The earth has nurtured thousands of creatures, and whether it is animals, plants or microorganisms, in addition to ensuring their survival, the most important thing is to reproduce and reproduce.

Overview

The earth has nurtured thousands of creatures. Whether it is animals, plants or microorganisms, is the most important thing in addition to ensuring its survival is to reproduce and reproduce.

However, only organisms belonging to the same species can mating and reproduce normally. . Between two different species, there is reproductive isolation preventing them from mating.

So, why can't mating be performed between different species? What is the role of reproductive isolation?

Reproductive Isolation

To understand this problem, you must first know what reproductive isolation is.

According to the encyclopedia definition, the so-called reproductive isolation refers to an isolation mechanism in which two different species do not mating or cannot produce fertile offspring under natural conditions.

From the definition, reproductive isolation has two prerequisites: one is “two species” and the other is “natural conditions”.

In biological classification, the species is the most basic unit "species", and below it is the subspecies.

For example, due to habitat differences, Leopard is divided into 9 different subspecies . These 9 subspecies can freely mate with each other and give birth to offspring, and there is no reproductive isolation.

However, this involves "natural conditions".

Dynamic, 9 subspecies of leopards can be freely mated, but in fact, Because these different species of leopards are distributed in different habitats, they are geographically isolated. This leads to the fact that these 9 subspecies of leopards do not have gene communication under natural conditions. This is geo-isolation in reproductive isolation.

In addition to geographical isolation, there are also seasonal isolation, ecological isolation, mechanical isolation, and behavioral isolation , etc., which all prevent cross-species mating behaviors from occurring.

In short, due to the limitations of many conditions, two different species will not mate under natural conditions, which is reproductive isolation.

The consequences of hybridization

If two species that should have existed in reproductive isolation forcibly engage in mating and also give birth to offspring, then their offspring will be a regrettable ending.

This is because, two species that cross reproductive isolation and forced mating will only have three outcomes.

first, hybrids are inactive. That is to say, even if the two hybridize to form a zygote, the zygote will survive, but the embryo will die during the development process, during the development of larvae, or before reaching the sexual maturity stage.

second, hybrid sterility. This situation will be slightly better. The hybrid offspring can develop to the maturity stage, but but it does not have the ability to reproduce offspring. For example, after a horse and donkey cross, they will give birth to mule , and mule cannot breed the next generation in most cases.

3rd, hybrid decay. In this case, the first generation of hybrid offspring may have fertility, but the second generation of hybrid offspring will not survive because the recombinant genotype cannot be coordinated.

can be seen that even if the offspring formed by cross-species can survive, there will be various genetic defects in them. . This is also the terrible part of reproductive isolation.

The common ancestor of humans and chimpanzees

tracing backwards. Millions of years ago, many similar species on the earth actually had common ancestors. Take humans as an example. Humans and chimpanzees had a common ancestor 7 million years ago, namely Chad apes.

At that time, neither humans nor chimpanzees had appeared on the earth, only Chadian apes distributed all over the world.

Later, over time, these were separated by geospatial Chad apes gradually lost their genetic communication with each other, and So, the genetic differences between different populations became increasingly larger. These differences may be very subtle at the beginning, but over the years, the subtle differences gradually become significant. At some point, appeared to reproductive isolation between the populations of Chad apes, and a new species was born.

One population evolved into the ancestor of chimpanzees, while the other population evolved into the ancestor of humans . After this, humans and chimpanzees evolved in their own directions, and now they have become two completely different creatures.

However, although from the current perspective, humans and chimpanzees are very different, if the origin of the gene is traced, these two species are very similar, and the difference between the gene is only 1%.

is also . Since the gene similarity between humans and chimpanzees is as high as 99%, some scientists have suspected that humans and chimpanzees may have hybridization and conducted related experiments.

Ape hybridization experiment

In the 1920s, a biologist named Ivanov conducted a controversial ape hybridization experiment. He hopes that through hybridization technology, will create the " Orangutan Man " that combines wisdom and strong physique.

At first, Ivanov used human male germ cells to inseminate three female chimpanzees , but all failed insemination.

Later, he transplanted the ovaries of human females to the female chimpanzee , and then inseminated them with human male germ cells, and this time it failed again.

Immediately afterwards, Ivanov tried to inseminate human women with male chimpanzee germ cells, , but because it violated ethics and morals, this experiment failed to continue.

undoubtedly, the Ape Hybrid Laboratory is extremely absurd, and I have to say that this biologist is really a bit crazy. However, in fact, this experiment was destined to not succeed from the beginning.

This is because human chromosomes are 23 pairs, one less pair than chimpanzees. obviously has reproductive isolation.

Therefore, even if humans cross with chimpanzees, the offspring of is highly likely to be infertile.

Therefore, there is reproductive isolation between humans and animals. So, is there also reproductive isolation between humans?

The answer is no. Although humans on the earth are distributed in different regions and have different skin colors, they actually belong to the same species, that is, Homo sapiens , then it is obvious that there is no reproductive isolation between people.

Conclusion

In fact, reproductive isolation is not terrible. If there is no reproductive isolation, it will be a disaster. Just imagine, if no reproductive isolation is available, any species can communicate freely, then genes will only become more and more homogeneous, species will become more and more single, and the earth will become monotonous and boring.