Photoreceptor evolution

There was a fair amount of interest in my discussion of eye evolution last week, so let’s get a little more in-depth. This is a lecture on the level of what I tell my first year students in intro biology, so let’s see if I can put you to sleep, too.

Premieres at 2pm Central this afternoon. I’ll check in then to answer any questions, if any.

I’ve got a nasty cold, but I think my voice held up as well as could be expected — at least I held off the sneezing & coughing & vulgar snerks.


  1. birgerjohansson says

    Thank you for making an effort despite the cold – it really drains the body and mind of energy.
    Fay Weldon has died at 91. I recall the film and TV series made of her breakthrough novel. 😥

  2. says

    cis form vs trans form? What has sex/gender to do with photoreception??

    <tongueincheek> Yet another example of nonscientists misappropriating well-accepted technical terms in chemistry for entirely irrelevant purposes that end up diluting both meanings. cis and trans refer to physical locations of functional groups around stable ring structures, not to “preferred” or “orientation” of sexual “bonds” relating to multicellular organisms (which are neither ring structures nor particularly stable, in just about any sense of the word). Meanwhile, I’m going to pour some more benzene into my coffee — hey, it’s organic!

    We won’t go into stereoisomers, where for our amino-acid metabolism left is right and right is wrong… wait a minute, wasn’t that male earring placement in the 70s and 80s?

    Bottom line: If it’s a quasipsychological/quasisociological term that “sounds like” it might have come from chemistry, there’s a good chance it’s a distortion.

    I’ve got a nasty cold, but I think my voice held up as well as could be expected — at least I held off the sneezing & coughing & vulgar snerks.

    I believe that the vulgar snerks are presently voting to (not) elect a Speaker of the House. Although that would be a great name for a punkish garage band.

  3. birgerjohansson says

    Wow you are really in need of rest and chicken soup. Take care.
    BTW I think Steven Jay Gould covered a lot about the intrrmediary stages in the development of the eye, but I look forward to your next lecture.

  4. Steve Morrison says

    Cis and trans only properly apply to Gallia Cisalpina and Gallia Transalpina and similar geographical terms! (Shakes fist at sky)

  5. cartomancer says


    cis- and trans- are ordinary Latin prefixes (trans is also a preposition) meaning “this side of” and “the other side of” (“across” as a preposition). Whatever else non-Romans did with them afterwards is immaterial!

  6. says

    Interesting. you mentioned that we have opsins in our skin which play a role in melanogenesis. Octopus are colour blind but have opsins in their skin and are able to generate colour patterns and camouflage themselves to match their surroundings or mimic other animals and objects. Are the opsins in their skin involved? Are they in effect “seeing’ with their skin?

  7. dadboyghost says

    No one tells you that the Northern Lights are essentially grey for most of the time. Bloody rod and cone evolution.