Reproduction is the ability of organisms.reproduce their own kind. Reproduction is one of the key features of all living things, so it is necessary to understand the biological significance of fertilization. This issue has been studied at a high level since the main stages and ending with molecular and genetic mechanisms.
Fertilization is a natural biological process of fusion of two germ cells: male and female. Male gametes are called sperm, and female gametes are called egg cells.
Последующим этапом после слияния половых клеток the formation of a zygote, which can be considered a new living organism. A zygote begins to divide mitosis, increasing the number of its constituent cells. A zygote develops from the embryo.
There are a large number of types of eggs and methods of crushing. All of them depend on the taxonomic affiliation of the living organism under consideration, as well as the degree of its evolutionary development.
Размножение является основным приспособлением для procreation. Its future depends on the reproductive abilities of individuals of the species under consideration, therefore different animals and plants have their own ways of adaptation to improve the quality of the whole process.
For example, wolves and lionesses always protect theiroffspring from potential predators. This increases the survival of the young and ensures their further adaptation to the conditions of life. Fish lay a large number of eggs, because the chance of external fertilization in the aquatic environment is quite low. As a result, out of thousands of potential fry, only a few hundred develop.
Биологическое значение оплодотворения заключается that two germ cells from different organisms merge and form a zygote that carries the genetic traits of both parents. This explains the dissimilarity of relatives to each other. And this is good, because the change in the gene pool of any population is an evolutionary adaptive mechanism. Descendants, generation after generation, are getting better compared to their parents. In the face of a gradual change of environment (climate change, the emergence of new external factors) adaptive skills are always relevant.
And what is the biological significance of fertilization at the biochemical level? Let's consider:
Plants compared to animals have somereproductive features. Representatives of angiosperms, which are characterized by double fertilization (opened by the Russian scientist Navashin in 1898), require special attention.
Structures that determine sexbelonging to flowering plants, are stamens and pistils. In the stamens, pollen ripens, which consists of a large number of grains. One grain contains two cells: vegetative and generative. The pollen grain is covered with two shells, and the outer one always has any outgrowths and recesses.
The pestle is a pear-shaped structure.forms consisting of stigma, post and ovary. In the ovary, one or several ovules form, within which the female sex cells will mature.
When pollen grain hits the stigma of the pistil,the vegetative cell begins to form a pollen tube. This channel is relatively long and ends at the micropyl ovule. In this case, the generative cell divides mitosis and forms two sperm cells, which through the pollen tube enter the ovule tissue.
Why two sperm?How does the biological significance of fertilization in plants differ from the same process in animals? The fact is that the embryo sac of the ovule is represented by seven cells, among which are the haploid female gamete and the diploid central cell. Both will merge with incoming sperm, forming a zygote and endosperm, respectively.
Seed formation is an important feature.reproductions in angiosperms. In order to fully mature in the soil, it needs a large amount of nutrients, among which will be various enzymes, carbohydrates and other organic / inorganic components.
Эндосперм у покрытосеменных триплоидный, так как diploid central embryonic sac cell fused with haploid sperm. Here is the biological significance of fertilization in plants: a triple set of chromosomes contributes to the high rate of increase in the mass of endosperm tissue. As a result, the seed receives many nutrients and energy reserves for germination.
Depending on the further fate of the endosperm, there are two main types of seeds:
Of course, to call such fertilization doubleIt will be wrong, as we now know the main features and functions of this process. When the central cell is fused with sperm, the zygote does not form, and the resulting genetic set becomes triple. Still, the seed does not consist of two independent embryos.
However, the biological value of doublefertilization is really great. Seeds during germination require a large amount of organic and inorganic substances, and this problem is solved by the formation of triploid endosperm.
