today's lecture is on land plants and we've already talked about various clades of organisms and uh the super clay archiplastida which included the typical plants and algae back in the day when we wanted to denote land plants we would say plantae right but with all of the advances in molecular biology we realize that uh plants land plants are really United with green algae and with other algae as well and we we now know that the green algae gave rise to plants to land plants land plants actually appeared about 475 million years ago and uh if you think about a green algae needing water and all of the Aquatic uh requirements uh when these algae evolved into land plants they had to obviously uh diversify such that they could become adapted to living on land which meant how are you going to keep your gametes moist how are you going to keep your zygotes moist uh how are you now going to obtain uh mineral and water on the land so there was some very very real hurdles when algae obviously went from an aquatic environment and now with the move onto land with the colonization of of land plants we have all sorts of great new adaptive zones that came about um you had organisms now living with plants on plants like never before uh so there was a whole suite of uh inter relationships with plants coming onto land and uh you had plants that had to undergo all sorts of structural chemical and reproductive adaptations okay so there are some really striking differences between obviously land plants and their ancestors the algae some of the characteristics of plants land plants we know that they're multicellular eukaryotes that obviously they evolved complex bodies with certain specializations so you had things like roots and leaves and stems we know that they're photosynthetic autotrophs and uh as I said before how were you now going to extract water and minerals from the soil you had to evolve what you had to evolve Roots how are you going to support yourself on land you had to obviously evolve stems and uh what about the exchange of oxygen and carbon dioxide you now have pores that we call stomates on leaves stomata that exist on leaves so there were all sorts of should we say terrestrial adaptations that had to uh take place you also had quite a number of chemical adaptations that that took place things like the secretion of waxy cuticles not all plants have this but many plants have this again one of the big problems was desiccation and dehydration so to prevent desiccation or dehydration uh many uh uh plants had evolved these uh waxy uh secretions and we call them secondary products because they obviously arise through biochemical pathways that are not common to to all plants for instance we would consider cellulose which is common to all plants a primary product but since waxy cuticles are not common to all plants we consider them what we refer to as a secondary product so I do want you to know secondary product versus a primary product another thing with the movement of plants onto land algae you had now the the incorporation of lignin as a cell wall component uh obviously to add strength and rigidity to the plants sporopollenin was was another adaptation this kind of very very tough Macro Molecule polymer uh that obviously allowed plants or or I should say spores to really become very very well adapted to dry environments so spores certain some of the obviously pollen grains they could uh they could last on land for for many many years in certain cases so that was an important adaptation to a terrestrial environment okay and when we look at the green algal ancestors as we talked before uh they share numerous uh characteristics so obviously chloroplast with photosynthetic pigments like chlorophyll A Chlorophyll B which you talked about in bio1 the carotenoids what else cell walls contain cellulose and starch typically stored in plastids as food reserves as we just stated coming on land there were certain problems like how are you going to keep your gametes moist how are you going to keep your embryos moist so we had to obviously evolve these structures that are called gametangia now we don't use the term gonads when we're referring to animals but these these uh structures that produce gametes we refer to as gametangia and it was the gametangia that allowed to allowed for gametes to be protected and to be moist and that sort of thing so there are two types of gametangia I can talk about antheridia uh which is the male gametangia that produces [Music] sperm and the [Music] archegonia which is the female gametangia that produces eggs and again these came about uh as an attempt to obviously protect and keep the gametes moist in a terrestrial environment let me erase some of this like the leaves obviously the embryos had to be protected and as I state here the egg is now fertilized within the female organ and that zygote now develops within the female organ uh and we now refer to these as embryophytes so any of the land plants are now known as embryophytes because their development the embryonic development takes place within the female gametangia which was again a a great evolutionary development they could be protected and obviously they can be uh kept moist so if I ask on an exam uh what is a synonym for uh embryophytes you will tell me uh land plants all plants exhibit what we refer to as alternation of uh Generations and I can show you this very very nicely I'm not going to read all of that I can show you it very very nicely with this graphic right here in the world of plants there are two generations you've got the gametophyte generation which is always haploid and if you look at the word gametophyte literally meaning gamete plant and this generation uh produces obviously gametes and you've got a generation that we refer to as the sporophyte and again we've got the word Spore plant as obviously it produces spores gametophytes are always haploid and sporophytes are always diploid and if you look at the world alternation you've got the word alternate to switch back and forth sporophyte to gametophyte gametophyte to sporophyte all the plants exhibit what we refer to as an alternation of generation then botantists ask the question which generation is dominant and what they mean by that which one is the most conspicuous which generation does uh does the plant most of its life as do they spend most of their life as a sporophyte or do they spend most of their life as a gametophyte and we're going to examine that uh in one minute okay so sporophyte as you can see here multicellular diploid under goes meiosis a reduction division to produce haploid spores spores uh obviously are dispersed they land on the ground they undergo mitosis and now develop into the gametophyte generation and as we said before that's their n okay uh the by the process of mitosis we produce gametes now I want to I want to say one thing in in bio1 you may have talked about the fact that we always produce quote always produce gametes by meiosis yes in human beings whales and box turtles but if you're a plant you produce gametes by mitosis those gametes fuse together fertilization you form a zygote that zygote under goes mitosis and voila we go back to the sporophyte generation okay so this is what we mean if you've got this schematic down this is extremely simple that again is a kind of a verbal uh explanation of what's going on but I think this this shows it extremely well what we mean by alternation of generations we then ask the question what is the difference between gametes and what's the difference between spores uh they're both small and they're both obviously haploid uh the difference between uh the Spore and the gamete is spores do not have to fuse with other cells with other spores to form an individual gametes have got to fuse with another gamete to form an individual so basically if I ask that on a test you'll know the difference between what do we mean what is the difference between spores and gametes let me erase this land plant philogyny remember we we had defined philogyny as evolutionary [Music] history and there are four big periods and again they opened up new adaptive zones for plants for organisms that are living on lants it completely changed when plants came on to land it completely changed the biosphere and the ecology and all the interactions that took place so let's go through the the four big periods uh origin from Aquatic ancestors like we said before previously we believe that the earliest ancestors of plants were the charophytes again about 475 million years ago and again we talked about the fact that they the evolution of these gametangia these gamete producing structures evolved as an attempt to keep the gametes protected and moist the evolution of vascular tissue okay when plants came on to land obviously you had to have water and minerals going up the plant roots evolving mining literally water and minerals and then uh you know xylem bringing up water and minerals up the plant and then you had the evolution of flum vascular tissue right bringing sugars obviously food uh from the leaves down the Plant so the whole evolution of vascular tissue to conduct water and obviously nutrients throughout the land plant the diversification of the next thing diversification of seedless vascular land plants okay so we had things like Ferns and we're going to talk later about the the Carboniferous forest and that sort of thing okay so seedless vascular plants like FMS the origin of the seed which was perhaps one of the greatest evolutionary inventions which now allowed obviously plants to uh uh develop this propagule uh with an embryo right protected by a seed [Music] coat and a food supply we call endosperm or starch they could be deposited on land and uh obviously uh they could stay dormant for quite some time until the conditions uh improved so this was quite an evolutionary Advanced now uh plants could really survive very well under all sorts of conditions on land okay and some of the earliest of them bore seeds as naked structures uh on cones and we call them gymnos sperms uh and uh conifers and ferns coexisted uh for more than 200 million years so uh these were some of the great early adaptations and then finally you had the Glorious flowering plants about 130 million years ago with the extinction of the dinosaur enter now the flowering plants and now you've got the these plants literally bearing seeds within the protective uh obviously uh ovaries uh this gymnos sperm meaning n nak seed the seeds were basically naked on some sort of cone likee structure and angiosperm literally meaning container seed referring to the fact that the seeds were now uh within the protective ovaries within the container if you will the ovaries and most of our uh you know we have hundreds of thousands of of uh flowering plants and and most of the Contemporary plants are uh the flowering plants and I know we're being a little redundant here again the uh the common ancestor of plants or what we refer to as the the kopites uh based on looking at uh the green algae cell wall composition the structure and pigmentation of the chloroplast uh and again uh the to reiterate carites we do believe to be the closest living uh relative of plants especially the carites the genus zigna and then choit adaptations to shallow water water let it is doubtful that algae just came on to land that would be extremely drastic and extremely harsh they were probably pre-adapted for living in shallow water in other words they were probably in environments where it rained for perhaps 6 months and then it was dry for 6 months we see this in in Florida with uh the genus Cara which I talked about musk weed or or skunk weed uh Cara can be obviously uh in the ditches filled with water in summertime and the winter time when the ditches let's say in Central Florida dry out Cara uh can exist and do extremely well so they were probably pre-adapted uh uh uh living in shallow water for life obviously on land okay it is doubtful as we said before that they that they literally uh just came on to land okay uh and again 440 million years ago you had glaciations you had climate changes that cause great fluctuations in in water they clearly had to survive this uh selection clearly favored those that uh could exist in shall water that dried up and uh if they were able to exist then obviously uh they were very well suited for coming on to land okay and again some of the adaptations we see in plants for terrestrial existence to resist desiccation would be waxy cuticles protection of the gametes protection of developing embryos eventually all these great uh adaptations accumulated and you had to and you had plants that were what were very well adapted for life on land okay um and I I talk about the fact that sunlight unfiltered uh by water and algae if you're an algae kind of floating around in the water you've got water over you uh that's protecting you from ultraviolet radiation millions of years ago we we believe that the sun was extrem extremely intense there was lots of ultraviolet radiation and uh and uh uh when you live in the water you have a layer of water on you that's basically going to repel that Ultra intense ultraviolet radiation but when plants came on to land they didn't have that protection initially okay uh soil obviously uh rich in Minerals Well now you're going to have to evolve Roots like we said before you've got to evolve roots and this was interesting absence of terrestrial herbivores when plants first came on to land obviously there were no herbivorous insects or animals and that sort of thing because why there was no uh there was no what there were no plants therefore there were no herbivores over time uh herbivores evolved they found a new food source so now plants had to evolve some sort sort of mechanism to repel herbivorous animals and so you had things like secretions you had things like Thorns you had all sorts of uh chemicals that may be produced that are going to repel herbivorous animals but again we make the point when plants initially came uh evolved on land there were no herbivorous animals and then plants had to evolve these these chemical adaptations to repel obviously herbivorous animals yes we expect you to know this chart the only part of the chart you don't have to know is obviously number of known species that's for your edification to show you that well when we look at horn warts there's only a 100 species but then when we look at mosses there's 15,000 species or so just to give you an idea as far as relative numbers so again we basically break down plants into nonvascular plants collectively known as Brites uh and their various lineage or clay names you have to know uh HEPA hepato meaning liver fyam meaning plant the liver warts liver plant bopa are the mosses and anthos the horn warts okay collectively these are known as Brites do not confuse Brites and bopa briaa is a single lineage exactly the Mosses but when we say Brites the term Brites can mean any nonvascular ular plant be it liver wart Moss or horn warts and then we've got obviously the vascular plants as we said before the vascular plants uh include seedless vascular plants and seed plants and again having vascular having vessels right [Music] now with these nonvascular plants not having vessels although admittedly some of the Mosses uh have vessels but they don't have xylem and they and they don't have FL okay uh but in the case of the vascular plants you've got xylm and you've got flum uh in these cases they rely on things like osmosis and diffusion they're not that far removed uh from the green algae actually uh the Brites are sometimes called the [Music] amphibians of the plant world because they have to have some moisture for reproduction and many of these things of done a flatulate sperm they're not that far removed from aquatic environments they're typically found in in low wet areas damp woods and that sort of thing vascular plants again you can be seedless vascular relying on spores and then obviously your seed plants where you've got your gymnosperms and uh you've got obviously uh angiosperms here uh seedless vascular plants you've got uh lopa the lop phyes and then the Manila phyes uh we'll talk about ferns and their allies with the uh gymnos sperms we're going to talk about all of these we're going to talk about gko and pads and the nites and then conifers pine trees and that sort of thing and then like we said before angiosperms the most successful with 250,000 probably closer to 300,000 species and again as far as the Brites or nonvascular plants uh they include obviously mosses liver warts horn warts and you've got to know the words for these these clades or lineages I will use the term CLA and I will use the word lineage interchangeably or groups okay I'll use that interchangeably that's the common names right if I've got something like an phospherous which is a horn wart if it's a Genus we're going to underline it or we're going to italicize it if it's not underlined or italicized it's some group lineage or clay which throughout the course I will use interchangeably okay what's interesting about the nonas plants we're talking about alternation of generations that might as well tell you now the dominant generation the one that is conspicuous that it spends most of its life as uh the dominant generation is the [Music] gight and I will go through these life cycles but I want to state that right now the haid gapy is the dominant gener ation okay uh and again we talk about this as a PIV pivotal adaptation the Brites again amphibians of of the plant world because they they really they're in a in a in a terrestrial environment but they do rely on moisture and certain aspects of a kind of almost an aquatic environment okay and again we talk about the fact that the antheridium which is the male gametangia producing flagellated sperm you still need a moist environment the aronium protecting the egg keeping keeping it moist producing a single egg okay and then again the ioy condition emphasizing the fact that the development takes place uh within uh the aronium and and and is protected in that way okay again we we make the statement that that the Brites are not totally free of their ancest habitat and again we've talked about all of these things right here they're not that far from uh some of these aquatic plants and again they don't have lignin so they've got this lowprofile this sprawling situation uh they're not going to be able to come become you know 300 ft like the size of a sequoia tree or an oak tree uh because the fact that they just cannot supp support these tall plants they lack the Woody tissue they lack alifi tissue okay again the gapy is the dominant generation you're going to find a lot of these are redundant but I don't mind them being redundant because we're emphasizing them let's talk specifically about the Mosses cover about 3% of of the surface of land V vast amounts of organic uh carbon literally tied up in in the in in mosses again uh they don't have uh vascular tissue but when you look at these Riso you look at these elongated uh filaments they allow the to literally anchor down much the same way as advanced plants use use Roots okay photosynthesis occurs Mo mostly in small stemlike and leaflike structures notice I say stemlike remember if it was an advanced plant in the stem it would have vascular tissue leaflike they're not true leaves they don't have vascular tissue so stemlike and leaflike and again these structures are not homologous with stems and leaves found in vascular land plants uh examples I want you to know notice we're um italicizing this the genus poly Trickum the genus n not minium and spum many of you perhaps have heard of spagna bogs or spagna moss and here's the genus poly Trickum for those of you who are going to be in the physical lab looking at these things and this nice ly illustrates the gapy generation that is quote the green moss plant that you see growing in the woods or under shaded situation sometimes what you're going to see is you're going to see this stock with a capsule at the end of it that's the sporify there's the sporify which you don't see all the time which is the diploid generation and there's the gapy which is it's a hloy generation this sporify literally parasitizes this gapy it derives the nutrition from there so very nice uh photograph showing the gapy generation the green moss plant itself and the sporify generation so then we put this alternation of generation that schematic we we showed you we put it to music well maybe not exactly music but now what does it all mean okay so here we go uh we're showing the male gight okay uh we're showing female gapy generation okay you got to know the terminology the gametangia remember the male gametangia the male G uh producing structure is called the antheridium it produces flagellated sperm and when we say a moist environment a lot of times all you need is literally raindrops falling that are going to carry uh the flagellated sperm from the antheridium of the male gapy to the aronium of the of the of the female gapy now remember it's not that it's going this great distance they separated them par remember they form tight packs like that so they're literally NE to each other okay and uh and literally that flagellated sperm swims down uh fertilizes the egg within the aragonian right we're emphasizing the embryo fide condition right that obviously land plants have that the development occurs within the aronium within the uh female uh organ after fertilization of the egg you've got a zygote forming that zygote under goes mitos is you've got an embryo that forms and literally now you've got a young sporify that's going to come out of that gapy and this is what we just showed you here is the sporify generation here is the gapy generation okay you should be able to identify in each of these what's the sporify what's the gapy okay when you look at the capsule here up close what's interesting about it is it's got this little what I call party hat but we won't write party hat on the exam it's called the operculum which is biology speak for cover or lid and what happens is if this is the capsule and this is the operculum right here uh what happens over time is this going is going to loosen and what happens the basically that operculum comes off okay basically the operculum comes off is blown off okay and if the wind is blowing what happens typically uh your capsule will have these teeth come out and kind of uh erupt what we ref refer to as the peristome teeth and when those parastone teeth uh come out they in a very very controlled way will release the spores and uh when the wind is blowing the spores will be carried a great distance uh this was a nice mechanism for kind of thrusting the spores out you want your spores away from obviously the parent plant so as to cut down competition the spores land okay and now what forms is what we refer to as the protonemata which is nothing more than a Spore that is now germinated and it kind of looks like filamentous green algae okay and and biologists have talked about the fact that there's might be some of your evidence of your alal uh ancestors so it very much looks like uh filament is green algae at the stage is called the protonema which is a Spore uh that uh has begun to germinate and then it's going to obviously develop into the gapy uh generation I like to ask on Tess uh is the protonema uh haploid or is it diploid and the answer is it's haploid because remember think of this kind of like as an immature gapy it's going to develop into the gapy and the gapy is n is haid so protonema is going to be n or if you want to think of it as a Spore that's just germinating it's it's it's n okay and then we go back to that so there we go with the alternation of generations uh alternating between obviously the diploid spori and the haid uh gapy right there