Biodiversity: It is defined as the part of nature which includes the
differences in the genes among the individuals of a species; the variety and
richness of all plants and animal species at different scales in a space -
local regions, country and the world along with the types of ecosystem. (Walter Rosen 1982) The diversity is with
respect to size (microscopic to macroscopic), shape, colour, form, mode of
nutrition, type of habitat, reproduction, motility, duration of life cycle
span, etc.
Levels
of Biodiversity:
Diversity of living world can be
observed at various levels, ranging from molecular to ecosystem level. Major hierarchical
and interrelated levels are genetic diversity, species diversity (community),
and ecosystem diversity (ecological).
a) Genetic diversity:
1)
It is the intraspecific
diversity.
2)
It is the diversity in the number
and types of genes as well as chromosomes present in different species and also
the variation in the genes and their alleles in the same species.
3)
It includes variation within a
population and diversity between populations that are associated with
adaptation to local conditions.
4)
Genetic variations (e.g. allelic
genes) lead to individual differences within species which gives evolution.
5)
They also improve chances of
continuation of species in the changing environmental conditions or allow the
best adapted to survive.
6)
Existence of sub-species races are
examples of genetic diversity.
7)
Greater the diversity better would
be sustenance of a species. You know about 1000 varieties of mangoes and 50,000
varieties of rice or wheat in India.
8)
Another case of genetic diversity
is: a medicinal plant Rauwolfia vomitoria which secretes active
component reserpine, is found in different Himalayan ranges. This plant shows
variations in terms of potency and concentration of active chemical, from
location to location.
9)
Genetic diversity or variability is
essential for a healthy breeding population of a species.
b) Species diversity:
1)
It
is the interspecific diversity.
2)
The
number of species of plants and animals that are present in a region,
constitutes its species diversity. Some areas or regions are richer in species
than in the other regions.
3)
Species
diversity deals with variety
of species (species richness) as well as number of individuals of
different species (species evenness) observed in area under study. E.g.
amphibian species diversity is more in western ghats than in eastern ghats.
4)
Natural
undisturbed tropical forests have much greater species richness than monoculture
plantation of timber plant, developed by forest plantation. India is one among
15 nations that are rich in species diversity.
