Biodiversity
The term biological diversity or biodiversity refers to the variety of life forms and habitats
found in a defined area. UNEP (1992) defines it “as the variety and variability of all
animals, plants and micro-organisms and the ecological complexes of which they are a
part”. The term biodiversity was coined by W.G. Rosen (1985).
Diversity characterizes most living organisms, the our earth supports something like 5 to 10
million species of plants and animals (IUCN, 1980) which have been the result of 3 billion
years of evolution involving mutation, recombination and natural selection.
Country like India with only 2.4% of the world’s land area has great habitat diversity and
high species diversity. India has 45,364 species of plants (includes bacteria, algae, fungi.
Lichens, bryophytes and higher plants). Similarly, a total of 89,315 species of animals are
known and described from India.
Types of Biodiversity:
Biodiversity is of three types:
1. Species diversity, 2. Genetic diversity, 3. Ecological diversity.
1. Species Diversity:
According to Biological Species Concepts (BSC), species is a basic unit of classification and is
defined as a group of similar organisms that interbreed with one another and produce
offspring’s and share a common lineage but reproductively isolated from other groups of
organisms. Species diversity refers to biodiversity at the most basic level and is the variety
and abundance of different types of individuals of a species within a community in a
given area.
Species diversity refers to variety of species in a region. Number of species per unit area is
called species richness. Evenness or equitability differs due to difference in number of
individuals in an area.
2. Genetic Diversity:
‘Genetic diversity pertains to the range of diversity in the genetic resources of the
organisms. Every individual member of a plant or animal species differs from other
individuals in its genetic constitution. Each individual has specific characters, which is due to
the genetic makeup or code. The genes present in the organisms can form infinite number
of combinations that causes genetic variability.
Thus, we find that each human, who is representative of the same species, i.e. Homo
sapiens, is distinct from another. The term ‘gene pool’ has been used to indicate the
genetic diversity in the different species. This also includes the diversity in the wild species,
which through intermixing in nature over millions of years have given rise to newer
varieties.
, 3. Ecological/Ecosystem Diversity:
Each ecosystem consists of organisms from many different species, living together in a
region connected by the flow of energy and nutrients. The Sun is the ultimate source of
energy for all the ecosystems. The Sun’s radiant energy is converted to chemical energy by
plants. This energy flows through the different systems when animals eat the plants and
then are eaten, in turn, by other animals. Fungi and bacteria derive energy from the
decomposing dead organisms, releasing nutrients back into the soil as they do so.
It relates to varieties of ecosystems seen on this earth like; savannas, rain forests, oceans,
lakes, marshes, deserts and all other environments where species evolve and live. Few
examples are: (i) Tropical rain forests, (ii) Grasslands, and (iii) Wetlands.
Levels of Biodiversity:
a. Alpha Diversity (with in community diversity):
It represents number of species in a given habitat. It represents the diversity of organisms
sharing the same community/habitat. A combination of equitability/evenness and species
richness is used to know that diversity prevalent within community or habitat.
Alpha diversity:
This is the diversity in species, i.e. the number of species within a community. This
depends on the interaction between the biotic and abiotic factors and also takes into
account immigration from other locations.
b. Beta Diversity (between community diversity):
The rate of turnover or replacement of species while moving from one habitat to another
within a given geographical area. For instance the differences in species composition
between a coral reef and the adjoining intertidal zone would be termed as beta diversity.
Beta diversity:
This is the change in the composition of the species with reference to the changes in the
environment.
c. Gamma Diversity:
This term is used for the rate of turnover or replacement of species between similar
habitats in different geographical areas. For example, the differences in species;
composition between the coral reef in the Gulf of Kutch and in the Andaman Islands would
be called as gamma diversity. Diversity of habitats are the total landscape or geographical
area is called gamma diversity.
Gamma diversity:
This refers to the overall diversity and is applied to larger geographical areas in which
both alpha and beta diversity are measured.
The term biological diversity or biodiversity refers to the variety of life forms and habitats
found in a defined area. UNEP (1992) defines it “as the variety and variability of all
animals, plants and micro-organisms and the ecological complexes of which they are a
part”. The term biodiversity was coined by W.G. Rosen (1985).
Diversity characterizes most living organisms, the our earth supports something like 5 to 10
million species of plants and animals (IUCN, 1980) which have been the result of 3 billion
years of evolution involving mutation, recombination and natural selection.
Country like India with only 2.4% of the world’s land area has great habitat diversity and
high species diversity. India has 45,364 species of plants (includes bacteria, algae, fungi.
Lichens, bryophytes and higher plants). Similarly, a total of 89,315 species of animals are
known and described from India.
Types of Biodiversity:
Biodiversity is of three types:
1. Species diversity, 2. Genetic diversity, 3. Ecological diversity.
1. Species Diversity:
According to Biological Species Concepts (BSC), species is a basic unit of classification and is
defined as a group of similar organisms that interbreed with one another and produce
offspring’s and share a common lineage but reproductively isolated from other groups of
organisms. Species diversity refers to biodiversity at the most basic level and is the variety
and abundance of different types of individuals of a species within a community in a
given area.
Species diversity refers to variety of species in a region. Number of species per unit area is
called species richness. Evenness or equitability differs due to difference in number of
individuals in an area.
2. Genetic Diversity:
‘Genetic diversity pertains to the range of diversity in the genetic resources of the
organisms. Every individual member of a plant or animal species differs from other
individuals in its genetic constitution. Each individual has specific characters, which is due to
the genetic makeup or code. The genes present in the organisms can form infinite number
of combinations that causes genetic variability.
Thus, we find that each human, who is representative of the same species, i.e. Homo
sapiens, is distinct from another. The term ‘gene pool’ has been used to indicate the
genetic diversity in the different species. This also includes the diversity in the wild species,
which through intermixing in nature over millions of years have given rise to newer
varieties.
, 3. Ecological/Ecosystem Diversity:
Each ecosystem consists of organisms from many different species, living together in a
region connected by the flow of energy and nutrients. The Sun is the ultimate source of
energy for all the ecosystems. The Sun’s radiant energy is converted to chemical energy by
plants. This energy flows through the different systems when animals eat the plants and
then are eaten, in turn, by other animals. Fungi and bacteria derive energy from the
decomposing dead organisms, releasing nutrients back into the soil as they do so.
It relates to varieties of ecosystems seen on this earth like; savannas, rain forests, oceans,
lakes, marshes, deserts and all other environments where species evolve and live. Few
examples are: (i) Tropical rain forests, (ii) Grasslands, and (iii) Wetlands.
Levels of Biodiversity:
a. Alpha Diversity (with in community diversity):
It represents number of species in a given habitat. It represents the diversity of organisms
sharing the same community/habitat. A combination of equitability/evenness and species
richness is used to know that diversity prevalent within community or habitat.
Alpha diversity:
This is the diversity in species, i.e. the number of species within a community. This
depends on the interaction between the biotic and abiotic factors and also takes into
account immigration from other locations.
b. Beta Diversity (between community diversity):
The rate of turnover or replacement of species while moving from one habitat to another
within a given geographical area. For instance the differences in species composition
between a coral reef and the adjoining intertidal zone would be termed as beta diversity.
Beta diversity:
This is the change in the composition of the species with reference to the changes in the
environment.
c. Gamma Diversity:
This term is used for the rate of turnover or replacement of species between similar
habitats in different geographical areas. For example, the differences in species;
composition between the coral reef in the Gulf of Kutch and in the Andaman Islands would
be called as gamma diversity. Diversity of habitats are the total landscape or geographical
area is called gamma diversity.
Gamma diversity:
This refers to the overall diversity and is applied to larger geographical areas in which
both alpha and beta diversity are measured.
