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Why Biodiversity

This page covers use and types of biodiversity

Biodiversity is the condition where different species of plants and animals, live together and depend on each other in the same habitat.

In the ecosystem there are different species of plants and animals which depend on one another. Let us take the example of a simple food chain: Planktons - Small Crustaceans - Fish – Man

Why Biodiversity?

There are different levels in an ecosystem. The following are the levels:

  • Plants
  • Animals
  • Scavengers

Plants produce their own food, whereas animals cannot do so and have to depend on plants. When plants and animals die, they are consumed by bacteria, which are known as the decomposers. In this particular hierarchy every animal plays an important role. The nutrients from the soil are recycled and the recycling can be complete only if the bacteria and other decomposers act on the dead organic matter.

Role of Small Animals and Insects in Biodiversity

Pollination: Pollination is a process by which plants propagate their species.

Small animals and insects plan an important role in Pollination. Insect pollination results in a uniform crop and, in some cases, an improvement of quality of the fruit. A very good example of an insect which is a good pollinator is the honey bee.

The members of a colony of honey bees visit about 100 flowers during a field trip and make about four million field trips every year. Fruit crops like apple, strawberry, lime, grapes, papaya and vegetables like lady's finger, brinjal, tomato and crops like cotton, alfa alfa, etc., depend on honey bees for pollination.

The value of honey bees in the pollination of crops is 15-20 times that of the honey and bee wax it produces.

If a colony has crops worth Rs.10/- the visit of the bees from the colony would have increased the crop yields to the value of Rs.100/- or Rs.150/- more than what the farmer would have got without bees. In Coimbatore it has been found that visits by honey bees has resulted in increased yields ranging from 23%-53% in cotton.

Predators and Parasites

Some insects are very valuable to man because they kill the insect pests feeding on the crops.


  • Mud wasps feed on caterpillars
  • Ants feed on various types of insects
  • Birds feed on insects, thus protecting the crop. It is always necessary therefore to grow trees in fields along the bunds, to enable birds to nest in them and feed on the insects in the field.

Birds are helpful in so many ways. They help in pollination, they feed on insect pests and prevent the crops from being destroyed. Similarly, snakes are very useful in the control of rodents in the field, which destroy huge quantities of grains.

Insects as Weed Killers

Some of the insects feed on menacing weeds and destroy them and so they are considered helpful to man. In many cases the presence of these insects has led to the complete eradication of the weed or at least in keeping it under check.

E.g.The grasshopper feeds on a variety of weeds.

Insects as Soil Builders

Some insects like ants, bees, larvae, flies, crickets, and earthworms are found in the soil. Ants, termites, bees and wasps build terrestrial nests and during the process of making tunnels and burrowing into the soil the soil particles get disintegrated. Soil aeration is facilitated. Sub-soil is brought to the surface resulting in the turning of the soil and the soil is enriched by addition of insect saliva. The excreta and the bodies of dead insects also enrich the soil. The earthworm also plays a very important role in soil building, in fact the earthworm is known as the "friend of the farmer".

Insects as scavengers

These are insects which feed upon the dead and decaying plant and animal matter. Since insects help to remove from the earth's surface the dead and decomposing bodies, which could otherwise be a health hazard, they are referred to as scavengers. In addition to cleaning the filth from human habitations, these insects help to convert dead bodies into simpler organic substances, before returning them to the soil where they become easily available as food for growing plants. e.g. termites, maggot of flies, larvae and adults of beetles, etc.

Thus we see that insects, plants, animals, bacteria, fungi, etc., all play a very important role in preserving the ecological balance. We can see the need for biodiversity where different organisms and plants depend on each other for survival.

Types of Biodiversity

Genetic diversity is the amount of genetic variability among individuals of a single species as also between species.

Species diversity refers to the variety of living organisms on earth and has been variously estimated to be between 5 and 50 million or more. Though, only about 1.4 million have actually been described.

Ecosystem diversity relates to the variety of habitats, biotic communities and ecological processes in the biosphere as well as the tremendous diversity within ecosystems in terms of habitat difference and variety of ecological processes.

Some other categories of biodiversity are also known. They are named with reference to a specific ecosystem, species etc.

Agro biodiversity is the component of biodiversity that is directly related to agriculture. It includes crop plants and their wild relatives, livestock and beneficial organisms such as pollinators, decomposers and predators which are normally associated with cultivated areas.

Endemic biodiversity refers to those forms of life that are exclusive to the given geographical area or ecosystem. For the sake of convenience, endemic biodiversity is often assessed within political boundaries. Islands for example are rich in endemic biodiversity.

Introduced biodiversity refers to diversity of micro-organisms, plants and animals that have been accidentally or deliberately transported by humans to landscapes, countries, regions or continents where they never occurred naturally. Disease-causing organisms,weeds, insects, pests and rats are examples of introduced biodiversity.

Microbial diversity refers to the variety in micro-organisms such as virus, bacteria, yeast, amoeba and certain fungi.

Uses of Biodiversity

All forms of life - plants, animals and humans - are so clearly interlinked that any disturbance in one gives rise to imbalance in the other. All life on earth is inter-dependent and man is only a strand in this delicate web of relationships. Our own species is subjected to evolutionary processes as any other life form, and the more we learn about them, the better we will be able to manage ourselves.

The greater the diversity of wild species, the greater is the opportunity for the production of new varieties. Almost all crops and livestock on which we depend for food production are hybrids, the result of cross breeding, originally from wild species. Hybrid species are vulnerable to an epidemic or any abnormal climatic variation, compared to their wild ancestor, which may kill them. Without the wild ancestor, it might not be possible to replace them.

The medicinal utilities of a variety of species are yet to be identified. The greater the variety of wildlife we conserve, the more will we be able to learn from them.

Loss of Biodiversity

Causes for the loss of variation in flora and fauna have generally been grouped into two categories: natural and man-made

The natural causes include floods, earthquakes, landslides, natural competition between species, lack of pollination and diseases.

The most serious man-made threat to biological diversity are the deliberate destruction of the ecosystem, especially in the tropics and the disappearance of habitats, in the wake of developmental activities like industrialisation, urbanisation, mining, construction of dams, deforestation, grazing, over-exploitation, fire, etc.

Source : CPR Environmental Education Centre, Chennai

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