Biologists have identified five different and distinct periods
when the Earth went through drastic and sometimes cataclysmic
environmental changes that destroyed significant percentages of
animal life on the planet. It generally takes over five million
years for evolution to restore most of the diversity in the animal
kingdom, and a complete recovery can take tens of millions
biologists say that we are currently in the midst of the 6th Extinction.
While Nature still plays a role in this process, human activities
have accelerated the destruction of species in this 6th Extinction.
Tree of Life
illustrates the difference between the evolution
of a new specie and the growing rate of extinction.
The goal is
not to preserve the existence of any one species. All species
have a natural rate of extinction as evolution refines and redefines
organisms according to environmental and genetic changes. During
the first five periods of extinction, the rate of extinction was
in balance with the rate of the creation of new species.
the period of the 6th extinction, species are disappearing at
a faster than normal rate. Pollution, the introduction of "exotic"
species and destruction of habitat all contribute to this
accelerated pace of extinction.
of species of plants and animals are still unidentified by scientists.
But many will go extinct before we can understand the role they
play in their ecosystems. And we could be destroying plants and
animals that may hold the key to undiscovered medicines and chemical
products beneficial to humans.
use substances produced by plants - such as aspirin, which is
derived from the meadowsweet plant. Most patients of two of the
deadliest cancers - Hodgkins' disease and acute lymphocytic leukemia
- can now take drugs derived from rosy periwinkle, a plant found
in Madagascar, to treat their deadly illnesses.
Lots of insects
communicate and defend themselves chemically - and humans may
be able to use these chemicals to treat diseases and make other
helpful chemicals. For instance, an anti-coagulant derived from
the saliva of leeches is used to treat rheumatism, hemorrhoids
and other conditions. And if leech spit proves beneficial, who
know what other miraculous cures the animal world will yield.
about the factors that
contribute to the
destruction of biodiversity.