this video will cover the higher level section of cell structure and it's all about the origin and evolution of cells we have a lot of evidence to suggest procaryotes were the first cells to form followed by ukar much later and there's a lot of supporting evidence that we'll talk about for this Theory called Endo symbiosis so if we break down this word Endo meaning inside and symbiosis they're working together somehow right so some kind of like relationship between these two things and this is all about the formation of those compartmentalized eukaryotic cells that resulted from engulfing procaryotic cells and we're going to focus in on two organel the mitochondria and chloroplast so the endosymbiosis Series starts like this we have early ukar and then procaryotes some of which are heterotrophic that means that they are consuming in things for the nutrition and autotrophic procaryotes so they are manufacturing their own um carbon compounds and these early ukar Nots are going to engulf them so that process would look something like this um each of these being engulfed okay by that early ukar and then they wind up on the inside of the cell and these are what then evolved into the mitochondria that that we know today and of course the chloroplast and so what we really want to think about is what is the evidence that this is the mechanism by which this happened and before we can touch on that evidence what I want you to pay careful attention to is the fact that the mitochondria and the chloroplast were once procaryotes and so we want to be looking for similarities between the mitochondria and and Chlor chloroplast and the procaryotes that they evolved from and those similarities look like this so mitochondria and chloroplast both have their own circular DNA just like procaryotes inside of a mitochondria and a chloroplast we're going to find 70s ribosomes just like procaryotes much different than the ukar ads ribosomes that I would find in the rest of the cell they synthesize their own proteins and they reproduce independently of the cell so mitochondria and chloroplast do their own thing to make new mitochondria and chloroplast it'ss independent of the rest of the cell and they use a process called binary fision which you guessed it is the same process that procaryotes use so these are all the ways in which the mitochondria and chloroplast are very similar to the procaryotes that they came from so it's important when you're talking about evidence that we want to link them together the other thing that's really interesting here is that mitochondria and chloroplast both have a double membrane one membrane from the original procaryote that they came from and another membrane from that engulfing process so lots of evidence here to support this endosymbiotic Theory now the endosymbiotic theory explains how one cell uh became specialized and compartmentalized that cell differentiation is a little bit of a different process so this is all about what happens in multi-cellular organisms that allows them to have different types of cells so multicellularity being multicellular many cells involves what we call cell specialization so that's the process by which cells develop different structures and functions and it happens during embryonic development so when we are an embryo all of our little stem cells here are undifferentiated they're all identical and they all have identical genes so the way that we get such a variety in different cell types is during embryonic development some of those genes are expressed and some of those genes are not you may have heard it referred to as some of those genes are turned on and some of them are turned off so for example this neuron is going to turn on all of the genes that tell it how to do neuron things and cardiac cells are not going to have those same genes turned on they're going to express the genes that help them to look like and function as cardiac cells now there are some genes that are expressed in every cell so genes like how to manufacture ribosomes or how to go through cell division those are going to be in common with every cell so again I'm thinking about this theme of unity and diversity so Unity here diversity in terms of which genes are expressed and which aren't and that's how we get different cell types in multicellular organisms so in thinking about the pathway of how living things evolved we started with procaryotes and then we got ukar and all of those were unicellular and eventually multicellularity evolved and now we see multicellularity in all animals so that's one of the parts of the definition of an animal we are all multicellular all plants are multicellular and then some fungi and some algae or multicellular not all of them but some of them and what makes multicellular organisms unique is that they have specialized cells but one of the maybe downfalls about these specialized cells is that they're doing specialized jobs and because they're doing specialized jobs that means if I take them out of the organism they won't be able to survive on their own because within the organism they rely on the other cell types to do the other functions of living things the only way to explain why multicellularity is found in so many organisms is that there must be an advantage there so most multicellular organisms have much longer lifespans and they grow to different sizes so so they can exploit different niches or different roles in ecosystems and they can differentiate into multiple cell types so that means that together they can um live a much more efficient life right so they can accomplish tasks at a much greater efficiency because they have specialist cells however in terms of number there are far more unicellular organisms on Earth than multicellular ones so unicellularity must also have some advant vages and there will be times where being multicellular isn't an advantage so again a great way of demonstrating both unity and then here in diversity