Hey there folks and welcome to the first video for chapter 17 the evolution of plant and fungal diversity Two things you may notice the first is I have the video of me off for this chapter. There are going to be some Lifecycle diagrams that I really want you to see well And I don’t want the video getting in the way the second is that my voice may sound a little tired I’ve had a cough. I am beating it back But it won’t leave just quite yet. So please be patient with me. Alright. Let’s talk plants So when we first talked about the shape of plants, and how they are structured The structures that we’re seeing are the result of major evolutionary ad obtained Adaptations that plants had to make in order to survive on land early plants were very very small and had to grow in the water because they did not have specialized ways of getting water up into the plant or Bringing water to the main body of the plant from quite a ways away so the vast majority of Adaptations that we see in common land plants have to do with keeping water inside the body maintaining moisture getting water and nutrients into the plant I Through things like apical meristems that these are the growing regions of roots and stems Way out toward the tips of the roots and the stems where actual new cells are made and growth occurs and These roots and stems have specialized tissues called vascular tissues that carry water and nutrients throughout the plant in specific directions The vascular tissues for plants are called xylem and phloem as You can see here on the upper, right. Xylem is marked out in green. Phloem is in yellow and the difference between these two diagrams is one is a stem and one is a root Xylem carries water up the plant from the roots phloem carries sugars that are made in the leaves and other nutrients Throughout the plant and Xylem can also carry nutrients from the works up to the plant as I said a lot of early plants were also very small and so moving onto land in order to grow larger Plants needed some new way of physically supporting themselves One of the earliest adaptations of this is called lignin and you’re already familiar with it Lignin is one of the major reinforcing molecules in that thick heavy very starchy stiff strong Plant cell wall, and this is part of what gives it its strength and that at a larger scale help support the whole plant Another adaptation plants had to make was reproducing in a whole new way They used to drop their spores into the water and let the water carry them But moving away from water and onto land man. We had to change that some so reproduction and dispersal Getting the new fertilized seeds or the sperm pollen the pollen grains spread away from the planet became a major thing Looking at these structures as we go through them. You’re going to find general structures called gametangia. Think gamete these are structures that make the gametes for the plant Male gametes tend to be pollen grains these are little grains that hold the sperm inside and the sperm shell protects the pollen grain Embryophytes are multicellular embryos that are dependent on nourishment of given by the parent plant so where we see fertilized egg, a zygote, develops into An embryo that in a plant that multicellular embryo is called a embryophyte. “Phyte” actually means plants So anytime you see something labeled “phyte” it is pertaining to it’s part of a plant yay. Vocabulary. We have so much of it in Very, very early plants which we still have by the way these plants are still picking around We’ll get to that. But in plants It evolved very early. They’re still using spores Pardon oh that cough I cannot wait for it to leave in plants that still use spores those spores are made in structures called sporangia and A spore is a cell that can develop into a new organism without going through fusing with another cell They can land and germinate elsewhere Alright alright, so let’s look at what this actually looks like over evolutionary time This is a diagram called a phylogenetic tree. You may also see it called a cladogram Don’t be fooled different names same exact thing the purpose of this diagram in evolutionary biology is to help us um show each other the Relationships the evolutionary relationships between different groups of organisms some very large and journal some very small in particular So that we can try and relate to each other and explain these things a cladogram shows general patterns of change from left to right Over time from bottom to top know what I say general this is there’s no specific “Exactly how many millions of years to take for this change to occur?” That’s not what this is about This is just so we can track which changes occurred between this species or this group of species Splitting off and that one and what this changes part alright So what you are looking at here is the basic giant family tree No pun intended for plants and their relatives Going agl the way back to really small simple Green algae algae act like plants They photosynthesize like plants, but they don’t have the structures that Classify a true plant so do not be fooled some of the oldest plants still in existence or the ever split off our Charophytes and Liverworts Charophytes are very very similar to algae They can be very confusing trying to keep them separate from plants But between Charophytes and liverworts they developed embryo protection Some kind of protected shell layer around that embryophyte hey, let’s use that new vocabulary To help protect it. Between liverworts and mosses and hornworts which are the next group We started to get apical growth so growing from the tips instead of from the roots together These plants are called bryophytes They resemble other plants because they have apical meristems and embryos But these plants don’t have true roots and leaves yet They look like they have teeny tiny leaves and they have root light structures, but true roots enter leaves are defined by having xylem and phloem those vascular tissues We were just discussing and those did not evolve until we get the next group club mosses now. We have true plants They have true they’re already true plants, but they have true leaves and true roots which are defined by having xylem and phloem and So far even up all the way through ferns We still have Spores we have not gotten to the point of using seeds yet Let alone pollen or flowers, so everything we have so far still uses spores and sporangia to reproduce their small usually they grow near water Because they don’t have up until we had club mosses They don’t have specialized tissues to help pull water and other nutrients up into the plant So they have to stay in your water, and they can’t be very big Once we get vascular tissues plant started to get bag Because they started to have more options Fern started getting much larger eventually firms develop spores that had a slightly thicker Coat, and this is the ancestor of the modern day seed we have two different forms of seed using plants gymnosperms and angiosperms gymnosperm means “naked seed” these are Seed-using plants That do not bear fruit the way you would recognize them These are classically things like conifers like pine Spruce and for all your classic Christmas trees these are gymnosperms Other examples that you may see around in about town are things like the ginkgo tree and cycads But also some very ancient species of desert plants in Africa that split off a very long time ago The most recently evolved group of plants is also one of the most successful. They outnumber all other plants for sheer numbers of species these are our angiosperms our flowering plants They produce flowers that bear pollen that attract pollinators or use the wind to spend their pollen many of them produce edible fruit Which attract animals to come spread those seeds for the plant and we’re going to talk later on about the very, very long evolutionary relationship between those flower- and fruit-producing plants and animals We use each other all the time first we need to talk about Just how some of this plant reproduction functions in most life on this planet Reproductions reproducing structures and the gametes that they use to reproduce Aren’t so distinct from each other one is very small and it relies on the other our eggs and sperm our gametes are Not terribly distinct from the rest of our body without our body they cannot survive Implants however they practice something called alternation of generations Which means that there is a haploid stage of life and a diploid stage of life that alternate one to the other Animals don’t do anything like this Our gametes get made the Haploid gametes get made inside the Diploid adult body but in plants these are two highly distinct stages of a plant’s life cycle a Sporophyte is the diploid adult stage of the plant Remember “phyte” refers to anything to do with plants, so the sporophyte makes the sporangium the sporangium makes the spores and the spore is What can spread away Pardon my throat is what can spread away from the adult plant land elsewhere Grow a haploid gametophyte That makes gametes that can go spread find other gametes undergo fertilization form a diploid zygote and you move back into the diploid side of the alternation generations, and they go back and forth over and over and over moss and ferns Still use this it’s a perfectly evolutionary adaptive life cycle Even flowering plants do this, but there they look a little odd by comparison Places where you really find These plants that use this major form of alternation of generations the seedless vascular plants were in the Carboniferous, era Roughly 360 to 299 million years ago when ferns really started to get enormous hundreds of feet high some of them potentially however over time these fossilized plants Were broken down and basically pressure cooked through heat pressure and time into coal and This is where we get oil and coal In the Earth’s surface, this is where our fossil fuels come from alright, that’s that’s from the time period This long time ago this Carboniferous period moving past that moving away from spores, and it to actually using pollen Pollination is a process were in pollen from one plant will land on the appropriate receptacle of another member of the same species and inside that pollen is a Sperm which can then work its way down into the new plant reach the ovules which are the eggs and undergo fertilization just like we do in in human gametes, just like we do in animals the resulting zygote Eventually develops into a seed with a protective seed coat like its own personal suit of armor that Protects the seed and keeps it from being damaged or dehydrated Pollen can look very different depending on their species some look like like strange mushrooms Others look like little folded up taco shells but all depends on what species different shapes sizes colors Textures you should see these guys in person it can be really quite eye-opening the variety we get of all of these Pollen using plants and how different their pollen grains can be from each other Pollen is made here in the anther Which purchase on top of the filament. It’s called the filament because it can be thin as a wire. The appropriate landing surface for that pollen is called the stigma and down this tube called the style at the base of the style. there is the ovary Just like there is in animals and inside the ovary are the eggs which are called all fuels surrounding this whole reproductive center of the flower are The petals and below the pedals are the sea poles the receptacle and the peduncle Which is basically the stem of the flower The anther and filament together are called the stamen The stigma and style as well as the overall together are called the pistil The stamen is the male part of the flower because it’s the site of pollen production remember pollen contains the sperm inside the male gamete The pistil is considered the female part of the flower because it houses and produces the female gametes the ovules so this is the overall anatomy and structure of your average flower These are our angiosperms, so successful Remember how I said that they were going to be Some diagrams, I really wanted you to see well Remember I also told you that the life cycle for angiosperms still used alternation of generations, but it was a little odd This is what I was referring to angiosperms still undergo alternation of generations There is still a haploid and a diploid part of this lifestyle They exist separately from another and they are very distinct that adult plant including the flower is The diploid part the sporophyte part of this life cycle It undergoes from fertilization the formation of the zygote It forms the seed which eventually germinates it sprouts it grows up into the adult plant It forms it grows flowers it makes the gametes Wherein we hop over into the haploid side of alternation of generations we start working with gametes Instead of the sporophytes, and there is your gametophyte right there it is the part of the plant that makes the gametes In these two separate places then the female ovaries are made and they mature and the male Sperm are made and they mature and they are then released inside their pollen grains Either to be carried by a pollinator or perhaps picked up by the wind to be taken to another flower All right, so even though this starts to look very complicated Remember it still boils down and simplifies down to the exact same thing Haploid and diploid alternation of generations You can even see the exact point where you hop over from haploid to diploid and back again Alright? Don’t let it fool you just because it looks more complicated. Okay? Take it one step at a time. You will be just fine Now I mentioned once or twice This long evolutionary history that specifically seed producing plants have with animals They use us to help spread their seeds around and we use them Seeds have a number of different ways of being dispersed Some are heavy, and they will fall to the ground like this acorn. They use gravity to get them away from the parent plant Many use animals we eat the fruit. We carry the seeds we deposit the seeds elsewhere sometimes animals get used without the benefit of getting a meal from the fruit and They and plants will make seeds that can hook onto a bird’s feathers or into a mammal’s fur and hitch a ride elsewhere Some seeds like this coconut are Buoyant they float and they can float in water others Explode outward when their capsules are ripe and mature and others yet still are so light and they have other structures to help them catch the breeze that the wind carries them away and Yet others We help as humans. We’re very unusual that we plant things on purpose But we do we help spread seeds around by planting them some other animals also plant, but they tend to do it by accident a good case for this or Squirrels who will plant acorns by hiding them in the ground With the plan more or less of coming back digging them up and eating them later But squirrel memory is not so hot and they tend to forget where at least some of their acorns are and there but end up planting new oaks by accident Plants don’t just use animals to help spread their seeds around They use us to help get those seeds fertilized in the first place This is a series of photos taken by a photographer that compare what we see is humans and what other animals can see when they can see into the UV range of light see Tons of flowers are pollinated by animals you’re familiar with bees hummingbirds But there are also mammals that pollen eyes flowers pollinate flowers like small primates Even bats will pollinate things like the saguaro cactus That has very large flowers that are made for a bat to just faceplant right in there and get pollen all over it. It’s adorable But a lot of these pollinating animals can see what we can’t They can see markings on the petals like here in photo that’s been treated so we can see what the UV patterns look like and here is what this flower would look like to a bee and These extra markings help direct pollinating animals especially insects and birds Which can see quite far into the UV range and can see these markings very clearly and they help direct these pollinating Insects and birds to find where the pollen is on the flower So what attracts them to those areas? Well, these pollinating animals get a reward frequently in the form of some kind of food either the pollen is edible or there’s some sugar-intense nectar there in the bottom of the flower that helps feed the pollinators so the pollinator learns that those markings at the center have food and In the meantime they get dusted with pollen when they go on to another flower of the same kind they get more food Rewarding them for coming to the flower and they end up delivering more pollen We’ve been going back and forth getting food and running errands to help plants reproduce for millions of years in the next video will continue in The meantime enjoy folks, and I’ll see you then. Bye!