And now we're going to talk about seed plants and uh seed plants further transformed the Earth and uh again, more uh organisms uh depending on plants, plants again interacting with all sorts of organisms, and now we see plants as uh the primary producers, the the principal producers in the ecosystem in other words, supplying food on land to uh herbivorous animals, the photosynthesizers, the autotrophs, so they become super important uh there are many reproductive adaptations of seed plants and uh obviously furthering more of their terrestrial or Earthly success you've got the reduction of the gametophyte uh, I go on to say they were retained in the moist reproductive tissue of the sporophyte generation and we'll show you that there not independent uh like we saw in uh some of the the lower plants, you have the origin of the seed which we said was a a great advance because now you've got your embryo uh protected by a seed coat package with a food supply starch we call endosperm so this was a great advance for living on land and surviving well on land um and uh I go on to say that seeds really did replace uh spores as the main means of dispersal. Spores are fairly hardy but you've got to remember that uh that seeds are multicellular. Spores are unicellular, they're less flimsy uh compared to uh spores uh and then the evolution of pollen this is a big one right here. Plants were no longer tied to water for fertilization. So if we look at something like Pinus pollen which is the pine tree the genus Pinus obviously the um pollen grain is wings so that it could be carried by wind it it's going to land in the female cone and obviously it's going to produce what we refer to as sperm nuclei and then obviously they're going to be conducted into the female cone. The reality is you no longer needed water for uh fertilization and we use sperm nucleus because again they're no longer flagellated so by the time you get to these advanced plants by the time you get to the seed plants you no longer needed water for fertilization and it was the the uh pollen that allowed for now the uh the u transport of gametes. The gametophytes of sea plants became even more reduced than the gametophytes of seedless vascular plants uh and again uh we know uh the the idea that now the sporophyte is the generation the dominant generation when you see a pine tree in fact you are looking at the sporophyte uh generation. Um it's interesting to note in this this concept here the dominance of the diploid generation may afford protection from solar radiation induced uh mutations of the genome. Uh what we're saying here is when you go back and you uh look at the green algae, the Charophytes, remember they were covered by water, uh ultraviolet radiation was extremely intense back then you now have them covered by water they were protected okay? When plants uh came onto land and you had things like like your Bryophytes right? Things like mosses and liverworts and hornworts and that sort of thing, they live in a moist environment they even have moisture on them so they're somewhat protected but when you get to more advanced plants literally coming onto full-fledged soil uh uh you know um earthly situations not just uh uh you know uh water dominated, now you had obviously ultraviolet radiation that was extremely intense and uh uh UV causes mutations. Well now, it would be nice if your vascular plants, your advanced plants, had two complete sets of chromosomes, were diploid, in case what? One of the sets of chromosomes or some of the chromosomes fried by ultraviolet radiation. Uh again, damaging radiation is more extensive on land than in aquatic habitats so the sporophyte became dominant, why? Because you had two sets of chromosomes so that in case some of these chromosomes became damaged by extensive ultraviolet radiation you would have a backup set. At least that's what biologists for the most part believe. In seed plants, the seed replaces spore as a main means of dispersal we talked about that seeds were hardier uh because of their multicellular nature, we talked about this, I would underline this, all seed plants again I'm I'm emphasizing this are heterosporous and again I'm not going to go through this because we already talked about megasporangia producing megaspores, microsporangia producing microspores...and the development of the seed is associated with the uh the megasporangium uh but we we're using the term megasporangium you're you're imagining this is a chamber, but it's not a real it's not a chamber at all it's actually a fleshy structure that we call uh the nucellus uh I'm going to show you the integuments that surround the megasporangia that contribute to the protective coat that's going to be ultimately become the seed coat and now we're going to have a structure that we call the ovule, and the ovule consists of the megaspore, the megasporangium and the integuments, let me show you that. So here we've got for instance an ovulate cone, a female cone. Now what we're going to do is we're going to again this is a pine cone and uh what they have done is uh and you can actually see this under the microscope they have enlarged this ovule, okay, and this is an unfertilized ovule, and again you see the megasporangium, the megaspore, and the integument. It's interesting to note what happens to this upon fertilization. So I like I said before by the time we get to these advanced plants you no longer needed water for fertilization here's the male gametophyte, which is uh literally the pollen grain and it may be hard to see but again that pollen grain in Pinus has got kind of wings on the side. That's going to land inside that female cone okay, and basically what's going to do as we said before you're going to have a pollen tube and it's going to discharge what? Sperm nucleus. So that sperm nucleus is going to fuse with that egg nucleus. Fertilization is going to take place, okay? There's the female gametophyte, okay? Now what's interesting to note is this female gametophyte ultimately is going to become the food supply that's going to become the nutritive tissue for that developing embryo, which is the sporophyte. Upon fertilization you now have a seed. What is a seed? A seed is nothing more than a fertilized ovule, okay? So here we've got the ovule with obviously the integument, the megaspore, the megasporangium, fertilization takes place okay, uh we've got the development of the female gametophyte and then upon fertilization of of the ovule, you now have the formation of of a seed, consisting of as we showed you before the embryo, the food supply, uh and obviously the seed coat, which was originally from what? The integuments right there. Okay so this nicely shows literally from unfertilized ovule, fertilized ovule, to ultimately the formation of a seed. Again we talk about pollen becoming vehicles for sperm cells, uh pollen grains are coated with the resistant sporopollenin, we've talked about this pollen grains uh can be carried by wind or animals, put an L there like bees...okay it's interesting to note here in some gymnosperms, for instance Cycads, the sperm cells are flagellated. I'm going to add one to that, we'll talk about the Cycads later. I'm going to add the interesting primitive gymnosperm that we call Ginkgo biloba So uh two gymnosperms that actually have flagellated sperm, the Cycads, check, and Ginkgo biloba and again they're maintaining their ancestral condition. But your other gymnosperms and angiosperms do not have flagellated sperm. So when we talk about seed plants, I want you to know the Cycads and Ginkgo biloba are the only ones that have flagellated sperm. Gymnosperms...which literally means "naked seed" because the seed is not contained within an ovary, hence naked seed. Uh again the Mesozoic was truly the age of gymnosperms, uh was also the age of dinosaurs of people interested in animals that sort of thing and they appeared obviously much earlier than the flowering plants um and again I'm going to say that gymnosperms lack enclosed chambers, ovaries, in which the seeds develop we talked about that, I will hold you to four extant groups of gymnosperms: the cycads, the ginkgo, the gnetophytes and the conifers. First let's consider the first one, Cycadophyta. Um if if I ask you for the complete name, the group is called the cycads, but if I ask you for the complete technical name on an exam the complete technical name of the group, or clade, would be Cycadophyta. This is kind of a a collective term common name for the group technically known as Cycadophyta. Uh 300 species tropical subtropical absolutely slow growing uh I really like this group um many of them are highly endanger there's a big black market on them they live some of them on mountain ranges or in very desolate places uh there is a lot of poaching of these things so unfortunately they're highly endangered highly endemic and many of them are are extremely interesting uh they're fern or palm-like in appearance many of you know in people's yards the "Sago Palm" right if I can if I can pull up for a minute some of the cycads, the reason I want to pull these up is because every Floridian, unless you got here 5 minutes ago, has seen these on the front of people's yards right or side yards that sort of thing. Oh look at the nice palm tree, they're not palms remember palms are flowering plants they're angiosperms, these are gymnosperms and uh they go they're living fossils they go back literally millions of years to the Mesozoic, so they are very very palm-like uh in appearance but they're not palms and again they've got that very very characteristic cone which is so typical of gymnosperms. Flagellated sperm, remember that was one of the few seed plants that have flagellated sperms along with obviously Ginkgophyta, 75% are threatened by habitat destruction human other activity we talked about this. I'll hold you to our only native cycad, which is planted all over campus here uh you can find it in certain places in Florida growing wild, Zamia integrifolia, the common name is the Florida Coontie, again genus and species and notice it is italicized, there's the common name, the next one: Ginkgophyta, represented by one species Ginkgo biloba, native to China, you' be pressed to find one growing in the wild in China uh if you go to places like Central Park in New York especially in the fall beautiful yellow leaves that are so characteristic, fan-shaped leaves and uh it's illegal to plant the female version in many places because the fleshy seeds contain butyric acid, which literally smells like vomit, but the reason they plant them in places like Chicago and New York is because they're very very tolerant of cold weather and they're very very tolerant of uh uh pollution and that sort of thing and again many perhaps have heard of this as a medicinal plant to increase memory and that sort of thing so Ginkgo biloba one species. Uh the next group: Gnetophyta, and it's a wonder that they're actually grouped together when you look at them but from the level of DNA and looking at the molecular aspects they obviously uh should be grouped together I will hold you to three genera: the genus Gnetum and again the "G" is silent, the genus Ephedra, and my favorite here Welwitschia or Welwitschia mirabilis, let's take a look at these and we show them with little pictures although these pictures are quite tiny, Ephedra, Gnetum, and Welwitschia, Gnetum can exist as a tree or vine and again, Africa, Asia about 35 species, I think we have a a species of Gnetum in the greenhouse, Ephedra, many of you perhaps have heard of the drug of ephedrine, many years ago was used obviously as a weight reduction drug, uh desert semi- desert area, uh I'll hold you to Ephedra viridis, Mormon tea produces ephedrine, which was used medically as a decongested weight control and that sort of thing as well uh and then the genus Welwitschia, one species Welwitschia mirabilis, uh Southwest Africa the Namib desert...literally radiocarbon dating up to 3 thou- uh up to 2,000 years maybe even pushing 3,000 years you basically and we had one many years ago you've got two strap-like leaves and uh and a long tap root, some botanical gardens attempt to grow them in pipes because of the very very long tap root, and what happens is these strap-like leaves which are some of the largest leaves of any plant in the world uh over you know if you're 700, 800 years old they're going to shred living in the Nami desert and it look it's going to look like many many leaves but it's originally just the two strap-like uh leaves very very interesting, probably one of the most bizarre plants in the world [PAUSE FOR BREAK] Okay, Coniferophyta the conifers. Conifer, literally meaning "cone bearing," largest group of gymnosperms uh we living in the Southeast here Pinus is the genus for the pine, some of you perhaps up North firs, spruces, larches may not be in your vocabulary if you live in Maine or New Hampshire you may know them use we use ornamentally junipers we have in Florida, cedar yes, cypress we have, redwoods out in California, so it's not not just pine trees, there's a whole suite of trees that are known as the conifers. Uh there are a lot of superlatives the tallest one is is the redwoods, I was just looking at this don't know how eucalyptus which is not in this somehow this got here but take that out eucalyptus uh the largest of the trees the giant sequoia, the oldest uh actually the oldest organism on the planet the bristle cone pine, uh so a lot of superlatives with with the conifers, if you go into Lowe's or you go into Home Depot you'll notice that most of the lumber actually is conifer wood you talking about pine or spruce or furring strips uh and then paper pulp comes from so economically conifers are extremely important and again uh needle-shaped leaves for dry condition so yes when you look at this uh I don't care if it's shaped like a little needle we still consider it a megaphyll with highly branched um vascular tissue so uh up North obviously uh especially tundra and boreal uh forest up North where it snows most of your water is locked up as snow and ice and and especially in cold climates when it can be uh cold uh air dry air that's blowing on this you're going to have a great loss of water from the leaves so it makes sense that your leaves are going to be slender, less surface area, they're going to have a thick cuticle which will keep them from drying out, the stomata, the stomates, those little openings are now going to be obviously in pits or depressions that's going to reduce water loss, so the whole design if you will adaptation of these needle-like leaves are especially for conifers that live up in uh up North where dry conditions or even in Florida during dry season okay this is interesting uh we're showing the uh some of the aspect of the life cycle of the pine or not the actual life cycle but we see some of the things that are involved in the life cycle of the pine and we've got words like seed cone here and we've got pollen cone and we've got young seed cone, so so basically we can talk about male uh uh cones let's and again we can say uh we can say Pinus although you can do a number of Evergreens like that Pinus the cones uh male and female remember when we use the word "micro" right so micro is male as I said previously, microsporangiate cone, obviously this pollen cone produces microspores, those microspores are going to uh become pollen grains, and then the pollen grains are going to produce the sperm nuclei. Okay microsporangiate cone or pollen cone I'm giving you synonyms...or staminate cone again uh the botanical word stamen signifying male, pistol signifying female so this could can be called called a microsporangiate cone, a pollen cone, or a staminate cone. Similarly when we go to the female cone, we can use the term megasporangia cone to denote the cone is producing megaspores, a megasporagiate cone, or ovulate cone, or seed cone, I don't much use seed cone in the class but I see it here okay that's a good one, or now pistillate cone, from again the botanical term pistol which denotes the female, okay, so I want you to know all these cones, cones sometimes called strobilus, plural strobili, lots of synonyms in biology, we don't have any shortage of terms in biology. We're all familiar with the typical pine cone that's your ovulate cone but look up in the trees particular times of the year you all seen pine pollen all over the car and sidewalk and that sort of thing and now you know obviously that uh pine pollen is responsible for ultimately production of sperm nuclei, okay, so when you're out there look up at the pine trees you will see these various cones...again I am not going to read all this this is probably uh a lot of it redundant again as you might imagine it is the sporophyte generation that is the dominant generation, it's a vascular plant when you actually look at a a pine tree that is the conspicuous sporophyte generation uh again multicellular gametophyte is reduced and develops from haploid spores retained within the sporangia, again I'd underline this it is the male gametophyte, or the male gametophyte is the pollen grain, okay, as we said before cuz I'll ask what's the sporophyte, what's the gametophyte of the various plants there is no antheridium, the female gametophyte consists of multicellular nutritive tissue, and an archegonium that develops within the ovule, we showed you before uh we showed you the fertilized ovule uh with the nutritive tissue and I said originally came from the female gametophyte. The cycles are heterosporous of course they're heterosporous they're typical uh uh you know seed plants okay again I I go over this because we go over it in the beginning but now I want to go over it as we do each plant section, okay? Um I talked about this already okay so all of the all of this we have stated this uh I am not uh it's interesting I'm not going to go through the complete description here, but uh because you can follow, again I'm big on charts I'm not reading all of this you can look at the Pinus life cycle and then look at this uh and see what's going on, but I'd rather reduce it talking about uh as it relates to a u uh to a diagram okay, but it does take nearly 3 years to complete the the pine life cycle and uh now that you've seen a number of life cycles this one does not seem as intimidating. The one part I do want to I I do want to call to your attention here is there are two phenomena that are going on, there's pollination and there's germination. Two things going on, pollination and germination. More than a year after pollination the eggs are ready to be fertilized. Two sperm cells have developed and the pollen tube has grown through the megasporangium the nucellus to the female uh gametophyte and then fertilization occurs when the sperm nuclei unites with an egg nucleus. Let me show you that in picture form uh rather than uh I like the verbal description, but that verbal description is for you. This is uh much more meaningful so let's point out the high points here. Here's a mature sporophyte, the pine tree. You know know you now know we've got the pollen cone, the male, the ovulate cone, the female and again I don't the the microsporocytes uh you don't actually have to know that terminology I like I like the the term uh microspores you know I you know there's obviously at varying times in the development there are there are various terms use I'm fine with the you know uh microspores. The microspores as we pointed out will become the pollen grains right that's your uh that's your male gametophyte, the pollen grains which are winged. Here's the ovulate cone right? Female. There's a section of that, there's the ovule I showed you that earlier, I showed you the ovule, when that ovule uh becomes uh fertilized it's going to produce the seed so as you might imagine there are seeds that are going to be produced in this cone, winged seeds that are going to be carried by the wind okay? What they did here is they took out a scale right uh a which is a modified leaf literally, the scales of the pine cone or modified leaf here's the integument we pointed that out that's going to be uh that's going to become the uh seed coat again here's the megaspore here's the megasporangium and now you've got the pollen grain okay? Basically they're showing uh meiosis, you've now got a uh a surviving megaspore, and now here is the female gametophyte. That is ultimately going to become the nutritive tissue uh in the seed for the developing embryo okay? Pollination has taken place and now fertilization. So what do we mean by pollination? Pollination means that the pollen has landed inside the female cone okay? More than a year after pollination, now fertilization occurs that's when you actually have the pollen tube growing uh into the female portion and now you've got uh the discharge of sperm nuclei okay? So pollination, fertilization takes place uh the discharge of the sperm nuclei and now fertilization takes place okay with the development of an embryo there's your seed coat and there's your food reserves folks this is the seed three parts of the seed, embryo, seed coat, food reserves. Notice here we've got obviously these seeds which are going to be winged they're going to be uh dispersed uh from the cone, they land on the ground they they uh germinate, there's your young sporophyte and there's your mature sporophyte. Uh but again the the most interesting thing is to see that this thing takes 3 years uh the complete life cycle because you've got pollination and then a year and a half or so after that now fertilization takes place.