Self-fertilization or autogamy or automixis (from Greek ldquo;autosrdquo; - ldquo;on your ownrdquo; and ldquo;mixisrdquo;) is one of the ways

Self-fertilization [Autogamy, Automixis]

Self-fertilization or autogamy or automixis (from Greek “autos” — “on your own” and “mixis”) is one of the ways of sexual reproduction. In this form of sexual reproduction egg is fertilized by the male gamete of the same organism.

Plants’ automixis is the result of self-pollination. It is found in many species (typical self-pollinated plants are the peas, violets, wheat, tomatoes, barley, beans). In animals, this type of sexual reproduction is extremely rare. Only flat parasitic tapeworms continually propagate by self-fertilization. All other species of animals, even hermaphrodites that can simultaneously produce male and female gametes, avoid it. This is achieved by the fact that the male copulatory organ is located on the body in such a way that self-fertilization is mechanically impossible. Cross-pollinating plants in the process of evolution also have developed a mechanism to prevent self-pollination. For example, in the same plant pollen and pistil ripen at different times. In addition, some plant species have specific genetic mechanisms that prevent self-pollination. If cross-pollinating plants are artificially pollinated with their own pollen for several generations in a row, you get a pure line — genetically identical offspring (diagram 15). Thus, all the self-pollinated plants are the pure lines (the exact same structure forms by vegetative propagation, when all offspring of one of the parent individual is called a clone). Thus, all the self-pollinated plants — is nothing but a collection of pure lines. Taken from http://worldofschool.org

Diagram 15. Laboratory lines of: a — house mouse and b — gray rat — typical examples of pure lines obtained artificially as a result of not less than 20 generations of inbreeding

Disadvantages of self-fertilization

Researches have shown that despite the mechanisms that prevent self-pollination, for example, in cross-pollinating conifers, part of seeds still form by self-pollination. Tracking the fate of the trees grown from such seeds, the researchers noted their low viability: they die very young. And all the centuries-old pine and spruce, as shown by a special genetic analysis, were descendants that have been obtained as a result of cross-pollination. Therefore, scientists believe that self-fertilization leads to reduced viability of the offspring, and therefore in the process of evolution have been worked out mechanisms to prevent automixis.

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Questions:
  • What mechanisms limit the self-fertilization in plants and animals?

  • Why in self-pollinating plants degeneration does not occur in several generations, while self-pollination in cross-pollinating inevitably leads to this result?