The total degeneration : meaning of the term and a brief description of

term total degeneration proposed another Russian scientist Severtsov at the turn of the XIX and XX centuries, relate to general concepts of evolution and means the loss of certain structures of the body.But unlike dystrophy, it occurs as a result of the development of the species (and up to the P-type), rather than at a particular individual.

Basic strategy for the development of live

Throughout the evolution of the living world of the Earth the same principles have been progress or regress.If a taxon (species, family, order, class) was not able to successfully adapt to the changing environment, its development led to regress.In the case of the opposite situation was observed progress.

For a correct understanding should be a little bit on these two terms.

Progress:

  • increase the number of individuals of a single group.This can be not only a look or a family, but even a class type.
  • Increase habitat area (range) of the representatives of these taxa.
  • diversity of species, families, orders within
    a superior rank.Most often it refers to a class.

most outstanding representatives of the living world today are viruses, cat, rats, mice, cockroaches.The main causes of the prosperity of these groups lie in a good plasticity - the degree of adaptability to changing environmental conditions.Rats are generally considered to be cosmopolitan - animals living on all continents (of course, including Antarctica).

Regression:

  • Reducing the number of animals the individual rank.Most often, it is in our time about the kinds.
  • Reduced habitat area.
  • Depletion taxonomic diversity groups.The class becomes smaller units.The family has fewer and fewer genera and species.And so on.

Today many examples of regression.For the most part the cause of this is human activity.

main ways to achieve progress

Each species tends to progress.Not only for prosperity.Without it, it is impossible to survive.There are three main mechanisms that allow species to go on the path of progressive development.

  1. Aromorphosis.Changes that lead to changes in class and typical characteristics.As a rule, it is the basis for the emergence of new groups.For example, the appearance of the limbs, pulmonary respiration in fish back in the Paleozoic gave rise to amphibians and allowed chordal master anhydrous environment.The emergence of flower plants served as an impetus for further evolution that led to the creation of the angiosperms.
  2. idioadaptatsy.The changes taking place within small groups, and reflect an adaptation to certain conditions.Any impact on the major taxa not play.For example, highly specialized types of beaks of finches on the Galapagos Islands, the development of fins, color zebra and leopard.All these changes are good only for a certain location.They lead to the emergence of small groups within the whole class type.
  3. total degeneration.The changes affect multiple organs and systems.They go through the simplification of the anatomy.However, these changes may lead not only to the appearance of species, genera, and families, and even classes of living organisms.

total degeneration and its mechanisms

This is important! Under the influence of the general degeneration there is a complete or partial restructuring of the body in the direction of simplification.That, however, leads to the progress of the biological group.As a result, not only can form new species, but other groups up to higher class.

Mechanisms total degeneration may take place with the participation of one or more organ systems.All of them are influenced by the environment.There are two main mechanisms.

  • Simplification to achieve "savings" energy.For example, there was a group of tapeworms (flatworms).Virtually all members of the family are deprived of the digestive system and nutrient intake occurs through the body surface.The energy in the food absorption and digestion, it is not wasted.
  • Simplification of the uselessness of certain functions.This mechanism always concerns only one or more individual bodies.Thus, among the mole there is degeneration of organs of vision.It is they simply do not need.Do apes no tail.To maintain balance it is no longer needed because of limb development.Parasitic roundworms form, in general, have no senses.

Both of these mechanisms can be implemented individually or together.Those Ascaris (roundworm representatives) but complete lack of vision have poorly developed nervous system.

Despite the seemingly "backward movement" total degeneration makes it possible to progress as a species, and larger taxa (family, team and even class).

bivalves, having lost many features of their ancestors structure, well able to adapt and thrive during the second half of the Mesozoic and Cenozoic almost all.Only a man could actively prevent their wide distribution.

In any case, the overall degeneration is nothing like one of the most effective ways in the way of the prosperity of some groups. It allows you to occupy such niches where there are other more advanced (in terms of morphology) essentially impossible.It is, first of all, to reduce the intensity of competition with other animals and "build" their numbers before the expansion to other niches and / or increase habitat.

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