The word ‘biodiversity’, made famous
by the naturalistic biologist Edward O. Wilson in his book
“BioDiversity” (Wilson, 1999), is employed to
describe the variety of living forms on Earth. More precisely,
it describes the result of the biological project present
within the genetic patrimony of a species and its phenotypic
characterization through adaptation to the environment.
It is the result of a continuous dialogue between génotype
et phénotype;
between the project of each species and also of its individuals
and their scope for development.
Biodiversity is generally considered three levels: genetic,
species l and ecosystems.
Genetic diversity refers to the variability
of the genetic patrimony within the framework of each species.
It includes genetic variations between different populations
of the same species, and genetic variations within the same
population. This genetic variability takes place through
recombination in populations with sexual reproduction and,
in each individual, by mutations of genes
and chromosomes
. In particular, genes that controll essential biochemical
processes are immutable in the different taxa
and, generally,have minimum variations. Other genes, more
specialised, have a more extensive gamma of variation.
Species diversity refers to the variability
of species in a habitat.
The two more common methods used to evaluate the species
diversity in a territory are: estimation of species richness,
which is the number of species in an area, and estimation
of the abundance of each species in the community.
Ecosystèms
diversity includes differences between different
typologies of ecosystems, as well as differences in habitats
and biological processes inside each ecosystem. The ecosystems
diversity is often evaluated by counting the relative abundance
of species. With the same number of species, an ecosystem
where the species are present in equal proportion is more
diversified than an ecosystem where some species are numerous
and others are rare.
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Actual biodiversity is the
result of millions of years of evolution.
(© 2005 Gaël Farano, Martino Coppola di Canzano).
Animal species make up around three quarters
of our biodiversity. More than half of these are insects,
numerically dominant on our Planet; there are however, many
species of bacteria, fungi and algae, microscopic or little-known
organisms.
The estimation of biodiversity on Earth is approximately of
one and a half million different species. However, this figure
is calculated by default, and more recent estimations indicate
that the number of different species could be much higher,
around 10-15 million. This means that at present only a 10%
of the real biodiversity is known (Dallai R., 2005).
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| Biodiversity
is of essential importance because the ecological equilibrium
of the Planet and the survival of our species depend
on its conservation. It is the most precious of our
resources. . (Dallai R., 2003). (Photos of animals©
2005 Martino Coppola di Canzano); (Photos of plants©
2005 E. Mattana; G. Bacchetta; C. Pontecorvo - CCB).
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