Gametogenesis is ... The stages of hematogenesis and the forms of sexual reproduction

Today we suggest you to disassemble the process of gametogenesis. If to speak briefly and extremely clearly, then this is the process of development of the sex cells. As it became clear, the article will be devoted to reproduction. Note that several forms of sexual reproduction are distinguished. Despite this fact, they are all based on the participation of two gametes (male and female sex cells). We suggest that you consider this issue in more detail.

Sexual reproduction

We have already mentioned that sexual reproduction is due to the participation of two different sexes. They have in certain organs formed special sex cells, which are commonly called gametes. And what is gametogenesis? This is the process of forming the very sex cells that are necessary for the continuation of the genus. It is also necessary to know that the process of fusion of gametes is commonly called fertilization. Meiosis gametogenesis is the main stage of development of the sex cells. We will pay attention to it a little later.

Now we shall single out the forms of sexual reproduction:

• Isogamy;
• heterogamy;
• Omogamy.

It is important to note that they differ in some features of the structure of the sex cells. For example, with isogamy, both male and female gametes are mobile, in addition, they have the same dimensions. The next form is very similar to the previous one. The main difference is the female sex cell is larger than the male, so it is not so mobile. The third type of sexual reproduction is most popular, as it occurs in most animals and plants. In this version, the female sex cell is immobile and much larger than the male. With this form of reproduction, the male gamete has a name - sperm, or sperm, and female - an egg.

The first two forms are common in primitive organisms, for example in algae. How does reproduction take place in eukaryotes? By the fusion of male and female gametes (ovum and sperm). As a result, fertilization occurs, and a zygote is formed. It is very important to understand that sex cells contain a number of chromosomes, which is half that of a somatic cell. This can be explained quite simply: if the number of chromosomes of the somatic and sexual cells were the same, then in every generation the chromosome would double. Why does not this happen? Because of meiosis, that is, cell division.

Advantages 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 males and females have similar features. We will discuss this in more detail later. Now we offer you a little to discuss the biological essence of reproduction and the benefits of sexual appearance. The instinct of reproduction of the offspring is laid genetically. At the same time with asexual reproduction the child organism completely duplicates its parent.

Sexual reproduction has several advantages:

• A combination of maternal and paternal genes, that is, there is no probability of an absolute genetic copy of one of the parents;
• Variability, the ability of the population to adapt to new conditions for the survival of the species;
• The process of speciation is facilitated, and so on.

Spermatogenesis

We already said earlier that gametogenesis is the process of development of the sex cells. Now we will consider in more detail spermatogenesis, that is, the formation of spermatozoa. There are four stages in total:

• Reproduction;
• growth;
• maturation;
• Formation.

At the stage of reproduction, mitotic division of spermatogonia occurs. After that the future spermatozoa pass into the stage of growth, now they have the name -spermatocytes. The stage of growth is characterized by a significant increase in germ cells, which becomes possible due to an increase in the cytoplasmic volume. The maturation phase is two divisions. The spermatocyte, which passed through the previous stages, undergoes division, resulting in the formation of two spermatocytes. Then each of them is divided again. In total, from one spermatocyte of the first order, we get four spermatids. The latter enter the fourth stage - the formation. Only after these stages the spermatozoon takes on a habitual form for us.

Ovogenesis

Ovogenesis is the development of female reproductive cells (oocytes). Below, the stages of this process will be listed and characterized.

• Reproduction. Ovonia is divided by mitosis, as a result, the number of future sex cells increases. It is important to note that the stage of reproduction occurs in the second month of intrauterine development of the girl.
• Growth. This stage completely duplicates the process of growth of male germ cells. The only difference is that the size of the future egg exceeds the size of the spermatocytes, this is due to the accumulation of the first nutrients.
• The last stage of ovogenesis is maturation. It is characterized by two successive divisions through meiosis. When spermatogenesis from one spermatocyte, four spermatozoa are formed. In the case of ovogenesis, one oocyte is able to form one ovule and three polar bodies.

Why do spermatozoa exceed in quantity but are inferior in size to the oocytes? Sperm does not accumulate nutrients, as its life cycle is rather short. The main function of the male germ cell is the delivery of genetic material to the egg. In addition, it must be very mobile. Spermatozoa in the search for an egg massively die, which explains their numerical advantage.