Why do camels have two humps?

Camels have big bodies and thick soles. You can also predict the change of wind power and know the location of underground water sources. Camel's eyelashes are very long, and their function is to prevent sand from entering the eyes. Even if sand enters your eyes, it only takes a few tears to wash it out. Therefore, even in sandstorm weather, camels can tell the direction and won't get lost. Camel is the most thirsty animal of all animals, with a record of not drinking water for 30 days. Once you drink water, you can drink more than 30 kilograms at a time. The above advantages of camel make it the most suitable animal to walk in the desert.

Anatomically, it is confirmed that the hump stores the deposited fat, not the water sac. Metabolic water produced by fat oxidation can meet the needs of camel life activities. So some people think that the hump actually stores "solid water". It is determined that 1g fat produces 1. 1g metabolic water, and a 45kg hump is equivalent to 50kg metabolic water. But in fact, the metabolism of fat is inseparable from the participation of oxygen, and in the process of oxygen inhalation, the water lost from the lungs is comparable to the water metabolized by fat. This fact shows that Luo Feng is not a solid reservoir at all, but a huge energy storage device, which provides material guarantee for camels to travel long distances in the desert.

The rumen of camel is divided into several blind sacs by muscle blocks, which are called "water sacs". Some people think that after a camel drinks water, it needs to store a lot of water in its stomach before it feels thirsty. In fact, those water bags can only hold 5 ~ 6L of water, which is mixed with fermented feed and presents a sticky green juice. The salt concentration in these green juices is roughly the same as that in blood, so it is difficult for camels to use the water in their stomachs. Moreover, the water sac can not be effectively isolated from other parts of rumen, and it is too small to form an effective water storage reservoir. Anatomically, apart from the hump and stomach, there is no organ dedicated to storing water. So it can be concluded that there is no reservoir for camels.

2. The water source of camel's life activities under the condition of water loss.

The research results of K.Schmidt—Nielsen show that camels don't drink too much water when they get water, or that the water they drink is only used to satisfy and relieve dehydration at that time, so that body fluids can return to normal volume level. From this point of view, in the case of not entering the water, the water needed by camels to maintain life activities comes from the reduction of body fluids. The normal amount of body fluid minus the maximum amount of body fluid during dehydration is the maximum amount of water that can be provided by camel's body fluid system. In the summer desert, camels can tolerate dehydration with a weight loss of 25% ~ 30%. For a camel weighing 500kg, it means water loss 125 ~ 150 kg. On the contrary, the water "reserve" of a 500kg camel is 125 ~ 150 kg. This is obviously much bigger than the water storage function of hump and water bag that people think. What really has a "reservoir" is the camel's body fluid system, not the wind or water sac.

Adapted to camel's high dehydration resistance, camel's blood has a special high concentration of protein, and this protein has a strong water retention capacity. Under the condition of extreme dehydration of camel, this plasma protein can still maintain the moisture in blood, ensure the normal operation of blood circulation, ensure the thermal diffusion of body nucleus to the body surface, and increase the viability under high temperature dehydration.

3. The structure and physiological mechanism to solve the water contradiction.

Water gain and water loss are two aspects of biological water metabolism. In the desert where water is extremely scarce, water is the most prominent contradiction faced by living things. Therefore, it is equally important for creatures in the desert to ensure water acquisition and reduce water loss. Camels have gradually formed a set of adaptive mechanisms from structure to physiology in the long-term evolution process to reduce water loss.

3. 1 Fine temperature regulation mode

Camels have a wide temperature range and are suitable for desert environments with large temperature difference between day and night and need to reduce water loss. During the day, camel's body temperature increases with the increase of environmental temperature, and the highest temperature can reach 465,438 0℃, and it decreases with the decrease of environmental temperature at night, and the lowest temperature can reach 34℃, and the fluctuation range of body temperature is 7℃, and this fluctuation is more obvious in dehydrated state. But it can't show the original mechanism of camel's constant temperature, but a more delicate way of body temperature regulation based on constant temperature.

In high temperature environment, raising body temperature can reduce the temperature difference between animal body and environment and reduce the inflow of external heat. At the same time, the increase of camel's body temperature also plays a role in storing heat, and this part of the stored heat can be diffused into the surrounding environment by conduction and radiation at night instead of evaporation, and the result is to reduce the evaporation and water loss that may be caused by maintaining a constant body temperature. The specific heat of a 500kg camel is 3.35 kJ/kg k, and a temperature rise of 7℃ is equivalent to storage of1.26×107 j. If the heat is lost through water evaporation, 5L of water will be lost.

3.2 Effective thermal barrier

Camel hair is long and fluffy, forming an effective thermal barrier on its body surface. The stagnant air layer between camel hair affects conduction and convection, reducing the loss of human heat at low temperature and the inflow of external heat at high temperature. The experiment shows that camels with hair thickness less than 1cm lose 3L per 100kg body weight every day on average, while camels with hair length of 3 ~ 14 cm only lose 2L per 100kg body weight every day. The effective heat insulation of camel hair indirectly reduces the evaporation of water.

In addition, the camel's nasal mucosa area is large, which increases the reabsorption of moisture in exhaled gas and reduces the loss of respiratory moisture; Concentrated urine reduces the consumption of water in discharged waste; Dry feces also play a role in reducing water.

In the long-term evolution, camels have adapted to the desert, an extremely water-deficient environment, and formed unique adaptive characteristics, which not only ensure that a large amount of water is stored in the body, but also ensure that the water in the body will not be excessively lost, thus effectively solving the most prominent contradiction faced by desert animals. At the same time, camels are also studied and discussed as typical animals adapted to high temperature and water shortage.