hello bisque 132 this is the beginning of recorded lecture 1 4 uh getting more into chapter 23 protists but but not actually getting into protists yet last time we uh briefly you know started talking about eukaryotes because protists are the first eukaryotes we've come across and uh we've got more to say about eukaryotes before we actually get into protists so uh we defined you know some of the features that eukaryotic cells have last time a nucleus mitochondria being a couple of those and if we go back to this once again uh eukaryotes uh evolved from prokaryotic cells so uh the the most ancient uh evolutionarily the most ancient type of cell uh is a prokaryotic cell so eukaryotes you know came off later you know split apart from archaea at a certain point so the question is how do we go how do we go from a simple prokaryotic cell without things like a nucleus or a chloroplast or mitochondria to a eukaryotic cell that does have these things so there are a couple of different answers to this question so uh let's start with the nucleus uh it is thought that the origin of the nucleus was simply in folding of the plasma membrane so here's what you could call a proto-eukaryotic cell and you know the nucle the nuclear envelope the nuclear membrane really is just a lipid bilayer it's thought that you know in folding of this membrane and then sort of pinching off could have created a membrane system that's that's internal and then of course all the you know genetic programming to to maintain this from cell division to cell division but that's a simple explanation for how you could have this kind of membrane-bound organelle so origin of nucleus in folding of cell membrane the mitochondria and the chloroplasts are a more complicated story so it is thought uh the the origin of mitochondria uh is through something called endosymbiosis or endosymbiotic theory uh this is essentially an extreme type of symbiotic relationship so it again it is thought here's the um you know uh primal eukaryotic cell uh that this engulfed a free living bacterium that was you know really good at breaking down sugars and at first that's just you know two separate living things what we would call a symbiotic relationship the eukaryotic cell provides you know protection and support and this bacterial cell uh you know gets sugars given to it and cranks out atp and exchange but it's thought that over time uh this relationship got more and more co-dependent to the point where these mitochondria now have lost uh all of the genes they would need to be able to live on their own and are completely dependent on this eukaryotic cell so we can't consider this really a symbiotic relationship anymore because it's not a relationship between two living things this uh once independent living thing is now a wholly dependent organelle within this modern eukaryotic cell so endosymbiosis to read from the key terms is the engulfment of one cell within another such that the engulfed cell survives and both cells benefit an endosymbiotic theory is just a theory that states that this is where that organelle came from um there's a lot of evidence for this for the mitochondria arising in this way one of these is that mitochondria physically resemble a type of bacteria called alpha proteobacteria just they're if you remember the scale of things with bacteria mitochondria they're about the same size they're about the same shape there's a physical resemblance there that in and of itself wouldn't be enough uh the biggest piece of evidence in my opinion is that these organelles have their own dna and if you sequence that dna and you can do that it doesn't look like because an alternative theory an alternative hypothesis might be that you know this organelle sort of pinched off from the nucleus and that's how it has its own dna if that were the case the dna in a mitochondrion would be very similar to eukaryotic dna but it's not if you sequence mitochondrial dna you do do the sequence alignment it's very simple similar to that of these alpha proteo bacteria which strongly supports this endosymbiosis and finally they reproduce somewhat independently of the cell and the way that they reproduce is very similar to that of bacteria okay so that's mitochondria what about chloroplasts well i'm going to use a term called plastids this is just a bit more broad uh a chloroplast is a type of plastid uh and so you know this explanation is gonna be true for chloroplasts but it's gonna be true for some of these other organelles that are very similar so that's why i'm saying plastids and the story here is exactly the same as it was for mitochondria that a eukaryotic cell engulfed a photosynthetic free living bacterium they lived together for so long that they became you know completely uh dependent on one another and to the point where the chloroplast you know has its own dna but can no longer live independently and this eukaryote can no longer do photosynthesis uh without the chloroplast so origin of plastids which includes the photosynthetic chloroplasts same as mitochondria i'm not gonna you know write all this again but everything i said here physically resemble bacteria they have their own dna they reproduce independently and all of that stuff is is true for the origin of plastids as well it is important to note the order of these events so all photosynthetic eukaryotes plants for example uh have mitochondria and a lot of people think and i tried to dispel this thought in bisque 130 at least that you know photosynthetic organisms have chloroplasts they don't need to break down sugars in a mitochondria because they are making sugars in a chloroplast but that's not true photosynthetic eukaryotes like plants have both of these organelles so the order of events here is the endosymbiosis of the mitochondrion uh mitochondria and then in some groups uh endosymbiosis of um the chloroplast so the order of events here such that all these groups end up having mitochondria so this endosymbiosis of plastids came after the mitochondria endosymbiosis all cells with plastids also have mitochondria okay so now with with that background now we know what it what a eukaryotic cell is and you know how it arose let's talk about protists as far as you know what does it mean to be a protist well the messiest thing about protists has to do with its phylogenetic tree so here is a phylogenetic tree that i i built myself it does not include every group we're going to talk about but it includes most of them uh you know this includes plants this includes fungi this includes animals so you might be wondering where's the protist like which one is protest when you know what a plant and a fungus of an animal is where's the protist the protist is literally everything else so this is an example of an incredibly paraphyletic group uh all these others plants fungi animals those are monophyletic groups those are clades the the quote-unquote kingdom protista is really just a grab bag that includes everything else every eukaryote that's not a plant a fungus or an animal it falls under the heading of of what we call a protist and we're gonna see when we look at these groups that yeah some of them are very similar to animals and some are going to be similar to fungi and some are going to be very similar to plants and they're going to be all over the place and that's because of their status as just a waste bin of just throw everything into this group that didn't fit anywhere else so kingdom protista quotes there uh is paraphyletic it's not a clade and obviously it ends up being incredibly diverse members so so what can we even say about protists well there are a few things we can say about protists um they're mostly unicellular there are going to be some multicellular protists but most of them are single-celled organisms they can be autotrophs uh or heterotrophs hey these terms should look familiar and here's my slide from the from the last chapter so they could be autotrophs or heterotrophs uh or here's something new uh some of them are what we call mixotrophs uh which is a very fun combination of these two yes a mixotroph is to read from the key terms an organism that can obtain nutrition by autotrophic or heterotrophic means so these are going to be cells swimming around eating bacteria like a heterotroph but also doing photosynthesis very weird but yeah we see these uh among protists we see something else new that we didn't see in bacteria some protists i can make all these statements with things like some some can engulf and take up large food particles in a process called phagocytosis so here's a diagram of that a large food particle uh sort of changing the shape of the cell itself engulfing this bringing it in extracting nutrients from it and then you know sending stuff out again bacterial cells could not do this because of their cell wall so that they couldn't be squishy like this and move around and be dynamic in the same way so this is a new mode of nutrition that we see in some protists this phagocytosis most are motile meaning they can get around one way or another they can do this using flagella cilia or something called the pseudopodia which are temporary projections of the cell here's more pseudo means false podia we're going to see a lot of poda throughout this corner i can assure you of that pota or podia means foot pseudopodia means false foot and yeah here's what pseudopodia look like this is not a permanent extension from the cell it's extending this extension crawling along and then sort of absorbing it back it's a temporary projection oh yeah here's the cilia we saw those in an earlier slide here's a flagellum we've seen these before these are all different mechanisms of of protist motility and we'll see a few examples of this don't worry we will not be memorizing these but they're always uh fun to look at a lot of protists end up having very complex life cycles so oh that that's all i can say about protists in general again it's such a grab bag uh tax on here uh that it's it's difficult to say things about them in general so the whole rest of this chapter is going to be looking at specific groups of protists so if you remember with bacteria things were too complicated to really get into all the different phyla all the different groups of bacteria with protists it's still really complicated but it's just complicated enough to be able to manage so um here is going to be our big major slide phylogenetic tree to sort of guide us through the whole rest of this chapter uh if you'll notice so this is a rooted phylogenetic tree but instead of you know rooted at the bottom and going up like a tree it's rooted on the left going right just because that's how we read from left to right for our convenience and this is not a protist phylogenetic tree this is all eukaryotes so all eukaryotes including we can find fungi and animals and plants in here all eukaryotes are are going to be part of this and color-coded for our convenience we can see that there are six major groups called super groups that exist within eukarya these are clades so each one of these color coded things is an ancestor and all of its descendants there are some dotted lines here because there's a little bit of uh um disagreement about exactly where they should fit but but each of these are pretty solidly clades so uh we're not just going to talk about protists but we're going to talk about where things like plants and fungi and animals land as we go through all of these six supergroups so there are six super groups in eukarya and all six of these are clades and of these six eukaryotic super groups let's start out and start somewhere let's let's start out in the middle here with a group called archaea plastida so maybe you can guess what's going to be part of this group just based on the name it's got plastida right there in the group name we just talked about plastids not that long ago and if you remember plastids included these photosynthetic chloroplasts so it would be a very good inference uh that archaea plastita includes photosynthetic organisms and yes members of this super group are photosynthetic and as you can see here this includes plants we'll talk about glorified star fights and land plants when we get to our plants chapters uh but you know all all three of these are are the clay that we call plants in fact there's only one clade of uh protists here in archaea plastita aside from plants uh and that is a group called red algae so red algae uh gets its name from the red appearance of some of its members but again that's only some of its members you know plenty of other members the the seaweed used in uh in nori and uh sushi wraps uh is a member of uh red the red algae group and it's not really red at all so whatever um and at first glance this looks a lot like a plant and it's closely related to plants so a very good question is why isn't this just a plant and these red algae are distinct from plants only if you look very closely at how they do photosynthesis so obviously they're they're members of the same super group they have a lot of similarities but they use different pigments and different proteins for their photosynthesis so that's what keeps these superficially plant-like things uh in the grab bag of protists and not real plants like all this fun stuff that we'll get into in our later chapter when we talk about plants so okay that was easy we talked about red algae and plants that's one super group down uh before we get to the next one i need a frustrating disclaimer so okay disclaimer the term amoeba when we call something an amoeba that refers to cells that are capable of creating pseudopodia of you know crawling along in this sort of manner uh you know extending temporary projections stuff like that if a cell can do this we call it an amoeba uh the clade that i'm about to get into has amiibo right in the name uh members of the following clade have this cell type but not all amoeba type cells are within this clade so the next clade we're going to talk about uh is amoeba zoa but there are going to be plenty of amoeba cells that are not within this clade i hope that makes sense so okay back to this amoeba zoa so okay three groups to talk about within this super group uh members of amoebazoa i can have pseudopodia do phagocytosis they have that that amoeba lifestyle that amoeba body body shape so let's do the two of these together gymnamiba and entamoebas um these are naked amoebas and amoebas with tests i wish i could tell you all of these were naked and all of these had tests but it's not true it's you mix and match whatever jim means naked so it was thought that these were all naked but that's not true anyway these two together uh include some amoebas that are naked and some that have tests so okay what is the test what does it mean to be naked well uh you're a naked amoeba if you don't have a test so okay what's a test a test is a shell so here's a naked amoeba very classic looking and here's what's called a testate amoeba so the the shell which is called a test is defined in the key terms a test is a porous shell that is built from various organic materials that's an important note there organic materials and typically hardened with calcium carbonate so this is you know a lot like a shell of other organisms but you know this is a single cell organism very various very small shell so yeah these two groups include some that are naked and some that have tests um some are pathogenic uh if you've heard of amoebic dysentery that's um a condition that's caused by these uh by pathogenic uh amoeba and so that takes care of uh of two of these the gymnames and entamoebas we have one more fun group under amoebazoa slime molds so what do we say about slime molds well slime molds produce spores that resist harsh conditions so here's an example of this uh again complicated life cycle this is definitely not the most complicated we'll see in this chapter but fairly complicated and yeah it's you're fusing cells you're making plasmodium you're dispersing spores and they can resist harsh conditions before growing up into into more of these uh amoeba this is very similar to the the mo of a fungus and so uh these were misidentified as a fungus for quite some time it was more thorough analysis including genetic analysis that puts them not with fungi but in the grab bag of protista so slime molds include two basic types plasmodial slime molds and cellular slime molds plasmodial slime molds are a multi-nucleated mass so that means a bunch of cells all connected together with a bunch of nuclei which again is a lot like what fungus is going to be like a multi-nucleated mass of cells that move along surfaces eating stuff you got to see what this looks like because it's freaky looking uh this includes the dog vomit slime mold it it doesn't move at a rate that you can see with your eyes but there are some cool stop-motion videos of this stuff crawling along that looks really neat and here's the pretzel slime mold as well again looks a lot like a fungus but again genetically evolutionarily it's just converged on a similar lifestyle living on the ground and you know eating stuff around it like a fungus would so this is a plasmodial slime mold those two cellular slime molds are not as big they're single celled but they form aggregates to to release those spores so here's a an image of sort of some slime molds forming these aggregates very complicated stages here slug mexican hat i don't name these things and then eventually getting into this fruiting body which i can barely see with the naked eye this uh aggregate of this slime mold again to release spores to go off and and and live somewhere else so this is another type of of slime mold okay so uh there's another group down we're moving through these fairly quickly but we will not keep up this pace for very long unfortunately so uh the next one to talk about is opis vocanta down here so members of opisthoconta uh all have a unique flagella structure it's not very exciting to look at but i mean it is one of those uh synapomorphies uh that tie members of this group together and if you look closely this uh super group includes animals and fungi so yep opisthoconta animals and fungi are here nothing to say about them now they will each get their own chapters in the future but you should be familiar now that these are members of this apistoconta supergroup uh so what are the protists in this super group well protists in this group include uh uh protists called choano or koano the h is silent uh coanoflagelets uh so these are colonial cells that have you guessed it flagella based on the uh flagellates there in the name uh coano actually means collard uh in latin i believe so these are collard flagellates uh they look like exactly what you would expect them to look like this is a a cell with a collar and a flagellum so coanoflagellates you're pretty on the nose and this is one of the most generic boring looking cells that you could possibly imagine uh they you know form these colonies they're single-celled organisms but they they group together and form these these aggregates these colonies to work together their claim to fame and we'll see this again when we talk about animals is these coanoflagellates are the closest living ancestors to animals when we look at the simplest animals there are sponges they're going to have a lot in common with these colonial protists and long story short uh it's thought that you know the the jump from colony to multicellular organism uh not a big jump uh is what led to the evolution of animals but anyway just for now know about these uh coated flagellates colonial cells with flagella they're closely related to animals the other group within opistoconta is a group called nuclearids double i right there i am not a stickler for just side note i am not a stickler for spelling on any of this stuff uh my tests as you know are all multiple choice i'm not gonna trick you with a question where you know one of the options i've misspelled in very subtle different ways so yeah i can't you know correctly spell half of these things myself but yeah anyway nuclear yids uh these are amoeba so again i told you that there would be cells with this uh amoeba body type outside of amoeba zoa uh these nuclearians are amoeba with thin pseudopodia and so this is a little bit different you know a pseudopod is a temporary projection from the cell and we talked about it uh previously as a way to move around a sort of crawling will moment movement uh the purpose of a thin pseudopodia like this and we're going to see this in several other groups of protists is to extend out the cell membrane and then absorb nutrients or other things through all this surface area this is a great way to sort of drink or absorb stuff from your surroundings uh these thin extensions uh really up your surface area so make it very very good for doing that but that's all i want you to know about nuclearians they're in nopistoconta they're amoeba with thin pseudopodia all right so uh what do we have next well next up is supergroup called rhizaria so this is gonna include three groups within this uh i have nothing to say about rise area as uh as a super group there are no easy uh synapomorphies or featured share features shared within all members so just know that the next three things are under this umbrella of of rhizaria uh so one group of riserians is a group of protests called forearms also amoeba within pseudopodia and you know i can't make this up here's a nuclearian which is opistoconta and here is a forearm which is rhizaria it's just it's an effective body plan it's an effective feeding strategy you can get two groups uh that are not closely related to one another there are the four amps here uh and the uh riseria uh we're elsewhere or the i'm sorry the uh nuclearians were down here uh distantly related but with very similar cell bodies that's convergent evolution for you so sorry if it's frustrating but it is the way it is so four amps are amoeba with thin pseudopodia uh they form complex tests so these are porous shells if you'll remember so they're able to extend these thin pseudopodia out through the holes in these tests so it can protect them but they can still do their thin pseudopodia importantly if you remember i made up i made a point of this that tests are composed of organic compounds that means carbon so these these forams make these tests and they die and these tests sink to the bottom of the ocean and they act and you know some of these very pretty looking uh very small these tests sink to the bottom of the ocean and form what's called a carbon sink which is very important all the carbon that's tied up in these dead forearm tests uh is carbon that's not in the atmosphere so uh very important for them for them to do this um another interesting thing about forearms a lot of these have symbiotic photosynthetic partners i don't have a good image for this but even as a single celled organism you can partner up and have a symbiotic relationship so a lot of them effectively do photosynthesis through this symbiotic relationship uh so that's four ams uh another member of this super group ryzeria is a group called radiolarians stop me if this sounds familiar amoeba within pseudopodius another one of these they form complex shells from silica which sounds familiar but it's not maybe the shell thing should be familiar but silica is is basically it's basically glass basically sand uh that's not the same thing as a test remember a test was calcium carbonate and organic compounds a silica shell even though it's still a shell is is not a carbon sink and it's made in a very different type of chemical compound here's what one of these looks like even smaller than those tests a curious thing to say about these is if you know what you're looking for these radiolarians have gone through different evolutionary events in the planet's history uh paleontologists can look at you know fossilized radiolarian shells and know what time period they're looking at by the the shapes of radiolaryns shells that are found in that rock so kind of a random fact but i mean something unique to this group uh that radiolarians make useful indicators uh in fossil records so moving along still within rise area our next group is a group called uh circus owens um diverse forms uh some of them have a test some of them don't have a test some of them have a shell some of them don't have a shell so again evolutionary evolution is a messy thing i i wish i could just like invent a group and they all have tests and events another group and they don't but whatever circus owens some with or without test with or without shell and some of these are photosynthetic so uh here's just some of these uh not particularly special looking but you know just to see some uh circus owens there is something interesting to point out here this doesn't sound you know like a big deal yes sure some of them are photosynthetic but if we go back to this big you know super group here uh these circus owens are photosynthetic which means they experience they had to have experienced that endosymbiosis event to acquire plastids to acquire photosynthetic chloroplasts but look at these other photosynthetic protists red algae these also were photosynthetic protists they're not closely related to one another what that means is these two groups of protists and they're going to be other photosynthetic protists as well these groups of photosynthetic protists had their endosymbiosis independently of one another this endosymbiosis event of plastids has occurred several different times within eukaryotes so the type of chloroplasts that circus owens have the endosymbiosis that allowed them to do photosynthesis completely independent of the endosymbiosis that allowed red algae and plants even to have their photosynthesis they're going to be other photosynthetic protists later as well so this is a point to to mention that this uh endosymbiosis has happened multiple times so okay some of these circuits ones are photosynthetic and some are parasites of fungi so this is uh kind of an interesting twist on uh this thin pseudopodia uh so i mentioned before these are good ways to you know absorb nutrients from the surroundings uh well this circus owen the vampirella uh le territo later tia um is actually a parasite of fungi uh that stabs i couldn't find a good image showing it doing this but you could imagine uh stabbing these thin pseudopodia into a fungal cell and then absorbing nutrients from its cytoplasm and earning the vampire part of its genus but yeah so some are parasites of fungi they steal nutrients from the cytoplasm of their host using needle-like thin pseudopods okay so that took us to the end of rhizaria radiolaurians forams and circus owens we've got a couple of big groups left but this is typically where i run out of time in lecture 1-4 so i'll cut things off here we'll finish up this chapter in the next recorded lecture