Is it possible for an organism to evolve an organ/system which can receive and/or transmit radio waves?
Many creatures have eyes, and some are bioluminescent.
Sharks and electric eels can sense prey by the electric fields their muscles give off.
What prevents an organism from using the low EM spectrum?
You mean, aside from evolving brains and opposeable thumbs sufficient to make machines to do it?
I don’t see any fundamental reason why a biological radio couldn’t exist. It’s just that, apparently, either the random mutations that fuel evolution just happen to not have stumbled upon such a system, or if they did, it wasn’t sufficiently advantageous to stick around.
Interesting idea. That would be pretty close to telepathy, wouldn’t it?
No more so than communicating using sound waves.
Now that I think about it, I guess you are right. It’s just that to a human observer it would seem like telepathy, with individuals communicating soundlessly with each other, and without visuals or scents, etc.
The thing is, sound wave communication is easier to implement, and the long-range distance bonus radio communication would offer probably doesn’t confer enough additional benefit – most dangers and situations organisms find themselves in are rather confined locally, within ‘shouting distance’.
So there’s probably no in principle insurmountable obstacle to developing radio communication, but there’s no sufficient need for it, either.
How energetic are radio waves from the sun that enter our atmosphere? Visible-light receptors work by photons impinging on an affecting photoreceptors. I’m wondering whether it might be more difficult for radio wave photons to cause chemical changes in receptor molecules.
Radio waves: from the bottom (ELF) all the way up to EHF.
The rainbow represents visible light.
Energy’s shown on the farthest right column, in order of ascending strength.
Sunlight’s quite a bit more powerful than the average radio wave.
Sound waves are a normal byproduct of things complex organisms do normally - walk, breathe, and so on. Radio waves aren’t. So it’s not quite the same thing - hearing developed to take advantage of something that occurs naturally.
This was the premise of Ralph Milne Farlkey’s “Radio Planet” stories. In his Burroughs-like stories (The Radio Man, The Radio Beasts, The Radio Planet and others), Venus is inhabited by creatures (giant ants and other insects, and amazingly human-like creatures with no ears, but antennae) who communicate by radio. His hero, Myles Cabot** has to build a radio from scratch to communicate with the inhabitants. Farley describes this in some detail, which is pretty impressive.
http://www.erbzine.com/mag15/1514.html
On the other Hand, although substances respond rapidly to mechanical effects like sound and vibration, or to visible, ultraviolet, and infrared light, low-intensity radio frequency is tougher. And generation by a biological mechanism (or a useful and evolutionarily useful common physical phenomenon) is pretty rare, too. You can literally see the advantage of being able to detect photons of visible light. But what gives off lots of radio signals that you can eat, warm yourself by, or observe reflections from? It’s hard to see why sensitivity to radio waves would develop in the first place.
There;s some evidence that people can “hear” some radio emissions. It’s been remarked upon several times that people claim to “hear” meteorites before the acoustic waves can possibly have reached them. But, if so, that’s a fortuitous accident
*pen-name for Roger Sherman Hoar. I can’t blame him for using the pseudonym. He was also a State Senator and assistant AG in Massachusetts
** How’s that for a stereotypical upper-crusty Massachusetts name? At first, all the heroes of these interplanetary romances seemed to be military men, or upper class, and usually both.
Another problem with radio: it doesn’t work over long distances underwater. Light will go farther, and sound even farther than that. If you eliminate all the aquatic species as candidates to develop the sense, you eliminate a pretty big majority of species and all of the oldest ones.
I suspect that we generate radio waves via discharge of static electricity under some circumstances. Likewise, the electric eels mentioned in the OP probably manage to generate radio waves during their electrical discharge events. Both of these events might be considered “natural” and “normal.” There’s no reason to suppose that evolution of the ability to detect radio waves would not occur.
if it could be had how would you tune and not just have noise?
it would be clutter beyond the levels we have with audio and visual noise.
Most organisms don’t give off visible light, either, but evolved receptors for the visible frequencies in sunlight. Since they already had receptors for visible light, communication through bioluminescence became feasible and some organisms developed ways to produce visible light.
Another consideration is that many objects are transparent to radio waves, including rock. Because of the lack of reflectance, unlike visible light organisms can’t use radio waves from the sun to detect much about their environment. Evolving a radio receptor would mostly just enable you to detect the position of the sun, but not “see” other things by reflected radio, and thus be of very limited utility. Unless radio detectors evolved first, there would be no benefit to organisms to be able to emit radio waves.
“That’s ridiculous. How can meat make a machine? You’re asking me to believe in sentient meat.”
Stranger
Well, sure, but unless you were in an environment where electric eels were your only predators (or prey), it would be a pretty useless adaptation. Evolution isn’t just about whether things are beneficial; it’s also about whether they’re harmful. Maintaining radio detection equipment in your skull (or groin, or knees, or wherever) requires energy and specialized tissue, so any creature that did evolve such an ability probably wasn’t reproductively successful.
I hadn’t thought quite that deeply about it, I admit. 
On the chicken-or-egg question of whether detectors or emitters would have come first, an antenna is an antenna. The circuitry is almost identical for a transmitter or for a receiver, so for the most part, it’s only one thing that would need to evolve, and which could then be used almost immediately for crude communication. I think the biggest barrier would probably be evolving an organic conductor (or assimilating environmental metal, I suppose), and having it be arranged in a long line in the body.
The problem is usefulness…
The sun may give off radio waves (and ultraviolet and xrays) but the peak of the energy output is, oddly enough, in the visible light spectrum.
Plus, visible light has an obvious use - it is very directional and easily blocked. Thus, a basic organism with a light-sensitive patch can tell if it is in shelter or not (Have I crawled under the rock) and whether something has suddenly blocked out the light (predator at 3 o’clock!). Radio is none of these, and light is much more useful. The great thing about our radio is that you can listen to it almost anywhere - but that means it is a steady background noise to our organism - unlikely to be directional or informative. Plus, there are not a lot of informative radio sources in the environment.
You would have to dream up an organism that would find significant advantage in receiving radio signals, and/or a signal source that provides useful information. Maybe the ability to sense magnetic/static events is as close as we’ll come on earth.
Many organisms can sense magnetic or electric fields directly, without being able to detect radio waves.
I dunno, seems like it wouldn’t be impossible for a creature that lived underground where other wavelengths are blocked to incorporate metal and/or crystals to use radio to navigate and or signal.