1967, American biologist margulis gulihs? (lynn margulis) published a paper pointing out that our mitochondria are ultimately inherited from a single bacterial cell. In the past, larger cells swallowed smaller cells, probably for absorption and digestion. The smaller cells managed to survive in the larger cells, and the two cells successfully merged to form a population. They may have complementary skills. Small cells may be able to burn food fuel in oxygen to produce energy (this is how mitochondria work in modern cells), while large cells may produce fuel to burn. Over time, these two partners evolved into the cell types that make up our bodies today. Mitochondria are still like bacteria, and a few genes in mitochondria are similar to bacterial genes. Similar biological events promoted the evolution of chloroplasts in photosynthetic tissues in green plants.
The evolution of fertilized eggs is actually the evolution from parasitism to * * *. There is no separation between nucleic acids because they have independent structures after subsequent evolution.
Mitochondrial phagocytosis
In the early evolution of cell membrane formation, that is, the period of ending the chaotic combination of ribosomes, there is actually a free combination relationship of genetic factors. After the cell membrane is formed, the word invasion is mutual evolution, and this relationship has evolved into parasitism between cells, birth and phagocytosis.
?
? Sperm eggs were born.
? Macroscopically, the animal kingdom in the world is very big, and the creatures are constantly evolving in the direction of enlargement. Finally, they can't take care of too small creatures, so parasites have room to live.
Egg cells are almost invincible because of their huge size. Egg cells evolved from sperm cells, and huge cells occupied the living space of small cells. However, when small cells grow bigger, they can be parasitic on large cells, and two cells of the same ancestor have parasitic relations. Because of the high similarity of genetic materials, sperm cells are easy to parasitize, bypass the ribosome review mechanism, invade directly, and the egg cells begin to activate specific immunity.
After parasitism, two sets of genetic materials are expressed at the same time, and two lifestyles are displayed in the same body. The aggressiveness of sperm cells and the anti-aggressiveness of egg cells enhance the overall strength, realize the perfection of functions, and become the most primitive fertilized egg. Finally, after tampering with the host cell, reassemble the protein needed by your own cell and leave it.
? Meiotic birth
Because * * * is more viable in the state of birth, it is naturally selected. At this time, a magical phenomenon happened, and the expression of genes showed stages, which was reflected in the reasonable arrangement of time. The winner stays in the host cell for a longer time, that is, the birth time is longer, so that * * * catches up with the expression of the gene that decides to replicate when it is too late to separate. * * * Dominant and recessive genes were expressed during the growth period, which laid the foundation for meiosis of copying first and then separating. During meiosis, it is still restricted by dominance and recessive. The structural chromosome parasitic to the cells born by * * * is naturally xy, and so is meiosis.
? The birth of female chromosomes
The structure of * * * evolved the expression of characters in co-evolution, and in the case of XY chromosome, the sperm cells of X chromosome were produced for the first time. After the sperm cells of X chromosome combine with the egg cells, the egg cells can be re-expressed immediately.
? Multicellular era is coming.
The competition between cells has intensified and become the mainstream with great strength. Sperm eggs produce single cells, which evolve into multicellular cells under the reaction of natural environment, and some of them give up the expression of meiosis and begin to differentiate.
The copied * * * living body is connected with two cells. Because of the convergence of survival advantages of the * * * living body structure, parasites leave the host for a longer time, so a structure appears, one part of which is copied and the other part develops into germ cells. Since then, two types of multicellular organisms have been born, female and male. In today's fish schools, females often discharge eggs into the water, while males find eggs near egg cells and discharge sperm eggs. In fact, this efficiency is not high.
With the intensification of natural competition, the way of ovulating while looking for eggs has evolved an interest in the opposite sex itself, and when ovulating, they are closer to each other, so sperm cells discharged into the water are more likely to complete fertilization, which greatly ensures the reproductive ability, evolves heterosexual relatives who attract the skin, and enhances the reproductive ability. In this case, some sperm were fertilized before the eggs were excluded, and some even parasitized directly in the mother's body, which led to the subsequent variation of tubal fertilization and evolved a uterus suitable for raising embryos.
? The originator of bisexual reproduction-small-limbed fish
So a creature called little limb fish was born and became the originator of bisexual reproduction.
Small-limbed fish are about 8 cm long. Their habitat is about present-day Scotland, but their fossils are also found in Estonia and China. The results showed that the L-shaped tail foot of male small-limbed fish is actually used for mating, while the female small-limbed fish has a pair of bones to lock the tail foot, which is convenient for male small-limbed fish to transfer sperm through the tail foot. This mating method is more effective than laying eggs. Then the embryo parasitized on the female body, and the mammal was born.
Finally, don't forget to pay attention to forwarding and likes! There will be similar article updates in the future.