hello bisque 132 this is the beginning of recorded lecture two two uh continuing on with chapter 24 fungi uh now getting into fungi symbiotic relationships uh there are three of these i want to go through starting with one called mycorrhizae a weird spelling of this word but it's pronounced mycorrhizae the key terms to find this as a mutualistic relationship between a plant and a fungus and if we look at this this at first glance doesn't look very mutualistic uh these fungal hyphae uh in some types are getting into you know past the cell walls into the cytoplasm of the plants this looks like some sort of uh horrible parasitic invasion of the plant cells but as you know the key terms defined this is actually mutualism so what's going on here is the hyphy as we mentioned earlier in this chapter are really good at absorbing stuff from the surroundings as good as roots are mycelium and fungal hyphae are the champions of absorbing nutrients from the surroundings but the problem is they need nutrients carbon in the surroundings in order to actually survive so the partnership here is that the plant will do photosynthesis and in doing so create sugars and give those sugars to the fungus in return the fungal hyphae will absorb mineral nutrients from the soil and water things that the roots can do on their own but mycelium can do even better and it will give the this water and these mineral nutrients to the plant in exchange for the the sugars the carbon so fungus uses hyphae to absorb water and mineral nutrients for the plant in return the plant gives sugars from photosynthesis to the fungus so they're both benefiting from this the fungus wouldn't be able to survive in this environment anyway because there's no organic matter you know decaying organic matter for it to absorb there are no nutrients just you know mineral nutrients you can't survive off of those alone there is no organic matter for the fungus but they're getting it from the plant sugars and the plant benefits from this i mean the plant could survive without the fungus but it benefits because it gets a more efficient uptake of these mineral nutrients and water from the surroundings so mutualism and here's a this is there have been scientific studies of course but this is you know from a website trying to sell this stuff that without mycorrhizae with mycorrhizae the plant benefits from this the plant grows faster the plant grows taller and larger premium mycorrhizae plant success this little shaker bottle to just i guess shake into your potting soil to ensure that this relationship establishes itself yeah this definitely benefits the plant and it benefits the fungus as well interestingly this is extremely commonplace about 90 of all vascular plant species can have this relationship most plants are capable of having this if they manage to you know come in contact with the right fungi there are two types of mycorrhizae as we saw here ecto mycorrhizae is uh when the fungal hyphae do not penetrate the root cells of the plant they sort of go around that's ectomycorrhizae the other uh also in the key terms endomycorrhizae also known as arbuscular mycorrhizae is when the fungal hyphae do penetrate the cell walls of the root cells and sort of get more in there so both of these are in the key terms and if you remember swinging back around our muscular mycorrhizae i mentioned these before uh when we were talking uh about this specific group of funga a fungi the glomero my coda so just tying things back around again okay so that's mycorrhizae that's one type of symbiotic relationship involving a fungus another uh common uh fungal symbiotic relationship is lichen so uh there are many types of lichen and you know different shapes and sizes and forms you know the crustos folios and fruticos but lichen itself is defined in the key terms as a close association of a fungus with a photosynthetic alga or bacterium so that's kind of generic because the actual partner that the fungus can have uh varies widely so yeah like the key terms just said it could be a bacterium it could be a quote unquote alga which could mean plant could mean protist the important thing is that the partner is something that does photosynthesis so once again we have the fungus growing in an environment that does not have readily available nutrients for for it to absorb this could be growing on a brick or a rock uh or a tree bark you know a tree that's not dead so it's not you know stealing nutrients from the tree it's just hanging out here uh all fungi are heterotrophs they need nutrients they need carbon to survive so their partner just like the partner in mycorrhizae is something that does photosynthesis so you can imagine the give and take here the partner provides sugars from photosynthesis and the fungus provides protection fungal cell walls are very protective and oftentimes this partner you know whether it's a eukaryote or a prokaryote or whatever is used to living in an aquatic environment in a pond or something like that algae algae is not going to survive you know living on the side of a rock it's not going to survive living on the side of a tree outside of water but if it's partnered with fungi it can survive in this condition so here's a don't sweat the details here but here's a cross-section of lichen and you can see here in this zone uh the the algae protected on all sides by the hyphy by the mycelium of this fungus keeping it you know completely protected um this we can consider this to be mutualism kind of looks like they're captured there's in in biology they're often a sort of gray zone of like are they being protected or are they prisoners but i mean we can we can rest assured that these algae would not be able to survive at all in these environments without this protection so we could we could call this mutualism the algae give protection uh and the the fungus gets nutrients gets sugars that it wouldn't otherwise get okay the third is even weirder so another uh fungi fungal symbiotic relationship uh involves leaf cutter ants so leafcutter ants earn their name well because they cut off pieces of leaves and they carry them sometimes long distances back to their home so if you were to see you know a bunch of ants like this you know carrying leaves down here you would probably guess that they're you know saving these leaves to eat in the winter or they're going to eat them later or maybe they're feeding these leaves to their queen or maybe they're feeding these leaves to their young but all of those things would be wrong what they are doing is far more bizarre what these ants are doing is they are bringing these leaves down into their their colony to feed to a fungus these are gardeners they have domesticated a fungus and they feed it with these leaves and then they will eat some of the fungus themselves just like we will you know care for the plants in our garden and then eat some of the products of those plants uh these fungus growing ants provide this fungus with all the sugars it needs from these leaves and in return eat some of it uh for for sustenance so we call these fungus growing ants several different species here also known as leaf cutter ants they feed leaves to the fungus they they care for the fungus uh you know they will uh they will weed it if you know if other species of fungus start growing on it and harming it they'll they'll clip those away just like you weed a garden they'll care for this fungus and then they'll eat some of this fungus and the fungus itself is again you can call this domesticated it really can't survive outside of this environment it has evolved alongside these ants uh its ability to live when it's not being completely taken care of uh is very limited so this is a domesticated fungus just like we'd have you know a domesticated animal and we can consider this to be mutualism the fungus has a pretty cushy job here all it has to do is grow and break down things that are brought to it and the ants definitely benefit from this as well this is their sole source of food uh eating this fungus so another example of mutualism uh to get away from uh the love and good times mutualism here there are plenty of fungi there are parasites and pathogens uh and just like the parasites and pathogens of previous chapters the textbook goes into some detail describing these i'm not going to make you memorize a big laundry list of these but there are a lot of fungal pathogens that affect plants a lot of times plants that we really rely on as sources of food so these have substantial economic impact additionally there are plenty of pathogens that infect us uh directly here's ringworm many species can can cause this again despite worm in the name this is a fungal infection not an actual worm um here's a species of fungus fungus uh responsible for athlete's foot or jock itch uh and some even cause pretty bad lung infections so again don't memorize all these all i want to say is this human fungal infections definitely exist and can be difficult to treat so antibiotics will take down a bacterium but fungal infections i mean fungi are eukaryotes just like us so if you're going to treat it with some you know chemical compound some drug it has to target fungi in a way that doesn't also target our animal cells so because we're both eukaryotes it's much more challenging to deal with these infections not impossible but more challenging because we're both eukaryotes definitely no antibiotics for a fungal infection and another section here that i'm you know largely skipping because just not important to make you uh memorize which fungi are involved in agriculture or whatever there is one thing i do want to say you know from this section is to introduce for the first time and not for the last time the concept of a model organism some fungi especially aspergillus are important model organisms a model organism is defined in the key terms as a species that researchers study and use as a model to understand the biological processes in other species represented by the model organism that's kind of a mouthful but these these are these are lab rats these are lab mice these are species that we can experiment on and study and understand as a way to understand us humans human development human disease i just finished saying that you know fungi are eukaryotes just like we are that's a liability when treating infections but it's a good thing when we're trying to understand things it's way easier to grow a fungus especially a yeast than it is to try to grow human cells but because we're both eukaryotes they actually do a lot of the same things we do so some fundamental processes of of cell biology and cell division and cell cycle control even though they seem so far removed from us as animals we're both eukaryotes and so a lot of fungi are very important research specimens because they serve as very effective very easy to use and grow model organisms for understanding all eukaryotes and you know applying this to humans and that does it for fungi so moving on uh we now come to plants uh plants are going to be divided into actually several chapters we're starting with chapter 25 seedless plants so uh what are plants well we've brought these up before there's this fun thing again uh plants were located here in this super group archaeoplasty this is a clade a monophyletic group an ancestor in all of its descendants all you know share this name of being called plants so kingdom plantae a monophyletic group all plants are photo autotrophs there's this figure again so that means they get their energy from sunlight and they get their carbon from inorganic sources from co2 they are distinct from a red or brown algae which again we discussed in a previous chapter these are protists due to again without showing you the details because it's too you know fiddly different photosynthetic pigments so yeah there are other organisms that are photoautotrophs but this is a distinct monophyletic group they have distinct photosynthetic pigments that you know separate them from these other photoautotrophs so this was a useful figure when we were looking at all eukaryotes but if we want to look at plants uh it's better to sort of zoom in so here's a phylogenetic tree uh showing plants let's orient ourselves a rooted phylogenetic tree uh an ancestor of all plants and then showing all of its descendants and what's going to be pretty cool about this and in my opinion is this phylogenetic tree kind of looks like a staircase going up so what we will be able to do as we go through this is keep track of evolutionary innovations we are going to start simple and we are going to in a stepwise fashion add new features add new bells and whistles add new cool uh evolutionary innovations is the best phrase i could think of until we get to the the most recent plants the most sophisticated plants that have an accumulation of all these cool things that have evolved one at a time so let's start with the simplest stuff the earliest plants were aquatic that we call green algae and if you think about plants and photosynthesis it makes sense that the earliest plants were aquatic photosynthesis you know uses up water it consumes h2o if you need if you have a constant need for h2o it the aquatic lifestyle makes perfect sense so the earliest plants were aquatic they're called green algae um algae is a terrible word you know there there are some protists that get called algae there are even some bacteria that are called blue-green algae and other plants that are called out that's why i'm using the quotes here green algae algae can confuse you a lot but if you see green algae we're talking about the group of plants um these plants are capable of asexual and sexual reproduction there are two major groups of uh green algae chlorophytes and charophytes uh chlorophytes some of these are unicellular and that's weird because once we get out of algae land all plants are going to be multicellular so kind of weird to see single-celled plants but yeah here we are don't memorize all these by the way these are just you know fun examples so yeah all of these are aquatic some of these being single celled some of these being multicellular uh so these are chlorophytes and charophytes these are also under the umbrella of green algae they're more closely related to land plants but they're still all aquatic so here are some char phytes living uh living in the water there's a unicellular one pretty cool looking but uh yeah these are also algae is the charified's algae okay so uh that's all i want to say about these uh these aquatic plants these uh these green algae our next evolutionary innovation is going to be the ability to live on land because as you know as cushy as it is to live in the water as a photosynthetic organism a third of the planet is land and that is a new untapped territory there's definitely selective pressure to be able to survive in the harsher environment of of being on land so advantages to life on land include less competition you know the waters are starting to get crowded if you can survive on land it's there's there's less competition there uh more sunlight you know as a photo autotroph you need light as a source of energy water filters out some of that energy so being on land gives you a more direct source of this uh this energy and no predators well at least at first they'll come later but an early selective pressure to colonizing land means not as many things trying to eat you however uh despite all these advantages there are definitely a lot of challenges related to to being able to survive on land first and foremost you need to not dry out you know the sun provides energy for photosynthesis but the sun will also evaporate water and so being able to survive in a drier environment is something that needs to be overcome you also need to transport water to the photosynthetic organs when you're surrounded by water this doesn't matter but if you're on land you need some way to sort of move this stuff to where it needs to go um you also need to support the weight of the plant body again you're somewhat weightless under water but gravity weighs down on you a lot more when you're outside of water so this is also a challenge and the sperm need to get to the eggs again we're talking about organisms that have a sexual life cycle sperm plus egg equals zygote uh in water they can easily swim to get to the eggs but on land that's going to be a lot more challenging so this is another issue that's going to come up when we talk about how land plants manage to survive on land so we're done with chlorophytes and charrophytes all further groups that we're going to talk about are going to fall under this umbrella category of land plants all further groups are quote unquote land plants and all land plants have what's called a haplodiplotic life cycle yes more life cycle stuff don't worry this is not as complicated as the fungi stuff so here is a very generic haplodiplotic life cycle but again this is important to understand because all further plants in this chapter and the next one are going to to follow this life cycle so there are two important things to to notice here one is you know the n and the 2n so 2n means diploid two copies of each chromosome we should be used to this we are diploid n or sometimes called 1n means haploid it means one copy of each chromosome uh we only use this in our eggs and sperm but what's strange straight from our perspective about the haplodiplotic life cycle is that these plants have a multicellular structure that is diploid and a multicellular structure that is haploid and again that's foreign to us because we are multicellular diploid but our haploid stuff our eggs and sperm don't form multicellular structures they just fuse and become diploid again uh so these two forms of the plant are called the sporophyte and the gametophyte the sporophyte is the multicellular diploid the gametophyte is the multicellular haploid got it written down here sporophytes equals multicellular diploids 2n being sort of the shorthand for diploid gametophytes are the multicellular haploids 1n or n importantly if you're wondering okay it's got two forms well which one's the plant uh it depends on the species it depends on the group in some groups the sporophyte you're going to you know look at a plant and say oh that's the sporophyte the gametophyte's like microscopic but in other plants the gametophyte is the plant and the sporophyte is some tiny little reproductive structure so either one of these may be the the prominent form of the plant so let's go through this cycle now again it's a circle there's really no beginning or ending but let's uh let's start here just to be arbitrary let's start with the sporophyte producing single-celled spores through the process of meiosis just like our meiosis makes eggs and sperm diploid to haploid their meiosis is making spores that are haploid these are not eggs and sperm the the job of egg or sperm is to fuse together but that's not the job of these spores the job of these haploid spores is to divide by mitosis and form this haploid gametophyte so again a number of these steps just to have this the sporophyte 2n produces unicellular haploid spores through the process of meiosis the spores will divide by mitosis to form this multicellular haploid gametophyte form so it's called the sporophyte because it makes spores makes sense the gametophyte is called the gametophyte because it makes gametes gamete is just a term that refers to egg or sperm so the gametophyte makes egg or sperm some of you have female gametophytes that only make eggs and male gametophytes that only make sperm but either way it's making a gamete of one form or another uh the egg and the sperm find each other they fuse one plus one is two you know you have two haploid cells forming one diploid zygote which is then going to divide and form the multicellular sporophyte so the gametophyte produces gametes that means eggs or sperm as the case may be by the process of mitosis egg plus sperm fuse to form zygote which again one plus one is two the zygote is diploid 2n and then the zygote divides by mitosis to form with sporophyte 2n we're right back uh to where we started so very very good uh figured as sort of a road map to everything to come we're going to see some small variations on this in the future but for the most part this is this is a good thing to keep in the back your head all further plants have a haplodyplantic life cycle so the first land plants were a group of plants called bryophytes so the the earliest land plants were bryophytes i'm double underlining this because there are going to be a couple of groups uh of bryophytes uh and i do want to point out like i'm trying to make this as as clear as possible when i'm talking about you know groups that contain other groups and you know where they're located in their relationships and i'm trying to make that clear in in the notes here but additionally i have a document on moodle called plants and organizational study aid or something like that it doesn't contain any new information so you don't need to read this everything you need is is in these slides with text but if you want just another way to to visually show which groups are part of which other groups and stuff like that that document exists on moodle anyway so bryophytes the earliest land plants uh their gametophyte is prominent and their sporophyte is hard to see so uh just to look at this this if you're you're looking at this it kind of looks like a leaf it's not a leaf but it kind of looks like a leaf this is the gametophyte the sporophyte is going to be a small little structure we'll see later that just kind of sticks up so prominent gametophyte in these bryophytes um importantly these are the first land plants uh and so they are not the best land plants they they manage to survive on land uh but not very effectively uh they do not have any vascular tissue so vascular tissue is going to be something that transports water or nutrients and because they don't have this they are not able to transport water or nutrients throughout their plant body uh which means they have to be small you only get to be you know a big tall oak tree if you have lots of vascular tissue to move stuff from the roots to the leaves and the leaves to everywhere else these bryophytes have to be small uh and they're called non-vascular plants because they don't have vascular tissue this means they don't have roots so real roots are a type of vascular tissue transporting water instead of roots they have things called rhizoids that will anchor them to the ground but again not actually transport water around because they're not real roots they don't have leaves either again a real leaf has vascular tissue and transports nutrients you know um the products of photosynthesis to other parts of the plant uh they have these structures called phthali or a phthalus is singular phthalate is pleural it looks a lot like a flat leaf but again it's not a real leaf because it doesn't have vascular tissue it's a photosynthetic organ but yeah it's not a real leaf and if we want to look at their reproduction eggs and sperm are produced by this prominent gametophyte on distinct structures so it looks complicated there's the phthalates we've been looking at here's the antheridium and the archegonium don't worry about those terms but here is a structure that on on the gametophyte uh that only produces sperm and here's a structure on the gametophyte that only produces egg so try not to get bogged down in the details here i'm trying to highlight the important things um this is all just trying to illustrate the point eggs and sperm produced by the gametophyte on these distinct structures these distinct structures can be on the same plant or on different plants so in this particular figure we're looking at a single plant that has the female structure and the male structure both on the same plant but just to look at a different example here's a different species of bryophyte where you have a female gametophyte that only makes the female structure that makes eggs and here's a male gametophyte that only has this male structure the antheridia that only makes sperm so it can be either way depending on the species they're produced by the gametophyte on the same plant or on different plants and as i discussed one of the issues with land plants is these uh these eggs and sperm have to somehow get to one another so they get to one another by swimming which uh isn't easy because you're outside of water but you can still do that if you're in a very moist environment or an environment where it rains a lot so you can you can see the flagella on the sperm uh if it's uh you know on the same uh gametophyte it's a much easier journey for these sperm to swim over to the eggs if you are on different individuals it's a bit more of a difficult journey to for these sperm to swim to another individual uh to get to the eggs there uh but but it is something that they manage uh so again these are land plants but they're the first land plants so the most primitive land plants they're not the best at it yet so they can survive outside of water but because these sperm need to swim using flagella to get to eggs they can only live in in moist environments in environments where where it rains a lot where there's water around even if it's not always around if there's water around for for this for this swimming to happen okay so there's more to say about bryophytes but this is typically where i run out of time in this lecture so uh we'll continue on with bryophytes and other more sophisticated plants next time this is the end of recorded lecture 2 2.