Posted: Aug 08, 2010 1:46 am
by Calilasseia
Oh, one of the fun parts about eye evolution is that there are single celled algae that have light sensitive structures sufficiently complex to be called "eyes". Look up Warnowiids on the Tree of Life website, and discover some amazing facts about dinoflagellate algae along the way.

Now, one of the blind assertions I've seen erected by creationists is that without a brain to respond to the signals, an eye is useless, and they then go on to assert that since neither of these structures could have evolved (despite the vast amount of scientific literature devoted to this that demonstrates that they can, and did), this means that Magic Man did it.

Yet dinoflagellate algae, being single celled organisms, don't have a brain, because a brain, by definition, is an organ composed of multiple cells. But, they manage to make use of a light sensitive structure that is comparable to metazoan eyes without a brain. Go here, and scroll down to the section on eyespots in dinoflagellate algae. Indeed, Warnowiids have a refractile lens in their eyespots, and can change the shape of this lens via microtubules within the cytoplasm. Scientists aren't yet clear how Warnowiids process the visual information, but they have to have some means of responding to this, because it's possible to construct experiments to test the response of Warowiids to various visual stimuli. Though I have yet to alight upon any papers devoted to Warnowiids in detail, I'm willing to bet that Warowiids have a Pax6 gene, and that manipulation of that gene will affect the eyespot.