Hi, so I was reading a post that said peppers were hot to protect themselves from bacteria and stuff like that, but why, in this example, is hotness and not, let’s say, poison or bad taste or something else and how does that process happen? Like does the organism decide it would be better to be spicy than to be poisonous? How does it “decide” that? And how does it happen?
In: Biology
Organisms that survive pass on their genes and that survival strategy to their offspring. Random mutations often slightly change proteins which manifest in different behaviors.
So, for example, some pepper ancestor developed a random mutation that caused a protein to fold a slightly different way which caused an enzyme to work differently that normal, which created what we now call capsaicin – the molecule that makes peppers spicy. Capsaicin didn’t appear from nothing, of course! It’s derived from another molecule which is derived from vanillin – the molecule that is responsible for vanilla flavor.
That first plant that made capsaicin survived and that mutation got passed on to some of its offspring. Among them, the ones that had the gene to code for making capsaicin were *slightly* more likely to survive, since the capsaicin deters fungal infections and probably also deters mammal predators that would destroy the seeds. So there would be *slightly* more individual plants producing capsaicin than ones not producing it. With each generation, the ones that make capsaicin are more likely to survive, and more likely to pass on their capsaicin-making genes, which means there is a greater and greater proportion of capsaicin-making individuals than ones that do not make it.
Or, there’s not enough of it to make a difference *yet* but it doesn’t hurt the plant’s odds of surviving so the mutation sticks around.
Among the plants with the gene to make it, there are continued small mutations. One mutation might cause a plant to make more of it. That plant is more likely to survive than ones that make less. So it survives and passes on its genes. Many of its offspring have that gene to make more of it, and they survive, and pass on their genes.
After thousands and thousands of generations, the species that survive are the ones that make the right amount of capsaicin.
This is the same process that creates every single living organism on Earth. The ones that are most likely to survive are the ones that pass on their genes. Any random change that makes them more capable of passing on their genes by definition makes those genes more likely to be passed on. Changes that make the organism less likely to survive are less likely to get passed on. Mutations never stop happening, and sexual reproduction which combines genes in unique ways almost never stops happening. So each generation will be slightly different from the last.
As the environment around the organisms change, it puts pressure on the organisms so that old strategies don’t work as well. New mutations continue to occur, and some of them make the organism more likely to survive in this new environment, so they probably do, so they probably pass on their genes.
Consider this experiment: write down the numbers 1 through 10 on pieces of paper and put them in a bag. Pick a number in your head, like…oh, 7. Then pull a random piece of paper from the bag. If it’s a 7, make another piece of paper with the number 7 on it and put both back in the bag. If it’s not a 7, throw it away. How long until you have nothing but 7s in the bag?
The pieces of paper obviously never *chose* to be 7s. And although you picked the number 7 initially, you didn’t choose to make the whole bag into 7s. But it still happened.
It doesn’t. It’s completely random, literally **completely random**, but then the ones that don’t defend themselves get eaten so we only see the ones that did.
It never decides at all. There are, say, a hundred wild pepper plants. All of them the same species but slightly different, just like you and I are slightly different. Some of those plants are spicy enough to prevent slugs from chewing holes in ‘em (I don’t know what preys on peppers), and a few are not quite hot enough to deter the slugs and they get too damaged to propagate. Repeat a bazillion times.
The spicier plants get eaten less and propagate more. Over time the plant species becomes spicier in the average because the traits that allow it to survive get passed on, and the traits that hinder its survival are not passed on. The entire process is blind and random. This is how all evolution works.
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