The Biology Topics of ecology involve studying the relationships between living organisms and their environment.
Biodiversity: Types of Diversity in Plants and Animals
Each organism in this world, whether it is a plant, an animal or a microorganism (viruses, bacteria, unicellular eukaryotes), is unique in itself. This uniqueness of individuals forms the basis of the diversity (L. diversitas = variety) among the living organisms.
The term “biodiversity” is a concise form of “Biological Diversity”. It was coined by Walter G. Rosen in 1986. Biodiversity refers to the diverse or varied forms of living beings which differ from one another in external appearance, size, colour pattern, internal structure, nutrition, behaviour, habitat, etc.
Currently, there are 1.7-1.8 million organisms, all of which are different from one another. They range in size from microscopic bacteria, hardly a few micrometers in size, to Blue whales (about 30m in length) and Redwood trees (Sequoia) of California (about 100m in height). Some pine trees (e.g., Pinus) live for thousands of years while many insects such as mosquitoes have a life span of a few days. The diversity extends to the habitat, habits, nutrition, forms, etc., of different organisms.
A few of the Biodiversity, present-day living forms are evolved versions of living beings that have existed on Earth for the past 3.5 billion years. We are familiar with most of the commonly known animals and plants, but the fauna and flora (biota) of inaccessible areas of forests, mountains, deserts, depths of oceans, etc., are largely unexplored. In fact, it has been calculated that about 92 percent biota of the world is still unexplored.
Types of Species Diversity
Each community has a variety of species, some of which are rare, while others are common. Thus, no community consists of species that are present in equal abundance. The following types of species diversity can be described:
- Point diversity: This is a diversity present on the smallest scale, i.e., the diversity of micro-habitat.
- Alpha diversity: Also known as local diversity and includes a variety of organisms local to a particular habitat.
- Gamma diversity: It represents the diversity of a larger unit such as an island or a landscape.
- Epsilon diversity: It is also called regional diversity and includes the total diversity of a group of gamma diversity areas.
For example, a single plant may be considered as a unit of alpha diversity; a leaf as an area of point diversity; a group of plants occurring together as an area of gamma diversity, and the forest within which the plants are located as an area of epsilon diversity.
The Uniqueness of Indian Biodiversity:
India is one of the 12 mega biodiversity countries in the world. The country is divided into 10 biogeographical regions. The wide variety of physical features and climatic conditions have resulted in a wide diversity of ecological habitats such as forests, grasslands, rivers and wetlands, coastal and marine ecosystems, and deserts which harbour and sustain immense biodiversity.
Earth’s Regions of Megadiversity
The variety of life forms found in a particular region forms biodiversity. Diverse life forms tend to share a common environment and are also affected by each other. Due to these interactions, a stable biotic community comprising different species comes into existence. In recent times, human activities (e.g., deforestation, hunting, pollution), have played a crucial role in changing the balance of such communities. Indeed, the diversity in such communities is affected by the changing characteristics of land, water, climate, and so on.
For example, the legs of an Asian bullfrog are regarded as a delicacy in Europe (especially France) and the United States. To fulfill their growing demand, bullfrogs are exported from India and Bangladesh (about 80 million frogs are collected each year from rice fields in Bangladesh alone). With so many insect-eating frogs removed from the ecosystem, rice production is threatened due to the uncontrolled flourishing of insect populations. Further, various consumers of frogs in the wild such as snakes, prey birds, etc., are also affected.
A rough estimate shows that there are about ten million species on the planet Earth, and at present, we are aware of only one or two million of them. The warm and humid tropical regions of the Earth, between the Tropic of Cancer and the Tropic of Capricorn, have a rich diversity of life, i.e., plants, animals, and microorganisms. This is called the region of megadiversity. Of the biodiversity of the planet Earth, more than half is concentrated in 12 countries, namely