The Evolution of eyes / A Evolução do Olho.

The Evolution of eyes

A Evolução do Olho.

Authors: Michael F. Land & Russell D Fernald

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Since the earth formed more than 5 billion years ago, sunlight has been the most potent selective force to control the evolution of living organisms. Consequences of this solar selection are most evident in eyes, the premier sensory outposts of the brain. Because organisms use light to see, eyes have evo lved into many shapes, sizes, and designs; within these structures, highlyconserved protein molecules for catching photons and bending light rays have also evolved. Although eyes themselves demonstrate many different solutions to the problem of obtaining an image-solutions reached relatively late in evolution-some of the molecules important for sight are, in fact, the same as in the earliest times. This suggests that once suitable biochemical solutions are found, they are retained, even though their "packaging" varies greatly. In this review, we concentrate on the diversity of eye types and their optical evolution, but first we consider briefly  evolution at the more fundamental levels of molecules and cells.