Read some of acclaimed biologist Edward O. Wilson's accounts of organisms and ecosystems teetering on extinction, in this excerpt from his book, A Window on Eternity: A Biologist's Walk Through Gorongosa National Park. Learn about the cascade that many ecosystems can suffer with the loss of a single species, however seemingly small or insignificant. Many types of symbiosis in the animal kingdom go unseen or misunderstood until it's too late.

To learn more about the book, click here.