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, let's take a closer look at what it is. Reproduction is the ability of all living beings to produce organisms similar to themselves. Without this ability, not a single living representative of nature could inhabit the earth.
Methods of reproduction
Now consider all types of reproduction, there are only two of them. They differ significantly from each other, but sometimes in the smallest details you can notice the similarity.
Asexual reproduction
Reproduction of organisms such as protozoa, fungi, bacteria, coelenterates, algae, sponges, tunicates, vascular plants and bryozoans is called asexual reproduction.
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 self-doubling. 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 is an increase in the population of unicellular and multicellular, but it manifests itself in different ways.
During the vegetative reproduction of multicellular animals, the division of their body into equal parts begins, then a living organism arises from it. Similarly, the population of flatworms, nemerteans, sponges, hydras and many other creatures is maintained. There is also such a thing as polyembryony in animals. During this process, the embryo at a certain time begins to divide into parts, which later develop into a separate organism. Such a course of reproduction is observed in armadillos. It is worth noting that they only reproduce sexually.
Vegetative reproduction of unicellular organisms has several forms - budding, fission and multiple fission.
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 division, the mitotic course of nuclear division occurs, where the cytoplasm constriction occurs further.
Now let's move on to asexual budding. Such reproduction is the emergence of special cells or spores containing a nucleus. They have a dense shell and can live for quite a long time in the most unfavorable conditions for this. This also works great for their further resettlement. This type of reproduction is typical for mosses, fungi, algae, bacteria and ferns. There is a possibility of zoospore formation from some green algae cells.
Reproduction of animals by sporulation can be found in Plasmodium malaria and sporozoans.
Many organisms can combine asexual reproduction with sexual reproduction.
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 sex cells). This process is called gametogenesis.
In this case, several categories can also be distinguished: the fusion of single-celled organisms and germ cells, such as sperm and eggs. In this process, zygotes appear, from which a new organism is formed. After it reaches maturity, it begins to reproduce gametes on its own.
There are several types of sexual reproduction, in which various cells and reproductive organs take part.
Forms and types of reproduction
Need to take a closer look at each process individually as they all have different bases and flows.
Gametogenesis has already been discussed before, so we will not repeat it.
Isogamy and anisogamy
Two cells are involved in these two species, however, isogamy means cells that are identical in structure, but descended from different parents. Anisogamy is based on differentgerm cells - microgametes and macrogametes, which differ in size.
Eggs and sperm
This is the name of female and male sex cells. They are formed in the genital organs of the respective individuals.
The egg consists of halide chromosomes and cannot divide on its own.
Sperms are slightly smaller than female cells. They have an amazing structure that provides them with active movement. The presence in the axoplasm of certain enzymes ensures the splitting of the walls of the egg for penetration and further fertilization. Each sex 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. It can be noted the change of typical and atypical reproduction. The female develops from fertilized eggs, and the male develops from unfertilized ones. Thus, there is an increase in the population of bees.
Other varieties of parthenogenesis are also known, namely constant and cyclic. In the first case, the offspring develops from eggs that are not subject to fertilization. This can be seen in individuals whose parental breeding partners are unable to meet.
In the case of cyclic parthenogenesis, environmental conditions play an important role. Under its influence, there is an alternation of typical reproduction with parthenogenesis.
All information provided is only a small part of the descriptionthe most amazing and mysterious process on earth - reproduction. Thanks to it, all living organisms and plants exist today. If you just think for a moment 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 are happening that are difficult for an ordinary person to understand.
