Category: 

When did Eyes Evolve?

Article Details
  • Written By: Michael Anissimov
  • Edited By: Bronwyn Harris
  • Last Modified Date: 27 March 2017
  • Copyright Protected:
    2003-2017
    Conjecture Corporation
  • Print this Article
Free Widgets for your Site/Blog
A Loughborough University study suggests that taking a hot bath can burn as many calories as walking for 30 minutes.  more...

April 25 ,  1983 :  USSR leader Yuri Andropov wrote to Samantha Smith, an American grade schooler.  more...

Eyes appear in the fossil record about 540 million years ago, at the dawn of the Cambrian period. On some television shows about paleontology, the evolution of the eye is cited as the cause of the Cambrian explosion, the rapid diversification of animal life during the Cambrian period, but this is just speculation. Numerous organisms with eyes appear in the fossil beds of the Cambrian, including trilobites, conodonts, and the large shrimp-like predator Anomalocaris.

Eyes are sometimes cited by creationists as an example of an organ that is too complex to have evolved incrementally, and must have been created by a designer. However, paleontologists have since demonstrated how the eye could have evolved incrementally from humble origins. Simple eye-like organs can be found in organisms such as planarians and numerous single-celled organisms including euglena, which has a light-sensitive patch.

The steps of the evolution of the eye were roughly as follows:

1) A region of photosensitive cells.
2) Photosensitive cells in a depressed area, allowing directional sensitivity.
3) A spherical water-filled chamber with a hole, also known as a pinhole eye, which is found in the nautilus.
4) A transparent humor fills the chamber, which is then sealed from the outside.
5) Distinct development of a lens and cornea.
6) Development of an iris and more sophisticated lens and cornea.

Ad

The eye is one of the oldest evolutionary developments, and emerged prior to the evolution of many modern phyla. The eye evolved not very long after the first shells, another very simple adaptation.

Ad

You might also Like

Recommended

Discuss this Article

Post your comments

Post Anonymously

Login

username
password
forgot password?

Register

username
password
confirm
email