in this video, we're gonna do a quick recap on the Endo Symbiotic theory, so recalled at the end of symbiotic theory explains the development of complex eukaryotic organisms such as ourselves. And it suggests that mitochondria and chloroplasts organelles were once independently living bacteria. And it also suggests that about 1.5 billion years ago, there was an aerobic bacteria or a bacteria that uses oxygen in its metabolism that was engulfed by an anaerobic host cell or hotel that does not use oxygen in its metabolism. And that created a symbiotic relationship. Were both organisms benefited, and so the Arabic bacterium was provided protection by the host cell, and the host cell was provided an Arabic metabolism by the bacterium. And over time, this Arabic bacterium would have lost many of its genes and abilities, including the ability to survive on its own. And it would have developed into today's mitochondria. And so in a similar fashion, a photosynthetic cyanobacteria would have also been engulfed by a host cell, and over time it would have evolved into today's chloroplasts. And so let's take a look at our example below and notice on the far left. We have our host cell, which again is anaerobic and does not use oxygen and notice that our host cell already has a nucleus. And so that means it's already a eukaryotic cell. And the end of symbiotic theory does not suggest the creation of a eukaryotic cell. It suggests the development of a eukaryotic cell, and so this anaerobic host cell would have engulfed an Arabic bacterium, and this Arabic bacterium would have developed into today's mitochondria and again in a similar fashion, the cyanobacteria would have been engulfed and developed into the chloroplast and host cells that had both organ Al's would have developed into plant cells and into today's plants. Now host cells that Onley, uh, engulfed the Arabic bacterium would have on Lee had mitochondria, and so these host cells would have developed into today's animal cells and in tow. Animals such as this Rafiki looking monkey appear with some yellow teeth. And so, uh, there's lots of supporting evidence to support this theory, and most of it has to do with the fact that mitochondria and chloroplasts resemble pro carry outs. And so mitochondria and chloroplasts both have small circular DNA, just like pro carry outs. They have 70 s ribosomes, just like procure yachts. And they replicate via binary fission, just like pro carry outs. And mitochondria and chloroplasts also have, uh, a double membrane and the double membrane. The membranes differ from one another, so the outside membrane more so resembles a eukaryotic cell in the inside membrane. More so resembles a pro carry attic cell, and that's suggestive of being engulfed. And so, in our next video, we're gonna do a quick recap on the mitochondria, so I'll see you guys in that video.