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Evoluti̇on of eye & Pigmentation

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Evoluti̇on of eye & Pigmentation

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Evoluti̇on of eye & Pigmentation

  1. 1. EVOLUTION OF EYE & PIGMENTATION MESUT AKPUNAR
  2. 2. EyesEyes  The eye is an organ for sensing light  About 97 percent of the animals known have eyes  More complex eye includesMore complex eye includes sense of vision, color, motionsense of vision, color, motion and textureand texture
  3. 3. Evolution of the Eye • To go from nothing to an eye would be a very big jump • Darwin proposed a series of what appeared to be relatively small steps (they are still gigantic leaps) that might be able to produce an eye
  4. 4. Proto - eye Eyes appeared around 500 m.y.a. but their complete evolution possibly took just a few million years  Proto-eye is a very primitive eye . photonElectric signal photon (to CNS)
  5. 5. Evolution of the eyes (I)  Early eyes were formed by patches of photoreceptive cells, called eyespots Unicellular euglena has maintained this kind of rudimental eyes
  6. 6. Evolution of the eyes (II)  The patch gradually invaginates into a cup Planarium has maintained the structure of cup eyespots
  7. 7. Evolution of the eyes (III)  This kind of eyes is thought to have developed during the Cambrian period The primitive nautilus eye functions similarly to a pinhole camera
  8. 8. Evolution of the eyes (IV) This kind of eye has a structure that makes it functional in and out of water Ability of filterin colors, blocking of UV radiation and higher refractive index are increased
  9. 9. Evolution of the eyes (V)  Cornea and  Lens formation
  10. 10. Evolution of the eyes (VI)  More complex eyes give the full sense of vision, including color, motion, and texture
  11. 11. Evolution of eye base on special gene and unit PAX-6 Opsin
  12. 12. Swich off Pax-6 gene in drosophila and mice eyeless Small eye http://www.img.cas.cz/resrep/zk/mouse-eye.html
  13. 13. head wing antenna paw Pax-6 gene expression in different body region Halder et al., 1995
  14. 14. Evolution of eye color • Eye color is a polygenic trait • Color is determined by amount and types of pigment (Melanin) • Lighther skin and hair have lower melanin so lighther color of eyes • OCA2 gene controls the amount of melanin  Albinism  Extremely low quantities of melanin  Severe form of albinisms may appear red eye
  15. 15. Blue eyes contain low amounts of melanin within the iris. Blue eyes are most common in Northern Europe and Central Europe and to a low rate in Southern Europe (e.g;Spain and Portugal , where 1-49% of the people are blue-eyed, through migration of Northern European and Central European settlers) and Southern Central Asia ; Afghanistan and Pakistan also found in North Africa, West Asia, and South Asia. This is the most dominant color in humans.In humans, brown eyes contain large amounts of melanin within the iris stroma. Brown eyes are most common in East Asia Southeast Asia, Oceania, Africa, South America and the Middle East Moderate amounts of melanin and probably represent the interaction of multiple variants within the OCA2 gene. Green eyes are commonly found in Northern and Central Europe. In Iceland 89% of women and 87% of men have either blue or green eye color. These color eyes have less melanin than blue eyes. Gray eyes exhibit small amounts of yellow and brown color in the iris. Gray eyes are most common in European, Russia, Sweden, Finland and the Baltic States.

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