 Okay, so last time I introduced you to the fungi and today we're going to look into more of the diversity of fungi. These are the most closely related organisms to us that we're going to talk about in this course, which may seem a little strange. It's still been a billion years since we shared a common ancestor, but as I pointed out last time, they show some interesting similarities to animals and some features that are completely bizarre and different that we're going to talk a little bit more about today as we go through these different groups of fungi. So last time, remember at the end, I just introduced you to the chitrids, which are the only group that has motile stages in the life cycle that actually have a whip-like flagellum that they can get around with or spores. And that flagellum is very similar to the one, for example, in human sperm. It's something that we share due to common ancestry with fungi. We're all called unicons, which isn't a term you have to know as I mentioned, but there are some features in addition to that. For example, the way we store our carbon is glycogen that we share with fungi as well. And the chitrids were the first group that we talked about. We'll go through these other groups, then I'll get into the life cycle of fungi. We'll talk about life cycles in general so that you have a little bit better understanding of what that's all about, because we'll keep coming back to life cycles as we look at different organisms. And then the importance of fungi, ecologically and economically. And I don't believe we'll have time to get to algae today, but we'll get into that right away next time. So after today's lecture, we'll be talking about photosynthetic organisms for the rest of this part of the course. Okay, so I showed you this tree last time, and this is a phylogenetic tree laying on its side with the root right here. So that's the base of the tree, and here are the five major phyla, these major clades of fungi that have been recognized. And the chitrids we talked about last time here. So now we're going to focus in on these four major phyla, which are the fungi that have always been recognized as fungi. They share the features we find across the main part of the group, and there hasn't been dispute about their position. Whereas the chitrids, I may have mentioned, have been considered protists at various times and haven't been necessarily recognized as fungi. And that's consistent with their early branching within the fungal tree of life. They have some features that they share with the rest of the fungi, and some features that are a little different that they've inherited from a common ancestry with other more distantly related groups. So let's first look at this Saigo Micoda, which you're probably familiar with if you haven't been all that careful about your refrigerator and cleaning it out once in a while, because the common black bread mold and some of these molds that attack produce like strawberries and peaches are probably familiar friends of yours. And these are the hyphae that you see here. We often are grossed out by these things, but if you look at them very closely under microscope, they're really fascinating and beautiful. But the Saigo Micoda are named this because, well, Micoda again remains fungus. The Saigo, you're probably familiar with that from Saigo, the product of the fusion of gametes. But in the case of this group, it's actually called that because of what's called the Saigo sporangium, which is a unique structure. You won't see this term used again for other groups. It's this resistant body here, which forms from the fusion of gametangia. So rather than the gametes themselves fusing together like sperm and egg, in this case, the actual sacs that bear the gametes fused together are these sexual hyphae fused together. And the two gametangia become this Saigo sporangium within which we have fusion of the nuclei to produce diploid nuclei, basically meiosis immediately following that to produce sexual spores. And we'll get into the life cycles here in a minute. So don't worry too much about meiosis and all, but the sexual spores are produced inside the structure. And it doesn't produce, members of this group don't produce a big, showy, fruiting body like a mushroom. We don't get big, sizable fruiting bodies. This is the main sexual structure that's formed, and this is a very tiny little structure. This is a microscopic view here. And typically, these things are reproducing largely by asexual spores and produced by sporangia where mitosis is occurring rather than meiosis. And those are responsible in part for a lot of the dark coloration that you see in these mycelia that infects your food. And the asexual sporangia of these groups can be really densely packed. This is a pilobolus. In class, you'll see Fisarum, the bread mold. And these are tiny, but they actually can eject their spores explosively for about two meters. And if you put that in perspective, if a flowering plant here in town had that kind of dispersal capability, it'd be shooting its seeds all the way across the city. I mean, this is a hugely dispersive group. They can shoot their spores a long distance away from the parent. And so these can colonize new substrates where they're not going to compete with their parent mycelium really effectively. So these guys are masters of dispersal. That's all I'm going to really say about the zygomycota. It's not as diverse a group as some of these so-called higher fungi that produce the large fruiting bodies. We'll get to those in a minute. This is a group that used to be considered part of the zygomycota. And its position has been a little questionable phylogenetically because there's no sexual structures known in this group. There's no sex that's been documented. And without the sexual structures, it's often difficult to identify organisms, botanical organisms. They do reproduce asexually. And you can see some spores here that have been produced asexually. This is a group of very low diversity that's known. There are only a couple hundred species described. And I think I mentioned last time there are over 100,000 known fungal species. But this is one of the most important groups of fungi from the standpoint of life on Earth because these are the ones that form those marbuscular mycorrhizal associations with plant roots. Remember, we talked about two different types of mycorrhizae last time, these associations between plant roots and fungi. There were the ectomycorrhizae that don't penetrate the cell walls. And then there were the arbuscular mycorrhizal fungi that do penetrate the cell walls of the roots. They don't penetrate the cell membranes, remember. They're hyphae spread out over the cell membrane of the cell roots. And here you can see that this tree-like branching. You can see it, I think, really beautifully here in this scanning electron micrograph of an arbuscule, as it's called, this tree-like structure of the mycorrhizal fungus that's in contact with the cell membrane of the root. And this allows for a lot of surface area in contact between the fungus and the root, where there's a major exchange of carbohydrates to the fungus and inorganic nutrients to the plant occur. And so this group, even though it's not known to be very diverse, only a couple hundred species, associates with the vast majority of land plants. More than 80% of land plant families have this association. And this includes some of the really early diverging lineages. And there's actually the oldest fossil fungi that are known come from this group. They go back over 450 million years. And so this group was around, we know, based on the fossils, it was around before the land plant or before at least the vascular plants began to diversify in a major way. And they probably were key to the success of the land plants because this association is so widespread. And as I'll show you later, it's really important to the performance of land plants. Okay, so now we're going to get into the fungi that have large fruiting bodies, the ones you're more familiar with. And the two major groups here are sister to one another. They're each other's closest relatives. The most diverse one is not the one that includes the true mushrooms, but the Ascomycota. These are the sac fungi. And they include about 65,000 species. I mean, the number's not important, but more than half of all known fungi belong to this group. And they have a wide diversity of different lifestyles. This is a really diverse group in terms of the way they make their living. But they all share this feature of these distinctive sacs called an ascus. Here's an individual ascus right here. It's this membranous sac. I mean, ascus literally means skin sac because the outside of it is membranous or skin-like. And that's where syngamy occurs, or should say where the nuclei fusion occurs associated the final stage of fertilization. And then we have meiosis leading to the production of sexual spores. And usually one mitosis as well, which is why you typically have eight spores rather than four. We'll get to meiosis again in a moment though. But this is where the sexual spores are formed. And these are distinctive throughout the whole group. You can find this kind of a structure bearing the sexual spores. And they're born on the surface of these depressions. You can see in this morel, which includes some choice edibles. Not all of them are choice, but some of them are choice edibles. You have these depressions in the fruiting body. And you can see this depressed summit to this fruiting body here. The fruiting bodies are called asco carps. Carp just refers to fruit. I mean, when we get technical about it, fungi don't really produce fruit. Fruit is something that only flowering plants produce, but that's the lay term that's used, the term that's typically used in the vernacular for the bodies that produce the sexual spores. And so these inner surfaces here, lined with these ascies are called that produce the spores. And one of the things about these fungi that produce these larger fruiting bodies, these ascomi seeds and the psidiumi seeds that make up the, you know, 90% of the known fungi, is that they have these septate hyphae that I talked about last time. So the zygomycetes and the glomeromycetes and the chytrids, those are the bread molds and the chytrids, and those are muscular fungi have these open senacitic hyphae. They don't have any septi within them, so you have nuclear divisions going on, nuclei divide, but we don't have cell membranes walling them off from one another. Here we have septiforming that are, remember, just partial. There's cytoplasm can flow through here. But larger particles like nuclei can't. And this is characteristic of both the ascomi coda and the psidiumi coda, and it's probably something that they share due to common ancestry. And this would be then the ancestral situation within fungi, because we see it in the chytrids that have hyphae and in the zygomycoda and the glomeromycoda. So this is an innovation here, these septi. Okay, so some of the, a lot of the ascomi coda and a few psidiumi coda actually include these unicellular organisms that we refer to as yeasts. And there's this popular misconception that yeast is one thing, and that's understandable because the yeast that we use for brewing alcohol and for fermenting alcohol fermentation and for baking bread is the same species, Saccharomyces civisii. But there's about a thousand, over a thousand described species of yeast. For example, the yeast that causes yeast infections is a completely different yeast. And there's nothing to this whole notion that women that have yeast infections shouldn't eat food with yeast in it because they're not closely related. But that's a very diverse group, and it's underrepresented by our taxonomy, no doubt, because these things have very few morphological characters. And the molecular data is showing that there's probably ten times the diversity we actually recognize here. And some of these ascomi seeds can go into an asexual life cycle, non-sexual life cycle that involves yeasts, but they can also have a sexual life, or I should say, some of the yeasts have both sexual and asexual life cycles, but typically they reproduce by budding. And you can see that budding going on here. This is a highly magnified view. So they're just undergoing mitosis, basically clonal reproduction, where one organism gives rise to two identical organisms, and they can of course reproduce really quickly. And we take advantage of that in brewing and baking. Okay, so that's the ascomi coda. So now finally the besidio micoda. This is the group that's probably most familiar to you, because it includes the true mushrooms, as well as what you've probably seen puffballs before, and bracket fungi growing on wood. I'll show you an example of that later. These are all called club fungi, and that's because the structure that produces the sexual spores looks sort of club-like if you use your imagination. I'll show you that in a minute. But there's a wide diversity of different types of fruiting bodies here, but they all produce what's called a besidium, or this club that produces the spores. We'll get to it. In addition to the fungi in this group that produce these large fruiting bodies, we also have some bizarre things like the jelly fungi that produce these weird jelly-like fruiting bodies. They're not so distantly related to rusts and smuts, and rusts and smuts, they have very small bodies, they're essentially microscopic, and they're really important pathogens, especially with plants, and cause a huge amount of economic damage and ecosystem damage in some cases, but they're important parts of the ecosystem. It's when they get introduced where they don't belong that they really cause the most trouble. But if you've heard of rust and smut, those organisms, they're part of the same group. We won't really get into them anymore. So the mycelium, which is the fungus body, literally means fungus body, the mycelium of besidium myseeds can be really extensive underground, and you're just seeing sort of the tip of the iceberg when they actually go to reproductive state like this. A lot of people think the mushroom is the main body of the fungus, but it's just the reproductive body. It's just getting its spores dispersed out into the atmosphere this way. But in order to feed, it needs to be in a situation where it's surrounded by food, which is typically underground. And these besidium carps are produced around the leading edge of that mycelium. So when the mycelium starts to really grow out it radiates out like spokes of a wheel and basically fills all the space in there taking advantage of all the resources and at a rate of roughly 30 centimeters a year so it's moving outward in all directions typically such that when it goes to produce its besidium carps, which literally means the fruiting body that produces a besidium where the spores are born, these fruiting bodies are in a ring which in ancient times was thought to have some mystical significance, often called fairy rings, and you can see basically the size of this mycelium by considering that everything internal to this ring is basically the mycelium underground. So the production of the fruiting bodies out here at the periphery is advantageous because that's where resources are richest where they haven't been exploited by the fungus. So it needs to mobilize a lot of resources quickly to these fruiting bodies which form overnight usually just in a few hours. So the mycelium is... it's advantageous for the mycelium to do that out around the periphery here where it hasn't exploited all the resources. And so people have gone in and looked at these fungi doing genetic tests of mycelia across different areas and fungal fruiting bodies across wide areas and have come to realize that some of the mycelia that are out there are absolutely huge. You can do genetic fingerprinting and determine that fruiting bodies that are widely scattered on the environment are genetically identical. And the evidence indicates that some of these mycelia that are producing these widely scattered identical fruiting bodies probably cover areas more than nearly 2,000 acres, six and a half square miles is the estimate for the largest one known, and that they actually estimate the size of some of these at hundreds of tons of hyphae and an age of thousands of years given their known rate of growth. And so of course some of the communities that have found out that some of their local fungi represent such ancient and huge organisms have tried to take advantage of this to attract tourists and you can see some of the efforts here in Michigan and Pacific Northwest but as you can imagine, people are generally disappointed if they go to these places looking for the giant mushroom expecting to find a fungal fruiting body the size of a giant sequoia or something like that because that's not where the biomass is located. So I've never been to one of these festivals. If anybody has or does go to one, I'd like to hear about it. Okay, finally there's a group that isn't on that tree that I showed you but it is a recognized phylum called the Deuteromycota and this is literally the fungi imperfecti and imperfect doesn't refer to bad ear or somehow flawed but they're not sexual. Okay, so they only reproduce asexually. So I guess there's some kind of assumption if you're not capable of sexual reproduction and you can only reproduce asexually that things aren't absolutely perfect but these actually are very successful groups and they include some really important ones like penicillium, our source of penicillin and even though now, so back maybe 20 years ago this was actually a group that included a lot of fungi but mycologists have gone in and with molecular techniques have been able to determine the phylogenetic position of a lot of these imperfect fungi with DNA when they didn't have the sexual structures and they're having to rely on morphology just on the form of these things, that wasn't possible. So the positions of these are mostly known now and they're mostly these asexual fungi are mostly in the Ascomycota, some are in the Basidiomycota but this group is actually maintained as a taxonomic group because mycologists want to continue to recognize this group in an ecological sense because they share this asexual life history. So it's an interesting case of where organisms are being described in a couple of different kind of parallel systems. I mean that's really an aside but I just wanted to point out that there are a lot of fungi that don't reproduce sexually and some of these are quite successful. Okay, so now in class, in lab this week you're going to see a couple of groups that we used to think were fungi but now we know are not fungi and this particular one, the Ohomycota, remember mycota means fungus, is not in fact a fungus, these are called the water molds even though they can occur in terrestrial habitats as well not just in aquatic habitats and these turn out to be more closely related to some algae and in particular some of the kelps the brown algae and the diatoms we'll get to those later but this is a group that you can see produces hyphae these filamentous structures that look a lot like the hyphae of fungi but these hyphae are diploid, they're not haploid all fungal hyphae, I should say the nuclei of fungal hyphae are haploid whereas the nuclei of these hyphae are diploid like the cells in our body and in fact the only haploid stage in this group are the gametes, just like in us and in fact their gametes look a lot like ours these guys have sperm and eggs that they have free swimming sperm and they have larger non-motile eggs that's the basis for the name Ohomycota, the egg fungi so they're very different it's long been recognized that they're pretty bizarre most other fungi and the reason is because they're not fungi and they include some really destructive pathogens you've probably heard of the Irish potato famine in the mid-1800s this was caused by a member of the genus Phytophthora the genus name is unimportant but this particular group, the Ohomycota include many species of this genus which are some of the worst plant pathogens that we know of and it led to widespread starvation in Ireland and mass immigration to other parts of the world because of the destruction of the potatoes by that by that water mold and here in the Bay Area we have an ongoing ongoing crisis with this organism called Phytophthora ramorum which causes a sudden oak death which has only been known for a little over not even 15 years here in the Bay Area Marin County was where it was first discovered and you can see some dead oaks here our native tan oak which is a really central tree to our mixed evergreen forest is dying out throughout its range it may go extinct within the next 50 years and it's endemic here to the west coast and the coast live oak which is a real iconic plant in California and it's one of the widely planted oaks here on campus is also a victim of this water mold and fortunately there is some resistance in it but a lot of this, there's been tens of thousands of coast live oaks that have died over the last few years because of this organism and the list goes on and on with Phytophthora that are destructive but these disease causing organisms that cause extinctions are typically ones that are non-native to the area where they're causing that kind of destruction you probably, you may have talked about this in ecology but diseases typically don't cause their host to go extinct that would be greatly disadvantaged to the disease causing organism too okay so this is one of the coolest groups of organisms that we're going to see in this class and these are the acute and cuddly slime molds which people actually love to keep as pets because they are so bizarre and interesting and they actually have beautiful coloration as you can see here in many cases these are things that used to be thought to be fungi but it turns out they're no more closely related to fungi than they are to animals so you have as much in common with these things as the fungi do as big a claim to a relationship and they start out as a spore the spore germinates and becomes an amoeboid organism you're probably familiar with the blob you know that amoeba like thing that moves along and can engulf small particles and digest them and is motile not, in this case it can move along sort of creeping along or it can move along by flagelli by a whip-like flagellum here and these are unicons like fungi and animals with a single whip-like flagellum and they can go interchangeably between these stages and when two mating types get together these amoeboid or what they're called swarm cells here they can fuse together to form a zygote and once that zygote is formed then this thing starts undergoing mitosis you get nuclear divisions one after the other but that's not accompanied by any kind of cell membrane formation to separate off those nuclei from one another and you just continue to get enlargement of this gigantic cellular-like structure it's like one big open cell full of nuclei that turns into this big mat or sheet which is called a plasmodium this big slimy mass that just moves along and digests whatever it encounters as it's radiating out you can see one out here as it's moving out in search of food and it can digest things like spores or bacteria, little particles that it engulfs and while this is happening if you look at this thing closely within these vein-like structures you can see the cytoplasm streaming one way and then the next so here's what that looks like I don't know if you can see it very well it's a little hard to see but you can see some little droplets here these food bodies moving along as the cytoplasm moves through this thing it'll go one direction and the next presumably it's moving nutrients and oxygen around and pretty mesmerizing to watch it actually they're pretty neat and then when they finally run out of food or if the climate gets foul for them if it gets cold for example they'll start to harden and produce sporangia like this and then the life cycle starts over again but if you keep feeding them with Quaker's oats or whatever you can get a fairly large pet and people do like to keep these things you can find them out on leaf litter and on tree stems on tree branches and such just out in the local mixed evergreen forest here in the Bay Area we have a lot of diversity of these things but most people just completely overlook them and don't know that they're there but it's really something else okay so now I want to get into life cycles and in order to really understand these botanical organisms the fungi and the real plants and the algae you really have to understand their whole life history and the life history of these things is quite different from that of you and me and I know if you've had zoology if you took Bio1a and you think you talk about life histories of animals that's pretty relatable because we're all adults here we don't necessarily know about the birds and the bees that's not something that you've just been introduced to hopefully but you definitely don't necessarily know about what sex is like for fungi and plants and in order to really understand life cycles you have to understand what sex is at the most fundamental level and we can get away with not knowing that when we're thinking about animals we can get away with that when we're talking about fungi and plants so to be a real expert in sexual reproduction you have to really think about it in this broad fundamental sense and so basically sexual reproduction when you get right down to the nitty gritty the real fundamental elements there are two things that have to occur okay one of them is fertilization or syngamy where the gametes we have the production of gametes these are haploid with one set of chromosomes and they fuse undergo this process of fertilization or syngamy which syn just refers to fusion it's used a lot in a lot of terminology syn and gamie of course refers to the gametes fertilization occurs to form a zygote which is a product of gametic fusion which is a diploid structure from which well let's just leave it there I think we all know this part of the process sperm and eggs are gametes and they fuse together to form a zygote okay so that's probably not so alien meiosis though is something that I'm sure you've heard about if you had high school biology or I'm sure it was discussed in the evolution part of this course as well but it's the other essential ingredient meiosis and fertilization are the two components of sex when it really comes down to it and meiosis is the process okay let's first make a distinction here with mitosis mitosis is the process leading to the production of two progeny cells from an original cell that are genetically identical so the kind of cell division that leads to the for example in animals leads to the zygote eventually becoming an adult person those cell divisions are mitotic because all the cells in our body are genetically identical right those are clonal we're just getting one round of DNA replication followed by division and one set of chromosomes going identical chromosomes going to each pole so that we end up with identical cells meiosis is completely different than that okay meiosis also involves one round of DNA replication but then we have crossing over between each of the chromosomes that were inherited from the two different parents so we have recombination between the parental chromosomes that for example we inherited from our mother and our father those chromosomes each of your mother's chromosomes associates with each of your father's chromosomes and homologous pairs and there's recombination between them and then we have two rounds not one round of cell division like in mitosis meiosis there are two rounds of cell division ultimately then we get four cells each with only one set of chromosomes rather than the two sets that we have in our body most of our bodies so that's the haploid condition with one set or one end condition as opposed to two end okay so in the end we have we end up it's often emphasized that this is the way to go from diploid to haploid which we have to which has to occur during the sexual life cycle but just as importantly within that haploid cell you have a unique assemblage of genes because the chromosomes between your mother and your father have recombined and so except for the Y chromosome in men which is handed down faithfully from one generation to the next it doesn't undergo recombination with another chromosome the other chromosomes are undergoing recombination between them so this is the way genetic variation is generated we also have independent assortment to the two poles so it's a we end up with recombined chromosomes of one set okay so is that clear to everybody? that's an essential thing to realize about that's all organisms that have sexual life cycles alternate meiosis and fertilization so here you can see an animal life cycle like ours here you can see a plant life cycle and here you can see a fungal life cycle on the right let's just focus on the animals we'll get to plants later so as I said sexual life cycles of all meiosis and fertilization and the way that they differ from one another these sexual life cycles is in the relative timing of meiosis and fertilization okay when these two processes occur relative to one another and so in animals you can see that as you know like in us fertilization I should say meiosis to produce gametes is immediately followed by fertilization there are no mitosis in that process we have meiosis giving rise to gametes directly and then we have fertilization giving rise to the zygote and then we have a lot of mitosis to make the animal body okay gamete is the only haploid stage meiosis immediately followed by fertilization so in the case of fungi it's almost the opposite we have fertilization giving rise to a zygote immediately followed by meiosis to give rise to spores that germinate to become the haploid fungal body okay so in this case it's the other way around the fertilization happens and then we immediately get meiosis so the zygote is the only diploid stage whereas here the gamete was the only haploid stage let's make a distinction now between gametes and spores this is something I think gets people confused a spore is just a unicellular reproductive structure that germinates to become an organism so it actually mitosis occur and you get an organism gametes are unicellular reproductive structures too but they undergo fusion with one another to produce a zygote so there's a distinction there we'll be talking about gametes and spores a lot during the rest of the course but just remember gametes fuse spores don't fuse with one another spores go ahead and directly germinate okay so the relative timing of mitosis and fertilization when we get to plants I'll point out that in plants we actually have a body an organism a body formed in this diploid stage as well as in the haploid stage and that's a bizarre concept for a human to think about for an animal to think about the biggest to think about if it could because that's a strange concept that in one species you would have two different kinds of organisms one that's haploid and one that's diploid and they alternate between one another we get this alternation of generations but that's not the case in animals in fungi and we'll stick with fungi for the moment and so as I mentioned whether mitosis is limited so another way in which you differentiate whether mitosis this clonal reproduction of cells is limited to one of the two stages the haploid stage here or the diploid stage here helps to distinguish these life cycles or whether it occurs in both in the case of plants so that's those are things to bear in mind and please try to absorb this as soon as possible in terms of trying to think about these life cycles or else you can get hopelessly confused it becomes pretty esoteric to talk about life cycles you don't keep in mind these major things life cycles all involve a diploid phase a diploid stage I should say haploid stage and we alternate between those by fertilization and mitosis so here's the fungal life cycle I should say this is a life cycle that is common to most fungi and by most I'm referring to the ascomycota and the basidiomycota which are over 90% of the known fungal species these are the ones that produce the larger fruiting bodies many times so here you can see an asexual cycle so here we have spore production by meiosis as I mentioned the zygote being the only diploid stage in the life cycle the zygote a meiosis immediately following that to give haploid spores which germinate remember spores don't fuse to one another they germinate to become a haploid fungal body or mycelium and then we can have production by mitosis of genetically identical spores and you can see some here that can then germinate a life cycle mycelium to the one that generated the spores that happens a lot as I mentioned in those asexual fungi imperfecti and in yeasts etc we see that but there's also a sexual life cycle over here and what happens here in these higher fungi that's a little bit of a wrinkle in this whole thing that is easy to comprehend when you think about it I think we're familiar with sperm and egg coming together gametes coming together this is done in two phases in the fungi so in the fungi we have first the fusion of the cytoplasm so we'll have these hyphae come together and fuse together so they have a common cytoplasm but their nuclei don't fuse together right away but normally when you form a zygote you get cytoplasmic fusion and the nuclei form a fuse right away too and the nuclear contents are in one structure but here we have what's called a dichariotic stage and that means two nuclei so in each one of those cellular partitions in these septate hyphae we have each of the parent nuclei remaining separate and then eventually in specialized cells we have the fusion of those nuclei from the zygote but this dichariotic stage can be very extended and during that stage you could have complex genetic expression it's just that the nuclei are not fused together so here let me just put this in a little bit more showing an actual example from the true fungi so here's a Bacidio Mycota life cycle from your book so we start out over here this is a spore that was formed from meiosis a sexual spore that's haploid it undergoes germination and we get faithful mitosis here producing a a bunch of genetically identical cells this is just a typical organism here and in this particular you probably can't see this very well at the back of the room but each of these two hyphae are from different spores and you can see one as a nuclei colored white and this one as its nuclei colored dark blue I mean they're not like that in real life in terms of being color coded as to different types of course but that's just to show that these are two different genetically distinct organisms here two different haploid hyphae and they grow along here and then they produce pheromones these sexual attracting hormones that draw these hyphae together of different mating types they don't just have male and female hyphae there's a lot of different mating types in fungi and compatible mating types get together and they fuse their cytoplasm and here you can see where the fusion occurred and now we have this dicariotic mycelium developing each one of the partitions here has one nucleus from one parent and another nucleus from the other parent the bulk of these mycelia underground they can get to be huge and ancient are dicariotic so the fertilization process is only really half way during most of the life cycle of the fungus the fungus is the main body of the fungus has undergone plasmagomy the fusion of cytoplasm but not karyagomy the fusion of the nuclei and then we get finally the production of the fruiting body the besidio carp here which is dicariotic throughout and then if you were to cut this cap down longitudinally here and look at it along the cut surface you'd see these gills not all the the mycelium have gills they have different kinds of surfaces but usually a really extensive surface area on which you get the production of these besidia right here this club shaped or what's been conceived as a club shaped thing this is a specialized cell out along the periphery of these gills where we get the fusion of the two nuclei and it's only in those cells that we get the fusion of the nuclei to produce a zygote and then that immediately undergoes myosis inside this besidium to produce the sexual spores that are haploid and you can see that they're protruded out on these little peg like appendages out at the tip they're four of those for each of the four products of myosis and then we get germination of those spores and we start over again so there's a really long extended period during which we have fertilization really incomplete in fungi okay so now I want to make a few notes about the importance of fungi and ecosystems and in our day to day lives we've already talked a bit about this with mycorrhizae which is one type of association between plant roots and fungi but there's another really common and important association that we see every day if we're looking closely and these are what are called lichens if we're out in a natural environment that is and a lichen is actually an association between a fungus usually an ascomycete and some sort of unicellular photosynthetic alga a green alga or a cyanobacterium a prokaryotic photosynthetic unicellular organism and this is one of those lichens that's been cut in half and you can see here an asco-carp the fruiting body of the fungus and here you can see so this is all hyphae in here this is the lichens this is the unicellular algae these green structures that are along the upper surface here the one closest to light and so we have photosynthesis occurring within this green alga nourishing the fungus in part with the products of photosynthesis the sugars and then the alga is gaining a habitat here where it's being kept moist and it's shielded to some extent from UV radiation it has its own little home in here where it may be there's some question as to how much benefit the alga really gets out of this relationship compared to the fungus but it is a symbiosis in any case and it's not considered an organism but this can be confusing because lichens are given taxonomic names and they were a discreet organism but in fact the two elements of this relationship can be pulled apart and they can reproduce separately in fact they don't they aren't highly integrated to the point where they can't live without one another typically but they they do disperse together asexually in most cases in these what are called ceridia the name's not important but the hyphae surrounding some of these algal cells can form little dispersal units that are asexual propagules that are dispersed out into the environment so they can't disperse together and get around so the association isn't broken and these are widespread in our environment there are various types the leafy lichens like you can see here you've probably seen such things growing on soil and they're often really important in formation of soils because some of the blue-green bacteria that associate with these fungi to form these lichens are capable of nitrogen fixation and nitrogen can be very limiting in soils and really important to plant growth survival of other organisms so you can see that the green colorations from the alga but the fruiting body here that you can see is an ascocarps that are formed the bulk of the body is fungal here so these are what are called folios or leafy lichens they're also fruticose lichens that produce these highly branching structures this one growing on wood and breaking down wood here and some of them actually grow on really sterile surfaces on rock faces and you've no doubt seen things like this on rocks the iron ear is in making the substrate suitable for other organisms breaking down the rock and nitrogen fixation may be occurring here to produce some nutrients and these things catch some soil that gets blown around and we get soil formation so lichens are really important play an important ecological role in primary succession and they're really an important association with ecologically for ecosystems in general as are the mycorrhizae we talked about last time and we don't have time to go into anything else today but I'll finish up on fungi it's economic importance and then we'll get into the algae next time and start checking out photosynthetic organisms