Ep 8 - Rise of the Eukaryote

Episode 8: The Rise of Eukaryotes — The Cell That Changed Everything | The Mitochondria and the Nucleus 

How did life become complex?

In this episode, we explore how eukaryotic cells evolved from simple prokaryotes through one of the most important events in biology: endosymbiosis — when one cell engulfed another and kept it alive.

Learn how mitochondria originated from bacteria, why more energy allowed complex life to evolve, and how this single evolutionary partnership led to animals, plants, and humans.

We also break down the difference between prokaryotic vs eukaryotic cells, the debated origin of the nucleus, and why evolution isn’t just “survival of the fittest” — it’s also about collaboration.

Transcript

Jackie 0:02

Hello. I'm your host Jackie Mullins and welcome to From Cells To Us, how the podcast where we figure out how life went from a single cell to complex creatures like us. Last episode, we watched oxygen show up, poison most of the planet, freeze the rust, and somehow still manage to become the most important molecule. In the history of life, a Robert Downey Junior level redemption arc for sure. We talked about the survivors, the ones who hid, the ones who adapted, and the ones who figured out how to use oxygen and suddenly had access to 16 times more energy then everyone else, and at the very end I teased something. I said, more energy means more possibilities, larger cells, more complex processes, and eventually eukaryotes. So what is a eukaryote and why does it matter? Well, every person, every animal, every plant, every fungus on this planet is made of eukaryotic cells. The cell that we are going to talk about today is a direct ancestor of every complex living thing that has ever existed on Earth. But right now at the time, we are talking about there are still only pro coyotes, bacteria and archea. Eukaryotes are, but a twinkle in Archie's eye. Let's see how that twinkle became the third great domain of life, how a wayward ArcHa cell hunted and ate another cell, and how that started one of the wildest collaborations that is still continuing to this day. And a quick recap on prokaryotic cells, those would be the studio apartments, everything in one room, no separation. And that's all that's living on earth at this point. Eukaryotic cells are more like mansions, separate rooms for everything, even rooms within rooms. So how did we get from a studio apartment to a mansion? Well, let's get into it. Let's take stock of where we are in our timeline. It's about 2 billion years ago. The great oxygenation event has happened. The anaerobic world is gone, or hiding. Oxygen is everywhere. And we are now in the Protozoic eon a time when oxygen has begun reshaping the planet, the sky actually starting to look familiar. Oxygen is building in the atmosphere, and for the first time in earth's history, the sky is turning blue. Not the deep rich blue that you know, more of a pale blue, but blue. Nonetheless, the ocean's clearer than they have been in billions of years. All that iron that once colored them had already been pulled out. Locked away in rock, right, which is exactly how we got the banded iron formations we talked about. The water is cleaner now, but stranger full of oxygen for the first time, and teeming with microbial life just beneath the surface. Vast mats of bacteria, blanketing the sea floor, like living carpets, but nothing you would recognize. You know, there's no fish, no shells, nothing with a backbone, nothing with a face, just microbes. Tiny individual cells doing what they've always done, just trying to survive and the land. Bear Rock completely, utterly naked rock. No plants, no soil, no moss, no anything, nothing. Holding the ground together, just wind and rain, battering empty stone across empty continents. Incomplete silence. No rustling leaves, no animal calls, no footsteps. Just. Weather hitting rock. If you somehow stood on the shore of that ancient ocean and looked out, you would think the world was dead. That pale, blue sky overhead, a clear, strange ocean in front of you. That silent, empty rock beneath your feet, but the world was anything but dead. It was absolutely seething with life. You just couldn't see it. And out there in the water, the world, you know, today was about to take its first steps. So here we are about 2 billion years ago. Oxygen is everywhere and ARL cells have hit the jackpot. They figured out aerobic respiration, they've reigned in that molecular stallion oxygen and domesticated it, and now they're sitting on an energy surplus. So significant. It basically changed every rule, every norm of what life can do at this point. Now these oxygen using cells have a big fat wallet and they decided to start spending not, uh, you know, I think I'll have dessert tonight spending, but how about we expand the house, a few thousand square feet type of spending? So. Some of these cells started using their extra energy to take up more real estate. AKA. You know, they got bigger and as they got bigger, they developed a new problem. A bigger cell has more volume, but the same amount of membrane surface, which means the ratio of the membrane two cell gets worse. The bigger you get, This is just like blowing up a balloon right before it's blown up. The middle of the balloon is pretty close to the outer balloon, but as you blow it up, the middle becomes further and further away. This is what's happening with the cell right now. It's growing, but food seeping in from the outside through the membrane is not reaching the far away middle now. You're getting bigger. But your ability to feed yourself isn't keeping up. And so. Their membranes started doing something new. They started extending outward little fingers, like little protrusions poking out from the cell surface into the ocean around them. Scientists call these fingers blebs, which. I think it's hilarious. Blebs, we're out here doing serious biology with twinkles in cell's eyes, and they're over there naming things. Blebs. Unbelievable. Anyway, these blebs are like a paint splatter, you know, now more surface area, touching the ocean. More places to absorb food, more of the cell getting fed. But then something interesting happened, those blebs, the finger-like membranes started. Reaching. They started sensing bacteria nearby and they started reaching for them. Instead of passively waiting for food to drift to them, they went to the food, reaching out with their blebs, they would grab a bacteria floating in the water, surround them with said blebs, and eventually they engulfed them entirely so that all that bacteria saw was bleb city. Lots of blebs. That's Phagocytosis being born in real time. A cell's ability to wrap itself around something and swallow it whole. And this was not a sudden invention, not a conscious decision, just blebs getting gradually better at grabbing things until one day they could swallow something whole, like a microscopic PAC Man wandering around eating everything in sight. The world was. Full of cherries, bananas, all sorts of Pac-Man fruit with all the points or you know, this case nutrition. And this was a game changer because suddenly, instead of just absorbing whatever dissolved nutrients floated by you. Could actively hunt. You could eat other cells. This is such a turning point. This is humans discovering they could hunt buffalo or big game, you know, no more foraging and being at the mercy of what accidentally grows. Now you could take care of yourself and digesting whole cells. Well, that gives you even more energy. So these cells, first they learn how to do aerobic respiration, using oxygen for energy, which moved up their energy meter. Now they're using that surplus of energy to grow bigger and hunt and eat other cells, which leads to even more energy. Energy meter is at full strength, but. There was a trade off for this amazing new found hunting skill. Because to grow out your blebs, to engulf your prey, you need flexibility. Remember when I said that pro caros had a cell wall and a cell membrane double protection, but your cells don't, your cells just have a membrane. And maybe when you heard that. You felt a little cheated. You know, like, where's my extra protection? I'd like my cells to be a mini panic room. Thank you very much. But losing the wall wasn't a downgrade. It was a trade, that's for sure. It definitely made those cells more vulnerable, but it also was the change that made everything possible. Their greatest weakness became their greatest weapon. So now let's move forward slightly in our timeline to around 1.5 to 2 billion years ago. Phagocytosis is established, cells are hunting, and one day something goes very differently. Okay, so roll with me on this one. Pretend you are this membrane only cell, this larger al AR related cell, you've ditched your cell wall, you're sucking down oxygen, and now you're one of the biggest, baddest things in the world. Yes, at about 10 micrometers wide. But you might as well be a great white shark because now you are the apex predator of this prehistoric world, and you are doing well. The sun is shining through the clear ocean. UV radiation is finally being blocked by the ozone layer that's been building up above you. You just hunted down a delicious bacterium for breakfast this morning. You've got this whole phagocytosis thing down, but that breakfast, you know, it's broken down, been completely digested, and, and now you're hungry again, but you're in luck. Floating just a bit ahead of you is another delicious looking bacterium. This one is a little different than the first. This one had figured out aerobic respiration, using oxygen to make energy very efficiently. But lunch is lunch, right? So you start stalking your prey which in this case means slowly drifting toward it, and then you attack. By which I mean you slowly start to smosh your membrane around it until you've engulfed it completely very dramatic, but deeply threatening. If you are also a single celled organism, after which you let your digestion get going, and you wait for your lunch to give you your energy, but this time your stomach starts crumbing a bit, you know, so to speak. Now normally like with breakfast, the bacterium gets digested. Enzymes deploy, it breaks apart. Quick cliff bar, right? End of story. But this time something went different. Maybe the bacterium had a way of resisting digestion. Maybe the host cells, digestive machinery, malfunctioned. Maybe it was just a fluke, a one in a trillion chance that happened to change everything. Whatever the reason the cell you just engulfed went. Mm, nuh I'm not being digested. You're not eating me. Like Marlon, the Clownfish, Nemo's dad, you know, just hanging on in the back of the whale's throat, just, nope, not being eaten, not happening. So that bacterium that was supposed to be food. Instead stayed inside the host cell fully functioning. And here's the crazy part, because instead of being a threat, that bacterium was actually incredibly useful. Now this swallowed cell was anything but lazy. But I feel like it would be like if the dude from Big Lebowski got eaten, but still function just like, hmm. Okay, I guess I'm in here now. And so that cell sat in the host cell that had just swallowed it and still kept running. Its aerobic respiration, making energy, lots of energy, more energy than the host cell could make on its own. And that cell was like, oh yes, I'll take this energy you're making. Thank you very much, and here's some oxygen for your trouble. Tell you what, I'll keep giving you some delicious O2 if you keep handing me that Precious a TP energy. If Dr. Seuss were to write a book about a TP, so the host cell had a choice. Well, not a conscious choice. Cells don't make choices, but evolutionarily speaking, it could expel this bacterium. It could try and digest it or, or it could keep it on like a tiny power plant. an evolution definitely favored the last cells that kept the bacterium alive did better than the cells that ended up destroying it. They had more energy. They thrived. They reproduced. And that bacterium, it was safe inside, protected fed. It didn't need to survive on its own. That's a lot less to worry about. And so they just. Stayed together. Now this is called Endosymbiosis, and I want you to really sit with how crazy this is one cell living permanently inside another cell, not as a parasite destroying its host, not as a prey being digested, but as a partner, a permanent resident, a roommate that pays rent in a TP and this bacterium. That was swallowed whole and stayed alive like Jonah and the whale. Well, it's still there today. Yes, folks, that was the origin story of the mitochondria. Your mitochondria, the powerhouse of the cell. Yes. That one. It was once a free living, bacteria swimming around in the ancient ocean and then it got eaten, survived, and never left, and now it lives in every single one of your cells. You know, it's like if we found out that thousands of years ago people were born without a liver. Not possible, but stay with me here. And one day you were out hunting when you spotted a wild liver living its best life eating grass or berries or maybe small rodents. Who knows? The point is that this liver is a free living animal right now. So you shot that wild liver and you ate it. However, instead of it becoming food, it made itself cozy and nestled right up next to your stomach and your intestines, and just started working, filtering toxins, managing your blood sugar, doing about 500 jobs you didn't even know needed doing. After a while that liver forgot how to be a wild liver. No more frolicking with raccoons and squirrels in the forest or something. All it knew now was how to live inside a human. And the human couldn't imagine life without it. They had in this mythical past liver land become inseparable. And that's Endosymbiosis one organism living permanently inside another. And in this case, it turned out to be a pretty good situation for both of them. Okay, so this might sound kind of insane and you might be thinking Cool story, Hansel, but how do we actually know this is what happened? You know, this isn't like a banded iron formation that we can literally see rust in rock record. How do you fossilize a cellular merger? Have we seen the word synergy in the geological records? No. No, we have not. No PowerPoint decks, no merger announcements, no press releases. Just two cells that figured it out anyway, and the evidence is actually very compelling. First of all, mitochondria have their own DNA. Now, this is huge. Every other structure inside your cells, your nucleus, your ribosomes, everything uses your DNA, your genetic blueprint. But mitochondria, they have their own separate genome, their own little instruction manual that they've been carrying around since before they moved in. Why would an organelle have its own DNA? Unless it was once a separate organism. It's like hiring a contractor that shows up with their own rule book. You know, it's the same building, same project, but they're operating under different instructions. They're part of the team, but they were never quite fully absorbed into the company. I personally know this from experience I once contracted at a company. Where everyone got to wear jeans and I had to show up in business casual. It was very annoying. Same building, different rules. That was my mitochondria moment. Alright, second. Mitochondria reproduce independently so when your cells divide, your mitochondria don't get copied along with everything else. They divide on their own by binary fission, which is exactly how bacteria reproduce. Believe it or not, your mitochondria are literally reproducing like bacteria inside your cells right now. Every other organelle takes orders from the cell mitochondria. Well, they replicate on their own schedule. Third mitochondria have double membranes. Most organelles in your cells have single membrane. Mitochondria have two. The outer membrane. From the host cell, the remnants of the bubble that formed when it was first engulfed. The inner membrane is the original bacterial membrane. You can still see the seam from the merger 1.5 billion years later. Fourth mitochondria are the right size. They're about the same size as a typical bacterium paired up with all the other evidence. This does not seem like a coincidence. And fifth, we can see this happening today. There are living examples of endosymbiosis occurring right now. There's an amoeba called Pollin that has relatively recently engulfed a Sano bacterium and that Sano bacterium is in the process of becoming an organelle. We are watching endo symbiosis happen in real time in a living organism. It's not just ancient history. It's a process that life figured out and apparently keeps using. So the evidence is overwhelming. Your mitochondria were once bacteria. This is not a sketchy hypothesis. This is about as well supported as evolution itself. The theory is called endo Symbiotic Theory, and it was championed by a scientist named Lynn Margulis in 1967, who by the way, was rejected from every major scientific journal when she first proposed it, because it was so out there that the scientific establishment basically were like, Hmm, no, I don't think so. However, the mounting evidence kept piling up, and now it's textbook biology.. Lynn Margulis was right. The scientific establishment was wrong. And your mitochondria are ancient bacteria. And I wanna bring up something about science in general here. There's a always sunny in Philadelphia episode where Mac. Debunks Science. I'm doing air quotes and yes, that was an unironic Instagram post title. My dad even sent it to me with a question mark now if you haven't seen it. The premise is simple Mac points out that famous scientists were wrong, like eventually as time moved on, and he uses that to argue we shouldn't trust them at all. It's a hilarious episode for sure. However, that's not a flaw in science. That's literally the point. Einstein's theory of relativity was so radical that the scientific establishment couldn't even fully evaluate it at first. They had to wait for him to give concrete evidence, which he did, and it took a solar eclipse in 1919 when light bent around the sun exactly as he predicted for the world to go. Oh. Oh, very interesting. Einstein, and even then, the Nobel Committee was so skeptical of relativity that when they finally gave Einstein the Nobel Prize, they gave it to him for something entirely different. The most famous physics theory in the 20th century was considered too controversial for the Nobel Prize. Lynn Margulis got rejected 15 times. Einstein couldn't get a Nobel Prize for his most important work. The pattern is pretty clear. Science isn't a collection of perfect answers handed down from on high. It's a process of getting less. Wrong over time. You can't stand on the shoulders of giants if the giants never stood up and the bar should be high. You wouldn't want a scientific community that changed its mind at every new idea. You'd want one that holds firm until the evidence is overwhelming, and then it changes. In science, the evidence eventually wins. It always does, and that's not a failure of science. Mr. Mack, the fact that previous scientists could be wrong and get corrected is science working exactly as it intended. Now let's do a quick checkpoint here. Make sure we got our timeline straight before we get going. Now, 2 billion years ago, oxygen is everywhere. Some cells are thriving, getting bigger, getting more complex. Still around 2 billion years ago, those cells start to lose their rigid wall and they gain a flexible membrane, phagocytosis and their vulnerability becomes their superpower. 1.5 to 2 billion years ago, one cell eats a bacterium. It doesn't digest, and they form a permanent partnership. That bacterium becomes mitochondria. One accident, everything changed. The evidence is overwhelming. Margulis was right. The scientific establishment. Was wrong and they eventually accepted it. Now the story isn't over because mitochondria are only part of what makes a eukaryote a eukaryote, there's still the question of the nucleus and of what happened to the relationship over the next billion and a half years. So let's keep it going Now happening roughly around the same time as the mitochondria merger and continuing to develop over hundreds of millions of years, something else is taking shape inside the cells. The nucleus, a special room the DNA lives in, because eukaryotes didn't just get mitochondria, they also got a nucleus. So at this point you might be thinking, all right, cool. DNA got its own room. Fancy love that for it. But why, like, why do you go through all this trouble of building an entire separate compartment just to hold your DNA? Because pro caros don't have a nuclei. They don't need no stinking nuclei. Their DNA runs wild and free in their studio apartment of a cell. So how and why did eukaryotic cells need a special room for this special DNA? But Also How do you organize everything? How do you protect your DNA? Because at this moment. Nothing is organized. It's just a jumbled mess of RNA. Strands moving all around. DNA, chilling in the center, ribosomes churning out proteins and having them float around to do chemical reactions wherever they seem fit. Rick, Mary and Tina are just a free for all, no real setup. And because of this, sometimes they bump into each other. Sometimes proteins get lost. Tina's never find Rick, and the proteins don't get made. It's like if instead of your dresser having six drawers, you know, like one for socks, t-shirts, pants, it just had this one big giant drawer and everything went in it. Sure you can try to organize things, but it's not likely to last. Also, once cells started using oxygen, it got way more chaotic. Remember from last episode, oxygen is incredible. It gives you way more energy. It's the reason mitochondria are such a big deal. But oxygen is also kind of a menace, right? Those dang free radicals bouncing around like little chemical gremlins and they can damage whatever they bump into. So now you've got two problems. Everything is chaos and the inside and oxygen has taken swings at your DNA from the outside, like Jake Paul, honestly a few billion years old. Might be exactly his target demographic. That's not like, oops, I messed up this photocopy. That's like, oh geez, I just corrupted the only instruction manual I have for building myself. So now you've got a problem. You've got more energy, you've got more reactions happening. You've got more moving parts and your most important asset, your DNA is just floating around in the middle of all this chaos. Absolutely not. So what do you do? Well, you build it a vault, you wrap it in a membrane, you separate it from the chaos. You create a controlled environment, that's the nucleus, but protection is only part of it. The nucleus also lets the cell do something that pro Caros could never do. It lets the cell slow things down. In pro Caros, everything happens at once. DNA gets read, RNA gets made, proteins get billed all in the same place, all overlapping, all kind of just happening in real time. Efficient, yes. Controlled, not really, but once you have a nucleus, you can separate those steps. You, DNA stays inside. RNA gets. Edited, processed, and then sent out. You've got checkpoints, now you've got control. Now you can decide what gets made, when it gets made, and how much of it gets made. It's the difference between a chaotic kitchen where everyone is cooking all at once or a full restaurant with stations. Timing and a head chef calling the shots. And this is the part that really matters because once you have that level of control, you can start doing more. You can get bigger, you can specialize, you can coordinate, you can become something more than just a single cell trying to survive. So mitochondria gave the cell energy to level up, but the nucleus. The nucleus gave it the control to survive that level up, you need both. Because energy without control is chaos and control without energy doesn't get you very far. But together, well that's the foundation of complex life. Okay, so we understand why we want a nucleus, but where did it actually come from? And honestly, this one's a little less clear. The mitochondria story has beautiful clean evidence. The nucleus story is still actively being debated, which is kind of exciting. You know, we don't have all the answers yet, and they're telling you we don't. But the leading idea right now is something called the Inside Out Model. And remember those blebs we talked about earlier, like the little membrane fingers that started reaching outward to solve the surface area problem, and eventually became phagocytosis that wrapped up and hunted well. It turns out they're responsible for the nucleus too. As those blebs kept growing further and further out from their original anchor point, the cell became mostly bleb, a giant sprawling membrane complex reaching out in every direction. And that small original anchor point, that little circle, all those fingers first started growing from, that's the nucleus. Yeah, the cell didn't build a room for its DNA. It accidentally left the DNA behind while it grew. Everything else around it. The nucleus wasn't a new addition. It's what was left when everything else expanded outward. I picture this kind of like a baby octopus, right at first. It's basically all head. But as it grows, the tentacles reach out further and further. And if the webbing went all the way to the tips of those tentacles, that's essentially what the cell did. The octopus's head is the nucleus, the tentacles are the blebs, and the webbing is the cytoplasm. The head didn't go anywhere. Everything else just grew away from it. The same thing happened here, which means the nucleus is the cell's own creation. The mitochondria are an immigrant that moved in and never left So now about 1.5 billion years ago, we have it, the full eukaryotic cell, flexible membrane nucleus mitochondria. Organized, energized, ready to go. But what does this have to do with you sitting here right now listening to this? Honestly everything, because this isn't ancient history that has nothing to do with you. This merger, this one accidental engulfment 1.5 billion years ago is the reason you exist. Without mitochondria, you couldn't be multicellular, you couldn't have muscles, you couldn't have a brain, you couldn't have any of this complexity that makes animals, plants, fungi, everything we think of as complex life. Remember our a TP story from last episode. Anaerobic cells getting $2 an hour, aerobic cells getting $32 an hour while eukaryotic cells with mitochondria didn't just get a raise. They got a whole new economic system. The energy surplus was so significant that cells could afford to do things pro caros couldn't even dream of. If they dream, they could get bigger, way bigger. They could develop internal organization rooms within rooms. They could eventually start working together, multiple cells, cooperating, specializing, becoming tissues and organs. They can become us. And here's where it gets personal, because those ancient bacterial residents that moved in 1.5 billion years ago, they're still in there right now. In every single cell of your body. But here's the thing about a relationship that lasts 1.5 billion years. Things change. Now. Should we ever be worried about our mitochondria? Like going on strike, inflating a big rat outside our membrane, threatening that it'll go back to being a free swimming, fully independent organism. Well, no. No, we should not because the changes that occurred to the mitochondria make this now impossible. Today, human mitochondria only have 37 genes left. A free living bacterium typically has thousands. Interestingly, the mitochondria gave our DNA, some of their genes, they were just like, uh, yeah, okay boss, I'm here now and here's a bunch of a TP, but you gotta do these things for me. DNA. Agreed. And now our nuclear DNA has bacterial genes from this process, You know, it's like moving in with someone and slowly getting rid of all your own furniture because they already have everything. And then one day you realize you don't own a single chair. You couldn't move out if you wanted to. It's like Ted, when he went to move in with Robin and how I met your mother. And she keeps being like, oh, you don't need your own pans. I have them. Oh, you don't need your own movies. I have mine. Ted wasn't feeling it. But the mitochondria decided that they were in. So they can't leave and we can't survive without them. The most successful codependent relationship in the history of life, or maybe tied with the Darth Vader suit of proteins and Rick. And here's something I honestly didn't know until I took a cell biology class my junior year of college. There is not just one mitochondria per cell. There might be hundreds or thousands of them in a single cell Heart cells can have up to 5,000. Your heart never stops beating, so it needs an enormous stockpile. That's a lot of powerhouses. There are about a quadrillion amount of mitochondria living inside you right now. You are housing a quadrillion amount of ancient bacteria. You are basically an ecosystem that thinks it's a person. Get that identity crisis yet. Okay, so we talked about what happened. Let's talk about what it means. Because endosymbiosis isn't just a cool origin story. It fundamentally changes how we should think about evolution. We tend to think of evolution as a slow grind, random mutations, small changes, survival of the fittest, one tiny step at a time, over millions of years. And that is true. That is how most of evolution works. But Endosymbiosis is something different because it's not a small step, it's a quantum leap. This would be like if aliens came down and they were like, here's the secret to space travel. It's that kind of leap, and here's what that means for how we think about life itself. Like you see it in movies all the time, right? The bad guy's like, sorry, babe. Survival of the fittest and peels out leaving her stranded in the forest or something. And honestly, you see it in real life too. There's a certain type of person who's really into the idea that evolution rewards being the most ruthless, the most dominant, the alpha. Everyone else is weak. I'm a man who discovered the wheel and built the Eiffel Tower out of metal and Braun, you're just a woman with a brain. The third, the size of us. It's science, oh, Ron Burgundy. So be the strongest, be the most ruthless, or don't survive. That's like the bumper sticker version of evolution. And it's wrong. I mean, dang, if they kept piggy around, made a partnership with maybe the smartest kid on the island, things definitely would've gone a little differently because the biggest leap evolution ever made wasn't a competition. It was a collaboration. One of the most powerful things evolution ever did was to not compete, but to merge two organisms becoming something. Neither could be alone. Not in spite of evolution, but because of it. In this case, evolution didn't favor the strongest or the most ruthless. It favored the best partnership. Collaboration isn't the exception to the rule. It might be one of evolution's oldest and most powerful traditions. all right, let's do this last checkpoint here. Make sure we have it all down. 2 billion years ago, oxygen is everywhere. The cells are thriving, getting bigger, getting more complex. The studio apartments are becoming houses still around 2 billion years ago. Flexible membranes replace rigid walls. Phagocytosis develops. Cells are hunting, the vulnerability becomes the superpower. 1.5 to 2 billion years ago, one cell eats a bacterium, doesn't digest it, and they form a permanent partnership. Endo symbiosis. That bacterium becomes mitochondria. Over the next hundreds of millions of years, the mitochondria sheds genes loses independence, becomes fully domesticated. 37 genes left, cannot survive outside a host. Around the same time, nucleus develops from the inside out. Blebs DNA gets accidentally left behind while everything else grows outward. The cell builds its own headquarters without meaning to, and the result, the eukaryotic cell organized, energized, controlled the foundation of every complex living thing that has ever existed. All right, so what is a U carry out? We asked that at the beginning, and here's your answer. It's a cell that compartmentalized everything, found a job, everything found a space, and because of that organization, complex things were able to happen. And this all happened because 1.5 billion years ago, a cell ate another cell. That accident set in motion everything that would eventually become complex life. So take A second and appreciate your mitochondria. They've been with you since the beginning. The least you can do is eat some antioxidants, you know, help 'em out a bit every once in a while. Next episode we're going to get into Chloroplast, the second great Endo symbiotic merger. The one that didn't just change cells, it also changed the entire planet. Again, All right, now, a quick after note. I apologize. This episode came out a day late, and as such, here is a special look into an unplanned guest. I had AKA, my 4-year-old daughter who showed up right next to me while I was recording when I thought she was sleeping. Enjoy. The anaerobic world. Oh, Jesus Christ. You scared the heck outta me. Come here. Say something.

Speaker 7 37:07

Uh, I love mommy and my family. I love Mommy and Finn and Phil and, um, daddy, and, but I love mommy. The best.

Speaker 6 37:22

We got that on.

Speaker 7 37:24

I love my thing because I love my shows, all my shows. Mm-hmm. Because I love my families and I got them because my mommy has a little nose in the eye and another eye and an mouth and, and a.

Jackie 37:43

Look at that. No cue cards or anything. I hope that brought a smile to you and thanks for joining me on this biological journey. I'm Jackie Mullins, and this has been from Cells to Us. How I'll see you next time. I.