evolution: shaping both life and the environment

One of the books I’m reading at the moment is about teaching evolution (NAS, 1998). I’ve come across an excellent and thought-provoking quote that I thought I’d share with you – for you to think about..

During the billions of years that life has been on earth, [evolution] has played an increasingly important role in altering the planet's physical environment. For example, the composition of our atmosphere is partly a consequence of living systems. During photosynthesis, which is a product of evolution, green plants absorb carbon dioxide and water, produce organic compounds, and release oxygen. This process has created and continues to maintain an atmosphere rich in oxygen. Living communities also profoundly affect weather and the movement of water among the oceans, atmosphere, and land. Much of the rainfall in the forests of the western Amazon basin consists of water that has already made one or more recent trips through a living plant. In addition, plants and soil microorganisms exert important controls over global temperature by absorbing or emitting 'greenhouse gases' (such as carbon dioxide and methane) that increase the earth's ability to retain heat.

In short, biological evolution accounts for three of the most fundamental features of the world around us: the similarities among living things, the diversity of life, and many features of the physical world we inhabit. Explanations of these phenomena draw on results from physics, chemistry, geology, many areas of biology, and other sciences. Thus, evolution is the central organising principle that biologists use to understand the world.

National Academy of Sciences (1998) Teaching about evolution and the nature of science. pub. National Academy Press, Washington DC

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