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Overview of Archaea, Protista, and Bacteria

Video transcript

in this video we're going to talk about the mostly unicellular organisms protists archaea and bacteria which together make up most of the living things on earth so remember that all living things come from a common ancestor so I drew it this way because one of the most important evolutionary differences is between the kingdoms of eukaryotes and prokaryotes and you can notice that the protists are eukaryotes while the archaea and bacteria are prokaryotes and since carry out means nucleus and proteins before it means that prokaryotes came before the nucleus so they don't have one whereas eukaryotes have a nucleus so we're going to talk about archaea first because they're the oldest ones and you can remember they're the oldest ones because its name sounds like archaic which just means really old they were pretty much the first organisms to appear on earth that means they're used to really extreme environments because earth when it was first starting barely had any oxygen in the atmosphere and they were really weird temperatures and weather conditions and they were probably also exposed to a lot of UV light because the atmosphere was still forming so you can imagine that they're extremophiles that means that they like extreme environments and there are three types there are thermophiles organisms that like really extreme temperatures so here I've drawn a Sun to represent extreme temperatures and there is also halophiles which like extremely salty environments kind of represented here by the puddle of NaCl and methanogens which make methane gas which is also a swamp gas or a particular type of human gas and in order to live in these extreme environments archaea actually have very different cell walls and cell rains then either bacteria or protists and for our purposes it's not too important to know what about those membranes our walls are different it's just enough to know that they aren't different so that's archaea now let's talk about Protista Protista are kind of the grab bag for unicellular organisms and some multicellular ones it basically is any kind of eukaryote and it's not a plant of fungus or an animal in fact really the only thing that they have in common is that they pretty much all live in moist or aquatic environments and because they're part of a grab bag they have been more easily categorized into photosynthesizing protists which are related to plants and these we call algae and non photosynthesizing protists which are related to fungi and animals and these are just simply called fungus like whereas the animal ones you might have heard of as protozoa and this includes amoebas while the fungal group includes slime molds so as you can imagine these eukaryotic protists have evolved these unique ways of getting to nutrients like photosynthesis and they also have evolved unique movement structures such as cilia flagella and of course the amoebas have evolved there amoeba-like movements and now we're going to talk about bacteria compared to Protista or archaea bacteria can be found in diverse environments and what do I mean by diverse environments well all around us and even inside of us so that is anywhere from the computer you're sitting at to a nearby lake or ocean and even inside of us inside of our gut and because of this they both can help and hurt us and so we need to get a really good understanding of bacteria so let's focus on talking about bacteria here is a general bacterial structure and we're going to go over each of these parts which are color-coded step-by-step first let's go over the outside doctors of the bacterium first there is a capsule and in some bacteria this is a slime layer instead and the difference between the two of these is that slime layers and parentheses can be washed off whereas capsules can't so underneath this capsule or slime layer is the cell wall and we're not going to go into this right now but this is different for gram positive or gram-negative bacteria underneath that cell wall is the plasma membrane and that's something you're familiar with because it's just a lipid bilayer and now there are only two things left on the outside of the cell that we haven't talked about yet one of them is the prokaryotic flagella many bacteria use flagella for movement and the reason that I specified prokaryotic flagella is because they are different from eukaryotic Litella and this is because it is made of the protein flagellum so just remember that proteins name bacteria need this flagella to get to nutrients via chemotaxis and chemotaxis is basically just sensing chemicals and moving towards or away from it and you can remember that because chemo for chemical and taxi is like taxiing or moving and the last external structure which are all of these little yellow projections is the fimbriae also called a pill eye and they're in parenthesis because not all cells have them now let's talk about what's inside of a bacteria so of course it has a cytoplasm and some ribosomes but you should notice that there is no nucleus it has a nucleoid area for its chromosome so notice that that's not a nucleus the chromosome is not membrane brown and is just sitting inside of the cytoplasm also keep in mind that unlike eukaryotic organisms bacterial chromosomes are made of circular double-stranded DNA and some bacteria also have plasmids drawn here in a darker blue which are basically extra pieces of DNA we're not going to go into too much detail now but these plasmids give important genetic advantages to a bacteria now you might notice that there's one thing left that we didn't label and those are those purple circles their inclusion bodies and all they do is store stuff for the bacteria like nutrients and this is actually super important because prokaryotes have no membrane bound organelles and because they have no membrane bound organelles like mitochondria to make ATP they actually have to get their nutrients straight from the environment and store them in these inclusion bodies so that brings us back to the flagella in order to get to those nutrients they use chemotaxis to both get to nutrients or or avoid toxins and now let's zoom out to get a picture of what we've talked about we talked about the differences between Protista archaea and bacteria and took a good look at general bacterial structure