The history and survival of Coral ReefThe coral reef is the oldest richest natural community on our planet. In them, that most wondrous and mysterious of all natural phenomena, life, has found its fullest expression. Nowhere else can one find so many diverse creatures living so closely together in such abundance. Complementing and enhancing this extraordinary intensity of life is its exquisite beauty of form, colour and motion. This is truly nature’s richest realm - a fairytale world beyond imagining were it not real. On a coral reef one can find, all together at the same place and time, living representatives of all the major levels of over a billion years of life’s evolution on our planet. The entire spectrum of being is present from blue-green algae and bacteria through all of the numerous types of invertebrate animals to fishes, reptiles, birds, and even mammals with brains larger and more complex than our own (whales and dolphins). These are vastly ancient communities. Primitive coral reefs existed nearly half a billion years ago, a time predating any evidence of life on land. Though these early reefs were quite different from modern reefs some of the same types of creatures which inhabited them still survive on today’s reefs. Many of the genera of present day reef animals are found as fillis dating back to the Eocene epoch some 50 million years ago and some date back to the Cretaceous period of age of dinosaurs about 100 million years ago. Even today’s living reefs often have surprisingly lengthy histories. Central Pacific atolls have reef strata dating back to the Eocene and the northern portion of the Great Barrier Reef began growing in the Miocene epoch about 25 million years ago. The persistence of these communities through vast spans of time with only gradual change underlies their richness. It has afforded a stable environment in which the products of evolution could survive, accumulate and fine tune themselves into the richest, most complex natural systems existing. A dive on a coral reef is like a trip in a time machine to the world before we humans even existed. If we could somehow go back in time for 10 million years we would find many of the same reefs we have today and their inhabitants would be little different from those we know. Evolution on reefs is a much more gradual process than in less stable environments where adaptation and extinction is mandated more frequently by significant changes in the ecosystem. In the American tropics we find a unique natural experiment which graphically demonstrates the rate of evolution of coral reef creatures. About 5 million years ago the Central American isthmus arose from the sea, dividing the coral reef area of that region. Since then the separate evolution of populations on either side has produced several hundred geminate or twin spines more or less and slight differences in colouration. Meanwhile our own ancestors evolved through four or more distinct and subsequently extinct species from ape to modern man. Other related pages:
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