What is sexual reproduction?

What Does Sexual reproduction Mean

We explain what sexual reproduction is in biology, its process and how it occurs in animals and humans. Also, asexual reproduction.

Sexual reproduction occurs by the union of sex cells from both parents.

What is sexual reproduction?

In biology , sexual reproduction is any process of generation of a new individual that involves two individuals of the same species but different sex. It differs from asexual reproduction because it involves combining the genetic materials of both parents to form a new one.

 

Sexual reproduction is characteristic of eukaryotic organisms , that is, of those whose cells have a well-defined nucleus , and especially of multicellular ones.

It occurs according to different mechanisms, which always lead to fertilization: the union of sex cells from each of the parents, to initiate a process of accelerated multiplication and form a zygote, which will later become an embryo and finally a new individual of the species, ready to join the ecosystem .

The origin of sexual reproduction is a biological mystery, but it is assumed that it arose on our planet 1.2 billion years ago , before the first multicellular organisms existed .

Some theories suggest that it was a consequence of viral infections, others to certain types of cellular phagocytosis that allowed the incorporation of the DNA of the devoured cells into that of the devourer. In any case, it made it possible to combat the genetic impoverishment of the communities , and gave way to a genetic variation that did not depend on sporadic mutations .

See also: Plant reproduction

Sexual selection

Individuals with attractive characteristics are able to reproduce by sexual selection.

The possibility of sexual reproduction, that is, of the combination of the genetic material of two individuals of the same species to form a new and unique one, led to the appearance in sexual living beings . That is, sexual dysmorphism arose : the differentiation of individuals based on their biological sex (male and female).

This differentiation is the product of sexual selection: an evolutionary process described by Charles Darwin in his work The Origin of Species (1859), and which involves the effect of competitive pressure, that is, natural selection , among the individuals of a same species, for accessing copulation, understood, for reproducing.

Put more simply: individuals of the same species compete with each other to reproduce effectively, through different mechanisms that, over time , were modifying and specializing their own bodies.

Thus, the body of males and females of the different species began to develop physical and biochemical characteristics that allowed them to have access to the sexual act, such as the specialization of certain parts of the body for reproductive purposes, or the development of others in order to carry out the sexual act. courtship and attracting a sexual partner, such as flashy colors .

Process of sexual reproduction

Reproduction is the meeting between the male and female gametes.

Sexual reproduction can occur according to different mechanisms, but always within a very similar scheme of biochemical and cellular processes, which we can describe as follows:

  • Gametogenesis. Organisms generate sex cells (gametes), which have half the genetic content of an ordinary cell and are specifically designed for reproduction . These cells originate through a process called meiosis , in specialized glands and organs of the body and are different depending on the sex. In the case of animals, they are sperm (male) and ovules (female).
  • Fertilization. This is the name given to the encounter between the female and male gametes, to fuse and produce a zygote, that is, a new cell endowed with a unique and unrepeatable genetic material, possessing all the potential to become a complete individual. For this cell to be produced, the gametes must physically unite, which can occur in the environment (external fertilization) or within the female body (internal fertilization). Depending on this, then a sexual act or intercourse should take place.
  • Embryonic development. In this stage, the zygote multiplies, grows and gains complexity, going through numerous stages until it produces an embryo: a new individual of the species of its parents, which from then on will grow, develop and eventually be ready to start a life of its own. This embryonic development will take place within the maternal body (in the case of internal fertilization) thus giving rise to pregnancy; or it will take place inside eggs (in the case of external fertilization).
  • Birth. When embryonic development is complete, the new individual appears into the world for the first time, which involves breaking the egg membrane or being expelled from the maternal body through the birth canal. From then on, there will be a new individual of the species in the world.

Sexual reproduction in animals

Most reptiles are oviparous.

The vast majority of animals reproduce sexually, which is why they also present sexual dysmorphism: physical differences between males and females. However, not all of them reproduce identically, as they exist:

  • Oviparous animals . Those that reproduce sexually, either through intercourse (internal fertilization) or the release of gametes (external fertilization), but always through eggs deposited by the female. These eggs are fertilized inside or outside the female by the male's sperm and each give rise to a new individual of the species (or several). They are examples of oviparous animals: insects, fish, reptiles and birds.
  • Viviparous animals . Those who reproduce sexually and through intercourse, that is, with internal fertilization, for which they go through a gestation or pregnancy, at the end of which the new individuals, already formed, ready to lead an independent life, are expelled alive. They are examples of viviparous animals: mammals and humans .
  • Ovoviviparous animals. Those that reproduce sexually and through intercourse, and by laying eggs, but the latter occurs within the mother's body, from which the formed individuals will later emerge. It is an intermediate option between the previous two. Examples of ovoviviparous animals are: sharks , rays and certain types of snake.

Human sexual reproduction

Human beings go through a prolonged pregnancy, 9 months.

Human beings, as mammals, reproduce sexually and through intercourse , with internal fertilization of the female, which then goes through a period of pregnancy or prolonged pregnancy, for approximately 9 months.

During this process, the mother's womb bulges as the zygote becomes an embryo and the latter becomes a fetus, to finally be expelled through the birth canal.

However, unlike other animal species, human beings have a prolonged and vulnerable childhood, especially in the first months of life, since the development of our brain is postpartum . Otherwise it would be very difficult for a child's rigid head to pass through the birth canal.

More in: Human reproduction

Asexual reproduction

Asexual reproduction does not require the participation of two sexes or gametes.

Unlike sexual reproduction, asexual does not require the participation of two sexes, or gametes, but starting from a single individual two offspring can be obtained , but with the exception that these will be genetically identical to the parent , that is, they will be your clones.

Asexual reproduction differs from sexual reproduction in that it is much cheaper in energy terms, and easier in its cellular procedures, but it lacks a fundamental element that is genetic variability. To do this, the species of living beings that reproduce in this way depend on spontaneous DNA mutations.

Follow on: Asexual reproduction

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