Flowers

hi. In this video, we're going to talk about angiosperms, reproduction and angiosperms. Reproductive structures. Flowers as you hopefully recall plants experience what's called alteration of generations. Essentially, what that means is, during the course of a plant's lifecycle, they'll alternate between a spore fight generation and a comedic fight generation. Now, angiosperms are actually a spore fight, dominant plant. And what that means is they basically spend all their time. A spore fights and they're committed. Fights are these very teeny little diminutive structures. In fact, when you're looking at a angiosperms, you're basically just looking at the sport of Fight I. Unless you really dug into the flowers, you've probably never seen the commuter fights. Now the spore fight is a deployed multi cellular stage of life, and it produces spores, hence its name. It produces these spores, which are a sexual units of reproduction or, rather, units of a sexual reproduction, and they are generally half Lloyd and uni cellular. So remember that, uh, the process of my Asus will take a deployed cell and generate half Lloyd cells from it. Now the committee fight is going to be a hap Lloyd multi cellular stage of life and it's going to produce gametes. Shocker, right? But you didn't see that one coming. Now, since it's Hap Lloyd, and since gametes are half Lloyd, it's actually going to produce its game. It's by my toe sis and the gametes that's going to be like this. Sperm and egg will fuse to form a deployed Zygo that will grow and become a new spore fight. So looking here we have a nice diagram of alteration of generations. So the spore fight that's going to basically be like, you know, uhh. The main part of the plant, the tree, whatever. And it's going. Thio have structures that produce spores. These spores will turn into a media fights, and these Gumede a fights will produce gametes. And of course, the gametes will fuse together to form the zygote which grows back into the spore fight. And we have this continue alteration of generations. Now you might notice here that these gametes are not distinguished from each other. They are they look interchangeable. The thing is, angiosperms actually have what's called hetero sporting. Basically, what that means is they produce two distinct types of spores. They produce micros brand Geum and Mega spear. Angie, Um, now, Micros Fran Jim will produce what are called micro sports sites that will become micro spores. And these micro spores will develop into the male gametes. So micro is gonna be male. Micro male Mega is going to be female In the Megacities brand Geum will produce mega Sephora sites which are a type of cell. And these mega sports sites become mega spores. And those mega spores will develop into female Kamuda fights like the egg. Right. So here in this chart, you can see what this alteration of generations looks like when you have header story. So I'm gonna get my head out of the way for a second and you can see that we have the uhh and I want you to ignore these terms here. Just focus on this. You have the mega me to fight. I'm sorry. Micro me to fight and Megumi to fight. And those are going to produce the sperm and the egg which will eventually result in the structure with a micro spore fight the structure with a mega spore fight. No, the thing about angiosperms is often you'll actually see the Micros branch. I'm sorry, Micros. for a fight or Micros brand Jim Rather and Mega brand Jim on the same plant. Now not, um, we'll get into the breakdown of that in just a moment. But for now, I just want you to realize that, um, angiosperms are going to basically produce sperm and egg. They're going to fights aren't all the same with that. Let's flip the page.

While sexual reproduction is all well and good, many plants are able to reproduce a sexually as well. And this a sexual reproduction is sometimes called vegetative reproduction, which results in genetically identical offspring or clones. Now, one way that plants will do this is by shooting off or one way that some plants can do. This, I should say, is by shooting off a stem that will form a new individual in the stem, will travel underground and then produce a new individual like you see there. We call these rhizomes. Now they're compliment, if you want to think of it that way, are stolen, which are stems that shoot off and produce new individuals above ground. So the rhizomes are underground, stolen zehr above ground, and these stolen will also produce Advantis cious roots, which are routes that are generated from this Stine. Now seeds occasionally can our plants can Some plants conform seeds without fertilization, meaning that the, uh, you don't need to have those GAM. It's getting together. You know, the sperm and the egg, so to speak, and forming a seed, which is something we'll talk about a little later in lesson. We call this a pro mixes so seeds forming without fertilization. So this is again going to result in a clone offspring. We're genetically identical offspring. Now. You can also split plants into fragments, and these fragments will develop into or in some plants, these fragments will develop into mature organisms, and we call this fragmentation. This is like the idea of making cuttings or clippings of plants to grow new individuals. Now, Uh, yeah. While this is all great in terms of efficiency, you know, the plants don't have thio get together and go through the hassle of sexual reproduction. It leaves them genetically vulnerable, shall we say, because they're producing genetically identical offspring. There is less genetic variation in the population, and this actually can have disastrous results. Sometimes, for example, bananas now, depending on how old you are, you may or may never have tasted the world's best banana because they don't exist anymore. You see, bananas are grown from clippings, right? They do this fragmentation, and they plant the clippings. And that's how you get in you banana trees. Problem is, they're all genetically identical, and every now and then a fungal infection or something like that will come around and wipe out an entire population of bananas. This is actually happened more than once. And that's why the bananas we have today are not nearly as good as the varieties that we used to have decades ago, which have disappeared due to unfortunate circumstances. So this I like to think of as the tragedy of the banana. Anyways, vegetative reproduction with human involvement, like with those bananas, will be called vegetative propagation. And again, this is making cuttings. And, uh, you know, using these cuttings to grow new organisms and those cuttings air gonna be able to produce roots because they'll have a callous at the wound site. Remember, that's gonna be a mass of cells that air able thio differentiate and develop into, you know, any kind of mature cells. They will be able to produce roots from the site of injury from that, cutting the place where the plant was cut. So enough of a sexual reproduction. Let's get into the reproductive structures of angiosperms, which are again flowers and these flowers are going thio pretty scam. It's embryos, fruits and seeds, and we're gonna talk about all these structures, but first little flower terminology. So you have what are is known as the sea people. These are, uh you can see one here in this image. They're kind of like these green leaves that you see on flowers and you can also see See, pols on this image behind my head. I'm gonna jump out of the way. This right here is a see people, these green leaf like things and they serve as protection for the flower buds. So when you see the flower, But initially it's completely covered by the sea pols, right? And then the flower petals will pop out of that. Generally speaking, see, pols will be green, not always. And when you take all the Cibeles together, So for example, in this image, you can see that we have 1234 and five Cibeles here all of those taken together, including what's hard to make out in this image. But if you've ever seen a flower, you've probably noticed this before this green cup like structure that the Cibeles connect Thio all of that taken together the Sequels the cup like structure is called the CA licks. So this whole thing here is it collects very cool looking word if I do say so myself. Now pedals are modified leaves, and they will surround the reproductive parts of the flower, and usually they're actually there to attract pollinators. We'll talk more about that later, too. And just like the collects is the entire group of Cipel's. The Corolla is the entire group of pedals. So all for of these pedals here, taken together is the Corolla and no thes air not made by Toyota. With that, let's flip the page.

the reproductive structures of flowers can be broken down into stamen and carpools stamen you can think of as the male reproductive parts and carpools you can think of as thief female reproductive parts. Thes stamen is going to be the structure that produces pollen, and it is made up of two portions what we call the filament, which is going to be this stalk like appendage here. So that is a filament. You can also see it pictured here and then We also have the answer, and the answer is what contains the micro spare Angie um, which will produce micro spores. And we'll talk about the fate of micro spores in a little bit moving on. We have the carpal, the female reproductive structure, which is this whole thing right here. That is a kharpal, and it's also made up of some components the stigma which you can see here. That's the tip of the carpool. So if I were to draw this structure out a little bit, the stigma would be the tip there. Oops. And that's going to be where the pollen lands where the pollen is received during the reproductive process. Again, talk more about that a little bit. The style is basically the pathway that leads from the stigma into the ovary, and you can see it pictured here. It's me. Choose a different color and make it more clear. It's going to be like this portion and then this bottom portion of the carpal is the ovary, and the ovary contains what are called AV equals. These are going to be things that receive sperm from the male portions of flowers gets all that later. Now flowers will also have a structure known as uh, the neck tary the neck. Torri is going to be the gland that secretes nectar, which is a super sugary solution. And that's what some pollinators air going to feed on and this nectar you can actually be located inside the flower or outside the flower. Um, it doesn't really matter for your understanding the difference between all that. Just know that it could be inside the flower. Sometimes it's outside the flower. Now moving on to those a view ALS the AV. You'll is the structure that contains theme mega sport, and it's what's going to develop into a seed after fertilization happens. So this AV you'll right here is, uh oops. Sorry. This AV You'll right here is going to have some structures you should be aware of. We have the Integra mint, which is this outer protective layer. And then the micro pile, which is the opening, uh, the apex of the Integra Mint, which is going thio. Allow the sperm to enter in and fertilize this structure. Let's turn the page.

pollen was a wonderful technological advancement in the evolutionary history of plants. Prior to pollen, plants had to use water to get the sperm to the egg. Pollen provided a knave anu, that allowed for a much more diverse variety of methods of connecting sperm and egg. Now pollen is the male gimme to fight, and it's surrounded by a water tight coating made of a material called Spore. A pollen in and it actually contains two cells, the generative cell and the tube cell. We'll talk about what those do momentarily now. Pollen forms when a micro sports micro sports site, which is a deployed cell, goes through, my oasis informs Micro spore, which is hap Lloyd and through the process of mitosis, will form micro comida fights. And you'll see in a little bit why I have a two right there. Because, as we'll see, there's actually going to be two microgram media fights or two sperm involved in angiosperms reproduction. Now the female component is the embryo sac. This is the female. Give me to fight, and it is contained within the AV you'll and it's what will develop into the embryo. It forms when a mega sports site. Deployed structure undergoes my ASUs two form mega spores and actually it's going to form four of them. Now three of these will degenerate. One will go on to form the mega Gumede a fight. And the reason I haven't ate right here is as you'll see, this mega gamy to fight is actually going to have eight nuclei in it. Two of these are going to be what are called the polar nuclei that are happily nuclei that are going to develop into endo sperm, which is something we'll talk about in just a second now. Pollination occurs when the pollen it, um, is transferred to the fuel. It begins with germination where pollen will land on the stigma, resume growth, usually by absorbing some water, and the tube cell in the pollen grain will generate a pollen tube. This pollen tube grows through the style and connects to the AV. You'll and it will transmit those male gametes or sperm. No, I said I'd get back to that to sperm thing, and here we are. The reason for it is something called double fertilization. So basically the pollen tube releases to sperm one is going to fertilize the egg and form the embryo. That's to be expected, right? The other does this funky thing. It interacts with those polar nuclei and will form endo sperm. And this Endo sperm is a nutrient rich material or tissue really that surrounds the embryo and provides it with things like starch, protein and oil. In fact, when you eat nuts, you're actually basically eating end of sperm. So, for example, if you've ever eaten a peanut, you might notice that on a peanut there's that little kind of nib thing on the end. Or if you crack the peanut in half, you'll see that there's like a little nub structure on one end that is, the embryo, actually the nut, most of what we're eating. What we think of as the nut is the end of sperm, and it's super nutrient rich, right and also delicious in many cases. Now, these two sperm not to get too sidetracked on endo sperm. But these two sperm, these two male Gumede a fights. I'm sorry. Male gametes will be produced by the generative cell, which divides by mitosis and produces those two sperm sends him down the pollen tube. No seeds will develop once the visual is fertilized and it contains the embryonic plant surrounded by a protective coat. It's also got some endo sperm in their right. Never forget the endo sperm. And just look at a nice overview of this process Here we have on one side our get my head out of the way. Here we have our, uh, micro sprang Geum producing micro spores. The micro sport will go through my oh, sis, right. That's what's going Oops, that's what's going on here. And then it will, uh, produce the micro me to fight through my toe, sis, because it has to make those to you. Sells the generative cell and the tube cell. And that is our microgram me to fight or pollen. So this whole thing right here is our pollen green. Now, on the female side here, you can see those four cells that we talked about, three of which are going to degenerate. And one is going to go on Thio, go through my ketosis and form those eight nuclei, right, And you can count them off in this image. It's a little small, but we have 123 on top, right here, these three guys, our polar nuclei. So that's four and five. And then, if you can see on the bottom here we have another three cells. So that's going to be 67 and eight so that that accounts for all of those eight nuclei. And that is all part of the mega Me to fight or the embryo sac. No, just to finish it off here, you can see the pollination happening. We have our pollen grain landing on the stigma, so that's a stigma. Remember, here's our little orange pollen grain. The tube cell is going to produce this pollen tube that goes down to the of you'll, and here you can see the pollen tube reaching the AV. You'll right, and it's going to send the sperm into theme. The AV you'll where they won, will interact with the egg cell right here, and one is going to interact with these polar nuclei to form the end of sperm. With that, let's turn the page

up to this point. We've been talking about all flowers like they're the same. But as with everything in biology, there are exceptions, and there is variety and diversity, and that's a good thing. And we need to go over some of that terminology. So we've actually been talking about what you'd call complete flowers. That is, flowers that contain see pols, pedals, stamen and pistols all parts. Some flowers, though, are considered incomplete, and that's because they're missing. One of those components may be more than one of those components. In fact, now you can also have what's called a perfect flower, which is going to be a bisexual flower that has statement and pistol structures within the same flower. That's as opposed to what's called an imperfectly flower, which has either stamen or pistols and is Eunice Sexual Now amongst Eunice sexual flowers. We can get another dichotomy, and that is the difference between munitions plants and delicious plants. Now money cious plants and diocese plants both have, you know, sexual flowers. But in mani cious plants, the male and female flowers will be found on the same plant, so one plant will have some flowers that have male parts, some flowers that have female parts. But it's all in the same plant di cious plants. On the other hand, we'll have just male flowers or just female flowers on the same plant. So the male and female floral organs are separated by plant. In here. You can see we have some images to represent all this stuff. So here we are, looking at in complete flowers, and this one is male. This one is female. And here we have a, uh, a perfect flower. Actually, I'm sorry. This supposed to be in perfect? Not in complete. Well, actually, it could be incomplete. It's both incomplete and imperfecta, actually. So in perfect. Perfect. But over here is where I wanted to show are incomplete. Complete dichotomy. Get my head out of the way. So this is a complete flower. It's got the, uh You can see the stigmas up at the top. There. Here are the answers. You know, this is the style The ovary is gonna be down in there. You can't really see it. It's got pedals. You can't see it, but it has Cibeles under there. It's a complete flower. This is an incomplete flower Oh, if you're curious, this is a yeah. On the left. Here we have a hibiscus flower on the right is a calla lily, and while this might actually look like a pedal, it's not. It's a leaf. It's a leaf that has had its color altered to appear, a za pedal to fool pollinators, so to speak. And this structure is actually a covered in pistols, though you'd have Thio look through a zoomed in lens to really see it. But the point is, it's incomplete. No, if we move on, we need to talk about how pollen gets around, as I'm sure you may have thought. You know, if ah flower has the male parts and the female parts well, then can't it pollinate itself? The answer is, sometimes some plants can self pollinate, but others can't. Others will cross pollinate, which is when a when pollen is transferred from the anther of one plant to the stigma of a different plant, and some plants are prevented from self pollinating by genetic mechanisms. We call this self incompatibility so that it that is when genetic mechanisms prevent self pollination, and this encourages what's known as out crossing, which is when you breed genetically unrelated individuals. Now there are other methods that plants use to prevent self pollination. One of these is known as temporal separation. Essentially, the male and female comedic fights on a plant will mature at different times, so that neither one is mature at the same time, meaning it can't pollinate itself. However, other plants will have their male and female Gumede a fights match maturing at, um, you know, on a different schedule and so those guys can get together. There's also spatial avoidance, which is basically spatial positioning of male and female flowers or floral organs to avoid self pollination. So if pollen has to get to stigma, for example, maybe all your female flowers are somewhere with the male flowers can't get their pollen to them. Or, for example, you put your stigma and anther within the same flower in a confirmation where the anther can't hope to get its pollen up to the stigma, for example. Now, lastly, we need to talk about pollination syndrome, which are flower traits that have evolved in response to pollen vectors. So these are going to be traits that influence a plants ability to pollinate by wind or by attracting bees or by attracting birds for that matter. And the reason that you have organisms that will pollinate these plants is because of mutual is, um, right. They're not doing this for free. It's not a charity. There's something that they get out of it. The animal pollinators like this dusty, be covered in pollen here or this be slurping up its meal or this hummingbird behind my head here, slurping up its meal. They're getting food. They're not. They're thinking, All right, I'm gonna take some of this pollen bringing to this other plant later. See? No, they're like, I'm getting a meal right now. And you know, it's got to get a little dirty to get this food right to get dusty in the process. I don't really care. I'm getting a delicious, sugary snack, and when I go to my next meal, I might rub off some of that dust that pollen on that plant, right? So the plants get to spread their pollen around the pollinators, get a meal out of it, and what we see often with these pollination syndromes is co evolution, which is when, uh, one species evolution influences the other species evolution. So ah, lot of these pollinators and flowers have co evolved. In fact, when Darwin, the father of the idea of natural selection and all that good stuff when he went to the Galapagos and he saw this particular flower that had this really long tube down to the neck tary, he said, I bet you that there is some organism that has evolved to have a feeding tube that will fit into that flower. He was not wrong. He didn't discover that moth, but he was right in predicting that it existed. And that is just one eloquent example of co evolution. And you're going to see that with these pollinators and the organisms that their pollinating for because they rely on each other. Right, This is the food source for those animals. And this is how these angiosperms are going to spread their pollen around. No, I should make note that not all vectors are animal vectors. You know, there's other stuff like wind, but the the really cool examples of co evolution come out with those animal pollinators. All right, that's all I have for this lesson. I'll see you guys next time