 I think it's time to get started. I just have one announcement before lecture today. Those of you that own the seventh edition of the textbook, they are now posted readings for the seventh edition on the syllabus page. They're not incorporated directly into the syllabus there. But if you click on the link up at the top of the column about the readings, it'll take you to a page where you can see the seventh edition readings that correspond with the eighth edition readings for each week or each lecture. So please check that out if you have the seventh edition. And I hope everyone's found the B-space lecture notes that I've been posting for each lecture afterwards. They're basically these keynote presentations I've been giving with additional notes down below that are incorporated. So please have a look at that because that's the main material that I'd like everybody to study for the exam. Any questions about any of that? Okay, so today we're gonna finish off the fungi. And we'll basically just today be talking about their ecological and economic significance, which is what I started in at the end of last lecture. And then we'll start talking about the algae and the origins of photosynthesis, which is something that we really just come to appreciate in the last few years to figure out. So last time at the end, I mentioned the importance of lichens, which are these associations between fungi, usually Ascomi seeds, and a unicellular alga, a green alga, a eukaryotic green alga, or a cyanobacterium, a blue-green bacterium. And their important pioneering role in primary succession in the development of soils, of substrate that other organisms can utilize on barren surfaces like rock faces or barren wood, areas that are just beginning for successional stages are really just beginning. And those that have associations with blue-green bacteria can actually fix nitrogen. And this is really important, as I mentioned earlier, as a limiting nutrient in a lot of ecosystem situations. So that's the lichens. And even though they're really pretty adept at dealing with environments that have very harsh conditions in terms of very few resources available, they're at the same time really vulnerable to air pollution. So for example, if you go to the LA basin and try to find lichens, you're not gonna find very much. But a hundred years ago, there were a lot of really great collections of lichens made there. And this is the case in other parts of the world. So these really ecologically important organisms are greatly diminished and threatened in areas where there's bad air quality. Sulfur dioxide, especially, really nails them. So this is a real problem. And we already talked about mycorrhizae, so I just wanna throw it in here just to mention again that most plants, with the exception of very few families, mustards and carnations, just a few families that don't have these associations, the others that do benefit in terms of their growth and fitness from this association. And presumably the fungus does as well, but the evidence there is not as well-established experimentally as it is with plants. So here you can see some plants where there is no mycorrhizal association, closely related individuals where it is well-established. These are of the same age, grown under same conditions otherwise. So mycorrhizae are really critical to plant success. And as I mentioned earlier, we're probably crucial to the original success of land plants in general, just getting established and diversifying. So, Fungi play a big role there. Now, one thing I hadn't mentioned is this association, which is more recently appreciated. And this is that there are fungi that actually live inside the leaves of most plants. And these are called endophytes, which literally means inside plants. So these are actually, the whole fungus is inside the leaf. And these are fungi that become established in the environment. They aren't present in the plant from the original seed stage up. They infect the leaves of the plant. And where this infection of the leaf by endophytes has been prevented, it's been seen, for example, in the cocoa tree here at Theobroma cacao, from which we get chocolate, that the plants that were prevented from being infected by these fungal endophytes actually were more vulnerable to disease, to pathogens than those that weren't. And it's not quite clear why. It could be that the fungus is producing something that is preventing pathogens from becoming established. It could also be that the plant is actually responding to the fungi in a way, some sort of defensive way, possibly, that's also preventing really serious infection by disease-causing organisms. But in any case, they appear to gain some benefit in terms of disease prevention from these fungi. And in grasses and some herbs where this has also been studied, the fungal endophytes appear to help repel herbivores and to increase the plant tolerance to physical environmental extremes as well. So it's uncertain, again, how this operates, but this is an important association that appears for plants as well. So we have associations with the leaves and the roots involving fungi that seem important to plant fitness. And the ecological importance that everybody's aware of, probably, that I've already mentioned, is that fungi are important decomposers. And of course, there are other organisms that are important decomposers, bacteria, et cetera, microbes. But some of the fungi, like this bracket fungus here, have enzymatic activity that actually can result in breaking down of substrates that are very difficult for other organisms to digest. And most significantly here is lignin, which is the substance in wood that imparts rigidity. And of course, cellulose is also pretty resistant to digestion. And some of these wood decaying fungi are really important for bringing the carbon and wood back into the ecosystem as far as availability goes. So these are particularly noteworthy. All right, so one thing you're probably also aware of is that fungi can cause diseases. And about 30% of described fungal species are parasites or pathogens. And most of these infect plants. So plants actually suffer, to some extent, from fungi as well as benefit. The most significant disease outbreaks we've had are the result of fungi being introduced into an alien environment where the plants hadn't been exposed to them previously. And some of the really serious diseases we have in North America, for example, are the chestnut blight, which causes these big cankers. And it's actually the result of a fungus that attacks chestnuts in Eurasia. But there, the trees have co-adapted with the fungus. Whereas in North America, they didn't have exposure. And our American chestnuts, which were one of our most important hardwoods in the Eastern deciduous forests back in the 1800s, this disease was introduced in the late 1800s. And now they're all gone. The American chestnuts, essentially biologically extinct except for stump sprouts that arise persistently from old stumps before they finally succumb. There are some isolated stands down in the southern Appalachians, where they're isolated. But for the most part, this is a functionally extinct plant in North America. And also an elm disease that affects our American elm was transmitted from Eurasia as well. And it's decimated our American elm. And here on the West Coast, we have pitch canker, which is a fungal disease that infects our pines, our closed cone pine forests, like the Monterey pine along the coast. And it's only been introduced in recent years. It's not quite clear what the outcome will be there. Oh, actually, I'm going to back off here for a second. I want to mention that also fungi can attack animals. And the consequences can be severe for an individual animal. But for taxa, those fungi that have co-evolved with animals or have been in the presence of particular species for long periods of time, of course, it doesn't behoove them to destroy their host. And in cases where we have fungal diseases that actually routinely kill the host, the infection rate tends to be fairly low. So the host isn't exterminated. And there are some really interesting fungal diseases that attack specific organisms. In particular, cordyceps, which is a genus in the Ascomyseeds, has undergone an amazing adaptive radiation, a diversification, across insects. There are about 400 species of these cordyceps that are known. And what happens is they get ingested by the insect. They germinate inside the insect body. And then they basically replace the insect tissue with mycelium. And eventually, the insect is so heavily infected that the fungus essentially takes over even its psychology. And the insect will climb up into actually in its last dying stages, exhibit a behavior that's beneficial to the fungus in terms of where it dies. And here's a victim here of one of these cordyceps fungi that's climbing up a grass stem. And eventually, or actually it's not a grass, but it's a tree stem here. And it's died, and it's now clinging to this stem. And you can see that the fungal fruiting body is starting to sprout out of its head. This is time-lapse photography, but you can see the fungal body growing out. It's just slowly working its way up, and it's eventually formed. This is an asco carp, fruiting body of an Ascomyseed. It'll form these ascii and release sexual spores. And then the life cycle will start over again. Spores are released, and another unfortunate victim will ingest them. And here you can see a number of different cordyceps. You can see their distinctive fruiting bodies that allow them to be easily identified morphologically as different species, attacking different ants, in this case, different groups of ants that have different behaviors. They end up dying in different situations that are beneficial to the fungus. So this is just one of the sort of perverse things that fungi can do. And there are other cases as well. So in terms of their importance to humans, fungi are, of course, critical to us in terms of these ecological services they provide. But they're also important in more direct ways, for example, as food. And these are some ways in which fungi are important as food that you may not think about every day. Everything in this table setting here is possible because of fungi. Basically, alcoholic beverages are the result of fermentation using brewer's yeast. And the raising of bread is the result of CO2 production by yeast under anaerobic conditions during the fermentation process. And also, cheeses, of course, are made using various fungi that are critical in regard to cheese production as well. So basically, having wine with bread and cheese wouldn't be possible without fungi. So that brings it home a little bit. But also, of course, fungi are edible in their own right just directly. The fruiting bodies truffles are ascomycetes that have underground fruiting bodies that are incredibly valuable. And choice, delicacies, morels as well among ascomycetes. And then among basidiomycetes, we have a large number of different edible fungi that range from our typical store-bought mushrooms, which are cultivated, to a lot of wild-collected mushrooms that are not cultivated. And of course, I'm sure you all know from not having been born yesterday that you don't just go out into the environment and start eating mushrooms because a lot of them produce some nasty secondary compounds that are extremely poisonous. And it sometimes takes some effort to distinguish edible mushrooms from absolutely deadly ones. And this is a case in point where one of these is a choice edible, and the other one is a deadly mushroom. And unfortunately, individuals who harvest this mushroom from the wild in some parts of the world will come here and think that this is the same species. And you can tell them apart by their spore prints. This one has a pink spore print. This one has a white spore print. But if you don't go to that trouble and you're not too careful, you can end up having a meal of the death cap, which is the world's most dangerous mushroom. And a single meal of a very small amount of this is enough to completely destroy your liver and damage your kidneys to the point where a lot of victims of this poisoning have to have liver transplants or they'll die. The aminite and the toxin basically just kills your liver. But it doesn't happen immediately. It can be hours to some period of time afterwards. And there is an anecdote. And one of the most effective ones is milk thistle, which is a plant. And the extract from milk thistle can disable this toxin. But once the damage is done, it's done. A more esoteric type of poisoning is from this organism, which isn't a basidiomycete, but an ascomycete. And that's claviceps purporea. And you can see it here on rye. So this is an organism that infects rye, which is, of course, a grain that's milled. And if you mill rye that's been infected with claviceps, it can result in widespread poisoning of the people that ingest that milled cereal. And it's happened numerous times in recorded history, resulting in the deaths of thousands of people. And what happens is the chemistry of this fungus is really insidious. It has a number of different effects that can cause vasoconstriction, resulting in gangrene. It also can cause seizures and some psychological effects, temporary insanity, and hallucinations. And one of the ingredients of this fungus are one of the chemicals it produces is lysergic acid, which is the raw material from which LSD is produced. And it's thought that, well, there's some speculation, at least, that the individuals accused of witchcraft, of being witches back in colonial America, back in the late 1600s, during the Salem witch trials, were actually victims of ergotism, as it's called, of having ingested this fungus. And their behavior led people to think that they were basically exhibiting satanic influences. So unfortunately, that was the end of several of them. They were hung, so an indirect cause of death there. So also, fungi can cause diseases, as I mentioned, in plants, but also in people. And some of these are incredibly insidious. But the more common ones that you're probably familiar with are things like athlete's foot, ringworm, and jock itch. And these are caused by different groups of Ascomycetes that are actually pretty closely related to one another. And these are typically not very dangerous and can be treated pretty readily. Nail fungi and things like that, fungi imperfecti here from Ascomycetes that cause these diseases typically. But there are some fungal diseases that are more serious. And one of them is actually endemic here to western North America, the valley fever. You might have heard of valley fever, which is found out in the San Joaquin Valley and in the deserts. It's an Ascomycetes that's pretty happy to live in the soil. But if it gets airborne and you inhale the spores, it can take up a pretty happy existence in your lungs and cause a serious lung ailment that can potentially lead to death, especially in immunocompromised people. And I have a whole series of slides that I won't show you this morning because you'll either lose your breakfast or possibly pass out. We've had an individual pass out in the past in this course from showing these slides of what can happen to people with some of these tropical fungal diseases where basically the mycelium takes over to the extent that it did in that ant that I showed you. And the fruiting bodies form out of the person's face, for example, out of an eye socket or something like that. So that's not typical, though. What's that? I could show those slides to people in office hour, but I won't post them. I don't think. They're really disgusting. And I don't want to, somebody might accidentally look at them that shouldn't see them. But I make that point at the same time as making this one that on balance, fungi are more important as disease-preventing agents for us than they are as disease-causing agents. And most significant in this regard is penicillin, which is a bactericidal compound produced by the ascomycea penicillium, which is a member of the fungi imperfecti. It's an ascomycea, but it's asexual exclusively. And here you can see a mycelium of penicillium radiating out from its central point here. And you can see this zone of death here where it's killed the bacterial colony that's been swabbed out on this petri dish. And it operates by destroying the cell, attacking the cell walls of bacteria. And of course, we don't have cell walls, fungi don't either. And so this was a real lifesaver, saved millions of lives beginning in the early 19th or early 20th century. OK, so that's really, yeah. Oh, right, I didn't mention there are mushrooms that have chemistry that can result in psychotropic effects that are like cellosabee that has LSD-like properties and also aminida muscaria, which is in the same genus as that death cap that I showed you, that has a red cap with little white inclusions on it that was used by Vedic priests back in early hundreds and hundreds of years ago as a way to induce religious states. I don't know exactly how to put it, but the problem with aminida muscaria is that you have to concentrate it for it to really become potent. And so the priests would actually drink their urine and the way to concentrate it is to drink your urine. And there's actually still a tradition of urine drinking that goes back, we think, to that original practice that's no longer connected to aminida muscaria. But in terms of what the benefit to the fungus is, it's potentially an herbivore defense, a defense against being eaten. I mean, some people find these effects desirable or beneficial, but that's not necessarily true with the most important potential herbivore that would attack the fungal fruiting body. And you want to protect these fruiting bodies. I mean, these are how you're reproducing. They're very exposed to the environment. They're easy to digest in terms of they're not particularly tough and difficult to digest. So poisons are a good way. OK, so any other questions about fungi before we move on? All right, so I want to talk now about algae. And this should be in quotes, actually, because algae are not a monophyletic group. They're not a natural group. And if we look at their distribution across the tree of life, this is the tree of life, the three major domains I showed earlier, the archaea, the bacteria, and the eukaryotes. Here's how they're distributed. I think I showed this earlier. But we have the cyanobacteria that are photosynthetic among the bacteria. And then we have several different groups of photosynthetic eukaryotes that are not each other's closest relatives in many cases. So the question arises, did photosynthesis evolve multiple times independently? And it's quite a complex process. It's quite interesting to think about that possibility. Certainly when you look at the different groups that have the ability to photosynthesize, they have radically different morphologies and ecologies. These major groups that are coming out in different parts of the tree of life based on molecular data, they certainly don't appear to be closest relatives. And I should mention that algae, the term basically applies to all photosynthetic organisms, except for the land plants that we'll talk about for most of the rest of this semester. And they generally occur in aquatic habitats, freshwater or marine situations rather than on land. But there are some exceptions. OK, and so if we look at their distribution again in a little more careful way, here's where the fungi are in the overall. This is the eukaryotic clade. These are all the eukaryotes here. That's the root of the eukaryotic part of the tree. Here you can see the fungi. Here you can see the animals. And here are the slime molds to just put you into the perspective of where we've just been talking about this clade. Now we're going to talk about each of the four of the five, the remaining four major super groups, as they're called, super groups of eukaryotes. So we have botanical organisms in all five, but in four of the five we actually have photosynthetic botanical organisms. And the ones that are photosynthetic are shown here in dark highlight. So one idea that was actually proposed almost a hundred years ago, but really came into its own in the 1960s in terms of explaining how this happened, how photosynthesis became widely distributed among different eukaryotes, is called endosymbiotic theory. And endosymbiosis basically just refers to the process of incorporating one organism within the cell of another. So we're not talking about the kinds of symbiosis that we were talking about earlier with mycorrhizae or lichens, where you have organisms living together, but separately in terms of their cells. Here we're having a case, in this particular idea we're talking about an organism becoming completely contained within the cell of another organism. So this was thought to, proposed initially to have happened as a multi-step process. And the first step in this process, and I should mention Lynn Margulis was the one who really provided the best evidence for this theory where it really took off. She's still a living biologist, it's not been that long ago, but the ancestral eukaryote envisioned as something like this that already has a nucleus, but doesn't have mitochondria or plastids, doesn't have these membrane-bound organelles. And the earliest eukaryotes would have already had a cytoskeleton, presumably of microfiberals and such that would allow it the ability to engulf other organisms. And we see this kind of ability in a lot of unicellular eukaryotes, and I should mention it in the slime molds as well, where they can actually surround and completely engulf another organism. And so this happened presumably initially with a bacterium, it turns out it looks like a proteobacterium, a true bacterium in this case. And rather than digest this potential food item, the bacterium survived the ingestion, and eventually this became a mutually beneficial relationship, and after evolutionary time we have exchange of genes between the genomes of the original prokaryote here, the bacterium, and the nucleus of the eukaryote. That's what these arrows are referring to is the exchange of genetic material. And once that had gone far enough, these two organisms could no longer live separately from one another, and they became inextricably bound together as a single organism. So it's one organism that originally started out as two, and they became totally integrated. So here it is in a little more detail, this is from your textbook, and you can see here a ancestral prokaryotic organism, and here we see the origin of the nucleus, which is not thought to be due to endosymbiosis, but instead of unfolding of the plasma membrane around the outside of the cell, and formation of a new membrane around the chromosomes, and also the formation of the endoplasmic reticulum in the same way. Okay, and then at some point after that happened, here we have the bacterium that became the mitochondria being engulfed here, and eventually incorporated. And then we have evolutionary diversification following this event. And in one of the lineages of early eukaryotes, then we have the ingestion of a cyanobacterium, a photosynthetic bacterium, a blue-green bacteria, that ultimately became the chloroplasts. And this didn't happen in some lineages. There are some lineages of eukaryotes that don't appear to have ever had plastids. And I've used this term plastid a lot. A plastid is any kind of organelle that ultimately descends from a cyanobacterium. There are plastids, for example, in roots that don't have a photosynthetic function. Chloroplasts are the ones that have a photosynthetic function. We find typically in the leaves, but all plant cells have some plastids, but they're all descended from the same ancestor from this original engulfed cyanobacterium. So the cool thing about the endosymbiotic theory is it really provides us this perspective, if in fact it's true, that it's this amazing cooperation between prokaryotes and eukaryotes, specifically bacteria and eukaryotes, that was probably key to the development of multicellular life on this planet and the world as we know it in terms of the biota. And one can ask then, is this really a true theory? Is this, what is the evidence for this theory? We can never absolutely prove a theory, but we can garner evidence in favor of it, or we can potentially shoot it down if we have evidence against it. And here you can see the tree of life with the proteobacterium being incorporated prior to the diversification of modern eukaryotes, and the plastid being incorporated after the beginning of the diversification of eukaryotes, just in one of the main lineages here. Okay, that's more or less what we just showed in a different perspective. So here's some of the evidence. The one thing that was brought up early on is the size of these organelles, their size and shape and their internal structure. When you look at that in the case of mitochondria and plastids, they look amazingly similar to a lot of putatively closely related bacteria. And if you, for example, compare a plastid, a chloroplast, in terms of its internal structure, these thylakoid membranes and all, they look very similar to what you find in a cyanobacterium in a blue-green algae. Another line of evidence is the way that they reproduce. So the nucleus of the eukaryotic cell does not code for the production of mitochondria and plastids. Plastids and mitochondria reproduce on their own by binary fission, which is the same process by which bacteria reproduce. And if you actually purge all of the plastids out of a cell, that cell is incapable of regenerating plastids. So you wouldn't want to do that with the mitochondria, the cell couldn't survive. They need the mitochondria for respiration, but there are some organisms that can withstand the loss of their plastids and they'll go on reproducing, but you'll never see another plastid in that cell line. So this is a pretty interesting line of evidence that suggests that the mitochondria and plastids came from an outside source they weren't generated from within. Another line of evidence is from the ribosomes that are found inside of mitochondria and plastids. So we actually have protein synthesis going on inside mitochondria and plastids. This involves their own machinery. They have their own ribosomes that are different from the ribosomes you find out in the main cytoplasm of the cell, of the eukaryotic cell that they're contained within. So ribosomes, to remind you, is basically a complex of ribosomal RNA and protein that's involved in translation of messenger RNA into polypeptides, which are the raw material for making proteins. And these ribosomes, both in their DNA sequence and in the proteins, are more similar to the ribosomes of bacteria than they are to the ribosomes of the eukaryote. So this is a pretty amazing line of evidence too that these things were not generated from the eukaryotic cell, the mitochondria and the plastids. And also there are some antibiotics. We just talked about penicillin, which is a bactericidal compound that attacks the cell wall. There are some bacteriostatic antibiotics that target protein synthesis in bacteria. So they're going after the ribosomes. And those same antibiotics, if they're applied correctly or can be poisonous to the ribosomes of mitochondria, for example, and not to the ribosomes of the eukaryotic cytoplasm at large. So this is another suggestive line of evidence that the ribosomes of mitochondria and plastids are of external origin. And genomes, you may not know it, but the mitochondria and the plastids have their own genomes separate from the nuclear genome and the nucleus. And if you look, here's a couple of these, or actually here you see two circular genomes. Here's a chloroplast genome here. And here we have the, I believe this is a bacterial, cyanobacterial genome. Bacterial genomes are circular as are both chloroplasts and mitochondrial genomes. Of course, nuclear chromosomes are not circular. And their structure and sequence of both mitochondrial and chloroplast genomes is indicative of a closer relationship to these different lineages of bacteria than to the eukaryotic nucleus that they live with, with the eukaryotic genes that are found in the same cells. You can do phylogenetic analyses based on genes in the chloroplast genome and mitochondrial genome. They don't come out in the phylogenetic analysis, they come out with bacteria, not with any eukaryotes. So that's a really powerful line of evidence that's been more recently acquired. Okay, so one of the more recent understandings that's happened with regard to endosymbiosis is that it looks like it's happened more than once, although the initial endosymbiosis that involved the incorporation of a cyanobacterium into a eukaryotic cell may have just happened one time or at least one common origin for all photosynthetic eukaryotes. But what's happened subsequent to that is photosynthetic eukaryotes that had acquired their plastids ultimately by an endosymbiotic event were engulfed by other eukaryotes in what's called a secondary endosymbiosis. So here you can see a photosynthetic unicellular eukaryote, a green alga in this case, being engulfed by an herbivorous protist of some kind and being incorporated into that cell. And the evidence for this in part is that if you look at these plastids that you find inside of some alga groups, rather than just two membranes around the plastid like you would expect based on the membrane constitution of a prokaryote, you can find three or four membranes. One of these membranes outside the original two would correspond then to the plasma membrane of the eukaryote that was engulfed and then the fourth membrane would correspond to the vacuolar membrane of the organism that engulfed it. So we have a serial process of a prokaryote, a prokaryote being engulfed, I mean a photosynthetic prokaryote being engulfed and then subsequently a photosynthetic eukaryote that descended from those ancestors that engulfed the prokaryote being engulfed by another eukaryote. And there are some cases where there's actually a vestigial, a remnant nuclear genome that resides in between the membrane, one of these outer membranes and the two inner membranes of the plastid that pretty much demonstrates convincingly that that was a eukaryote that was ingested that gave rise to that, the presence of plastids in that particular group of organisms. So there are any questions about that, that's a relatively recent understanding, yeah. Yeah, that's the next slide, yeah. We're gonna get right, thanks, that's a good lead in. So here's the tree basically of endosymbiotic events. And what we start out with here is the primary endosymbiosis where we're engulfing the cyanobacterium, this is from your textbook. So after this happened, based on molecular data, it appears that, and also based on the actual anatomy of the plastids, it appears we had a divergence event, just an evolutionary divergence that led to the green algae, the eukaryotic green algae on the one hand, and the red algae, which are mostly marine organisms, saltwater, taxa, these both just appear to have, they have two membranes around their plastids and they appear to be each other's closest relatives based on molecular lines of evidence. So this appears to be just a regular evolutionary divergence and that accounting for photosynthesis in green eukaryotic algae and red eukaryotic algae. Then next we have three different, a minimum of three different secondary endosymbiotic events that can be estimated based on molecular evidence and other evidence. Two of these involve green algae and they led to lineages that are found in two different parts of the overall eukaryotic tree, the chloroarachneophytes, which are really an obscure group of marine unicellular organisms that we're not gonna talk about anymore, and the euglenids, which I'll show you again later, which are distantly related to all these other algae based on their nuclear genome. And then there was a putative single endosymbiotic event involving red algae that led to the bulk of a large number of different groups of algae. The stromenopiles includes the brown algae, the diatoms, and the golden algae that I'll talk about in a minute. And then the dinoflagellates I'll talk about in a minute is a really important planktonic group, unicellular group for the most part. But I wanna mention the apicomplexans right here because this is a group that's not photosynthetic, but they have a vestigial plastid. So this is a group that appears to have lost the photosynthetic ability, but still has a remnant little body there that wasn't really appreciated as a plastid until these data became available. And this group includes the malaria vector, the malaria agent, the genus plasmodium, not to be confused with plasmodial slime molds, completely different. But the malaria disease, of course, once you catch malaria, there's no known cure. But having made this discovery that this thing actually contains a plastid, there's interest in trying to target that plastid since it's of cyanobacterial origin. It's something that if its destruction led to the death of the organism, we could target that and it wouldn't affect human cells. So this understanding of secondary endosymbiosis might actually end up having some important medical outcomes. That's still up in the air at this point. That's a bit of an aside actually, but I just wanted to point that out as a potential fringe benefit of having made this discovery. Okay, so here we are again with all of the various algal groups. Now I want to introduce you to those groups and give you a sense of this diversity, which is pretty amazing and pretty important for life on earth. So we can break these things down, these major groups of algae into ecological groups. These are not phylogenetic groupings by relationship but by ecology. Here again is the photosynthetic bacteria, the blue-green bacteria, the cyanobacteria, and then a number of these eukaryotic groups. These are all the results of secondary endosymbiosis here. And these constitute most of our phytoplankton, our photosynthetic community that occurs in open water and is responsible for fixing the bulk of carbon from our atmosphere, the major primary productivity of our environment, absolutely critical for oxygen production and for taking carbon dioxide out of the atmosphere, which of course is getting more and more important. And then we have some groups here that are primarily multicellular, not all of them, I mean, there are unicellular organisms in these groups, but all of our so-called seaweeds are in the brown algae, the red algae, and the green algae. As I mentioned, the reds and the greens are each other's closest relatives. The browns used to be thought to be closely related to these, but they're very distantly related, secondary endosymbiants, and we'll see those in a moment. So here's blue-green algae again, the cyanobacteria. These are unicellular organisms like other bacteria. But they commonly occur as filaments, and these filaments can get up to a meter in length, in some cases or more. And even though they're commonly found in aquatic habitats, there are some important terrestrial ones that I want to mention. And some of these are incorporated into what are called cryptogamic crust, which it's not an important term, but they occur in association with other microorganisms on the surface of soils and help to hold down the soil from wind erosion and also the blue-green bacteria in these associations. These crusts are fixing nitrogen, and so they can be important in developing soil as far as nitrogen content. Okay, and as I mentioned, these are a fairly diverse group in terms of recognized taxa, but only one of these lineages, we think, was involved in the initial endosymbiosis that gave rise to the plastids and all of the other algae, either by the primary endosymbiotic event or the secondary events. So these are the guys that invented photosynthesis, and everybody else just basically borrowed it from them. Okay, so the dinoflagellates are one of the weirdest of the algae, and these are mostly unicellular, and you can see they're strange, they have all kinds of strange confirmations that are the result of having this armor on their outside, this cellulose armor that protects them to some extent. These cellulose plates, they have a couple of flagelli, and the distinctive thing is that one of their flagelli actually encircles their body like a belt, and it's a ribbon-like thing that causes them to spin as they move through the water column. So they have the spinning motion as they move, and it's very distinctive. These are secondary endosymbiants. They, remember, these are the ones I showed in that tree, you can go back to it later in the notes, but they share a common secondary endosymbiotic origin of the plastid with the brown algae and the diatoms and some other groups. No, I'm sorry, that's not right. It's with the, yeah, that's right, of course. All of these red algal endosymbiants, these guys have an incorporated red alga, all the red algae have been incorporated from a single endosymbiotic event. And one of the things you might have heard before here on the Pacific Coast are things called red tides, and here you can see this orange coloration from the carotenoids, these pigments that they produce in their plastids from the red algal plastids that they've incorporated. And these tides are not only visible to the naked eye, but they also are often associated with the production of a lot of toxins. When these things are in high concentration, it can be a real problem because they do produce toxins that they potentially use to ward off predators or to stun prey. Some of the dinoflagellates have lost their ability to photosynthesize and they're heterotrophic and they can even kill fish with these toxins, even though there's tiny microorganisms, they can kill fish and then just swarm in on them and consume them. So they're a pretty amazing, amazingly diverse group. They also include some of our most important photosynthetic algae in terms of the amount of carbon they fix from the atmosphere. So they're really important ecologically, but they can, as I mentioned, kill fish and we can have mass fish kills from these red tides. And also they can poison shellfish. The shellfish can ingest these toxins. It doesn't kill the shellfish, but if we eat them, it can potentially kill us. So you have to be careful when you harvest shellfish that this is done at the right time and more it can be serious consequences. Now this may look a little bizarre at first. Dynaflagellates also have bioluminescent capability. They have compounds that they can enzymatically degrade to produce a flash of light, a really brief burst of blue light like this. And there's some, you go on YouTube online, you can see some really cool examples of this. But this guy here is just lying in the water, moving his arms and that much disturbance is enough to freak out the dynaflagellates to produce this bioluminescence, which you can see at night really well. And this may help to startle predators and allow them to get away while things like copepods and small predators are still trying to understand what happened. Okay, so the last group I wanna talk about today in the last few seconds here are the euglenoids. And these are one of these secondary endosymbionts that captured a chloroplast from, I'm sorry, they captured a unicellular green alga. This is one of the results, the only one we're gonna talk about that actually engulfed a green eukaryote. And these are very diverse. Some of them are heterotrophic and can engulf prey. Some of them can do both, photosynthesize and engulf prey. So this is a diverse group of unicellular algae, or green algae essentially, that have a unique flagellum. Here you can see their flagellum and you can just see them move there. But their plastid looks very much like a green alga. Other aspects of their cell are completely different and they represent a different origin, of a different origin in the eukaryotic lineage. Okay, so next time we'll talk about diatoms which are really amazing and get on to some of these other alga groups. So we'll see you on Friday. Thank you.