Biodiversity: A basic understanding ...

Biodiversity is the variation of life forms within a given ecosystem, biome, or for the entire Earth. Biodiversity is often used as a measure of the health of biological systems. The biodiversity found on Earth today consists of many millions of distinct biological species, which is the product of nearly 3.5 billion years of evolution.

Biologists most often define "biological diversity" or "biodiversity" as the "totality of genes, species, and ecosystems of a region". An advantage of this definition is that it seems to describe most circumstances and present a unified view of the traditional three levels at which biological variety has been identified:

· Genetic diversity

· Species diversity

· Ecosystem diversity

BIODIVERSITY refers to the varieties of living forms of the world. Just twenty years ago, the word 'biodiversity' was not a part of our vocabulary. But since the organization of the UN Conference on Environment and Development in 1992 in Rio de Janeiro, biodiversity has become a widely known word. Presently, the loss of biodiversity has been causing a great concern worldwide.

The word 'biodiversity' is a contraction of the words: biological diversity and that encompasses all species of plants, animals, microorganisms, and ecosystems of which they are part. It is usually considered at tl1fee different levels: genetic diversity, species diversity and ecosystem diversity.

Till date, about 1.44 million of plants and animals have been described or recorded. But in reality, this figure is merely a part of the total in existence. In fact, the higher plants and the vertebrate animals are relatively well known but many hyper-diverse groups of small organisms like, insects, nematodes, protozoans, fungi, bacteria, etc. are still insufficiently explored and documented.

Many scientists presume that about 30-50 million species exist. Biodiversity is distributed unevenly over the countries of the world. A few countries, lying in the tropics and subtropics, hold high proportion of the world's biodiversity and are recognized as the 'megadiversity countries'. India is one of the top twelve mega-diversity countries of the world (viz., Colombia, Ecuador, Brazil, Peru, Mexico, Zaire, Madagascar, China, India, Indonesia, Malaysia and Australia).

Biological resources give enormous benefit to the welfare of the society. Most of the foods we consume, the dresses we wear and the drugs we take are derived from either plants or animals or microbes. The major feedstocks of our energy (viz., oil and coal) are derived from the extinct animals and plants. The living resources also provide extensive material values such as,

(i) the role of plants, animals and microbes in storage and cycling of nutrients like, carbon, nitrogen, oxygen, minerals and maintenance of carbon dioxide-oxygen balance;

(ii) the role of plants in photosynthetic fixation of solar energy and transforming this energy into food chains;

(iii) the role of plants in .regulation of climates;

(iv) the role of soil microorganisms, earthworms and arthropods, and pollinators in successful agriculture; and many more.

Only a little part of the world's biodiversity has yet been utilized for human benefit but the other elements of it may become beneficial if the values are discovered. Each passing day however, makes it clearer to us that the biological diversity or the natural heritage of the world is endangered. Major threats to the biodiversity are posed by

(i) habitat destruction and deforestation,

(ii) chemical pollution of air, water and land,

(iii) climate change in different continents, and

(iv) introduction of exotic species of plants and animals in many areas.

Considering the resource potential of biodiversity and this as a snpportive base of life it has been imperative for the human society to conserve the world's biodiversity for the existence of the humankind.

Genetic diversity is a level of biodiversity that refers to the total number of genetic characteristics in the genetic makeup of a species. It is distinguished from genetic variability, which describes the tendency of genetic characteristics to vary.

Species diversity is an index that incorporates the number of species in an area and also their relative abundance. It is generally a much more useful value than species richness.

The most common index of species diversity is a family of equations called Simpson's Diversity Index.

Here is one such example

D = (n / N)²

Where n is the total number of organisms of a particular species and N is the total number of organisms of all species. D is the value of diversity. It can range between 0 and 1, where 0 is infinite diversity, and 1 is the least diverse an ecosystem can possibly be (i.e. only one species present).

Humans have a huge effect on species diversity; the main reasons are:
- Destruction, Modification, and/or Fragmentation of Habitat
- Introduction of Exotic Species
- Overharvest
- Global Climate Change

Ecosystem diversity refers to the diversity of a place at the level of ecosystems. It is contrasted with biodiversity, which refers to variation in species rather than ecosystems.