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Lecture 4

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Louise Dawe

BIOLOGY September 16, 2013 -1.3 Light as a source of information -photoreceptor basic light-sensing system, found almost universally in all organisms -Phodopsin is the most common photoreceptor in nature -basis of vision in animals -also used by many organism -Rhodopsin: a highly conserved photoreceptor -consists of a pigment molecule (retinal) bound to a protein (opsin) Eyespot -sensing light without eyes -allows sensing of light direction and intensity -organism responds by phototaxis The Eye -What distinguishes the eye of a simple invertebrate from the eyespot of the green algae C. reinhardtii? Vision -Requires a brain to interpret signals sent from eye – Co-evolution Darwin and the Evolution of the Eye- -Darwin is the most important biologist there ever has been. “if numerous gradations from a simple and imperfect eye to one complex and perfect can be shown to exist”. -variation is REQUIRED for evolution to occur. Evolution of the Eye -camera eyes evolved by variation and natural selection from a simple primitive eye -improved eyes give a huge advantage to organism -read sections on different types of eyes and eye evolution (sections 1.3c and 1.3d) -PBS VIDEO ON THE EVO OF THE EYE -
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