Reproduction of life on Earth universal model
to date, sexual reproduction is a common mode of reproduction of life on Earth. Sexual reproduction has many advantages over asexual reproduction, but the process is also very complicated. During this period, people need to find a mating partner, mix the DNA of both parties during the mating process, and always pay attention to the influence of the environment on the DNA mixing, and protect themselves to complete the mission of reproduction of offspring.
Therefore, not all organisms on the earth need to reproduce sexually. For example, many invertebrates reproduce asexually to produce offspring. Even some animals with complex structures, such as Komodo dragons (a type of lizard), vipers and sharks, will give birth to asexual offspring.
There are some species that reproduced asexually long ago, but with the need of evolution, sexual reproduction models have also evolved, such as tiny crustacean water fleas and amoeba. In 2011, scientists discovered the existence of sexual reproduction in the study of amoeba, which broke the long-standing view that the amoeba is a pure asexual organism.
In fact, both sexual reproduction and asexual reproduction require gene exchange and fusion, and this mode of gene exchange and fusion has therefore become a norm for the reproduction of life on earth. And this kind of gene exchange and fusion can increase the diversity of genes, which can improve the chances of giving new genes to form life and adapt to the environment. Even prokaryotes without a nucleus-bacteria are the same, they will swallow other bacterial DNA, under different environmental influences, form infectious viruses or plasmid circular DNA molecules.
Sexual reproduction is a necessary requirement of evolution
from the evolution of life on earth situation, the scientists point out, it is the largest complex of sexual reproduction lead to eukaryotic cells (the vast majority of people and animals are eukaryotic cells evolved) evolution the reason. Sexual reproduction can better adapt to the changeable and unpredictable natural environment. The fusion of males and females can produce more variant types of offspring. At least a few idiotypes can survive under harsh environments and obtain reproduction offspring. opportunity.
A study in 2011 showed that sexual reproduction can effectively fight pathogens and parasites, and that sexual reproduction can allow biological genes to be mixed with another gene, combining the forces of both parties to promote evolution to resist the invasion of parasites. Therefore, when organisms encounter the threat of parasites, choosing sexual reproduction can produce some “genetic weapons” to resist parasite attacks.
The research team genetically modified a kind of roundworm called “Caenorhabditis elegans” and divided it into three groups: the first group can only reproduce asexually, the second group can only reproduce sexually, and the third group can only reproduce sexually. You can switch between asexual reproduction and sexual reproduction at will. Subsequently, the researchers exposed these roundworms to parasitic bacteria. They found that the asexually reproduced Caenorhabditis elegans became extinct in less than 20 generations. The other two groups survived well.
Therefore, scientists speculate that an important question that determines whether aliens reproduce through sexual reproduction is what their cell structure is. If alien life is also eukaryotic like most animals on Earth, they will also benefit from sexual reproduction. Because on any planet that can produce life, its environment is rarely static. The environment of offspring is often different from that of the parent generation. In the process of reproduction, they will combine the strength of their parents to adapt to the environment in order to be more Survive well. Therefore, when the change is a constant, the genetic variation of sexual reproduction will be very helpful to biological evolution. This means that if aliens are advanced and complex beings, they must also reproduce sexually.
Double world of breeding
British scientist Richard Dawkins was published in 2014, the alien speech, he pointed out, sexual and asexual reproduction have advantages and disadvantages, sexual reproduction and strong anti-risk ability of future generations, but future generations The number is small; the offspring of asexual reproduction are weak against risks, but the number of offspring is large. Therefore, the reproduction mode of extraterrestrial life is likely to be a way of combining sexuality and asexuality to complement each other.
Examples of this method of reproduction can also be found on earth. Aphids (small insects that suck plant sap) are just such a bisexual organism. When food is sufficient, they will clone themselves through asexual reproduction, and they will reproduce multiple generations of offspring, which not only nurture children in their bodies, but also Children with children are as rich as a matryoshka, so as to accelerate their reproduction speed with the support of abundant resources. However, at the end of the growing season, due to environmental changes (such as the advent of a cold winter) and reduced food resources, aphids will turn to sexual reproduction to produce fewer and more refined offspring. Similar creatures and some water flea species, when the food supply declines or the environment deteriorates, they will change from asexual reproduction to sexual reproduction.
Although alien life may have the ability to reproduce sexually, even if alien life has sex, it is not necessarily the same as human beings. There may be other forms of sexual behavior, or both. This is the case with the sexual reproduction of amoeba. Their cells are first divided into packets of genetic material, then recombined, and then combined with other amoeba packets. In fact, the reproduction methods of life on earth are diverse. If it is true as Richard Dawkins said, then the sexual behavior of alien life should also have diverse patterns due to the environment.
All in all, alien life may use sexual reproduction to reproduce offspring, or asexual reproduction to reproduce offspring, or both. However, scientists are sure that it is difficult for extraterrestrial life to form a more complex way of reproduction than life on Earth.
Reproduction of life on Earth universal model