It has been estimated that more than 50 million species of plants, animals and micro-organisms are existing in the world. Out of these, about 1.4 million species have been identified so far. Each species is adapted to live in specific environment, from mountain peaks to the depth of seas, from polar ice caps to tropical rain forests and deserts. All this diversity of life is confined to only about one kilometer thick layer of lithosphere hydrosphere and atmosphere which form biosphere.
Though the study of environment and ecology is quite old, the term biodiversity has been introduced by Walter Rosen in 1986. Biological diversity or Biodiversity is defined as the variety and variability among the living organisms and the ecological complexes in which they occur.
It refers to the variability’s among species of plants, animals and microorganisms; ecosystems; ecosystem including terrestrial, aerial, marine and other aquatic system and ecological complexes of which they are part.
Significance of Biodiversity:
Biodiversity, besides its ecological significance provides a socio-economic and monetary asset to the nation. Human society depends on biological resources, their diversity and the ecosystems that sustain them to provide essential goods and services.
Values related to biodiversity can be grouped into three categories as below:
This is assigned to the products that are commercially harvested for exchange in formal markets and is, therefore, the only value of biological resources that is concerned in national income. Biodiversity provides us many products, such as fuel, timber, fish, fodder, skin, fruits, cereals and medicines. In 1994-95 the income from agriculture, forestry and fisheries in India was nearly 30 per cent or 736.88 billion rupees.
Consumption value is related to natural products that are consumed directly, i.e., the goods which do not come under normal circulation of trade. For example, a significant number of such non-timber forest products as soft broom grass and cane come under this category.
Indirect use of biodiversity is of much significance because this value is related primarily with functions of ecosystem and is concerned with national accounting systems. They may provide us indirect benefits as non-consumptive values. Maintenance of ecological balance, conservation of natural resources and prevention of soil erosion may be considered as the examples of indirect use of biodiversity.
Types of Biodiversity:
Biodiversity is of three types:
- Species diversity
- Genetic diversity
- 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. Species diversity refers to biodiversity at the most basic level and is the ‘variety and abundance of different types of individuals of a species in a given area’. It includes all the species on Earth, ranging from plants such as bacteria, viruses, fungi, algae, bryophytes, pteridophytes, gymnosperms, angiosperms and all the species of animals including unicellular protozoans to mammals.
Certain regions support a more diverse populations than others. Regions that are rich in nutrients and have well balanced climatic factors, such as moderate temperature, proper light and adequate rainfall, show high degree of diversity in their life forms. The tropical areas support more diverse plant and animal communities than the desert and polar areas, as for examples, tropical forest has a higher species diversity as compared to a timber plantation. The regions that are rich in species diversity are called hotspots of biodiversity.
- 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. Similarly, there are many varieties within the same species such as rice, wheat, apples, mangoes, etc. that differ from one another in shape, size, colour of flowers and taste of fruits and seeds due to the variations at the genetic level.
- 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.
An ecosystem, therefore, is a collection of living components, like microbes, plants, animals, fungi, etc. and non-living components, like climate, matter and energy that are connected by energy flow. Ecological diversity refers to the ‘variability among the species of plants and animals living together and connected by flow of energy and cycling of nutrients in different ecosystems or ecological complexes’. It also includes variability within the same species and variability among the different species of plants, animals and microorganisms of an ecosystem. Thus, it pertains to the richness of flora, fauna and microorganisms with in an ecosystem or biotic community.
There are various mathematical ways of measuring biodiversity, which calculate the number of species diversity in different regions. The measure of diversity of species is also known as species richness.
These are as follows:
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.
This is the change in the composition of the species with reference to the changes in the environment.
This refers to the overall diversity and is applied to larger areas in which both alpha and beta diversity are measured.