Plant Evolution Transcript

  • MarySusan Potts-Santone: Alright. Let me go over a couple of quick announcements.

    0:03

  • MarySusan Potts-Santone: Today we are going on into plant evolution. No, it's not on tomorrow's test.

    0:05

  • MarySusan Potts-Santone: All right, plants will be the focus of the 3rd exam. In fact.

    0:10

  • MarySusan Potts-Santone: there are a couple of reminders about your second exam.

    0:14

  • MarySusan Potts-Santone: There are some videos that you're responsible for the microbes within us was the longest you need to pay attention to that as if it were a regular lecture. So take good notes there.

    0:17

  • MarySusan Potts-Santone: bobtail squid we did for our in-class activity.

    0:26

  • MarySusan Potts-Santone: All right. So make sure you're up on that one. It was a short video you need to pay attention to again the things that we talked about relative to that video. The malaria lifecycle illustrates what we focused on for the malaria, the organism's life cycle plasmodium. There were 2 videos, one in the mosquito, one in the human and both are short. And then the Wood wide web is just an illustration of the relationship between the fungus underground and the network of trees in a forest, for example.

    0:30

  • MarySusan Potts-Santone: But basically, when you think about mycorrhiza that came a little bit later in fungi. Again, the idea is that virtually all of our lamb plants

    0:59

  • MarySusan Potts-Santone: that association with fungi, and again, that facilitates their development and growth and life cycle on land. And again, we're going to continue to talk about plants going forward.

    1:09

  • MarySusan Potts-Santone: I told you about your exam. One grades.

    1:20

  • MarySusan Potts-Santone: Exam, 2 is tomorrow. The review sheet's been available.

    1:22

  • MarySusan Potts-Santone: If you see things on the review sheet that you don't recognize, feel free to ask me about them again. Those get put out early

    1:26

  • MarySusan Potts-Santone: the focus of tomorrow's exam. Lots of diversity

    1:33

  • MarySusan Potts-Santone: viruses, bacteria, Archaea protists, fungi.

    1:36

  • MarySusan Potts-Santone: All right. I know that there's a lot of new organisms for most of you in this group.

    1:41

  • MarySusan Potts-Santone: It's 1 of the things that makes this exam probably more challenging than either the animals or the plants, because you've heard about animals and plants in your biology careers before now, but not necessarily about all of these organisms.

    1:46

  • MarySusan Potts-Santone: Format wise. Expect 50 questions, multiple choice, true, false, matching. Expect that there'll be some pictures or so.

    1:59

  • MarySusan Potts-Santone: you know, scattered around on canvas. Check your respondents tonight if you think about it so that you don't run into any issues of updating tomorrow. I never know what respondus is doing in that regard. But again, you'll get the passcode when you come into class. You have to be physically present in class to take the exam

    2:06

  • MarySusan Potts-Santone: office hours tonight on zoom the links on our homepage.

    2:26

  • MarySusan Potts-Santone: Remember, the tutoring's been available.

    2:30

  • MarySusan Potts-Santone: and if you got a progress report from me last week. I haven't heard from too many people I expect to hear from you. If you get a progress report.

    2:32

  • MarySusan Potts-Santone: either pop by office hours reach out by email. Again, we want to check and make sure that you're on track. Taking advantage of resources, do not just wait for another exam to go by and figure that that's going to correct itself. Okay, you really want to think about how you're studying how you're approaching the course. All right. Being here is important. All right. So again, we should have a conversation if you got a progress report from me based on your 1st exam score.

    2:40

  • MarySusan Potts-Santone: All right.

    3:07

  • MarySusan Potts-Santone: So questions about exam 2,

    3:08

  • MarySusan Potts-Santone: everybody good.

    3:10

  • MarySusan Potts-Santone: which ones

    3:21

  • MarySusan Potts-Santone: we didn't. Those weren't in the videos.

    3:29

  • MarySusan Potts-Santone: Yeah, they were there.

    3:33

  • MarySusan Potts-Santone: Okay, I was just saying I hadn't heard that one before. I would have expected to hear about that from you if it wasn't if we hadn't cut everything the day before the test. So yeah, go back and check those.

    3:35

  • MarySusan Potts-Santone: Yeah, make sure. Yeah, okay.

    3:50

  • MarySusan Potts-Santone: other questions. Anything in particular

    3:54

  • MarySusan Potts-Santone: don't hesitate to pop by office hours tonight.

    3:58

  • MarySusan Potts-Santone: Okay, if that fits your schedule. If it doesn't fit your schedule and you have questions again, you can get them to you by email, or we can try to set up something else.

    4:00

  • MarySusan Potts-Santone: All right. So let me know.

    4:08

  • MarySusan Potts-Santone: All right, let's get out of the business stuff

    4:12

  • MarySusan Potts-Santone: and let's head to.

    4:17

  • MarySusan Potts-Santone: If you're trying to figure out where we are in the syllabus. Yeah, I'm about a day behind. I know

    4:20

  • MarySusan Potts-Santone: it probably will never catch up at this point.

    4:26

  • MarySusan Potts-Santone: but we'll figure things out. We'll get it all in there, I promise.

    4:30

  • MarySusan Potts-Santone: Usually at this point in the semester. I'm always a little bit behind.

    4:34

  • MarySusan Potts-Santone: all right. So

    4:37

  • MarySusan Potts-Santone: we are moving into obviously a new group.

    4:39

  • MarySusan Potts-Santone: new supergroup as well.

    4:43

  • MarySusan Potts-Santone: We're getting out of the Apisiconta. Briefly, we're going to take a detour into the archiplastodon and talk about the lamb plants.

    4:44

  • MarySusan Potts-Santone: Okay? And then we'll come back and talk about the animals for the rest of the semester. Basically.

    4:52

  • MarySusan Potts-Santone: All right. So where are we here with the plants.

    4:56

  • MarySusan Potts-Santone: Well, this

    5:00

  • MarySusan Potts-Santone: slide shows you just a very small smattering of the tremendous diversity that exists

    5:02

  • MarySusan Potts-Santone: across the plants.

    5:09

  • MarySusan Potts-Santone: All right. The clade or kingdom is plant day.

    5:11

  • MarySusan Potts-Santone: all right. Tons of diversity, and I hope you get to appreciate the glass flowers a little bit when you go over to the Museum at Harvard. That is the only collection like that in the entire world. It is very spectacular, I think.

    5:15

  • MarySusan Potts-Santone: I can't imagine these were actually used as teaching specimens, but in fact, they were

    5:28

  • MarySusan Potts-Santone: so appreciate that.

    5:34

  • MarySusan Potts-Santone: And you should also appreciate plant diversity as you walk around Northeastern's campus.

    5:36

  • MarySusan Potts-Santone: because, as of 2019,

    5:42

  • MarySusan Potts-Santone: our campus was designated as a level 2 arboretum.

    5:44

  • MarySusan Potts-Santone: which means that we have to have over a hundred species of plants. In fact.

    5:49

  • MarySusan Potts-Santone: these are just a few of the most recent numbers. We've got 11.5 acres of arboretum out of our total 72 acre campus.

    5:53

  • MarySusan Potts-Santone: and our plant code is just under 2,000

    6:01

  • MarySusan Potts-Santone: with woody plant taxa coming in at about

    6:06

  • MarySusan Potts-Santone: 450, almost

    6:10

  • MarySusan Potts-Santone: all right. So we've got lots of plants to observe on campus.

    6:13

  • MarySusan Potts-Santone: Some of the leaves will start. Turning in our lounge, I saw the grounds crew, you know, busy with the leaf blowers when I was on my way over here?

    6:16

  • MarySusan Potts-Santone: In our biosphere more than 98% of all terrestrial biomass is, in fact, plants.

    6:24

  • MarySusan Potts-Santone: And how do we characterize them? How do we put them in perspective. They are multicellular, all

    6:30

  • MarySusan Potts-Santone: photosynthetic. They are autotrophs using energy and sunlight to run photosynthesis. You talked a lot about photosynthesis in bio one

    6:36

  • MarySusan Potts-Santone: and all of their cells are eukaryotic cells like ours.

    6:45

  • MarySusan Potts-Santone: So we've got something like 382,000 known species.

    6:49

  • MarySusan Potts-Santone: About 85 to 90% of those are flowering plants. We're going to talk a lot about flowering plants in particular, because they are the most successful.

    6:55

  • MarySusan Potts-Santone: Okay, we rely on them for lots of different resources.

    7:03

  • MarySusan Potts-Santone: But as you walk around campus, take note of the diverse plant life, we'll talk about some of the different categories. All of our plant life is marked by a metal tag that was some graduate student's job to go out and again identify. You can find the app that goes with it as well.

    7:07

  • MarySusan Potts-Santone: But if you're looking for even more diversity to explore

    7:25

  • MarySusan Potts-Santone: a short train, ride away is the Arnold Arboretum, managed by Harvard.

    7:29

  • MarySusan Potts-Santone: It was formed in 1872. It is the oldest public arboretum in North America.

    7:34

  • MarySusan Potts-Santone: all right. It is a spectacular collection, and this time of year it is really beautiful, but it's also really beautiful. I think in the springtime, when the lilacs are blooming, you can go, and, you know, enjoy the

    7:40

  • MarySusan Potts-Santone: nature out there. There's wildlife. You know there are paths you can picnic as long as you pick up all of your stuff. They've been various programs, but if you have not been there. It's a really cool place to explore. And again, it's the idea of, you know nature bathing is good for you. Remember the article that you read earlier in the semester. All right. So take advantage of some of the resources that we have in our immediate surroundings.

    7:52

  • MarySusan Potts-Santone: Without plans there would be no life on Earth.

    8:14

  • MarySusan Potts-Santone: Why do we say that we'd have no oxygen? Okay, they are responsible in large part for the oxygen that we rely on for aerobic respiration

    8:17

  • MarySusan Potts-Santone: they are thought to have evolved from freshwater green algae a group called the Charophytes, and that's why, in the Archiplasty we've got the Red algae, the green algae and the lamb plants all right. Charrophytes are also known as stoneworts, and this is kind of what they look like.

    8:27

  • MarySusan Potts-Santone: What are some of the features that are important in linking the chaurophytes to modern green plants.

    8:42

  • MarySusan Potts-Santone: a cell wall of cellulose.

    8:47

  • MarySusan Potts-Santone: It's 1 of the most abundant organic materials in the biosphere, because of all the plant matter.

    8:50

  • MarySusan Potts-Santone: Chlorophylls A and B allow them to run photosynthesis by absorbing the energy in those wavelengths of light

    8:55

  • MarySusan Potts-Santone: apical cells are at the tops of the plants. That's where they're going to be growing continuously from

    9:04

  • MarySusan Potts-Santone: plasma dismata are the connections between plant cells, the passageways that allow communication.

    9:10

  • MarySusan Potts-Santone: and then the placenta is associated with the embryo.

    9:16

  • MarySusan Potts-Santone: We're providing protection for that embryo as it develops, and we'll talk certainly about, you know, seeds and things as well. But the placenta is a group of designated cells that provide nutrients for a diploid zygote.

    9:19

  • MarySusan Potts-Santone: So keep those things in mind.

    9:34

  • MarySusan Potts-Santone: and we're going to look a little bit more closely. Now at the evolutionary history of plants.

    9:38

  • MarySusan Potts-Santone: we're going to talk about the major groups because each major group of plants we've got 4 non-vascular plants, seedless vascular plants, gymnosperms, and angiosperms, as our seed plants, and then angiosperms in particular, as our flowering plants

    9:42

  • MarySusan Potts-Santone: all are separated into these different groups by major evolutionary events.

    10:00

  • MarySusan Potts-Santone: we've got 4 major evolutionary events that again are associated with each major group of plants.

    10:07

  • MarySusan Potts-Santone: So here's our. And again, you don't need to know the Times on this. I marked them roughly in the yellow boxes

    10:13

  • MarySusan Potts-Santone: to help interpret this phylogenetic tree.

    10:20

  • MarySusan Potts-Santone: You can see geologic time in millions of years, you know, running along the bottom all the way up to present day.

    10:22

  • MarySusan Potts-Santone: So when we look at the ancient origins of plants coming from that green algal ancestor.

    10:29

  • MarySusan Potts-Santone: One of the 1st advances is nourishment of the embryo within the female plant. That's an advance that our nonvascular plants have over the green algae that they are related to

    10:36

  • MarySusan Potts-Santone: that particular event is one that came about roughly 500 million years ago.

    10:49

  • MarySusan Potts-Santone: And you'll see our early groups of plants include

    10:54

  • MarySusan Potts-Santone: these ones here known as the bryophytes.

    10:58

  • MarySusan Potts-Santone: They are also called the non vascular plants.

    11:01

  • MarySusan Potts-Santone: because they don't have vascular tissue. That's something that's going to be very important very soon.

    11:05

  • MarySusan Potts-Santone: But in the bryophytes we're going to talk about the mosses, the Hornworts, and the liverworts, mostly the mosses, because that's the biggest group.

    11:11

  • MarySusan Potts-Santone: Now.

    11:19

  • MarySusan Potts-Santone: if we skip forward in time.

    11:20

  • MarySusan Potts-Santone: Our next big group of plants are the seedless vascular plants

    11:23

  • MarySusan Potts-Santone: and the seedless vascular plants

    11:28

  • MarySusan Potts-Santone: evolved vascular tissue roughly 430 million years ago.

    11:30

  • MarySusan Potts-Santone: and the term vascular should remind you about your cardiovascular system.

    11:36

  • MarySusan Potts-Santone: When I say cardiovascular system hopefully, you're thinking immediately of your heart.

    11:42

  • MarySusan Potts-Santone: your blood vessels, your arteries, your capillaries, your veins, that transport your blood.

    11:47

  • MarySusan Potts-Santone: Well, vascular tissue in plants does roughly the same thing. There is no pump

    11:53

  • MarySusan Potts-Santone: but vascular tissue is transport tissue.

    11:58

  • MarySusan Potts-Santone: It's transporting water through the xylem. It's transporting organic matter through the phloem xylem and phloem are the 2 types of vascular tissue that led to plants becoming much larger, because now their parts could be farther away from each other, and farther away from the sources of water and nutrients, because we had these tubes that can carry material through the body of the plant.

    12:01

  • MarySusan Potts-Santone: So in our vascular plants

    12:28

  • MarySusan Potts-Santone: we have our seedless vascular plants that have vascular tissue

    12:31

  • MarySusan Potts-Santone: gymnosperms, and angiosperms, and flowering plants also all have vascular tissue, but again, they have other features as well, and vascular. Tissue is crucial for allowing plants to be of larger size

    12:34

  • MarySusan Potts-Santone: in the seedless vascular plants. In particular, we're going to talk about the lycophytes

    12:45

  • MarySusan Potts-Santone: and the ferns and their relatives.

    12:51

  • MarySusan Potts-Santone: Now, when you get multiple strands of vascular tissue.

    12:55

  • MarySusan Potts-Santone: and in particular the evolution of seeds.

    13:00

  • MarySusan Potts-Santone: Here you get to your seed plants.

    13:04

  • MarySusan Potts-Santone: So your vascular seed plants include the Gymnosperms and the Angiosperms.

    13:08

  • MarySusan Potts-Santone: All right. They are both producing seeds and seeds are a crucial innovation that came about roughly 300 million years ago, because seeds allow better dispersal.

    13:13

  • MarySusan Potts-Santone: They allow movement of the plant throughout the environment. Yeah.

    13:24

  • MarySusan Potts-Santone: yes.

    13:33

  • MarySusan Potts-Santone: yes.

    13:35

  • MarySusan Potts-Santone: yeah. We're adding to them kind of as we go through.

    13:37

  • MarySusan Potts-Santone: All right. So seeds are going to allow dispersal. They're going to allow the offspring to be farther away from the parents. And that's going to move them into different environments.

    13:43

  • MarySusan Potts-Santone: Okay, seeds are a crucial adaptation because they resist drying out. They protect the embryo. They provide an important dispersal mechanism as well.

    13:52

  • MarySusan Potts-Santone: And then, finally, we get to flowers.

    14:01

  • MarySusan Potts-Santone: Flowering plants. Okay, have seeds.

    14:04

  • MarySusan Potts-Santone: but they also have flowers to attract pollinators.

    14:07

  • MarySusan Potts-Santone: and those pollinators enhance reproduction.

    14:12

  • MarySusan Potts-Santone: and in particular the seeds in the case of the flowering plants are enclosed within fruits.

    14:16

  • MarySusan Potts-Santone: We're going to talk about fruit diversity we'll talk about. You know, pollinator diversity. Okay, but this the fruit is designed to attract the agents of seed dispersal, namely, animals.

    14:21

  • MarySusan Potts-Santone: to carry those seeds far and wide.

    14:30

  • MarySusan Potts-Santone: All right. So most plants, in fact, in our surroundings today

    14:33

  • MarySusan Potts-Santone: that 85 to 95% number, again, is made up of flowering plants because they are the group that is the most successful. They have all the previous adaptations, plus some new ones, and flowering plants evolved roughly 130 million years ago.

    14:36

  • MarySusan Potts-Santone: All right. And again, you can see some other characters that we're listing here in our phylogenetic tree.

    14:51

  • MarySusan Potts-Santone: But those are our basic groups.

    14:56

  • MarySusan Potts-Santone: Before we get into looking at the basic groups, we want to talk about the general life cycle for plants.

    14:59

  • MarySusan Potts-Santone: Okay, and that general life cycle involves something known as alternation of generations

    15:05

  • MarySusan Potts-Santone: in alternation of generations. You'll notice that

    15:11

  • MarySusan Potts-Santone: half the life cycle, roughly is spent in the diploid phase.

    15:16

  • MarySusan Potts-Santone: and roughly, half the life cycle is spent as haploid.

    15:19

  • MarySusan Potts-Santone: We have 2 multicellular entities over the course of the plant lifecycle.

    15:23

  • MarySusan Potts-Santone: One is diploid, one is haploid. So you get this kind of switching between those generations again over the life cycle.

    15:30

  • MarySusan Potts-Santone: All right? So again, later on, we can contrast that with the haploid life cycle for fungi. Later on we'll contrast it with the diploid life cycle for animals, all right. But this is the alternation of generations. Life cycle, again that plants follow.

    15:40

  • MarySusan Potts-Santone: So

    15:54

  • MarySusan Potts-Santone: let's start with what we generally recognize as the plant. So think about all the trees and the bushes and the flowers that you see on campus. Those, in fact, represent diploid sporophytes.

    15:55

  • MarySusan Potts-Santone: And when you're walking around campus you're seeing the trees. That's a diploid sporophyte

    16:07

  • MarySusan Potts-Santone: that is a multicellular individual

    16:13

  • MarySusan Potts-Santone: that produces spores by meiosis

    16:16

  • MarySusan Potts-Santone: is going to remember. Only in the diploid generation. Can Meiosis take place because meiosis is going to reduce the chromosome number into half

    16:20

  • MarySusan Potts-Santone: into haploid.

    16:28

  • MarySusan Potts-Santone: So

    16:30

  • MarySusan Potts-Santone: in the body of that plant.

    16:31

  • MarySusan Potts-Santone: in structures called sporangia.

    16:34

  • MarySusan Potts-Santone: that are situated within the flowers.

    16:37

  • MarySusan Potts-Santone: Okay, meiosis is ultimately going to take place

    16:40

  • MarySusan Potts-Santone: producing haploid spores.

    16:44

  • MarySusan Potts-Santone: And you notice we'd use the term spore a lot.

    16:48

  • MarySusan Potts-Santone: And we're talking about fungi when we're talking about plants. Okay, the spore is a haploid cell

    16:51

  • MarySusan Potts-Santone: that in the body of the sporophyte, for most plants within the anatomy of the flower, in fact.

    16:57

  • MarySusan Potts-Santone: that spore

    17:05

  • MarySusan Potts-Santone: goes through meiosis

    17:06

  • MarySusan Potts-Santone: and produces a haploid gametophyte.

    17:08

  • MarySusan Potts-Santone: That haploid gamitified is a multicellular entity.

    17:13

  • MarySusan Potts-Santone: You'd have to dissect the flowers to actually find it

    17:18

  • MarySusan Potts-Santone: all right, but it's in the body of the sporophyte for most plants.

    17:21

  • MarySusan Potts-Santone: and the gametophyde is a multicellular haploid entity

    17:25

  • MarySusan Potts-Santone: that through mitosis

    17:30

  • MarySusan Potts-Santone: produces egg and sperm

    17:33

  • MarySusan Potts-Santone: gametes.

    17:36

  • MarySusan Potts-Santone: haploid gametes.

    17:38

  • MarySusan Potts-Santone: Now

    17:41

  • MarySusan Potts-Santone: the egg in flowering plants is contained within the ovule. In the female anatomy

    17:42

  • MarySusan Potts-Santone: the sperm is actually contained in the pollen grains

    17:48

  • MarySusan Potts-Santone: all right. So when the pollen lands on the stigma of the female part.

    17:52

  • MarySusan Potts-Santone: a pollen tube will ultimately deliver the sperm, the male gamete gamete

    17:58

  • MarySusan Potts-Santone: to the egg for fertilization, resulting in the formation of a new diploid zygote.

    18:05

  • MarySusan Potts-Santone: Now for flowering plants

    18:12

  • MarySusan Potts-Santone: that diploid zygote is contained within the seed.

    18:15

  • MarySusan Potts-Santone: You plant the seed.

    18:19

  • MarySusan Potts-Santone: What does it grow into

    18:21

  • MarySusan Potts-Santone: a diploid sporophyte?

    18:22

  • MarySusan Potts-Santone: So if you were to take, you might have done this in kindergarten.

    18:25

  • MarySusan Potts-Santone: If you take the black watermelon seeds all right.

    18:28

  • MarySusan Potts-Santone: Those, in fact, are zygotes. Okay for the watermelon that we like to eat.

    18:32

  • MarySusan Potts-Santone: Watermelon's the fruit

    18:37

  • MarySusan Potts-Santone: all right. When you plant that, you get the you get the watermelon plants

    18:39

  • MarySusan Potts-Santone: all right. That is the diploid sporophyte.

    18:42

  • MarySusan Potts-Santone: and when the flowers again are pollinated

    18:46

  • MarySusan Potts-Santone: you end up with again a couple of rounds of mitosis mitosis occurs to produce the haploid gametophyte.

    18:50

  • MarySusan Potts-Santone: Mitosis occurs again to produce haploid gametes from that gametophyte.

    18:57

  • MarySusan Potts-Santone: and then the zygote. The seed okay, is the next generation, and through mitosis grows into the diploid sporophyte.

    19:03

  • MarySusan Potts-Santone: So you want to try to keep straight when you're looking at flowering plants again. You can't necessarily see all of the parts and pieces without some dissection going on, and closer inspection. But we've got 2 multicellular entities. The gametophyte is multicellular and haploid

    19:14

  • MarySusan Potts-Santone: typically contained within the body of the sporophyte. The sporophyte is multicellular and diploid

    19:29

  • MarySusan Potts-Santone: all right, and again, there are various mechanisms of protection

    19:37

  • MarySusan Potts-Santone: coatings around the seed coatings around the spores all right again to prevent things like drying out and to ensure their success.

    19:41

  • MarySusan Potts-Santone: because in order for plants to grow, they need water. They need light, they need carbon dioxide. They need support. All right. So again, we're going to look at some of the evolutionary advantages that plants have acquired adaptations that plants have acquired that have allowed them to be so incredibly successful.

    19:48

  • MarySusan Potts-Santone: So that's the basic life cycle.

    20:10

  • MarySusan Potts-Santone: Now, there are some differences to how that life cycle occurs over the over the different groups of plants.

    20:13

  • MarySusan Potts-Santone: What I just described to you mostly refers to this last group here of the Angiosperms and the Gymnosperms.

    20:22

  • MarySusan Potts-Santone: All right. So when you're seeing pine trees, those are gymnosperms. We'll talk about some other examples

    20:31

  • MarySusan Potts-Santone: when you're seeing flowering like the birch. Any of the trees that are dropping their leaves.

    20:36

  • MarySusan Potts-Santone: apple trees, any of the fruit trees that you might like again. Those are, in fact, angiosperms.

    20:42

  • MarySusan Potts-Santone: All right. Seed plants

    20:48

  • MarySusan Potts-Santone: all right, and what we recognize as the plant is the sporophyte generation.

    20:50

  • MarySusan Potts-Santone: So most of the plants you're going to walk around on campus and look at. Those are sporophytes. They are diploid organisms, and deep within their tissues is where ultimately the haploid part of the life cycle will exist.

    20:57

  • MarySusan Potts-Santone: You'll notice that comparatively, the sporophyte generation increases as we go from more primitive plants to more recent plants and more successful plants.

    21:11

  • MarySusan Potts-Santone: and the

    21:22

  • MarySusan Potts-Santone: gaminophyte generation in size decreases until ultimately it's contained within the body of the sporophyte.

    21:24

  • MarySusan Potts-Santone: So this alternation of generation life cycles, appearance

    21:34

  • MarySusan Potts-Santone: varies pretty widely across the different groups of plants.

    21:38

  • MarySusan Potts-Santone: so everybody's probably seen moss. At some point you might run across some campus, the bases of some of the plant plantings when they put them in the buckets.

    21:43

  • MarySusan Potts-Santone: sometimes in and around in the various beds and whatnot in and around some of the trees. You might see some

    21:53

  • MarySusan Potts-Santone: when you're looking at mosses, our most common group of bryophytes.

    21:58

  • MarySusan Potts-Santone: What we recognize as the plant is actually the gametophyte generation.

    22:02

  • MarySusan Potts-Santone: When you see a moss, you are looking at the gametophyte.

    22:08

  • MarySusan Potts-Santone: the sporophyte actually grows up from the body of the gametophyte.

    22:13

  • MarySusan Potts-Santone: producing spores that travel in the wind in the water.

    22:17

  • MarySusan Potts-Santone: and when they land, give rise to the next sporophyte. The next gametophyte generation.

    22:21

  • MarySusan Potts-Santone: All right. So their life cycle is a little bit altered.

    22:29

  • MarySusan Potts-Santone: and what we recognize as the plant is, in fact, the haploid generation.

    22:32

  • MarySusan Potts-Santone: the haploid gametophyte

    22:38

  • MarySusan Potts-Santone: when it comes to seed seedless, vascular plants.

    22:41

  • MarySusan Potts-Santone: you're going to think ferns as the most common example

    22:45

  • MarySusan Potts-Santone: we now have. The egg contained in a structure called the Archegonium, that provides protection.

    22:49

  • MarySusan Potts-Santone: and the sperm is going to have to swim to the egg in the Archegonium, across a film of water.

    22:56

  • MarySusan Potts-Santone: and that happens on the surface of the gametophyte generation.

    23:02

  • MarySusan Potts-Santone: which, in the case of ferns, is kind of low growing.

    23:07

  • MarySusan Potts-Santone: and looks kind of like heart-shaped.

    23:10

  • MarySusan Potts-Santone: and then from the surface of that gametophyte.

    23:12

  • MarySusan Potts-Santone: the fern fronds. Okay. The parts we recognize as the fern.

    23:16

  • MarySusan Potts-Santone: all right, are, in fact, the sporophyte generation. So you look like you've got kind of a 50 50 ish split here between again the gametophyte generation and the sporophyte generation.

    23:21

  • MarySusan Potts-Santone: But in seed plants.

    23:32

  • MarySusan Potts-Santone: angiosperms, and gymnosperms. What we recognize as the plant is the sporophyte.

    23:35

  • MarySusan Potts-Santone: and within the body of that plant the gametophyte is formed.

    23:40

  • MarySusan Potts-Santone: Okay, the female gametophyte forms the embryo sac. There's an egg in the ovule. Ultimately, at fertilization that ovule becomes the seed you plant. It gives rise to the next sporophyte generation.

    23:45

  • MarySusan Potts-Santone: So in seed plants, gymnosperms and angiosperms.

    23:57

  • MarySusan Potts-Santone: Pollen grains are the mature sperm bearing male gametophytes

    24:00

  • MarySusan Potts-Santone: and the embryo sac with the ovule is the female gametophyte so when the pollen lands on the female anatomy. Again, that sperm is delivered to the egg, you get fertilization, creating seeds within the flowers.

    24:06

  • MarySusan Potts-Santone: Right? So again, things look a little bit different, depending upon what type of play out we're talking about.

    24:20

  • MarySusan Potts-Santone: But in particular you want to remember the differences, and in the seedless vascular plants

    24:25

  • MarySusan Potts-Santone: what we recognize as the plant is. The sporophyte is the gametophyte.

    24:30

  • MarySusan Potts-Santone: and in most of the others what we recognize as the plant is the sporophyte generation.

    24:34

  • MarySusan Potts-Santone: But both parts are still there

    24:40

  • MarySusan Potts-Santone: now, living on land is a tough proposition.

    24:44

  • MarySusan Potts-Santone: because on land you've got lots of access to carbon dioxide in the atmosphere. You've got lots of access to sunlight much better than in water, in fact.

    24:47

  • MarySusan Potts-Santone: But the biggest limitation to life on land is that water is in much less supply than in the aquatic environment.

    24:56

  • MarySusan Potts-Santone: You're at much greater risk for drying out. Okay, if you live on land and we're going to talk about this for both plants, and later on for animals.

    25:05

  • MarySusan Potts-Santone: So terrestrial adaptations come about in plants evolutionarily because they are favored because they provide protection.

    25:13

  • MarySusan Potts-Santone: So we've got the egg within the Archegonium, ultimately giving rise to again the female gametophytes. All right, the eggs protected internally within the tissues of the plant.

    25:22

  • MarySusan Potts-Santone: Vascular tissue.

    25:35

  • MarySusan Potts-Santone: You can see phloem here you can see xylem here. They look like tubes. Okay, vascular tissue

    25:37

  • MarySusan Potts-Santone: transports water and nutrients throughout the body of the plant

    25:44

  • MarySusan Potts-Santone: on the leaves. We're going to have a waxy cuticle

    25:48

  • MarySusan Potts-Santone: that provides an effective barrier to water loss.

    25:51

  • MarySusan Potts-Santone: And then we've got openings on the undersides of those leaves to regulate gas exchange when the stomata are open, water can be evaporated or transpired into the atmosphere, but gases can be exchanged.

    25:54

  • MarySusan Potts-Santone: Why is the Gas exchange important? You need carbon dioxide to run photosynthesis. You need to remove the oxygen that's being generated.

    26:08

  • MarySusan Potts-Santone: Okay? But also you're at risk for drying out. So plants can regulate the opening and closing of the stomata in order to help retain water in the body of the plant.

    26:16

  • MarySusan Potts-Santone: And again, we'll see some of those features also later on.

    26:28

  • MarySusan Potts-Santone: Now, this is another version of the phylogenetic tree.

    26:33

  • MarySusan Potts-Santone: When it comes to modern plants, we've kind of tipped it on side.

    26:36

  • MarySusan Potts-Santone: And again, you can see the green algae that are the ancestors.

    26:41

  • MarySusan Potts-Santone: and the evolution of some of the characters that I mentioned. Like chlorophyll, A and B.

    26:45

  • MarySusan Potts-Santone: Starch in plastids.

    26:51

  • MarySusan Potts-Santone: cellulose, cell wall plasmodesmata.

    26:53

  • MarySusan Potts-Santone: And now we get into the alternation of generation life cycle that characterizes all of our plants.

    26:57

  • MarySusan Potts-Santone: So again, this is just a different version of looking at

    27:04

  • MarySusan Potts-Santone: the same thing we saw before. We've got the bryophytes as the nonvascular plants.

    27:07

  • MarySusan Potts-Santone: We've got seedless vascular plants. We've got gymnosperms, and then we've got angiosperms.

    27:12

  • MarySusan Potts-Santone: So these are the Phylo plants that we're going to be talking about.

    27:19

  • MarySusan Potts-Santone: Liverworts, mosses, and hornworts are this are the bryophytes.

    27:22

  • MarySusan Potts-Santone: lycophytes and pteritophytes are our seedless vascular plants.

    27:27

  • MarySusan Potts-Santone: cycads, ginkgos, and conifers are our gymnosperms.

    27:31

  • MarySusan Potts-Santone: and then we'll talk about the angiosperms as well.

    27:35

  • MarySusan Potts-Santone: So again, remember anytime we create

    27:38

  • MarySusan Potts-Santone: a cladogram

    27:41

  • MarySusan Potts-Santone: and we write out the characters, you can see what features we're using to look at how our different groups are related to each other.

    27:42

  • MarySusan Potts-Santone: So the most recently evolved group of plants are the Angiosperms. The flowering plants came last. They have been incredibly successful throughout. Pretty much all of the Cenozoic era. All right.

    27:51

  • MarySusan Potts-Santone: all right. And again we'll talk about some of their care, their adaptations.

    28:05

  • MarySusan Potts-Santone: so distinctive features of life on

    28:09

  • MarySusan Potts-Santone: for land life.

    28:12

  • MarySusan Potts-Santone: early adaptations to land

    28:13

  • MarySusan Potts-Santone: body is composed of three-dimensional tissue multicellular.

    28:16

  • MarySusan Potts-Santone: the ability to avoid water loss

    28:20

  • MarySusan Potts-Santone: tissues arising from what are called the apical meristems. That's where plants grow from

    28:23

  • MarySusan Potts-Santone: okay, the root apical meristem, the shoot. Apical meristem. We'll talk a little bit more about plant anatomy and physiology later on.

    28:27

  • MarySusan Potts-Santone: The ability to produce thick, robust bodies is important.

    28:36

  • MarySusan Potts-Santone: Our tallest trees, in fact, are the the redwoods in California.

    28:39

  • MarySusan Potts-Santone: All right. Eucalyptus is the tallest of the flowering plants.

    28:45

  • MarySusan Potts-Santone: all right.

    28:50

  • MarySusan Potts-Santone: but again they grow from their tips, both the roots and the shoots, and the bigger and thicker and more structural the body is, the less likely they are to be eaten

    28:51

  • MarySusan Potts-Santone: or impacted by herbivores. We'll talk about some of the defenses that plants have against herbivores

    29:01

  • MarySusan Potts-Santone: in the body of plants. We have tissues and organs. We have organ systems, in fact, okay, with specialized functions.

    29:09

  • MarySusan Potts-Santone: we have distinctive reproductive features, including alternation of generation, that I mentioned the ability to dry out in their reproductive cells and then specialized structures to generate, protect, and disperse reproductive cells again, moving that next generation farther away from the parents increases their chances for success.

    29:15

  • MarySusan Potts-Santone: Now

    29:40

  • MarySusan Potts-Santone: we're going to start looking at

    29:42

  • MarySusan Potts-Santone: representatives. Okay, of the different major evolutionary groups of plants.

    29:44

  • MarySusan Potts-Santone: And we're going to start with the more simple

    29:50

  • MarySusan Potts-Santone: and work our way up into the most complicated.

    29:52

  • MarySusan Potts-Santone: So as we do that, then obviously, we're going to start with the nonvascular plants also known as the Bryophytes.

    29:56

  • MarySusan Potts-Santone: Those 2 terms are pretty interchangeable.

    30:01

  • MarySusan Potts-Santone: and you want to keep in mind that in this group of bryophytes we've got 3 major groups of plants.

    30:04

  • MarySusan Potts-Santone: liverworts, and hornworts. We're going to dispense with pretty quickly. They are very small, low, growing plants, which all bryophytes, in fact, are.

    30:10

  • MarySusan Potts-Santone: The mosses, are the most abundant and the most recognizable group of bryophytes.

    30:19

  • MarySusan Potts-Santone: But what these 3 groups have in common is that they were the earliest plants to evolve on land.

    30:25

  • MarySusan Potts-Santone: They don't have a specialized means of transporting water and organic nutrients.

    30:31

  • MarySusan Potts-Santone: so no tubes in the body to carry things, which means they have to be small because they have to be able to absorb the water and the nutrients from the surroundings.

    30:36

  • MarySusan Potts-Santone: and because they don't have vascular tissue.

    30:48

  • MarySusan Potts-Santone: they do not have true roots.

    30:51

  • MarySusan Potts-Santone: true stems, or true leaves.

    30:54

  • MarySusan Potts-Santone: root stems and leaves are the organs of a plant

    30:57

  • MarySusan Potts-Santone: right? Each one of these groups, we know, does form a monophyletic phylum.

    31:02

  • MarySusan Potts-Santone: All right. Again, we've been looking at their ancestry.

    31:07

  • MarySusan Potts-Santone: They share structural, reproductive, and ecological features.

    31:09

  • MarySusan Potts-Santone: and they are the models of our earliest terrestrial plants.

    31:13

  • MarySusan Potts-Santone: And the biggest thing you want to remember is that when you're looking at a moss, a liverwort, or a hornwort.

    31:17

  • MarySusan Potts-Santone: what you recognize as the plant, you've probably all seen versions of this before.

    31:23

  • MarySusan Potts-Santone: What you recognize as the plant is the gametophyte.

    31:28

  • MarySusan Potts-Santone: The egg is within the Archegonia.

    31:31

  • MarySusan Potts-Santone: There's going to be a flagellated sperm in the antheridia. That's the male anatomy, and the sperm has to swim to the egg in a film of water in order to create the next generation starting with the zygote.

    31:34

  • MarySusan Potts-Santone: Now, why is that important to remember.

    31:47

  • MarySusan Potts-Santone: It places a restriction on these plants.

    31:50

  • MarySusan Potts-Santone: and the restriction is there has to be water available. There has to be a certain amount of water in order to allow the sperm to swim to the egg.

    31:54

  • MarySusan Potts-Santone: All right. So there are restrictions there. Remember, they don't have internal transport tubes.

    32:03

  • MarySusan Potts-Santone: so most bryophytes are small in size, and they tend to reside in harsh environments.

    32:07

  • MarySusan Potts-Santone: So we're going to look very quickly at the hornworts and the liverworts so that you recognize their diversity.

    32:15

  • MarySusan Potts-Santone: again, they have these kind of leafy structures where the gametophyte is close to the ground.

    32:22

  • MarySusan Potts-Santone: the sporophyte grows up

    32:27

  • MarySusan Potts-Santone: okay in order to disperse the spores. They look like little green broom handles all right. The liverworts are probably the oldest and 1st group of bryophytes to evolve. They have these little cup-like structures.

    32:29

  • MarySusan Potts-Santone: Why, they're called liver warts is because somebody thought that the leafy appearance looked like the lobes of a liver. I don't quite get it, but

    32:43

  • MarySusan Potts-Santone: I'll take their word for it

    32:51

  • MarySusan Potts-Santone: all right, so you can see here the male gametophyte, the Female Gametophyte. The egg is going to swim to the sperm. The sperm is going to swim to the egg through a film of water. A lot of times you get these little cup like structures that facilitate that

    32:53

  • MarySusan Potts-Santone: they either have a flattened body or kind of a leafy appearance.

    33:09

  • MarySusan Potts-Santone: Now, you'll also notice that I put numbers on these groups.

    33:13

  • MarySusan Potts-Santone: You do not need to memorize the numbers.

    33:17

  • MarySusan Potts-Santone: but they help us to think about well, which are the most abundant, which are the least abundant.

    33:20

  • MarySusan Potts-Santone: Okay, well, liverworts are a pretty good sized group. There's about 6,500 species

    33:26

  • MarySusan Potts-Santone: hornwarts. On the other hand, there's only about a hundred species that we know of.

    33:31

  • MarySusan Potts-Santone: Corn warts are closer to vascular plants. Phylogenetically

    33:36

  • MarySusan Potts-Santone: they have small sporophytes that carry on photosynthesis. And again, structurally, again, what we recognize as the plant is the gametophyte

    33:40

  • MarySusan Potts-Santone: and the sporophyte then grows up from that surface.

    33:47

  • MarySusan Potts-Santone: The more important bryophytes are the mosses.

    33:54

  • MarySusan Potts-Santone: and we're going to spend a little bit more time looking at the mosses. You can see mosses number about 12,000 species.

    33:57

  • MarySusan Potts-Santone: all right. So the bigger the number tells you about the success of the group. All right. What kind of adaptations they may have that facilitate that success again, are important things to look for.

    34:04

  • MarySusan Potts-Santone: Mosses usually have a leafy shoot, some are flattened.

    34:15

  • MarySusan Potts-Santone: they can reproduce asexually by fragmentation, which means, if you take moss and break it into pieces.

    34:19

  • MarySusan Potts-Santone: put it in good soil, grow it, you know, stay and grow, and reproduce, as you know, new entities.

    34:25

  • MarySusan Potts-Santone: What we recognize as the plant is the gametophyte.

    34:31

  • MarySusan Potts-Santone: It's larger. It's longer lived.

    34:34

  • MarySusan Potts-Santone: So when you see something like sphagnum moss which is used a lot in

    34:37

  • MarySusan Potts-Santone: floral displays. They pack it around the base of plantings to hold water. That's 1 of the big characteristics of mosses in general is that they retain water.

    34:42

  • MarySusan Potts-Santone: Okay. They also provide a home for small animals and insects that can live in and amongst the the moss.

    34:53

  • MarySusan Potts-Santone: All right. Native Americans actually use sphagnum moss as a diaper. They put cloth around it holds water. Okay.

    34:59

  • MarySusan Potts-Santone: they use sphagnum moss in World War one to pack wounds to prevent gangrene, because again, it would keep the tissue moist.

    35:08

  • MarySusan Potts-Santone: You can turn various mosses into quite a lot of things. You can use it to make whiskey.

    35:16

  • MarySusan Potts-Santone: we can use it as building material for homes. You can burn it for energy here. I'm talking about peat moss in particular, which is a type of sphagnum that grows again in more northern climates, creating peat bogs that ecologically, are very important. We'll talk about why in a second.

    35:23

  • MarySusan Potts-Santone: So what we recognize as the plant is the gametophyte.

    35:42

  • MarySusan Potts-Santone: Okay? And then from that gametophyte, you see these little stalks growing up.

    35:47

  • MarySusan Potts-Santone: Okay, they occur seasonally. That's the sporophyte.

    35:51

  • MarySusan Potts-Santone: There's a foot down there, there's a stalk, there's a sporangium at the top that's going to disperse the spores into the surroundings again. Mosses are generally found from the Arctic to the Antarctic in damp, shady locations, some in the desert, more often around streams and water sources and in bogs on the walls of caves. You might have copper moss that needs copper deposits in order to grow

    35:54

  • MarySusan Potts-Santone: luminous. Moth bioluminesces. Okay. Found on cave walls. It'll glow in the dark

    36:18

  • MarySusan Potts-Santone: all right again, giving off light as a result of the chemical reactions that, in fact, are taking place.

    36:23

  • MarySusan Potts-Santone: And all of these mosses and bryophytes and hornworts

    36:29

  • MarySusan Potts-Santone: okay are connected to the soil

    36:35

  • MarySusan Potts-Santone: by these root-like structures called rhizoids.

    36:37

  • MarySusan Potts-Santone: Okay, remember, we don't have true roots. We don't have true leaves. We don't have true stems.

    36:42

  • MarySusan Potts-Santone: Rhizoids is the network of root-like hairs that again allow the plant to absorb water and nutrients from the surrounding soil. But they have to be low growing because they don't have that internal transport system.

    36:47

  • MarySusan Potts-Santone: All right. So mosses are by far and away the most abundant and ecologically incredibly important

    37:03

  • MarySusan Potts-Santone: because seedless vascular plants actually transformed Earth's ecology.

    37:08

  • MarySusan Potts-Santone: We're going to talk a little bit about how

    37:14

  • MarySusan Potts-Santone: modern bryophytes can store. Co. 2.

    37:17

  • MarySusan Potts-Santone: They can operate as Co. 2 sinks, because one of the things that plants are doing. Taking Co. 2 out of the atmosphere, fixing that carbon dioxide and generating oxygen as a result.

    37:20

  • MarySusan Potts-Santone: So how do you see this vascular plants respond

    37:32

  • MarySusan Potts-Santone: when conditions are cooler than normal in the atmosphere.

    37:36

  • MarySusan Potts-Santone: Sphagnum moss grows more slowly

    37:41

  • MarySusan Potts-Santone: and because it's growing more slowly, it absorbs less. Co. 2.

    37:44

  • MarySusan Potts-Santone: Okay, because that Co 2 is being turned into plant biomass, carbohydrates, cellulose, whatever the plant body requires.

    37:48

  • MarySusan Potts-Santone: So when sphagnum's growing more slowly, and this is a peat bog in the background here.

    37:57

  • MarySusan Potts-Santone: Okay, again, we can cut bricks out of that and burn it for energy. People used it originally to build homes, particularly in the British Isles, because that's where the peat bogs, in fact, were very abundant.

    38:01

  • MarySusan Potts-Santone: but under cooler conditions phagnum grows more slowly, absorbs less Co. 2, and that allows more Co 2 in the atmosphere. And if there's more Co 2 in the atmosphere

    38:12

  • MarySusan Potts-Santone: that helps with the temperature temperature goes up

    38:22

  • MarySusan Potts-Santone: because as Co. 2 rises again, that traps the heat. Okay, closer to the surface. So the atmospheric Co 2 helps to warm earth's climate.

    38:24

  • MarySusan Potts-Santone: it increasing co 2 warms the climate.

    38:35

  • MarySusan Potts-Santone: and when the climate warms sufficiently

    38:39

  • MarySusan Potts-Santone: well, then the sphagnum starts growing faster.

    38:42

  • MarySusan Potts-Santone: and as it grows faster it sponges up more Co. 2 and deposits that Co. 2 in the form of peat in the structural biomass of a peat bog, for example.

    38:44

  • MarySusan Potts-Santone: and that works to reduce atmospheric Co. 2,

    38:56

  • MarySusan Potts-Santone: bringing the atmosphere to slightly cooler conditions.

    39:00

  • MarySusan Potts-Santone: All right. So when the temperature goes up a little bit, the sphagnum responds. When the temperature goes down a little bit, the sphagnum, responds. One of the biggest issues we have right now is that we have done tremendous destruction to our peat bogs, and we can't really rely on them for their temperature, moderating effects nearly as much as we have been able to in the past. Certainly

    39:04

  • MarySusan Potts-Santone: they are something again that is very important for helping us to manage the climate

    39:27

  • MarySusan Potts-Santone: all right again

    39:32

  • MarySusan Potts-Santone: in something as simple as a peat bog.

    39:33

  • MarySusan Potts-Santone: Peat moss is very important in the carbon cycle. Again, regulating the amount of Co. 2 in the atmosphere, and that in turn influences the temperature

    39:36

  • MarySusan Potts-Santone: and the climate.

    39:46

  • MarySusan Potts-Santone: Now.

    39:49

  • MarySusan Potts-Santone: we're obviously going to spend a lot of time talking about vascular plants

    39:51

  • MarySusan Potts-Santone: and vascular plants by definition, have transport tissues within them.

    39:54

  • MarySusan Potts-Santone: Xylem's job is to conduct water and minerals up from the roots through the stem to the leaves, which are the sites of photosynthesis.

    40:00

  • MarySusan Potts-Santone: phloem conducts, sucrose, and other organic compounds throughout the body of the plant.

    40:08

  • MarySusan Potts-Santone: Along with these vascular tissues comes the need for support.

    40:13

  • MarySusan Potts-Santone: and that comes in the form of lignin

    40:18

  • MarySusan Potts-Santone: lignin strengthens the walls of the conducting cells in Xylem.

    40:21

  • MarySusan Potts-Santone: and the evolution of Lignin has been crucial in the evolution of trees. Again, much, much larger. Think about trees that are meters high. For example, you can drive through the California redwoods trees are incredibly long lived. We have bristlecone pines on the California coast that are 4,500 years old.

    40:26

  • MarySusan Potts-Santone: All right. So again, these characteristics are ones that have really again suited them well for life. On land

    40:44

  • MarySusan Potts-Santone: most seedless vascular plants are considered to be homosporous. They produce one type of spore that are generally blown on the wind.

    40:52

  • MarySusan Potts-Santone: Seed plants, as we'll see, are heterosporous where we have distinct male and female gametophytes, but the seed's job is to disperse the offspring. And again, we'll talk about that later on.

    41:00

  • MarySusan Potts-Santone: But you can see through the roots.

    41:10

  • MarySusan Potts-Santone: stems, and into the leaves this transport tissue that makes the plant a vascular plant, and again allows much larger sizes.

    41:13

  • MarySusan Potts-Santone: So we've got a couple of groups of seedless vascular plants to consider.

    41:24

  • MarySusan Potts-Santone: We've got the lycophytes also known as the club bosses.

    41:29

  • MarySusan Potts-Santone: There's about a thousand species. There's not a ton of them.

    41:32

  • MarySusan Potts-Santone: They have these short branching rhizomes that send up aerial stems. You can see the Stroboli at the end.

    41:35

  • MarySusan Potts-Santone: These leaves look like single strands.

    41:45

  • MarySusan Potts-Santone: The leaves are called microfills, because they only have one strand of vascular tissue in them.

    41:48

  • MarySusan Potts-Santone: The sporangia occur on the surface of the sporophylls.

    41:55

  • MarySusan Potts-Santone: But now we've got

    41:59

  • MarySusan Potts-Santone: true roots.

    42:00

  • MarySusan Potts-Santone: true stems, true leaves, because we have vascular tissue.

    42:02

  • MarySusan Potts-Santone: so lycophytes are known as club mosses.

    42:08

  • MarySusan Potts-Santone: Pteritophytes is only about 15 species.

    42:10

  • MarySusan Potts-Santone: Territophytes were very common throughout New England. They're known as horsetails, because somebody thought this particular arrangement looked like a horse's tail again. I don't quite get it

    42:13

  • MarySusan Potts-Santone: all right, but again you've got

    42:24

  • MarySusan Potts-Santone: nodes at which the leaves spiral around the stem. You've got the structure called the strobilus. Up at the top again the rhizome or the root structure, produces a tall aerial stem with whorls of slender green branches.

    42:26

  • MarySusan Potts-Santone: and again within the leaves. Now we've got what are called megafilms.

    42:41

  • MarySusan Potts-Santone: Megaphils are broader leaves with several strands of vascular tissue.

    42:46

  • MarySusan Potts-Santone: and the more transport tissue you have.

    42:51

  • MarySusan Potts-Santone: the more activity can go on because you've got more water, more nutrients going out to those sites of photosynthesis.

    42:54

  • MarySusan Potts-Santone: The leaves tend to be kind of scale-like and abrasive. They actually have silica in the stem.

    43:01

  • MarySusan Potts-Santone: So the other name for territophytes is scouring rush.

    43:07

  • MarySusan Potts-Santone: The pilgrims, for example, would have used these plants to clean out their pots and pans.

    43:11

  • MarySusan Potts-Santone: All right, because again, the glass in the stem would be an abrasive. Okay, so these are called scouring rushes. There's only one genus equisetum. Okay? You can see equis for horse. Okay, in the horsetail name. But these are the treetophytes, 2 small groups.

    43:16

  • MarySusan Potts-Santone: And then we've got the big group

    43:32

  • MarySusan Potts-Santone: and the big group are the firms.

    43:34

  • MarySusan Potts-Santone: Okay, if you're thinking about a typical Torita fight, it's a farm.

    43:36

  • MarySusan Potts-Santone: all right. There are 10,500 species at least.

    43:40

  • MarySusan Potts-Santone: and they have very conspicuous fronds. The fronds are the leaves.

    43:45

  • MarySusan Potts-Santone: they're divided into leaflets

    43:51

  • MarySusan Potts-Santone: and the dominant sporophyte. Again, what we recognize as the plant

    43:53

  • MarySusan Potts-Santone: produces Sori on the underside of the leaves. All these little red things are sorry.

    43:58

  • MarySusan Potts-Santone: and they're going to deposit spores

    44:04

  • MarySusan Potts-Santone: and again grow into the next generation.

    44:06

  • MarySusan Potts-Santone: So this image over here in the corner

    44:10

  • MarySusan Potts-Santone: is a forest from the Carboniferous period.

    44:13

  • MarySusan Potts-Santone: when the ferns, the Lycophytes, and the horsetails again, were dominant, vascular plants on land, achieving much larger sizes than they have around us today, because again, they've been ultimately outcompeted by the Gymnosperms and the angiosperms that came along later on.

    44:17

  • MarySusan Potts-Santone: All right. So if you ever get flowers roses in particular, they always pack in some fern. Okay for decorative displays. Oftentimes you'll see these little tannish color particles that get left on your table. Okay? Those, in fact, are spores looking for looking for soil.

    44:35

  • MarySusan Potts-Santone: If you like to eat fiddleheads.

    44:51

  • MarySusan Potts-Santone: Yeah, you can buy them in the supermarket. They have them over at whole foods.

    44:54

  • MarySusan Potts-Santone: Those, in fact, are curled up fronds of ferns.

    44:57

  • MarySusan Potts-Santone: They're in an immature state. Lots of people cook them and enjoy them all right. But again, you can see the fronds divided into the individual leaflets, giving you a broad surface area for lots and lots of photosynthesis.

    45:01

  • MarySusan Potts-Santone: But again, they're all going to be larger, because they also have that internal transport tissue. The gametophyte looks like this

    45:14

  • MarySusan Potts-Santone: kind of heart-shaped, glowing, growing close to the ground.

    45:22

  • MarySusan Potts-Santone: A film of water is necessary for the sperm to swim to the egg.

    45:26

  • MarySusan Potts-Santone: So ferns require a lot of water. Okay, they hold a lot of water because of that feature.

    45:31

  • MarySusan Potts-Santone: all right. And then the sporophyte generation grows up from the surface.

    45:37

  • MarySusan Potts-Santone: Now.

    45:44

  • MarySusan Potts-Santone: when it comes to our spermatophytes. Those are our seed plants

    45:46

  • MarySusan Potts-Santone: by far and away. These are the most plentiful plants.

    45:51

  • MarySusan Potts-Santone: The seed itself has a coat for protection.

    45:54

  • MarySusan Potts-Santone: and inside is going to be stored food that allows that embryo to survive pretty harsh conditions.

    45:57

  • MarySusan Potts-Santone: Seeds can sit on a shelf for hundreds of years.

    46:04

  • MarySusan Potts-Santone: You can buy various heirloom species that again, some farmer may have had in seed form for 100 200 years.

    46:08

  • MarySusan Potts-Santone: Plant it and give it what it needs, namely, water.

    46:16

  • MarySusan Potts-Santone: Okay, the right environment, some soil, all right. So its nutritional needs are met. It will germinate.

    46:20

  • MarySusan Potts-Santone: You can see our germinating seed over here with its very 1st leaf, stem and leaf coming out.

    46:26

  • MarySusan Potts-Santone: These are watermelon seeds.

    46:33

  • MarySusan Potts-Santone: all right. And again, we're dealing with heterosporous plants. We've got male and female

    46:35

  • MarySusan Potts-Santone: drought resistant pollen grains that becomes the male gametophyte. The ovule develops into the seed ultimately with fertilization.

    46:40

  • MarySusan Potts-Santone: So our seed plants include both the Gymnosperms and the angiosperms.

    46:48

  • MarySusan Potts-Santone: We're going to talk about gymnosperms first, st and then we'll get into the flowers.

    46:53

  • MarySusan Potts-Santone: But there are many ecological advantages when it comes to seeds.

    46:57

  • MarySusan Potts-Santone: Seeds are a huge adaptation for reproduction on land, because again, it allows that embryo to be protected, have food.

    47:02

  • MarySusan Potts-Santone: and again allows it to tough out harsh conditions.

    47:10

  • MarySusan Potts-Santone: It improves dispersal.

    47:13

  • MarySusan Potts-Santone: It provides food.

    47:15

  • MarySusan Potts-Santone: and again, the sperm can now reach the egg without having to swim through water. So there's less dependence on water in order for successful reproduction. And this is just a small insert of a variety of different types of seeds.

    47:17

  • MarySusan Potts-Santone: All right. So we'll pick up there after your exam.

    47:32

  • MarySusan Potts-Santone: If you have exam questions. Make sure you get them to me

    47:35

  • MarySusan Potts-Santone: again. Think about your time tomorrow. Make sure you're on time for class, so you have the full amount of time for your exam.