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The evolution of complex characters—Two Themes:

The evolution of complex characters—Two Themes: Complex characters can evolve gradually via intermediate forms (if those forms have adaptive value) Cooption of pre-existing genes for new purposes We will focus first on #1. “What good is half an eye?”.

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The evolution of complex characters—Two Themes:

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  1. The evolution of complex characters—Two Themes: • Complex characters can evolve gradually via intermediate forms • (if those forms have adaptive value) • Cooption of pre-existing genes for new purposes • We will focus first on #1. “What good is half an eye?”

  2. Even single-celled organisms can sense light Euglena respond to light by moving flagellum http://www.youtube.com/watch?v=J3sgoy22Ij4 Does this lowly form of vision have adaptive value? What could it be?

  3. These are representatives of different eye types currently found in nature. They may be similar to the intermediate stages long ago passed on the way to our eye. It is unlikely to evolve a complex eye “from nothing”—i.e., Boeing 747 mutations. But incremental improvements from simple photoreceptors to more complex eyes are very likely.

  4. Fig. 25-24 Pigmented cells Pigmented cells (photoreceptors) Epithelium Nerve fibers Nerve fibers (b) Eyecup-slit-shell mollusc (a) Patch of pigmented cells-limpet Fluid-filled cavity Cellular mass (lens) Cornea Epithelium Optic nerve Pigmented layer (retina) Optic nerve (c) Pinhole camera-type eye-Nautilus (d) Eye with simple lens-marine snail Cornea Lens Retina Optic nerve (e) Complex camera-type eye-squid

  5. http://richarddawkins.net/videos/527044-bang-goes-the-theory-richard-dawkins-on-eye-evolutionhttp://richarddawkins.net/videos/527044-bang-goes-the-theory-richard-dawkins-on-eye-evolution

  6. http://www.pbs.org/wgbh/nova/evolution/intelligent-design-trial.htmlhttp://www.pbs.org/wgbh/nova/evolution/intelligent-design-trial.html Watch Behe at 1:06

  7. http://cosmiclog.msnbc.msn.com/_news/2011/04/08/6433919-intelligent-design-in-tenn-schoolshttp://cosmiclog.msnbc.msn.com/_news/2011/04/08/6433919-intelligent-design-in-tenn-schools

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