Evolution of the eye

Major stages in the evolution of the eye in vertebrates

Many scientists have found the evolution of the eye attractive to study because the eye distinctively exemplifies an analogous organ found in many animal forms. Simple light detection is found in bacteria, single-celled organisms, plants and animals. Complex, image-forming eyes have evolved independently several times.[1]

Diverse eyes are known from the Burgess shale of the Middle Cambrian, and from the slightly older Emu Bay Shale.[2] Eyes vary in their visual acuity, the range of wavelengths they can detect, their sensitivity in no light, their ability to detect motion or to resolve objects, and whether they can discriminate colours.

  1. ^ ""An important cue for understanding eye evolution is the distinction between different types of photoreceptor cells. Salvini-Plawen and Mayr ( 1977 ) noted a remarkable diversity of photoreceptor cell morphology across the animal kingdom, and suggested that photoreceptors evolved independently numerous times." – Land, M.F. and Nilsson, D.-E., Animal Eyes(2-nd ed.), Oxford University Press, Oxford (2012), p. 7.
  2. ^ Lee, M. S. Y.; Jago, J. B.; Garcia-Bellido, D. C.; Edgecombe, G. E.; Gehling, J. G; Paterson, J. R. (2011). "Modern optics in exceptionally preserved eyes of Early Cambrian arthropods from Australia". Nature. 474 (7353): 631–634. Bibcode:2011Natur.474..631L. doi:10.1038/nature10097. PMID 21720369. S2CID 4417647.

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