Every species has a particular role in an ecosystem and when its duty is over, the species is no more required. For example, vultures, hyenas etc. have the role to eliminate the dead organic materials from the terrestrial ecosystems and thus cleaning the environment. In majority of the developing countries, man has taken the role to eliminate the dead organic matters from terrestrial ecosystems. Man being the most powerful and well adapted species has forced the other competitors to leave the environment cleaning job for man. Thus, man is pushing the the competitor species towards extinction through putting severe competition. For example, any kind of flesh is used to make the most costly ingredient of poultry feed or meat meal and bone meal. A number of poor people are involved in providing raw material for poultry industry. These people collect wasted flesh, bones etc. from slaughter houses as well as from nature thus leaving no carcass in nature for the scavengers like vultures, hyenas etc.
Extinction is a natural phenomenon, and we know this since we can document the extinction of species in the fossil record spanning more than 500 million years. It is not, however, a foregone conclusion. There is no reason why any species must definitely become extinct. It is either a failure to adapt to changing environments (physical and biological), or the failure of individuals to acclimatize to rapidly changing circumstances. Species play the roles in ecosystems that they evolved in order to ensure their own survival, not the proper functioning of an ecosystem. The fact that ecosystems work, I think, is the result of continuous selection of species and communities by the environment. There is absolutely no way in which humans can replace the functions of all the species that we are causing to go extinct, and we are rapidly eliminating the evolutionary potential and options for adaptation in the future.
http://proopnarine.wordpress.com/2012/07/19/extinction-is-not-an-evolutionary-imperative/
Dear Peter Roopnarine, Thanks a lot for comments and clarifications.
It is supposed to be a natural phenomenon. But due to lot of survival pressure, it happened much earlier.
surely extinction of species is a natural phenomenon, only the thing is that the rate of extinction may vary from time to time. rate of extinction of species is very high these days due to over exploitation of natural resources and population explosion.Both need urgent attention.We can significantly reduce the rate of extinction of species simply by making our environment clean and sustainable. Better natural resource planning will reduce the chances of loss of species.
I'm not so sure animals "have a role" in ecosystems. They just grab opportunities.
By "roles" I do not mean to imply design. But if you accept that a community or ecosystem is a functioning system, and it is by virtue of the interaction of multiple semi-independently acting entities, and the transfer and distribution of energy, then it is perfectly acceptable, and in fact necessary, to define the roles of organisms and species in the system. I disagree with the notion that animals, or any organism, grabs opportunities. Opportunities of the sort that I think you mean, arise in contemporary and ecological time. Organisms, on the other hand, are constrained by evolutionary history to take advantage of a specific set of opportunities, any subset of which may or may not arise during the lifetime of an organism.
@Peter: My brief statement wasn't in response to your initial comment, but to the initial question of the thread, which I felt gave the impression that an ecosystem has a set of pre-defined roles to fill. I believe I largely agree with you. But I do think animals grab opportunities, in contemporary time, like when a predator launches for a passing prey. Their "talents" in doing so are products of evolution by natural selection, as you describe. It is unclear to me whether this view differs from your phrase "to take advantage of ... opportunities" - I tend to think not.
Dear Dr. Trond, you said "that animals do not have a role in ecosystems and they just grab opportunities. If so, then would you please mention which components of an ecosystem have some role ? If animals just grab opportunities, is it not a role or contribution to the proper functioning of the system ? If any group in an ecosystem like producers, primary consumers or secondary consumers are left without any checks and balances then what will happen ? Will that system run properly ? I think not only the animals but all the live forms in an ecosystem grab opportunities for their own survival and these are their contributions to the system because all components collectively make a system.
My initial statement was; every species has a particular role in an ecosystem and when that role or duty is over, the species is no more required. I quoted the example of white-backed vulture in Indian subcontinent whose role has been taken up by human and hence this species is no more required and have almost disappeared.
I was inquiring that extinction of species is a natural phenomenon but the major factor behind this phenomenon is the end of the duty of the species which is disappearing. The species which fails to adapt according to the changing environments, the nature discards him. But the process is very slow and gradually that duties of that particular species are allocated to other competitor species. But now-a-days, man being the most powerful competitor, has forcefully taken the role of a number of species and hence has increased the pace of species extinction. The species which were supposed to be extinct in decades, man has made them extinct in few years. Thus, although extinction of species is a natural phenomenon but man has influenced it a lot.
The real issue, as you just noted, is not whether the death of a species is a natural process or not. It is. Paleontologists have long established that distinct peaks of global species extinctions took place, way before the emergence of hominids: five extinction waves so far, the last one some 65 million years ago in the Cretaceous.
A really burning issue is whether mankind's industrialized impact- through global overexploitation of natural resources, continuing habitat degradation and fragmentation, new contaminants, etc- is pushing the planet towards a sixth wave of extinction in the coming century.
According to many biologists the writing in on the wall, in terrestrial systems (where massive forest clearing continues, and where persistent contaminants are threatening the survival of critical vectors like pollinators) and in marine systems (where governments seem powerless to stop overfishing and deep sea trawling). On the latter:
http://newswatch.nationalgeographic.com/2012/10/22/species-missing-in-action-just-rare-or-already-extinct/
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