Today we suggest you to analyze the gametogenesis process. In short and very clear, this is the process of development of germ cells. As it became clear, the article will be devoted to reproduction. Note that there are several forms of sexual reproduction. Despite this fact, they are all based on the participation of two gametes (male and female germ cells). We invite you to consider this issue in more detail.
Sexual reproduction
We have already mentioned that sexual reproduction is due to the participation of two heterosexual individuals. Special germ cells are formed in certain organs in them, which are commonly called gametes. But what is gametogenesis? This is the process of formation of the same germ cells that are necessary for procreation. It is also necessary to know that the process of merging gametes is usually called fertilization. Meiosis gametogenesis is the main stage in the development of germ cells. We will pay attention to him a little later.
Now we highlight the forms of sexual reproduction:
- isogamy;
- heterogamy;
- ovogamy.
It is important to note that they differ in some structural features of germ cells. So, for example, with isogamy, both male and female gametes are mobile, in addition, they have the same size. The following form is very similar to the previous one. The main difference of the second is that the female reproductive cell is larger than the male, as it is not so mobile. The third type of sexual reproduction is the most popular, as it is found in most animals and plants. In this embodiment, the female reproductive cell is motionless and significantly larger than the male. In this form of reproduction, the male gamete has the name - sperm, or sperm, and the female - the egg.
The first two forms are common in primitive organisms, such as algae. How do eukaryotes breed? By the fusion of male and female gametes (ovum and sperm). As a result, fertilization occurs and a zygote forms. It is very important to understand that germ cells contain the number of chromosomes, which is half as much as in a somatic cell. This can be explained quite simply: if the number of chromosomes of the somatic and germ cells were the same, then in each generation there would be a doubling of the chromosomes. Why is this not happening? Due to meiosis, that is, cell division.
Benefits of Sexual Reproduction
Gametogenesis is the development of germ cells. Sexual reproduction without the formation of gametes is impossible. It is also important to note that the stages of gametogenesis in male and female individuals have similar features. In more detail we will consider this a little later. Now we offer you a little discussion of the biological essence of reproduction and the benefits of the sexual species. The reproductive instinct is laid genetically. Moreover, with asexual reproduction, the daughter organism completely duplicates its parent.
Sexual reproduction has several advantages:
- a combination of maternal and paternal genes, that is, there is no likelihood of absolute genetic copying of one of the parents;
- variability, the ability of the population to adapt to new conditions for the survival of the species;
- speciation is facilitated and so on.
Spermatogenesis
We have already said that gametogenesis is a process of development of germ cells. Now we will consider spermatogenesis, that is, the formation of spermatozoa, in more detail. There are four stages in total:
- reproduction;
- height;
- maturation;
- formation.
At the stage of reproduction, mitotic division of spermatogonia occurs. After that, the future sperm go into the growth stage, now they have the name - spermatocytes. The growth stage is characterized by a significant increase in germ cells, which is made possible by an increase in the volume of the cytoplasm. The ripening phase is two divisions. A spermatocyte that has gone through past stages undergoes division, resulting in two spermatocytes. Then each of them is divided again. Total, from one first-order spermatocyte we get four spermatids. The latter enter the fourth stage - formation. Only after these stages does the sperm take on the form familiar to us.
Ovogenesis
Ovogenesis is the development of female germ cells (ova). Below will be listed and characterized the stages of this process.
- Reproduction. Ovogony is divided by mitosis, as a result, the number of future germ cells increases. It is important to note that the stage of reproduction falls on the second month of the intrauterine development of the girl.
- Height. This stage completely duplicates the process of male germ cell growth. The only difference is that the size of the future egg exceeds the size of spermatocytes, this is due to the accumulation of the first nutrient.
- The last stage of ovogenesis is maturation. It is characterized by two successive divisions by meiosis. During spermatogenesis, four spermatozoa are formed from one spermatocyte. In the case of ovogenesis, one oocyte is able to form one egg and three polar bodies.
Why are spermatozoa outnumbered but inferior in egg size? The sperm does not accumulate nutrients, as its life cycle is quite short. The main function of the male reproductive cell is the delivery of genetic material to the egg. In addition, it must be very mobile. Sperm cells in search of an egg die in large numbers, which explains their numerical advantage.