 So humans, good bacteria aside, humans are rather obsessed and rightly so with killing bad bacteria which are considered pathogenic, pathogenic bacteria. And pathogenic bacteria are going to cause disease. And just for a little bit of perspective, pathogenic bacteria, it was pretty much a given back in the day. If you got a bacterial infection, chances were excellent that your game was over. Bacterial infections often meant death. When you think about wars back in the day when we had like dude, brilliant, let's go out and kill each other, what a great idea. So humans are out there killing each other. Well, chances were phenomenal that if you were injured, were wounded by some sort of weapon from another human trying to kill you, it wasn't often, if you survived that, who cares? Because the pathogenic bacteria were going to come in and you would probably get an infection and that would cause you to die. So I just did a face plant on the sidewalk the other day when I was out running. I totally tripped over something and like the hands face first down, hamburger palms, like the full nine yards. And I didn't even think about it because I came home, I washed it all up, like slightly humiliated that I crashed and burned. Very happy that no one around me had actually witnessed such a thing. And then I went and got my little, what's it called, that antibiotic stuff, what's it called, neosporin. I got my neosporin, smeared it all over the wound, whacked on my little band-aids, whatever, and didn't even think about it again. And it's been, I don't know, six days since the wounding occurred. And you know, I can definitely tell that I did some damage, but it's much better. It's not red, it's not pussy, it's not disgusting, why? I threw some antibiotic ointment in there and kept it clean and killed any bacteria that might have been stoked about setting up home in my hand and maybe I would have had to chop my hand off. So thank you, antibiotics. Antibiotics, however, holy, we better be careful because the fact is that antibiotics are severely overused. Antibiotics are substances, chemicals that kill only bacteria. They don't kill eukaryotes. Now think about that, they kill bacteria. If they killed eukaryotes, they'd kill you. And we've tried all sorts of drugs, I do throw that drug in there, but it kills you. That's what causes side effects. So antibiotics are magic because they, for whatever reason, they target the bacterium and not you. And so you get to continue living but the bacterium gets killed. Now, I think it was World War II-ish when penicillin was discovered. This was our first antibiotic. It was produced by a fungus and the scientist had a little petri dish and he looked in there and he saw a little fungal colony and it was in the bacteria also in the colony and surrounding the fungus was this ring of no bacteria. He was like, dude, what's going on with that? So he attempted to isolate the substance and it was penicillin. He isolated this substance that killed bacteria. It was like a jackpot. He went out and started mass producing this stuff which back in the day was not an easy task but he started giving it to the soldiers when they got injured during World War II and they survived. Like the death toll was severely diminished even though the death toll was ridiculous because wars are incredible where humans kill humans. Antibiotics are a very good thing but I want you to take a second, push pause and think about what's the negative, what's the downside of using antibiotics. I'm going to give you a hint. We've been talking about evolution and it's related. So while you're thinking about that, you push pause. I have a little visual for you here. So I want you to think about the fact that if this, all these dots represented a population of bacteria living like infecting you. These are all bad bacteria but do you agree that their genetic makeup is going to lead to diversity? There's going to be some diversity amongst, within the population, they're all the same species but there's going to be some genetic diversity in there. And I've tried to illustrate the genetic diversity with different colors just so you could imagine it. Now what I'm going to do is I'm going to show you what happens when you take your antibiotics. Antibiotics are awesome. On day one, a group of bacteria are killed by the antibiotic but did I kill all of them? No, and if you notice, I killed all the yellow ones. I'm not exactly sure why because yellow is my favorite color. It's just cold blooded. On day two of taking the antibiotics, I killed the next. It looks like I killed green, next. Green was slightly different. They had a slightly different phenotype or genotype and it let them survive an extra day. If you took one day of antibiotics, you would only kill the yellow bacteria. Remember, these are all the same species. These are all the same bacteria that are causing you to get sick. Day two, we kill a few more. Day three, the purple ones are done. Day four, let's get rid of those blue ones. You're probably feeling better now, aren't you? You've gotten your antibiotics. You were sicker than a dog. Now you're feeling better but you're only on day four of let's say an eight or nine day prescription. What's going to happen if you stop taking your antibiotics right now? Who's left? Who's left to repopulate the colony of bacteria that were living in you, that were infecting you? The guys that can survive against the antibiotics for four days, those guys are the only ones that are left. But if you suck it up and you take your antibiotics for day five, maybe you kill a few more, maybe not. Day six, finally, you've killed most of them but who's left? Dude, this is bad, bad bacteria. This is the one that's like, go ahead, man. Go ahead, take some more antibiotics. Seven days, eight days of antibiotics and this one still isn't dead. Do you think he's starting to get worried though? And this is a nine-day treatment. Finally, after nine days of being exposed to the antibiotic, that crazy guy died. That crazy guy, if you hadn't finished your antibiotics, that crazy guy would live and be the only one reproducing. Think about that. What happened to your population? What used to be like awesome like that? You now have a whole population just of these red guys or a heck of a lot more of the red guys who are the only ones that are reproducing. This is a connection between natural selection, that's a fantastic example of natural selection and why we should be very careful about antibiotic use. Before we start talking about our eukaryotes, I want to take just a second to talk about our chians because they are not as familiar to us but they're actually really cool also.