The world is unpredictable. There are many things in the world that we can’t control, some of which are even beyond our imagination. For example, in the process of biological evolution, some animals will slowly disappear, just like dinosaurs. Once dominating the world, they will never return. Some animals are constantly changing with the passage of time. Darwin’s theory of evolution tells us the survival of the fittest. Every animal in nature changes with the change of environment, including the change of reproduction. When it comes to animal reproduction, we have to talk about the sexual evolution of animals, which creates the miracle of life reproduction.
The picture shows cell division
Tracing back to the origin of life, cell self reproduction evolved sexual behavior, everything is for survival
1. Gene recombination evolves sex, which is divided into sexual reproduction and asexual reproduction
In the early stage after the formation of the earth, there was no life. With the emergence of the microorganism Luca, there was life on the earth. In the process of biological evolution, there was sexual differentiation in the late Proterozoic. Through gene recombination, cell reproduction, sexual function gradually improved. In other words, many animals in the process of mating, they move quickly, the offspring is very strong, can resist a variety of living environment. In biology, the origin of life is divided into sexual reproduction and asexual reproduction. Sexual mating requires close physical contact between the two sides, but when it comes to asexual reproduction or cloning, there is no such sexual ability. Asexual reproduction can happen anytime and anywhere, and it can transmit its complete genes to the offspring.
The picture shows the grafting technique
Some netizens can’t help asking: “sexual reproduction can give birth to offspring, so how can asexual reproduction give birth to life? What exactly is asexual reproduction? ” In fact, asexual propagation is very simple. For example, when we cultivate plants, we can make them grow new varieties by grafting. After grafting, these plants will maintain the excellent characteristics of varieties and grow new leaves in a short time until they blossom and bear fruit. This cultivation method is called asexual propagation. Its disadvantage is that the ability to adapt to the environment is relatively poor, root development is not good, there will be a short life. From a certain level, “sex” is common in nature, and almost all eukaryotes have sexual behavior. The sexual behavior of each species is unique. Whether it is unicellular protozoa, Drosophila or human, the sexual behavior is different.
In the process of biological evolution, sexual differentiation has also appeared. In the fossil algae more than 600 million years ago, scientists found the differentiation of male and female reproductive organs, which is a major discovery in the world so far. With the evolution of sex, there is reproduction, and then there are a lot of creatures. So, what is the fundamental proposition of their survival in nature? The answer is predation, confrontation, survival of the fittest in the natural environment, and, most importantly, reproductive evolution. So who has the initiative in animal breeding? In the hands of the female, the female animals have the initiative, and the male will continue to adapt to the female animals.
The picture shows the lion tribe in matriarchal society
In the process of single cell reproduction, are females born first or males born first?
Every animal in nature survives after continuous evolution and reproduction. In order to better adapt to the natural environment, they constantly change their organs and pass on the most dominant DNA to their offspring through gene transfer. If we say that sex is the result of biological evolution, then the reproductive organs are also the inevitable result of sexual evolution. The reproductive organs of animals are different. So in the development of sexual evolution, are there female animals or male animals first?
This is the most difficult question in biology. Animals and plants are usually divided into male and female. To find out whether there are female animals or male animals first, we need to understand the most primitive form of biological existence, that is, single celled organisms.
It is characterized by simple structure and simple propagation mode. It belongs to asexual propagation. After cell division, it will develop into other single cells. These cells are asexual organisms. Cell reproduction is very fast, and even self replication can be achieved. Of course, there are disadvantages in the process of replication, because there is no difference in this way of replication, and even it is almost the same as the mother cell,
We call it homogamy.
The picture shows homogamy
Because there is no exchange of genes, the offspring have no competitive advantage, and this asexual creature is easy to be completely extinct in nature. It can be seen that animals want to survive in nature, the environment is the biggest challenge for them, so in the future
Gradually developed a “heterogamy”, that is, the exchange of two cells, and then the emergence of new cells
It also gradually evolved into the final “sperm egg reproduction”, that is, one side of the mating party provides half of the genes, and the other side provides nutrients.
The picture shows the reproduction of sperm and egg
Some people will say: “the emergence of individual life should be the result of maternal breeding.” In fact, this sentence is not entirely true. Hermaphroditic animals are sexual animals, because they already contain both male and female. However, if fertilization is allogeneic or homozygous, then it will be inherited and reproduced. In other words, hermaphroditic animals appear at the same time. In the early stage of biological evolution, single cell had hermaphroditism in the process of reproduction. We can also understand that female animals and male animals appeared almost at the same time. In order to meet the needs of gene evolution, organisms had to start to distinguish male and female. This is the greatest division of revolutionary times in the history of biological evolution. The genes of hermaphroditism animals can complement each other, and this change is accelerating With the rapid development of biological evolution, animals and plants in nature are following this pattern of gene evolution.
The picture shows sea bass
Which animals in nature are androgynous? Among the millions of animals in nature, the number of hermaphroditic animals is very small. For example, a kind of fish living in the sea is called sea bass, which is very delicious. This kind of fish likes to grow in the deep sea. In the process of evolution, sea bass can self fertilize and become mature male from mature female. Of course, this process is not “from childhood”, only to the present It’s not until the sea bass is five years old that sex change occurs.
In addition to sea bass, sea rabbits are also hermaphroditic marine creatures. The sea hare is a kind of snail in the sea. They can’t mate with each other, so they develop into hermaphrodite in the process of evolution. In the process of mating, they will carry out group overlap mating. These sea hares mainly live in the equatorial and temperate coastal areas.
The picture shows the sea hare
During the long mating process, the reproductive organs of male and female animals have also undergone evolutionary changes
From the process of biological evolution, we found that the emergence of male and female animals is the inevitable result of single-cell reproductive evolution and gene recombination. It is not the result of “artificial setting” after the emergence of organisms in nature. In all biological organs in nature, the reproductive organs of animals are very single. Male animals store abundant sperm, and female animals receive sperm through fertilization Due to sperm transport, the shape of reproductive organs of female animals is single, and the process of mating with male animals is long. Moreover, for some organisms, mating methods can improve their quality of life. For example, in insects, female crickets usually use most of their energy to lay eggs after mating, so they are more susceptible to diseases. But in fact, female crickets become more tenacious after mating. Compared with unmated female crickets, mated crickets tend to have stronger survival ability and immune response. However, the degree of enhancement varies.
The picture shows a cricket mating
In addition, ducks are the most common animals in our life. On the surface, it is difficult to distinguish male and female ducks. They are very different when they grow up. The shape of female ducks’ reproductive organs is like a bottle opener. In the process of mating, as long as they want to refuse male ducks, they will close their genitals at any time. If they can’t mate, the male ducks will die completely.
When scientists visited Slovenia, they found that it is very complicated for male spiders to complete mating with female spiders. The appearance volume of female spiders is much larger than that of male spiders, so male spiders will face many challenges during mating. It is even possible that male spiders will be eaten by female spiders after mating, and the genitals of female spiders will be destroyed by male spiders before mating Drop it. In many spiders, female individuals with several branches will evolve into relatively large size. At the same time, the sexual mating behavior of these female spiders will be extreme, such as their genitals will be destroyed, or the male spiders will be tied with spider webs.
The picture shows spiders mating
In addition to spiders, scientists also found that bedbugs also have changes in their reproductive organs. The genitals of male bedbugs are like syringes. During mating, they will directly inject sperm into female bedbugs. With the evolution of bedbugs, the genitals of female bedbugs have changed, adding a brand new reproductive organ. Male bedbugs can complete mating on the right side of their abdomen, but there is no difference This new reproductive organ is like a filter, which can screen out sperm that you don’t want.
In addition to animals, plants also have their own reproductive organs. In the process of reproduction, seeds blossom, pollinate and bear fruits, and the seeds in the fruits reproduce. Among them, the flower is the reproductive organ of the plant, and the stamen is the reproductive organ. The stamen is divided into pistil and stamen, and the stamen is an important part of the flower. No matter animals or plants, the internal structure of any living substance is not accumulated. In the long-term evolution process, after adapting to the ecological environment, the living substance gradually evolved into different reproductive organs through cell division in the way of reproduction.
The picture shows bees helping pollination
Generally speaking, female and male animals are the result of direct division and reproduction of single celled organisms. Through long-term reproduction and evolution, there is sexual behavior everywhere in female and male organisms. Almost every eukaryote has sexual intercourse. For single celled insects, plants, including us, the way of sexual behavior is very different. In addition to the benefits of self fertilization and sexual maturity for individual survival, it can also repair damaged DNA. Nowadays, sex plays an increasingly important role in biology, which is the inevitable result of single cell self reproduction evolution!