In biology and ecology, extinction is the end of an organism or group of taxa. The moment of extinction is generally considered to be the death of the last individual of that species (although the capacity to breed and recover may have been lost before this point). Because a species' potential range may be very large, determining this moment is difficult, and is usually done retrospectively.
Through evolution, new species arise through the process of speciation—where new varieties of organisms arise and thrive when they are able to find and exploit an ecological niche—and species become extinct when they are no longer able to survive in changing conditions or against superior competition. A typical species becomes extinct within 10 million years of its first appearance, although some species, called living fossils, survive virtually unchanged for hundreds of millions of years. Extinction, though, is usually a natural phenomenon; it is estimated that 99.9% of all species that have ever lived are now extinct.
Dr. Edward O. Wilson of Harvard University estimates that if 1% of the world's tropical rain forests are destroyed each year—a conservative estimate based on current rates of deforestation—then over 100 years there would be a loss of at least 20% of all species, assuming extinction rates remain constant. Based on a total of 10 million species, the current annual loss has been calculated to be 20,000 to 30,000 species.CAUSES:
There are a variety of causes that can contribute directly or indirectly to the extinction of a species or group of species.
Humans can cause extinction of a species through (1) overharvesting, (2) genetic pollution, (3) habitat destruction, (4) introduction of new predators and food competitors, (5) overhunting, and (6) other influences such as global warming.
The best known groups of organisms are birds and mammals. Since the year 1600, a total of 83 mammals species (2.1%) and 113 birds (1.3%) are known to have become extinct. This number is expected to rise rapidly as the breeding populations of many species continue to decline.
1. How will it (extinction of some animals and plants) affect the ecosystem?
(Paano makakaapekto ang tuluyang pagkawala ng ilang mga hayop at halaman sa ekosystema?)
2. Although extinction is a natural process, can we prevent extinction of some plants and animals, particulaly in the Philippines? How?
(Paano natin mapipigilan ang tuluyang pagkawala o pagkaubos ng ilang mga hayop at halaman, lalong-lalo na dito sa Pilipinas?)