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Q. 1. What do you mean by Loss of Biodiversity? What are its causes?
Ans. LOSS OF BIODIVERSITY: Biodiversity exists at three different levels, namely
(1) species diversity, which is reflected by morphological, physiological and genetic features;
(2) genetic diversity, which comprises genetic or other variations within a species; and
(3) ecosystem diversity, which is reflected in diverse bio-geographic zones, such as lakes, deserts, coasts, estuaries etc. The conservation of these ecosystems is a major challenge.
Human influence. Humans have directly influenced the kind and distribution of the earth's biotic stock. Increasing impact of humans on the biotic patterns of the earth is an outcome of a growing population and its requirement for food and shelter. Human demands for resources result in the death of some species and survival of others. The early humans were hunters and gatherers. We may call them primitive but from the ecological point of view they were not backward. Their lifestyle was a successful adaptation to the call of nature given the knowledge and technology of the time.
Extinction of Species. The prehistoric overkill ling by early humans in association with deterioration in climate has been recognised as principal factors for the mammal extinction during the geological period (Pleistocene, about 2 million years ago). This episode of megafaunal extinction has not ended, it is presently being extended to the earth's marine environment.
This is the result of technology that has increased the influence of humans within the depths of the world's oceans. The modern age of extinction is not centred on any group of animals such as megafauna, but has affected a variety of animals, especially birds, fish and reptiles. Technological innovations and socio-economic factors serve to fuel the modern age of extinction. Influence of Mechanisation and Industrialisation. In the wake of extinction, a new food source based on domesticated plants and animals became increasingly important. Mechanisation and industrialisation of till agriculture has created enormous grain surpluses. But in the course of producing these surpluses, human's series of changes in the land has caused disruption in the pattern of natural communities and soils. These changes in turn have resulted in degradation of communities, both near and far. Fresh water systems have undergone especially large changes: till agriculture has also affected organisms of the marine environment.
(1) In this age of industry and urbanisation, the growing population translates into more lands being cleared of their forests.
(2) More soils being tilled to grow crops and
(3) more areas used to erect homes, construct roads, build parking lots and all the activities.
(4) those channel resources toward urban locations.
(5) The loss of soil, movement of nutrients and contamination of the environment with toxic materials are symptomatic of the excessive use of energy and unchecked outputs.
(6) Human manipulation of nature results in fragmented and incomplete systems. They have negative impact on air, water, soil and biotic resources of the planet.
(1) Nearly 2 per cent of the known animals and 8 per cent of the known plants of the world today are at risk of extinction. Virtually, every industrial activity has a negative effect on water quality.
(2) Rain has become acid;
(3) till agriculture is a problem because of irrigation, erosion and runoff of pesticides and fertilisers; urban areas and highways are a problem because of altered runoff and spillage of toxic substances:
(4) mining presents a problem because of its impact on drainage and runoff of mine wastes; industrial and urban sewerage contain hazardous substances and cause eutrophication; all diminish the quality of fresh water systems.
Future. Life has evolved over millions of years into a highly integrated fabric. Life is resilient but it needs space. When any part of the pattern of plant, animal or soil life is destroyed, the whole fabric of life becomes diminished. The desirable condition is a world where, instead of deterioration of major resources, there is recovery; where instead of extinction of species. It is within the power of humans to make cultural adjustments that would enhance the future patterns of life. Future generations will realise the wisdom (or lack there of) of our age by noting the failures and successes we have had in sustaining biodiversity and hence the quality of life on the earth.
Future. Biodiversity today is the result of 2.5 – 3.5 billion years of evolution. Since the advent of humans, the biodiversity has a rapid decline. The number of species globally vary from 2 million to 100 million. New species are regularly discovered. Tropical forests are very rich in biodiversity.
Q. 2. Explain the extinction of species.
Ans. Extinction of Species. The prehistoric overkilling by early humans in association with deterioration in climate has been recognised as principal factors for the mammal extinction during the geological period (Pleistocene, about 2 million years ago). This episode of megafaunal extinction has not ended, it is presently being extended to earth’s marine environment. This is the result of technology that has increased the influence of humans within the depths of the world’s ocean. The modern age of extinction is not centred on any group of animals such as megafauna, but has affected a variety of animals.