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6.5.3.1. Asexual reproduction

Asexual reproduction

Asexual reproduction in unicellular organisms

Asexual reproduction is the simplest and most primitive reproductive mechanism. No specialized cells are needed for reproduction. Living beings reproduce from themselves. A cell (mother) gives rise to two more cells (daughters) identical to each other and to the mother, since they have the same genetic information.

Asexual reproduction in multicellular organisms

The cells of multicellular organisms divide by mitosis, in such a way that two cells arise from one cell, the same as the mother. However, reproduction occurs in special structures that grow together with the parent and that will give rise to the new individual when they separate.

Asexually reproducing organisms are the simplest and least evolved, such as porifera and cnidarians, in which there are also no different sexes (neither male nor female).

  • In asexual reproduction only one individual is involved .
  • All offspring are genetically identical , like clones, and come from one or more cells in the parent's body .

Asexual reproduction has advantages and disadvantages:

  • Advantages of asexual reproduction. Many individuals identical to the parent can be obtained in a short time. If the environment is favorable, they can be easily developed.
  • Disadvantages of asexual reproduction. Since all offspring are the same, if the environmental conditions change and become adverse, it is possible that none of them will survive.

There are several types of asexual reproduction :

Gemmation

In gemmation, the individual produces a group of cells, the buds, which grow until they separate and new individuals arise.

Budding can also occur in unicellular individuals, such as yeasts, in which the parent cell divides into two daughter cells of different sizes.


Sporulation

The individual that reproduces by sporulation produces many small cells called spores. Spores are formed when the nucleus divides into several parts, each of which is surrounded by cytoplasm and a membrane. The spores remain in the cell until the membrane breaks and they come out, released into the air or water.

Some unicellular protozoafungi, and algae reproduce by sporulation.

Fragmentation

Through fragmentation, an organism can break off, naturally or by accident, from a fragment that will later become an individual. For example, this occurs in many vegetables.