One of the most complex, mysterious and amazing processes in nature is reproduction. It is very important, and thanks to it, the life of absolutely all living organisms on earth is supported. To begin with, we will examine in more detail what it is. Reproduction is the ability of all living things to produce similar organisms. Without this ability, no living representative of nature could not dwell on earth.
Breeding methods
Now consider all types of reproduction, there are only two of them. They differ significantly from each other, but sometimes in the most insignificant little things you can notice a similarity.
Reproduction asexual
Propagation of organisms such as protozoa, fungi, bacteria, intestinal, algae, sponges, tunicates, vascular plants and bryozoans is called asexual.
The simplest type of reproduction can be attributed to viruses. In this process, nucleic acids play an important role , as well as the ability of their molecules to independently double. It is also based on fragile hydrogen bonds among nucleotides.
There are other ways of asexual reproduction for organisms - vegetative and due to spore formation.
First, consider the vegetative. Such reproduction is the development of a new organism from a part separated from the mother. A similar method leads to an increase in the population of unicellular and multicellular, but it manifests itself in different ways.
During the vegetative propagation of multicellular animals, the division of their body into equal parts begins, then a living organism arises from it. Similarly, a population of flatworms, nemerthins, sponges, hydras, and many other creatures is maintained. There is still such a thing as polyembryony in animals. During this process, the embryo at a certain time begins to divide into parts, which subsequently develop into a separate organism. Such a course of reproduction is observed in armadillos. It is worth noting that they reproduce only sexually.
Vegetative reproduction of unicellular has several forms - budding, division and multiple division.
Multiple division is also called schizogony, in this case the nucleus is divided and then the cytoplasm is separated into parts.
In the process of simple fission, there is a mitotic course of fission of the nucleus, where further constriction of the cytoplasm occurs.
Now let's move on to asexual budding. Such reproduction is the emergence of special cells or spores containing the nucleus. They have a dense shell and for quite a long time can live in the most adverse conditions for this. This also works great for their further resettlement. This type of reproduction is characteristic of mosses, fungi, algae, bacteria, and ferns. There is the possibility of the formation of zoospores from some cells of green algae.
Reproduction of animals by spore formation can be found in plasmodium malaria and sporozoans.
Many organisms can combine reproduction asexually with sexual.
Sexual reproduction
Sexual reproduction is a more complex process, and two individuals, male and female, are needed for a full course. In the course of it, genetic data is exchanged through gametes (these are germ cells). This process is called gametogenesis.
In this case, several categories can also be distinguished: the fusion of single-cell and germ-cell organisms, such as sperm and egg cells. In this process, zygotes appear, from which a new organism is formed. After he reaches maturity, he begins to reproduce gametes on his own.
There are several types of sexual reproduction, in which various cells and reproductive organs take part.
Forms and types of reproduction
It is necessary to consider each process separately in more detail, since they all have different fundamentals and processes.
Gametogenesis has already been discussed earlier, so we will not repeat it.
Isogamy and Anisogamy
In these two species, two cells take part, however, isogamy implies the same structure of cells, but descended from different parents. Anisogamy takes as a basis different sex cells - microgametes and macrogametes, which differ in size.
Ovum and sperm
So-called female and male germ cells. They are formed in the genitals of the corresponding individuals.
The egg is composed of halide chromosomes and cannot divide by itself.
Sperm cells are slightly smaller than female cells. They have an amazing structure that provides them with active movement. The presence of certain enzymes in the axoplasm ensures the cleavage of the egg wall for penetration and further fertilization. Each reproductive cell contains a part of the genetic information of the parents and is transmitted to future offspring.
Parthenogenesis optional
Such reproduction is an atypical sexual process. In it, a change in typical and atypical reproduction can be noted. The female develops from fertilized eggs, and the male from unfertilized. Thus, an increase in the bee population occurs.
Other varieties of parthenogenesis are also known, namely, constant and cyclic. In the first case, the offspring develops from eggs that are not susceptible to fertilization. This can be observed in such individuals whose parent partners for breeding do not have the opportunity to meet.
In the case of cyclic parthenogenesis, environmental conditions play a large role. Under its influence, an alternation of typical reproduction with parthenogenesis occurs.
All the information presented is only a small part of the description of the most amazing and mysterious process on earth - reproduction. Thanks to him, today there are all living organisms and plants. If only for a moment to think about how everything in this process is carefully, wisely thought out and arranged, then you can realize the power of all nature. At the level of molecules and chromosomes, amazing things happen that are hard for a simple person to understand.