Three levels

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Intraspecific biodiversity observed in the ears of corn

Biodiversity is the diversity of all life forms. It is usually divided into three levels:

  • The genetic diversity, it is defined by the variability of genes within a species or population. It is characterized by the difference between two individuals of the same species or subspecies (intraspecific diversity).
  • The species diversity, is the diversity of species (interspecific diversity). Thus, each defined group can then be characterized by the number of species which compose it, see taxonomy. However, to characterize the number of anatomical organization plan, it is preferable to use the term disparity.
  • Ecosystem diversity, which corresponds to the diversity of ecosystems found on Earth, the interactions of natural populations and their physical environments.


According to the Neo-Darwinians, the gene is the fundamental unit of natural selection, thus the evolution, and some, like EO Wilson, believe that the only biodiversity "useful" is genetic diversity. However, in practice, when studying the biodiversity field, here is the unit more accessible.



Biodiversity domestic and wild biodiversity

The Convention on Biodiversity Ecological June 5, 1992 defined the term biodiversity as "the variability among living organisms from all sources including, inter alia, terrestrial, marine and other aquatic ecosystems and the ecological complexes of which they are this includes diversity within species, between species and of ecosystems ".

Biodiversity therefore concerns all the living and dynamic interactions within the living, whether natural (wild biodiversity) or managed by humans (domestic biodiversity). In these two categories combined biodiversity commensal of man, ie species which, while not being handled by humans adapt to environments that he creates (and the rat the blues in town for example).

Assessing biodiversity

How to measure biodiversity? 

According to the terms defined above, there can be a single objective measure of biodiversity, but only measures on trends or targets specific use or application. We should thus rather speak of "evidence" of biodiversity than real indicators. They begin to be addressed globally, through biodiversity observatories, in particular from the IMoSEB.

Conservationists seek to assess quantitatively and qualitatively valued, recognized by those for whom they make this estimate, and an element of decision support for species or habitats in need of protection. Others seek a more easily defensible from a economic standpoint, to ensure the continued use (including future generations) of biodiversity and its potential for development, ensuring the protection of 'environment in a changing world.
Biologists attach increasing importance to the genetic diversity and gene flow. The future is unknown, no one can know which genes are most important for the evolution. So there is consensus that the best conservation of biodiversity is to safeguard the wider gene pool possible habitats sufficiently representative and interconnected for the exchange of genes are possible.

Some view this approach as inadequate and sometimes too restrictive, especially because it does not take into account the functions aménitaires and cultural biodiversity.

A recent study shows that the decline of butterflies in a given area is related to the biodiversity in this same area. The presence or absence of butterflies would be a good index for measuring biodiversity.


The different dimensions of biodiversity

The Darwin's finches of the Galapagos illustrate how an adaptive radiation, a kind original, four types of bill for thirteen species in all have appeared.
 
The Darwin's finches of the Galapagos illustrate how an adaptive radiation, a kind original, four types of bill for thirteen species in all have appeared.

Biodiversity must both be considered as process dynamics, in terms of its time. It is a changing point of view of the case as that of the individual. The half-life of an average case is about one million years and 99% of species that have lived on Earth are now extinct.

It may also be considered in its component space: Biodiversity is not distributed evenly over the ground. The flora and fauna differ according to various criteria such as climate, altitude, soil or other species (criteria that man changes more sharply and quickly).

The inventory of species

The systematic explores biodiversity in its ability to distinguish an organism or taxon to another. It faces the problems of time and numbers: 1.75 million species have been described, but estimates range from 3.6 to more than 100 million species. The routine is only one aspect of biodiversity, however, useful to the understanding of ecosystems, the biosphere and their functions and interactions.


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