From our Easily Amazed Department: a July 1, 2015 detailed piece of sub-cellular anatomy finds in a particular dinoflagellate–a motile predatory alga type consisting of a single cell per individual–this remarkable enormous “eyespot” that is far more than the dot of phototaxic pigment we learned about in in Biology 101 that you saw something like Euglena for modifying the flagellum to vaguely move towards the light for improved photosynthesis.
This is a true “camera eye”, not a simple eyespot, and so like an animal eye it was once thought to be a digestive remnant of something this dinoflagellate had ingested.
In this case, the eye-covering “cornea” and light-refracting “lens” are made up of inter-connecting mitochondria, that you probably learned about as the “powerhouse” ATP generating parts of a typical cell.
The lower portion that is red in this illustration (Credit: Hoppenrath and Leander) consists of plasmids, whose general purpose typically is to convert light to energy (like chloroplasts.) And these, ostensibly, convey chemically (since there are no nerves) a message to the organism to–well, it is not known what or how this happens.
Dinoflagellate “eyes” then predate animal “camera eyes” of even the most primitive vertebrates by many hundreds of million years, solving the same “problem” with a remarkably similar solution from molecular parts on hand.Â The technical name for this duplication of solutions is “convergent evolution.”
Having a term for it, I suppose, helps; but it leaves a lot of questions unanswered, even as I marvel at the answers living matter finds to carry on.