BIODIVERSITY
The total number of races, varieties or species and the ecological complexes of which they are a part is referred to as biological diversity or biodiversity. Biodiversity can be examined at different levels. It has now become customary to study the concept of biodiversity at three hierarchical levels; each of which has its own significance. They are 1) Genetic diversity 2) Species diversity and 3) Ecosystem diversity
1) Genetic diversity
The diversity in the genetic makeup of a species is referred to as genetic diversity. Due to this genetic diversity, we can see a number of varieties, races or strains within a species that are
slightly different from each other in one or more characters such as shape, size, quality, and resistance to diseases, ability to withstand adverse conditions of environment etc. These differences are due to slight variations in their genetic set up. A species with a large number of races, strains or varieties is considered to be rich and diverse in its genetic organisation. A greater genetic diversity within a species enables it to adapt and survive in the extremes of environment in a more effective way.
2) Species diversity
The total number of different species in an ecosystem is referred to as species diversity. A community, in which each species has more or less the same number of individuals as others, would be the most diverse, whereas a community with one species making up most of the individuals would be the least diverse. Further, species that are very different from each other contribute more to overall diversity than species that are similar to each other.
3) Ecosystem diversity (landscape diversity)
The distinctive assemblage of different ecosystems in an area is called ecosystem diversity. Depending mainly upon the availability of abiotic resources and conditions of the environment,
different types of ecosystem develop with its own characteristic community of living organisms. For example, different types of forests, grass-lands, lakes, ponds, rivers, wet-lands etc. present in
a given geographical area, each with a characteristic biotic community, represent ecosystem diversity.
Patterns of Biodiversity
Biodiversity varies greatly from place to place. The centres of greater biodiversity tend to be in the region between tropic of Cancer and Capricorn. In terrestrial environment,
1. Areas with warmer climate hold more species than the areas with colder climates.
2. Areas which are moist hold more species than drier areas e.g. the moist tropical forests
3. Areas with varied climate and topography hold more species than the areas of uniform climate ad topography.
4. Areas at lower altitudes hold more species than the high altitude areas.
Similarly, in the case of surface oceans, there tends to be more species in warmer waters i.e. at
lower latitudes.
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