walk on snow without sinking， the nostrils are covered with feathers， can withstand the Arctic storms， but also conducive to the snow peck food. The Thunderbird's beak is thick and short， and is guaranteed to survive by digging the roots under the snow. It is good at running， flying fast， but there is no way to fly very far.

Thunderbird is different from the average bird， it changes its feathers for four seasons. Immatures and winter feather completely replaced the new plume， and the spring feather and Autumn feather is only partial replacement. Females change the plume 3 times a year， and the plume is not as showy as the male， it is easy to conceal itself and protect the chicks， while the male's showy feathers are the capital they attract females to get more mating opportunities. In the spring， when the snow melts and the layers of the people emerge， the Thunderbird begins to grow brown-spotted feathers on the white "coat"， adapting to the surrounding environment. In summer， it was dressed like a "summer dress" of bark. To protect yourself by changing chestnut brown feathers with irregular black or brown markings. Autumn came， vegetation withered， leaves fly， Thunderbird also replaced with their own clothes， put on the brown， with black spots on the "Autumn clothes." And in the winter， Thunderbird seems to like the white snow， in addition to the top and tail feathers are black， the whole body is wearing a set of snow-white "winter"， even the feet are also wearing a "white socks." Although Thunderbird belongs to the Grouse department， but it does not have a chicken as hard as the mouth and sharp beak， size and relatively weak， when the enemy， there is no strong body， there is a lack of offensive "weapons"， had to rely on their own four seasons to change the color of the feather and the habitat of the environment to maintain consistent， so as to avoid predators and protect themselves.

The octopus is a mollusk， The octopus color-changing stunt is amazing， it can change the color of its skin at any time according to the environment， and keep in harmony with the surrounding environment. It also has the ability to discolor， even in the case of injury， because there are many pigment cells hidden beneath its skin. This pigment cell， also known as the pigment body， is a biological pigment cell developed by the neural crest of the embryo and plays an important role in changes in the skin and eyes. The pigment cells showed yellow pigment cells， red pigment cells， rainbow pigment cells， melanin cells and blue pigment cells under white light. In the octopus pigment cells are also equipped with different colors of liquid， each pigment cell has several extenders， it can make pigment cells contraction freely.The pigment cells of city animals can change the color of the body quickly according to the change of pigment position and the direction of luminous structure. Octopus is the use of muscle to control the organs of the pigment cells. The skin changes color quickly when it encounters a danger or excitement. The eye and the brain are the command system that controls the color change of the octopus body， and if one eye or brain is faulty， the other side will form a fixed color， but the other side will continue to change color. It can be seen that the octopus is a color-changing master， it is a very short period of time to change their colors， is a very magical thing.

Prairie Overlord The lion's hair is short， yellow， the lion also has a long mane， generally dark brown， but also black， light brown or reddish brown and the surrounding environment is natural， conducive to hunting disguised themselves not to be found by prey. These bristles extend from the face to the shoulders and chest. These bristles may make males look bigger in the eyes of other predators such as hyenas. Another theory is that long bristles are more attractive to females. The observation of the wilderness seems to prove that a particularly dark and long mane is indeed more appealing to females. The mane of an Asian lion is shorter than that of an African lion. The Cubs have no violent hair. It takes five years for a general cub to acquire a complete mane.

Polar bears do not fear the mystery of the cold polar bear is also called White Bear， living in the Arctic， the whole body of white hair， even their ears and feet are also long hair， only the nose is black， it looks charmingly na?ve， very cute， and the Arctic ice and snow is a shining contrast. It has a very thick blubber and hair to keep warm， its white appearance on Snow White snow is a good protective color， so in the Arctic this extremely harsh climate to survive. The polar bear has a white fur， which is the protective suit that it lives in the snowy Binghai. This hair is actually a transparent hollow tube， like a root quartz fiber. These hairs scatter light from the sun and make the hairs look white， creating an excellent protective color for the polar bear. At the same time， the Maomaofa also transmits scattered radiation to the surface of the skin， where radiation is absorbed and transformed into heat， which complements the polar bear's metabolic heat. Surprisingly， the polar bear's natural solar collector is highly efficient， and it gathers the faintest projected light to convert more than 95% of the Sun's radiant energy into heat. According to research， One-fourth of the polar bear's heat demand is provided by the white fur. These hairs are natural heat shields， so the polar bear's body heat is seldom dissipated， so the polar bear is not afraid of cold.

To know that fur is one of the characteristics of mammals， more than 99% of all terrestrial mammals have fur， elephants are rare exceptions.

What is the reason for this？

Some people say that when the ancestor elephant's size evolved into an elephant， the density of the hair follicle would naturally be greatly reduced， and the elephant's body hair would certainly become sparse. But that is not the right thing to say. Being large does not mean that the hair becomes sparse. In fact， the mammoth， which had been extinct 10，000 years ago， has a dense shaggy hair. If necessary， existing elephants can also wear hair.

Mammoths live in frigid climates， need hair to warm the cold， and existing elephants live in the tropics without the need. So climate is one of the factors that elephants do not have long hair. But many mammals， such as zebras， giraffes， and lions， who live in the same place as elephants， have hair， and why do elephants have severe degeneration of their body hair？ Mammals are temperature-controlled animals， must maintain temperature at one by one specific temperature to ensure normal physiological activities， such as the elephant's body temperature must be maintained at about 36 degrees Celsius， too high or too low are life-threatening. Body heat is produced in the process of cell metabolism， their total volume is almost fixed， but the temperature of the environment is constantly changing. If the temperature is lower than the body temperature， then it is necessary to prevent body heat loss， which is the main function of hair. If the temperature is higher than the body temperature， try to disperse the body heat as much as possible.

The body heat is distributed mainly through the skin， the larger the body table and the greater the heat， the faster. However， the surface area is not larger when the size of the animal， the volume increases in the same proportion： the volume increases by cubic， while the surface area by the square increase， volume technology cubic increase than the surface area much faster.

. Long pair of huge ears is the another way to rejection of heat. The elephant's ear is not only large， but thin， filled with blood vessels， blood flow through here， it is easy to dissipate heat. In particular， fan up， more easily the blood in the ear of the temperature down， can let the blood temperature down 5 degrees Celsius， cooling blood circulating in the body， help the whole body temperature down.

When I was a child， I wondered why there were no green cats， pink dogs or other weird colors. With the accumulation of experience and the increase of experience， I found that the fur of animals and the surrounding environment and function， not what animals want to become what， all this is the result of long-term natural selection

References：

[1] "Who knows the stunt of animals" Zhou Rui China City Press January 2010 First Printing

[2] "Animal encyclopedia" Zisheping Editor of China Materials Press March 2004 1th time Printing "ferocious animal Mystery" Cao Liyun compilation Sunshine Publishing house Central Compiler Press September 2009 1th time printing.

[3] "An Anthology of Genetics"， "Austria" Mendel， is waiting for Peking University Press for the 1th time in January 2012.

作者簡(jiǎn)介：杜茜（1993—），女，土家族，籍貫：湖北恩施，單位：武漢學(xué)院，研究方向：自然科學(xué)。