Reproduction is the ability of organisms to reproduce their own kind. Reproduction is one of the key features of all living things, so you need to understand what the biological significance of fertilization is. This question has been studied at a high level today, starting from the main stages and ending with molecular and genetic mechanisms.
What is fertilization?
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 ova.
The next step after the fusion of germ cells is the formation of a zygote, which can be considered a new living organism. The zygote begins to share mitosis, increasing the number of its constituent cells. An embryo develops from a zygote.
There are a large number of egg types and crushing methods. All of them depend on the taxonomic affiliation of the living organism in question, as well as the degree of its evolutionary development.
What is the biological significance of fertilization
Reproduction is the main device for procreation. The future depends on the reproductive abilities of individuals of the species in question, therefore, different animals and plants have their own adaptation methods to improve the quality of the whole process.
For example, wolves and lionesses always protect their offspring from potential predators. This increases the survival of the cubs and guarantees their future adaptability to living conditions. 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.
The biological significance of fertilization is that two germ cells from different organisms merge and form a zygote that carries the genetic characteristics of both parents. This explains the dissimilarity of relatives to each other. And this is good, because changing the gene pool of any population is an evolutionary adaptive mechanism. Descendants, generation after generation, are getting better than their parents. In a gradual change of environment (climate change, the emergence of new external factors), adaptive skills are always appropriate.
And what is the biological significance of fertilization at the biochemical level? Let's consider:
- This is the final egg formation.
- This is the sex determination of the future embryo due to the corresponding genes brought by male gametes.
- And, finally, fertilization plays a role in restoring the diploid set of chromosomes, as germ cells are individually haploid.
Propagation of flowering plants
Plants in comparison with animals have some reproductive characteristics. Special attention is required by representatives of angiosperms, which are characterized by double fertilization (discovered by the Russian scientist Navashin in 1898).
The structures determining the gender of flowering plants are stamens and pistils. In 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 indentations.
The pestle is a pear-shaped structure consisting of a stigma, a column and an ovary. In the ovary, one or more ovules form, inside of which the female reproductive cells will mature.
When pollen grains enter the stigma of a pestle, the vegetative cell begins to form a pollen tube. This channel has a relatively large length and ends at the micropile ovule. In this case, the generative cell divides by mitosis and forms two sperm, which enter the ovum through the pollen tube.
Why two sperm? How is the biological significance of fertilization in plants different from the same process in animals? The fact is that the germinal sac of the ovule is represented by seven cells, among which there is a haploid female gamete and a diploid central cell. Both will merge with the incoming sperm, forming a zygote and endosperm, respectively.
The biological significance of double fertilization in plants
Seed formation is an important feature of reproduction in angiosperms. For complete maturation in the soil, it needs a large amount of nutrients, among which there will be various enzymes, carbohydrates and other organic / inorganic components.
In angiosperms, the endosperm is triploid, since the diploid central cell of the embryo sac merged with haploid sperm. This is the biological significance of fertilization in plants: a triple set of chromosomes contributes to a high rate of increase in endosperm tissue mass. As a result, the seed receives a lot of nutrients and energy reserves for germination.
Seed types
Depending on the fate of the endosperm, two main types of seeds are distinguished:
- Seeds of monocotyledonous plants. They clearly visible well-developed endosperm, which occupies a larger volume. The cotyledon is reduced and presented in the form of a shield. This type of seed is characteristic for all representatives of cereals.
- Seeds of dicotyledonous plants. Here, the endosperm is either absent or remains in the form of small accumulations of tissue on the periphery. The nutritional function of such seeds is performed by two large cotyledons. Examples of plants: peas, beans, tomatoes, cucumbers, potatoes.
conclusions
Of course, to call such fertilization double would be a mistake, since we now know the main signs and functions of this process. When the central cell merges with sperm, the formation of a zygote does not occur, and the resulting genetic set becomes triple. Still, the seed does not consist of two independent embryos.
However, the biological significance of double fertilization is really great. Seeds during germination require a large number of organic and inorganic substances, and this problem is solved by the formation of a triploid endosperm.