mule , a kind of magical existence, has been living in people's controversy for a long time, but it has made a great contribution to mankind. In the eyes of ordinary people, its image is hard-working, obscure, honest and honest, but the mule is not a species.
As we all know, mules are the offspring of horses and donkeys. Among them, horse mule is the offspring of male donkey and mare crossing. Horse mules are bigger than horses and look like horses, but they are called It sounds like a donkey; donkey mule is the offspring of a male horse and a female donkey. The body shape is biased towards donkeys. In general, it is not as good as the horse mule species. What they have in common is that they cannot bear offspring.
The product of the horse and the donkey, the mule
The horse is a sign of the Chinese zodiac and lives in people's impressions with a faithful, tall and majestic posture. Even if you have never seen a real horse, you must have seen a war horse galloping on the battlefield in TV dramas or movies. In ancient times, horses were indeed widely used in transportation or military activities. Until now, horses are also used. Used in many places of transportation or equestrian sports.
Donkey, with very docile temperament, easily tamed by others. In the cartoon, Avanti and his little donkey let many people know that the donkey is an unknown, hard-working animal. Since ancient times, donkeys have been used by people for riding or farming.
These two animals were originally separated by thousands of miles, one galloping on the battlefield and used for long-distance transportation, and the other working hard at home in farm work, and can also be used as short-distance transportation. I don't know what force caused these two animals to tie together and give birth to the mule.
At the beginning, the mule is also divided into horse mule and donkey mule.The horse mule is large in size. It not only has the load-bearing capacity of a donkey, but also the flexibility and running ability of a horse. The most important thing is that the horse mule saves more forage than the horse's forage, and its strength is greater than that of the horse. It can be said to eat They do less and do more, but the average horse mule does not run as fast as a horse.
Donkey mules are generally small in size, not as powerful as horse mules, but they are also much more flexible than donkey , and they are also very convenient for home use. Generally speaking, they are used in rural homes. Horse mule, this kind of horse mule born of a combination of male donkey and mare is the choice of most people.
After many generations of human breeding and breeding, mules have excellent varieties and many advantages. In agricultural and civilian use, mules have much better performance than horses and donkeys, low feeding costs, strong strength, honesty and hard work. They bear hardships and stand hard work and are very obedient. Their physique is also very strong, disease resistance and adaptability are very strong. They are the treasures in the eyes of ordinary people.
In fact, as an excellent livestock, mule is not a species. Species are the basic unit of biological classification and classification. Although mules have genitals and share males and females, they have almost no reproduction. Ability, so it can’t be counted as a new species. A mule is an infertile hybrid offspring at best, a hybrid between a horse and a donkey. It can be said that it is an animal, but it is not a species.
Can mules reproduce?
Can mules really breed? Strictly speaking, it is not. In theory, it is almost impossible for mules to reproduce and give birth to offspring. However, the magical nature always brings us many surprises, that is, a small part of mules will give birth to offspring. In 1988, Henan, my country There was one such exception.
A female mule mated with another male donkey and gave birth to offspring,And this is not the only case. In 1884, the British BBC News reported that there were also cases of mules giving birth to offspring in Morocco in the UK. According to statistics, there are currently more than 60 cases of mules giving birth to offspring.
Why does the birth of mules make biologists feel so incredible? In fact, biologically, the chromosomes of germ cells are half of somatic cell chromosome, that is, half of the paternal chromosome plus half of the maternal chromosome to form a fertilized egg.
Horses have 32 pairs of chromosomes, and donkeys have 31 pairs of chromosomes. Although their blood relationship is very close, they can mate to form fertilized eggs and develop into complete individuals, but their offspring mules have chromosomes in the cells of mules. The number becomes 32+31, a kind of 63, no matter what, there is always one chromosome that is lonely, so mules are generally unable to give birth to offspring.
These examples of female mules being able to fertile are generally because the chromosomes in the somatic cells of a donkey constitute a trisomy, and there must be three extra chromosomes, that is to say, during meiosis , It does not simply separate the 31 pairs of chromosomes from each other, and then randomly allocate the extra one.
In the process of separation, their chromosomes tend to separate randomly and freely combine. Although the fertility of trisomy organisms that can survive is very low, except for that one Except for the extra chromosomes, the rest can be paired normally and separated from each other. This is why mules are theoretically infertile, but there are also cases of mules giving birth.
Finally, in any case, the contribution of mules to mankind is tremendous.The ruler is longer and the inch is shorter. While taking advantage of the advantages of mules, we must also accept the fact that they are difficult to bear.
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