Brief introduction to Biodiversity

1. 1
Biodiversity – Introduction
‘‘Biodiversity’’ was first used in its long version (biological diversity) by Lovejoy
(1980) and is most commonly used to describe the number of species.
1992 United Nations Earth Summit defined “biological diversity” 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 part: this includes diversity within species,
between species and of ecosystems”.

2. 2
Biodiversity – Introduction & Index
Species diversity - It is represented as the number of species a
community consists of. It depends mainly on climatic conditions.
Ecosystem diversity- describes the aggregation of and interaction of species
with one another and deals with the variations in ecosystems within a
geographical location and its overall impact on human existence and the
environment especially during stress conditions.
Genetic diversity - the total number of genetic characteristics in the genetic
makeup of a species & is distinguished from genetic variability, which describes
the tendency of genetic characteristics to vary. The magnitude of variation
increases along with size and environmental parameters

3. 3
Biodiversity – Introduction & Index
Whittaker (1965) divided diversity into 3 classes.
α-Diversity-It tells the species diversity in a given community and
depends upon species richness and evenness.
β-Diversity - It describes a range of communities formed due to
replacement of species. This situation arises due to the presence of different
microhabitats, niches and environmental conditions
γ – Diversity - It describes diversity of habitat over a total land escape
or geographical area

4. 4

5. 5
Factors determine degree of biodiversity:
(a) Habitat stress: Diversity is low in habitats under any stress (pollution).
(b) Geographic isolation: Isolation can lead to special species located to that
area only. If a species in an island disappear due to random events, it cannot be
easily replaced.
(c) Dominance of one species: Dominance of one species doesn’t allow others to
grow and flourish.
(d) Availability of ecological niches: A complex community offers variety of niches
than a simple species and promotes greater diversity.
(e) Edge effect: Ecotones have greater biodiversity.
(f) Geological history: Old and stable ecosystems like Amazon forests have
greater diversity as they are more resistant to change.