Land Plants

Hello, everyone. Today we're going to be talking about the different types of land plants and how they evolved over time. Alright, so land plants originally evolved from algae that lived in the water, specifically green algae. Because there are different lineages of algae, there's brown algae and red algae in green algae land. Plans on Lee came from green algae, so they evolved from these aquatic organisms and they evolved to live on land, which means they had very specific adaptations toe live on land because their environments drastically changed. Now this change happened around, I believe, 850 million years ago is when plants began to colonize dry land, which is a really long time ago. And they came from these freshwater green algae and they're gonna have very specific adaptations because, as you can imagine, moving from an aquatic environment to a terrestrial environment has its issues. And some of the adaptations which you will all learn more about in later lessons, are going to be things like the cuticle, which is a waxy covering of the plants which helps them retain water because they're no longer living in the water there now, living in the air, they have the possibility of drying out. They also have things like seeds, vascular tissue. Some of them even have Paul in, which allows them to reproduce without water, which is very interesting. So there are many adaptations which we will learn more about in later lessons. But right now let's talk about the lineage and the evolution of these land plants. So land plant, as we normally call them, is a very informal name. It's just talking about all of the plants on land, but this is a very informal name, and it's actually very interesting. Land plants also encompasses some plants that went back to an aquatic ecosystem that air now aquatic again. They went from aquatic to terrestrial to aquatic through their evolutionary processes. So land plants. If you want to be more specific, you're going to call them embryo fights. Embryo fights are a specific type of organism that holds the embryo or the developing offspring inside, off the tissues of the parent. Don't don't worry, you will learn more about that specific quality and later lessons when we talk about plant reproduction. I was just telling you why they have this particular name Now there are three types of land plants, non vascular, seedless vascular and seed plants, and they did evolve in that particular order. Non vascular plants came first, then seedless vascular and then seed plants. The majority of the plants that you think of are going to be seed plants, and they're going to be the youngest and generally the most specialized plants that live on dry land. But first, let's talk about non vascular plants. These were going to be the first plants that actually colonized land, and they're gonna be very similar to the green fresh water algae that they evolved from. So these were the first land plants, and they lacked these particular structures, called Trey kids. Now Trey kids are going to be a type of plant cell and trey kids ourselves with very thick walls made of lignin. Lignin is like cellulose. It is a very important structural component of most plants, except for non vascular plants. You'll find that seedless vascular and seed plants have this ligament cell wall component to their anatomy, and this is going to be very important for structure. This is going to give them the ability to grow taller and larger but non vascular plants. The first land plants didn't have Trey kids. They didn't have lignin, so they were not able to grow to great size so they could not support large vertical growth. They couldn't grow really tall. Now you would be knowing this. Now. You're probably not surprised. Thio here that non vascular plants are going to be things like moss and liver warts, which sounds awful, but they're actually not as awful as they sound. So moss, liver warts. I also believe horn warts are non vascular plants, and these were going to be plants that are also called Braila fights, which will learn more about in their own lesson. There's a whole lesson on Bryan fights, but these are very short plants, very small plants, Mosses, kind of like little little Tufts of hair or grass on the ground. They don't get very tall, and the reason is is because they did not evolve. Trey kids, they're the first land plants. They didn't have this adaptation as of yet. Now these plants are a gammy to fight dominant life cycle. You will find that the other two types of plants seedless, vascular and seeded plants are not. Give me to fight dominant life cycle there. Spore fight, dominant life cycle. And this means because they're gay. Me to fight dominant life cycle that they are hap Lloyd Most of their life, they only have one set of chromosomes the majority of their life, their dominant part of their life. Now they do have some sort of internal water conducting tissue, but they don't have vascular tissue that the larger plants of land today actively have, so they don't have as specialized water and nutrient conducting tissues. So that's also why they're very small. Now let's go into the next type of plants. We have the seedless vascular plants thes. We're going to be the ones that evolved. Next, seedless vascular plants are a para file ethic group, which I'll explain more when we look at the file a genie down here in just a second. Basically, what that means is seedless vascular plants that term. That group name encompasses the ancestor of vascular plants, but it doesn't encompass all of the descendants of that ancestor because the other descendants of that ancestor are going to be seated plants, and obviously they're not seedless vascular plants. They're seated vascular plants. So but don't get too much into the specifics. I'll show you guys the biology in just a second. Okay, So what's new about these plants is that they have vascular tissue. That means that they have specialized water conducting and nutrient conducting tissue that acts a lot like our blood vessel system does. It is able to transport water and nutrients to the extremities of the plant. This allows the plants to get a lot bigger because they're able to move water and nutrients farther. So these are also going to be plants that have a spore fight, dominant life cycle. Remember that non vascular, organ modified, dominant life cycle. See, this vascular plants are spore fight dominant life cycle, meaning that most of their life they're going to be deployed. They're gonna have two sets of chromosomes in their cells. Also, they evolved lignin like we talked about earlier, and this allows them to have strong vascular networks, and it allows them to support more vertical growth. So these were going to be larger plants thes. They're gonna be things like ferns and horse tails are also seedless vascular plants, so they have vascular conducting tissue. They're able to grow taller because of their lignin, but they don't have seeds as of yet. So now let's move on to the seeded vascular plants. So we just call these seed plants. But these air most of the plants that you think of today, whenever you think of a plant and this is going to encompass the gym, No sperms and the angiosperms. Two different types of seeded plants. Jim, no sperms have naked seeds. These air gonna be things like Conifers. Basically, what this means is they don't have an active protection around their seeds, and they don't have any parental part around their seeds. So the opposite of that is gonna be angiosperms. Angiosperms are enclosed seeds, so you'll find the angiosperms will commonly hold their seeds inside. I'm sorry I'm in the way. You guys, they'll commonly hold their seeds inside of a nut or inside of a fruit so their seed is enclosed. While Jim no sperms have naked seeds. It's not enclosed, so angiosperms are going to be all types of flowering plants. That is what makes angiosperms Sony unique. They are flowering plants, and they have pollen. So all seeded plants are gonna have pollen as well. These gym no sperms have pollen and so do these angiosperms. So they have vascular tissue. They have lignin. They have Trey kids, they have seeds. Seeds is a very important adaptation because seeds protect the developing embryo and they allow that embryo to have a better chance of survival. Alright, so just you guys know remember the gym? No, sperms are generally Conifers, so things like pine trees. All right, so now let's go down And let's have a look at this biology that we have here. So this is a pretty big file, a genie, and let me scroll down so you guys can see the bottom. So if the bottom here, you all can see that we have thes green algae species and these green algae species are going to be the ancestors to land plants. Now land plants are going to be from here and above. So those are going to be our land plants which you guys can see. It's as embryo fighter. So these air, the embryo fights or the land plants and the first particular types of land plants to evolve are going to be those Braila fights. Those are the non vascular plants, so non vascular plants are the bride of fights and these air going to contain the horn words, the Mosses and the liver, warts. Very low profile, very small plants. Now, as we go up in the file a genetic tree, we're going to move on to things like ferns and horse tails. So these are going to be our seedless vascular plants that evolved from our non vascular seedless plants. These are gonna be things like the ferns and the horse tales that we talked about, remember, They're now able to grow taller. They have lignin and they they have vascular tissue. They're able to transport water and nutrients around their bodies, so they're able to get larger. And this includes all of the vascular plants here, which is the vascular seedless plants and the vascular seeded plants. And as we move further up the file a genie, we can move on to the seeded plants, which are going to be things like Jim, no sperms and angiosperms. So these are our flowering plants are Conifers, our site cads, argan coz, and those are going to be gin goes and psych odds are not as common as Conifers and flowering plants, so you might not know exactly what they look like. Definitely recommend looking them up if you would like to know. But these were going to be more specialized plants, more specialized toe living on land because they're going to have things like pollen. They're gonna have things like seeds and flowers there, specifically adapted to live and reproduce on land. And remember, guys, they also have this vascular tissue and this lignin so angiosperms and Jim knows firms are generally the largest plants on our planet because of their structural abilities. And angiosperms are going to be the most successful, I guess you could say, or the most prominent types of plants on our planet, because flowering plants have done so incredibly well because they interact with the environment greatly and the interact with animal and insect pollinators very well as well. Okay, everyone. Now let's go on and learn more about specific types of plants and these specific adaptations that land plants acquired

Hello, everyone. In this lesson, we're going to be talking about the specific adaptations that land plants acquired in their transition from their aquatic environment to their new terrestrial environment. Now plants had to come up with many adaptations because their ecosystems, their environments, drastically changed. You could imagine living in complete aquatic environment to moving to living in a terrestrial environment would be quite dramatically different. So plants evolved many structural features that allowed them to live on land. Now what do you think the majority of these new adaptations are going to do? Well, if you go from living in water to not living in water, you're going to find that the majority of these new adaptations that these plants have is going to help them retain water, going to help them not dry out from living in very dry air. So the majority of these adaptations help them retain water, and some of the major adaptations for retaining water are going to be the cuticle feast Omada and the guard cells. So the cuticle is going to be the main line of defense against desiccation or drying out. This is going to be a waxy film covering the epidermis, or outer layer of cells off many plants. You can actually see the cuticle right here. It actually looks like this, this clear layer of wax, and that's pretty much exactly what it is is it's clear layer of wax that goes directly over the outer layer of plant cells. It's kind of like a raincoat, but instead of keeping the rain out, it wants to keep the water inside of the tissues of the plant. So the cuticles main job is to keep water in, so it keeps the plant cells from losing water. Also, the cuticle is very important for keeping out pathogens, but we'll learn more about that whenever we learn about the immune system that you find inside of plants. All right, so now let's talk about these stone mata so moderate are going to be pores in the tissues of the cells, generally, the leaves that are going to control gas exchange and they're going to regulate water loss. Still, mata are basically pores or holes in the tissues of the plant that air ableto open and are able to close. You can actually see a stone mata or a stoma that is the singular version. Stone Mata is plural. You can actually see a stone MMA right here. This is a stone, This hole in the surface off the leaf. This is a cross section of a leaf. If you guys were wondering, here is the leaf. Here's the cross section of the cells of the leaf, and we have a poor in the bottom of the leaf right there, which is a stone MMA. Now the stone mama are actually able the stone Mott are actually able to open and close. And the way that they're able to open and close is because they have the specialized guard cells and these guard cells air able to change their shape based on their turgid iti, which is going to be the amount of water pressure that they have inside of them. And they're able to open and close the stone. Mama. Now, why would a stone a need to open and close? Well, plants need access to the air to do photosynthesis. Photosynthesis requires co two, and it gets rid of oxygen, so it needs to interact with the gas. Is that air in the air? So the stone mata need toe open for that particular reason for gas exchange for photosynthesis. But because the internal tissues of the plants are interacting with the air, that means that water is actively evaporating out of the leaves, which is bad because we don't want these plants to lose too much water. So this is why Stone Mata opening close. They open so that the plant can do photosynthesis and exchange gasses. But they close so that the plant doesn't lose too much water when it's not doing photosynthesis. In most plants, they're going to close at night when they're not doing photosynthesis because the sun is not out. There are some specialized cases that we will learn about later. Now, I wanted to show you guys how these air actually going to work. So whenever you have these guard cells, whenever they have low water pressure, so low pressure inside of them they are going to be closed. So these are closed guard cells, meaning that the stone model is close. So these guys down here, our guard cells. Now, whenever water is actively pumped into these cells, they're going to become turgid or have a very high water pressure inside of them. and they're going to form this kind of like macaroni shape and this is going to allow the poor to open. So this is gonna have high pressure, and this is going to allow the Stoma Thio open. So now we can have these gas is so we can have co two entering the plants and we can have oh, to leaving the plants because this stone mata or this stone MMA is open. And that's high water pressure versus low water pressure. So this is going to be how the stone mama actually opens and closes. And generally the stone mater are going to be found on the bottom off the leaf, as you guys can see right here. So those were going to be three major adaptations for living on land. Generally toe allow these plants to do gas exchange, but mostly to allow them to retain water Now. Also, we learned that most plants not all land plants, have vascular tissue, but vascular plants did in fact evolve vascular tissue. Vascular tissue is very, very important because it allows these plants to transport water and nutrients throughout the entire body of the plant. This allows plants to grow quite large because they can transport water and nutrients to their extremities. You can kind of think of this particular system. Um, as an analogy to our blood vessel system, our blood vessel system actually transports water and nutrients as well to our extremities. Same thing with the plant, except it's a little bit different. They have vascular tissue and they have one type of vascular tissue that is specific for water on one type of vascular tissue that is specific for nutrients. And these two types of vascular tissue are going to be asylum and flow. Um, xylem is going to be the transport vascular tissue, the transports, water and minerals. This is going to be the one that transports for water. Now, Would is very interesting. It is a form of vascular tissue, specifically xylem, and you can look at the Greek word that xylem came from. So xylem is the English. Word in the Greek word is actually Zylon, and in Greek, it actually means would and would is a form of xylem tissue of water, conducting tissue. Now, xylem tissue is going to have very specific structural components, and one of those is going to be the tray kids. We talked about Trey kids in our lesson whenever we talked about the different types of land plants. And remember that Trey kids are going to be these very important structural cells. But I didn't tell you that they're part of these asylum conducting tissue. So, Trey, kids are gonna be these very long cells that help carry water up from the roots. And they contain secondary cell walls. We know all plant cells have a cell wall, but these trey kid cells have another cell wall on top of that for increased rigidity. Now, what's inside of the secondary cell wall is going to be that lignin component that we talked about increased structural integrity. So because these cells have two walls, their name the primary cell wall, which all plant cells have, which is made of cellulose, and the secondary cell wall which traded specifically, had have, which is made of lignin. Now a great example of a track it seen here in pink. So this is going to be xylem vascular tissue shown in pink, and I hope you guys can see. But those cells in pink actually do have to sell walls So this wall here, which I am highlighting for you guys in blue, is the secondary cell wall, and the secondary cell wall is actually exterior to the primary cell wall. So the primary cell wall, which is still in pink, and the secondary cell wall which is now in blue, which I highlighted for you, are the two cell walls surrounding a TRACON sell. Most plant cells only have a primary cell wall. This is made of cellulose. So this is made of cellulose, which is very important structurally, and the secondary cell wall is made of lignin, which is another strong component. So both of these together make these cells very, very strong, and this allows these plants to grow quite large. Now, the primary cell wall cellulose is gonna be closest to the plant cell. The secondary cell wall. Lignin is going to be on the outside of that primary cell wall, and water and nutrients will be moving through These cells. Look something like that so water will be moving through these cells throughout the plant to distribute needed water. Now the other type of vascular tissue is flow um, flow. Um, is going to transport sugars and amino acids and nutrients. So basically, think of zyla moves water and minerals and flow. Um, moves food for the plant. So flow, um, the word flow, um also comes from another Greek word, and the Greek word for flow, um is actually flow yous. I believe it's how you say it, and this translates to bark and a particular type of flow, um is actually bark the bark on the outside of most trees that, you will see is a type of flow, um, tissue. So this flow, um, tissue is going to transport nutrients and sugars. Specifically, it mostly transports the sugars that were made via photosynthesis to the different areas of the plant that need that energy now flowing is a little more complex than asylum. It's got mawr components, and this depiction here in green is depicting some flow of vascular tissue and flow. Um, is gonna have some major. It's gonna have some major key players and they're going to be the sieve elements which you guys can see here. Let me highlight them for you. This is a sieve element, and it's also going to have these parent came of cells and it is going to have companion cells, so sieve elements are the really important ones here. Sieve elements, which are right here. Let me circle them for you. So this is a sieve element cell right here. Sieve element cells are basically tubes, and the cell has almost nothing inside of it because it's just a transportation tube for sugars and the sieve element. Because it has no real internal structures, it can't take care of itself. It can't metabolize its own sugars, so it's going to have things like companion cells. So a companion cell, which is going to be one of these cells right here a companion cell is basically going to take care of and feed thesis if tube element because it cannot do it itself. So Flown is going to have these tube elements. The transport sugars throughout the body of the plant, and it's going to have these companion cells, and it's also going to have these parent chema cells, which I believe is this cell right here. Thes parent kinda sells basically store the sugars that are being transported by this transportation system. Now that's all I have for you on the specific adaptations off these land plants. Don't worry if the vascular tissue seems a little complex. We do have lessons that specifically go over the vascular tissue and vascular transport of food and water in plants, so we will return to this topic. But now let's go on to the different organs of plants like branches and stems and leaves. Okay, everyone, let's go into our next topic.

vascular tissue allowed vascular plants to develop roots, which are organs that generally live below ground. However, there are certain species that have aerial roots. Don't really worry about it there. There's always an exception in biology, Um, but the's roots absorb water and nutrients for the plants. They also route it into the ground, so they allow plants to grow taller because they provide stability to the above ground portion of the organism. Vascular tissue also allowed for the development of leaves, which are in Oregon that is specialized for photosynthesis. And actually we're going to see leaves come in two flavors. There are micro fills, which are small leaves, that air supported by a singular strand, a vascular tissue. And you can see an example of that. Here we have a micro Phil in red. This is our vascular tissue, and you can see that in this micro feel leaf. There's this Onley, this one strand of vascular tissue, whereas mega fills, which you can see an example of here. Mega fills, um, have a much more branched vascular system in the leaf. And of course, I've included a picture of a make belief. There. You can see the vasculature going through the leaf. I'm not gonna draw in all the little lines, but you can see it pretty distinctly in the sleep. This is an example of a mega Phil. And why did I pick a maple leaf? Because I love maple syrup. Now, seedless vascular plants, uh, again show that transition from Gumede a fight dominant to spore fight, dominant life cycles. We've discussed alteration of generations before All land plants show alteration of generations. And this is again just a life cycle in which both the deployed and half Lloyd stages are multi cellular. You have your Amiga fight, which is that half Lloyd multicellular stage of life that produces the Grammys and the sport of fight, which is the deployed multi cellular cellular stage of life. Uh, responsible for producing spores being my Asus, right on a sport again, it's just a a sexual, uh, unit of a sexual reproduction. It's usually half Lloyd, and usually, you know, cellular, uh, plants specifically evolved what are called spore fills. And of course, since these air modified leaves, this has to be vascular plants were talking about. So these, uh, spore fills bear what are called sparrow Ranjha, which are basically just enclosed structures in which sports were formed. You can see an example of Speranza here. All of these, uh, kind of like reddish brown dots on the back sides of these leaves is actually fern leaf. All of these are Esperon JIA. Um, so let's actually turn the page and take a look at some other adaptations.

non vascular plants and most seedless vascular plants are homeless porous, which means that they only produce one type of sport. Now, some seedless vascular plants and all the seed plants are hetero sports, meaning that they produced two distinct types of spores. And those two distinct types are micro spores, which are made from micros baranja, and these developed into male Gumede A fights, so these will ultimately lead to production of sperm. And then you have Mega Spa Ranjha, which produce mega spores. And those mega spores will develop into female Janita fights or eggs. Now, in terms of reproduction, uh, non vascular plants and seedless vascular plants have a big disadvantage compared thio uh, you know, later plants, and that is that they their sperm requires water in order to get to the egg. Not only does it require water basically requires a continuous path of water to get to the egg, so essentially this means that those organisms can Onley produce when it's wet out, and this kind of restricts them to environments where there's enough moisture. The adaptation of pollen, which is the male gimme to fight, surrounded by a spore, a pollen and coating Basically, this is like a tough coating allows for, uh, the male comida fights. And ultimately, the sperm thio exist without water for a much longer period of time. They can be exposed to the air for a long time, and furthermore, they can actually take advantage of the air as a medium through which to travel to the egg. So pollen was a huge important adaptation, and it essentially allows thes sperm to travel through the air to the egg and not require water. Thio actually fertilize the egg, and we'll talk about the specifics of that later when we talk about seed plants now, the seed itself, as I said, was a big evolutionary adaptation, and seed is basically just the embryonic plant, right. The embryo of the plant and a food supply on this is all surrounded by a tough coating that allows the seed thio resist environmental damage and degradation from being digested by a non organism, for example, and seeds form from fertilization by pollen. You can see, uh, pollen here. All these little yellow dots are bits of pollen here. We actually have, uh, an electron microscope image of pollen. You can see that There's, Ah lot of diversity in, uh, you know, uh, inform. There's a lot of pollen can take a lot of different shapes and here we actually are looking at the inside of a seats. This is a seed cut in half and let me jump out of the image here. This is our embryonic plant. It's a dichotomy. You'll learn. Why later? Don't worry about it now, but if you know why it's die Kat thumbs up, it's because it has these two things again. We'll talk about this later, so don't worry if you don't know what I'm talking about right just yet. So this is our embryonic plant, and this is what's called Endo sperm. And basically it's the food supply. It's the food supply for the embryo. The embryo is going to use this endo sperm for energy to grow and, you know, turned into a sprout and you can't really see it. But there you can just make out this coding around the outside of the seed here, and that's gonna be a theme, tough protective shell that, uh, will allow the seed thio, you know, lay dormant for a long time and resist digestion for example, until the conditions air right for the, uh, seed to sprout. So essentially, uh, in a way, the adaptation of Pollen, The adaptation of seeds. Kind of a similar theme. They allow thes, you know, facets of reproduction to persist in a terrestrial environment much longer, rather than requiring, for example, the presence of water. Now, the last major evolutionary adaptation, I want to talk about our flowers and these air the reproductive structures of angiosperms. We're gonna talk about them in much more detail when we talk about angiosperms, but that the flower is one of the last major evolutionary adaptations of land plants. And it's in part due to the flower that angiosperms saw this explosion of diversification. Uh, they, in fact, what they saw was an adaptive radiation. So, uh, angiosperms actually are one of the most diverse groups of land plants around today, and it's in part because of the evolution of the flower. All right, that's all I have for this video. I'll see you guys next time