Despite all the poetry out there about eyes, these sensory organs simply help living things find food or spot predators. From the simplest “eye” to the most complex ones, they do their part to give organisms a competitive edge. Human peepers are pretty good, but they’re not the best. Like most appendages, we only evolve body parts that are just decent enough, but not exactly perfect.
A Red Dot
The simplest “eye” isn’t even a true eye, it’s a collection of red protein rods inside a simple animal or single-celled organism. If you’ve ever peered into a microscope and observed a drop of water, you might notice that euglenas, rotifers, and water bears all have this red dot. The purpose is to guide the organism to light. This totally makes sense if your sole purpose is to either photosynthesize or eat things that photosynthesize!
The eyes of cephalopods work just like a camera. These highly evolved organs are similar to human eyes…. just better. They’re made of the same parts - a lens, retina, photoreceptors, and an optic nerve. Octopi (a type of cephalopod) have better eye mechanics, better vision (thanks to more photoreceptors), and they physiologically don’t have a blind spot. When an octopus sees something, it focuses on the object by pushing the lens in and out, just like a camera! We humans have to use muscles to squeeze the lens in order to focus. Oof!
Just Good Enough To Do The Job
Despite their awesome eyes, did you know that octopi can’t see colors? Strange, right? But if you study octopi, it doesn’t make sense for an animal living in dark crevices at the bottom of the ocean to see color. Noticing small creatures is more important than deciphering what color they are. For humans though, colors are crucial for survival. They help us identify poisonous berries from edible ones, venomous animals from harmless ones, and ripe fruit from non-ripe fruit. Evolution gives organisms the traits they need to survive, not extra ones that are just cool to have.
Evolution Rule #1: Use It Or Lose It
You’ve probably seen this rule before in our other newsletters, but it’s an important one! When animals live in places with no sunlight, they lose their eyes. It’s similar to any other organ that isn’t used (like the poor appendix). Life requires energy and there’s no point in wasting it on something useless. So, whether you’re a visual learner, an artist, or just someone who loves to look at beautiful things, you’ll want to own our eye necklace. This piece also comes in gold and makes a wonderful gift for ophthalmologists, octopus lovers, that special someone you’ve got your eyes on, or starry-eyed pre-med students.
written by Science with Evie