Animal Reproduction， Let the Life River Flow

In the world-famous science fiction Jurassic Park， there is such a sentence to lay the book of the motto： "life， always find their own way out." In this mixed with life sciences and paleontology novels， people use "Archives" in the prehistoric amber mosquitoes carrying a little bit of dinosaur blood， extracted from the dinosaur gene， and then frog gene fill part of the defect， which resurrected part of the dinosaur. For ease of management， all dinosaurs have been artificially set to females and contain human-made genetic defects. But after a natural disaster， the dinosaurs who escaped the cage not only overcome the "yoke" of genetic defects， but also develop themselves as parthenogenetic animals.

Put aside content in the books on the resurrection of dinosaurs that are not rigorous set， we can feel the powerful energe of species in order to extend life. It can be said that there is no life without the continuation of reproduction， there is no evolution of the process， nor colorful biodiversity on the planet. Some lizards as a special case of sexual reproduction， when it is necessary， are able for parthenogenesis， and even developed into only female "single sex species." Some fish can convert sex in specific circumstances and complete gene exchange with homosexual homogeneity to maintain the survival of the population and the whole species. In the ocean， the male hippocampus evolved to improve the pouch， and hatching and raising the baby's responsibility belong to the male.

It is also common to see low-grade animals reserving the asexual reproduction and sexual reproduction at the same time. Looking back at the process of reproduction of the paramecium， you may remember that this very simple single-celled animal has two ways of breeding： they can make the body into two， breeding two genetic information exactly the same "offspring"； can also be ditched together by the two paramecium， through a complex process of exchange of genetic material， and ultimately split into 8 “pffsprings” with slightly different genetic materials.

Why most animals will choose seemingly more "inefficient" way of sexual reproduction？ More than 100 years ago， the German zoologist Auguste Weissman argued that the genetic material exchange in sexual reproduction allowed the genetic diversity of the animals have more freedom to be amplified by this mixture.

However， from that time until today， we still know little about the origin of male and female or the origin of sexual reproduction. But many examples let us understand that with sexual reproduction and diversification of genetic combinations， so that species have more chances to "try mistakes"， without affecting the survival of the species itself. In contrast， animals that rely entirely on asexual reproduction， sometimes even because of the accumulation of harmful variants， embark on the evolution of the "path"， and finally "lose the full game".

And for animals of sexual reproduction， opportunities to “try mistakes” are not always abundant. After the great catastrophe of species， even with the relics of individual re-development and growth， the genetic diversity will be significantly reduced. For example， about a million years ago， the cheetah had been down to only a few dozen because of a catastrophe. Although they survived today， but the “scar” after the survival still engraved in their genes. If the randomly select two cheetahs for tissue transplantation， it is likely that no rejection will occur； but it also means that a serious epidemic may make this species completely disappear.

Now， with the advancement of science and technology， animals are used in modern biotechnology， in addition to breeding through natural means， artificial insemination， embryo transfer， in vitro fertilization， gender control， genetically modified， cloned， stem cell technology， are playing active role for animals reproduction. We hope that through the efforts of mankind， so that all kinds of animals can long live and reproduce on this vastly changing planet caused by human activities.