natural selection and antibiotic resitance....?

Question

what does natural selection have to do with antibiotic resistance? please explain in details and don't get too big word on me cuz im only 15. thanks

Answer 1

Natural selection means "survival of the fittest," for the most part (it's a little more complex, but that's good enough for now).

Let's say you have a big population of bacteria, and you dump a bunch of antibiotics on them. We'll use penicillin as our example.

So you've just totally soaked these bacteria in penicillin, but some of them just won't die. Why not?

Bacteria, like people, have all of their genetic information packaged in the form of DNA. DNA is a big, stranded molecule that has all of our genes...each gene is a portion of the DNA. So a bunch of genes stranded together - that's all DNA is.

Back to our story - some bacteria, by a stroke of dumb luck, will have genes that make them resistant to penicillin. This could be because the penicillin works a certain way and interferes with some sort of bacterial life process, but these genes make the process just a little bit different - maybe a protein in the cell is shaped differently, or something like that. It still does the job of helping the cell live, but penicillin can't touch it.

This means that no matter how much penicillin you hit these bacteria with, they won't die.

Eventually, these bacteria will replicate, because that's what bacteria do. And each of their little daughter cells will have those genes that make them penicillin resistant. This means that, eventually, in a land full of penicillin (like our society is today), you'll have a bunch of bacteria that are resistant to it, and that's all you'll have, because the other bacteria that penicillin kills will have...well, they'd have been killed.

And there you have it - natural selection creating a population of antibiotic-resistant bacteria.

Answer 2

Antibiotics kill bacteria. However, some survive, because they are resistant. The resistant ones, not being dead, live to breed. Their young (most of them) also have this resistance. Eventually, the whole population is resistant, so had adapted to the new environment (one that has antibiotics in it)