Permisoo

How is extinction defined?

Extinction is defined as the death of the final animal in a species. Another handy term, however, is functionally extinct. That means that a certain species'population has plummeted below viable levels. This could be because there are too few specimens still alive to maintain genetic diversity, or because the survivors are located too far apart to be able to findand breed with one another. So even though that last critical death hasn't occurred, the species is all but done for.

The concept of global warming and whether it's caused by people is still atopic for debate in some circles. But most scientists agree that the temperature is rising — and human activity is the cause. As researchers explore the most remote parts of the world, it can seem likenew and unusual species crop up every day. But just as frequent are headlines that warn of species that are dying out, or becoming extinct. The idea that we're in the middle of a widespread,human-caused mass extinction is prevalent in the scientific community.
Researchers have documented a fraction of the species on Earth, so how can we know or even suspect that we're in the middle of a massextinction?
Earth has experienced an ongoing cycle of extinction and development throughout its history. Most of these extinctions are separated by 100 million years.
The difference between pastextinctions and the one most scientists agree is happening today is the cause. Previous extinctions came about because of factors that life on Earth had little control over. But most of the research suggeststhat an ongoing mass extinction taking place now would have its roots in human activity. To some minds, the question isn't whether we're in a mass extinction but how big it is. According to theAmerican Museum of Natural History, seven out of 10 biologists surveyed believe the Earth is undergoing a mass extinction. Researchers on the other side of the fence point out that mass extinctions take...