What is the essence of sexual reproduction (biology, Grade 8)

What is the essence of sexual reproduction and what are its advantages? This issue has long been of interest to many scientists, because the reproduction by organisms of their own kind is a necessary condition for life on planet Earth.

What is multiplication?

The essence of this process is to reproduce your own kind. And this is not about the color of the eyes or the structure of the hair. It is important that the organism, which only appeared in the light in a certain habitat, could survive in it. Only the characteristic features of the structure inherited from the ancestors can provide this. Otherwise, everyone would suffer through agony, like a human amphibian from the movie of the same name.

Methods of reproduction of organisms

Are there any fundamental differences between asexual and sexual reproduction? Certainly. In the first case gametes do not take part, in the second their presence is simply necessary. There are several ways of asexual reproduction. The simplest of these is the division of the cell in two. So bacteria, single-celled animals and algae reproduce. For malaria plasmodia is characterized by multiple division, as a result of which from a single mother cell several dozens of daughter are formed at once. Thanks to the ability of cells to divide, damaged tissues and organs are restored, and many animals are capable of rapid regeneration. For example, the freshwater hydra, which is a representative of the type of the intestinal cancers, can recover from the 1/200 part.

This organism reproduces by budding. At the same time, a protrusion is first formed on the body, which grows, acquires the features of the mother's body, and after it is split off and begins to exist independently.

Everyone used food yeast. So, increasing their number is nothing more than the process of budding mushrooms.

Plants are capable of vegetative reproduction. This method consists in separating the multicellular part from the whole organism. Violets use leaves for this, potatoes have modified underground shoots (tubers), and grapes have cuttings.

What is the essence of sexual reproduction?

This process occurs only with the participation of gamete - specialized sex cells: male - spermatozoa, and female - oocytes. They contain in their nuclei hereditary information contained in DNA molecules.

The essence of the process of sexual reproduction is the recombination of this material. And for this, gametes are not always necessary. So, the infusoria of the shoe is conjugated. In this case, two organisms approach each other, and between them a cytoplasmic bridge is formed, along which the nuclei exchange their contents.

Advantages of sexual reproduction

Thanks to the recombination of genes - sections of DNA molecules - the body can acquire new useful signs. The main significance of sexual reproduction is in this. After all, when dividing the maternal cell, its exact copy is formed. Other signs are simply nowhere to take. If environmental conditions change, such organisms will not be able to adapt, which will inevitably lead to their destruction and reduction of species diversity as a whole.

New traits are formed only with a change in genetic material. Then they can be inherited and fixed in a number of generations.

Sexual process in plants and animals

What is the essence of sexual reproduction of plants, we can consider the example of a fern, which is the highest spore plant. On the underside of its green leaves mature special structures - srusy. They contain spores - cells of asexual reproduction. Falling into moist soil, they germinate, forming a small green sprout. It generates eggs and spermatozoa, which, in pairs merging, give rise to a new leaf-stalk plant. This is how the alternation of the sex generation - gametophyte, and asexual - sporophyte occurs.

Flower plants have a flower for generative reproduction. In his pestle, the female gamete ripens, and in the anthers the stamens are male. As a result of fertilization, a seed germ is formed. For future development and protection, it has a large number of reserve substances, juicy or leathery shells of the fruit.

Animals also have specialized cells and organs in which they are located - glands. Representatives of this kingdom, there are several types of fertilization. When external, the fusion of gametes takes place outside the body of the female, as in fish or amphibians, when the female swings into the water with caviar, and the male water it with seminal fluid. Why are there so many eggs? This is a biological mechanism for maintaining the size of the adult population, because cells are defenseless, and most of them are eaten by predators. In case of internal fertilization, the future organism is in the mother's body for a certain time. Therefore, the number of eggs that are capable of fertilization will not be so impressive.

This is the essence of sexual reproduction, as a result of which new varieties of plants and species of animals arise, and also thanks to which it becomes possible to create hybrid and cloned organisms.