The fundamental units of biodiversity are the species; the multitude of plants, animals and micro-organisms that have evolved over hundreds of millions of years of evolutionary experiments. Species alive today represent only a small fraction of those that have ever lived, many being victims of several major catastrophic extinction events. These extinction events result in the sudden reduction in biodiversity. The most well-known event was the extinction of the dinosaurs at the end of the Cretaceous Period, 65 million years ago. The six most notable extinction events of the past were:
We are now facing the ‘Seventh Extinction’, the Holocene, or present-day, extinction. This new event differs significantly from the others that were caused by catastrophic natural disasters or gradual changes to the Earth's chemistry and physical environment. Today, it is happening over a very short time period, within decades, not millennia, and it is a direct result of one species substantially modifying the planet at the expense of the other 5-100 million species. The species at fault is Homo sapiens, that is, us.
It is estimated that at the current rate of habitat destruction, about half of the world's existing species may be extinct within the next hundred years or so. This does not include the countless thousands of species we have already sent down that path. Human impact on the environment has been, and continues to be, catastrophic. The rate of species loss during this ‘Seventh Extinction’ is estimated to be somewhere between 100 to 1000 times more rapid than during any of the previous extinction events.
Today, many species are dying from small changes in climate or habitat conditions and their inability to adapt to the change. Irrespective of the huge technological advances made in science and the recent hype surrounding genetic cloning, extinction is fundamentally a one-way street. That is, we can’t re-create dinosaurs or any extinct species at present.
It is crucial that no more species go down the path to extinction and that all life on Earth be valued. Sponges, the simplest of all multicellular organisms, are the most bioactive animals on Earth. If these humble organisms have the potential to produce chemicals of pharmaceutical benefit for humankind, the genetic diversity contained in all the other life forms provides an even greater economic potential for us. This is justification enough for the need to conserve our existing species and preserve our genetic diversity for future generations.
You may like to try the Matching Worksheet and two Multiple Choice Quizzes in the For Teachers section.