Up to this point, we've been talking about all flowers like they're the same. But as with everything in biology, there are exceptions, and there is variety and diversity, and that's a good thing. And we need to go over some of that terminology. So we've actually been talking about what you'd call complete flowers. That is flowers that contain sepals, petals, stamen, and pistils. All parts. Some flowers, though, are considered incomplete, and that's because they are missing one of those components, maybe more than one of those components, in fact. Now, you can also have what's called a perfect flower, which is going to be a bisexual flower that has stamen and pistil structures within the same flower. That's as opposed to what's called an imperfect flower, which has either stamen or pistils, and is unisexual. Now amongst unisexual flowers, we can get another dichotomy, and that is, the difference between monoecious plants and dioecious plants. Now, monoecious plants and dioecious plants both have unisexual flowers. But in monoecious plants, the male and female flowers will be found on the same plant. So one plant will have some flowers that have male parts, some that have female parts, but it's all on the same plant. Dioecious plants, on the other hand, will have just male flowers or just female flowers on the same plant. So the male and female floral organs are separated by plant. And here you can see we have some images to represent all this stuff. So here we are looking at incomplete flowers, and this one is male, this one is female, and here we have a perfect flower. Actually, I'm sorry. This is supposed to be imperfect, not incomplete. Well, actually, it could be incomplete. It's both incomplete and imperfect actually. So imperfect perfect, but over here is where I wanted to show our incomplete-complete dichotomy. Let me get my head out of the way. So this is a complete flower, It's, got the, you can see the stigmas up at the top there, here are the anthers, you know, this is the style, the ovary is going to be down in there, you can't really see it. It's got, petals, you can't see it, but it has sepals under there. It's a complete flower. This is an incomplete flower. Oh, if you're curious, this is a, on the left here we have a hibiscus flower, on the right is a calla lily. And while this might actually look like a petal, it's not, it's a leaf. It's a leaf that has had its color altered to appear as a petal to fool pollinators, so to speak. And this structure is actually, covered in pistils. Though you'd have to look through a zoomed-in lens to really see it, but the point is, it's incomplete. Now, if we move on, we need to talk about how pollen gets around. As I'm sure you may have thought, you know, if a flower has the male parts and the female parts, well then can't it pollinate itself? The answer is sometimes. Some plants can self-pollinate, but others can't. Others will cross-pollinate, which is when pollen is transferred from the anther of one plant to the stigma of a different plant. And some plants are prevented from self-pollinating by genetic mechanisms. We call this self-incompatibility. So that is when genetic mechanisms prevent self-pollination, and this encourages what's known as outcrossing, which is when you breed genetically unrelated individuals. Now there are other methods that plants use to prevent self-pollination. One of these is known as temporal separation. Essentially, the male and female gametophytes on a plant will mature at different times, so that neither one is mature at the same time, meaning it can't pollinate itself. However, other plants will have their male and female gametophytes maturing at, you know, on a different schedule, and so those guys can get together. There's also spatial avoidance, which is basically spatial positioning of male and female flowers or floral organs to avoid self-pollination. So if pollen has to get to stigma, for example, maybe all your female flowers are somewhere where the, male flowers can't get their pollen to them, or, for example, you put your, stigma and anther within the same flower in a configuration where the anther can't hope to get its pollen up to the stigma, for example. Now, lastly, we need to talk about pollination syndrome, which are flower traits that have evolved in response to pollen vectors. So these are going to be traits that influence a plant's ability to pollinate by wind, or by attracting bees, or by attracting birds, for that matter. And, the reason that you have organisms that will pollinate these plants is because of mutualism. Right? They're not doing this for free, it's not charity. There's something that they get out of it. The animal pollinators, like this dusty bee covered in pollen here, or this bee slurping up its meal, or this hummingbird behind my head here slurping up its meal, they're getting food. They're not there thinking, alright, I'm going to take some of this pollen, bring it to this other plant later. See? No. They're like, I'm getting a meal right now, and, you know, it's I've got to get a little dirty to get this food. Right? I get dusty in the process. I don't really care, I'm getting a delicious sugary snack. And when I go to my next meal, I might rub off some of that dust, that pollen on that plant. Right? So the plants get to spread their pollen around, the pollinators get a meal out of it. And what we see often with these pollination syndromes is coevolution, which is when, one species' evolution influences the other species' evolution. So a lot of these pollinators and flowers have co-evolved. In fact, when Darwin, the father of the idea of natural selection and all that good stuff, when he went to the Galapagos and he saw this particular flower that had this really long tube down to the nectary, he said, I bet you that there is some organism that has evolved to have a feeding tube that will fit into that flower. He was not wrong. He didn't discover that moth, but he was right in predicting that it existed, and that is just one eloquent example of coevolution, and you're going to see that with these pollinators and the organisms that they're pollinating for, because they rely on each other. Right? This is the food source for those animals, and this is how these angiosperms are going to spread their pollen around. Now, I should make note that not all vectors are animal vectors, you know, there's other stuff like wind, but the, you know, the really cool examples of coevolution come out with those animal pollinators. Alright, that's all I have for this lesson. I'll see you guys next time.
Table of contents
- 1. Introduction to Biology2h 40m
- 2. Chemistry3h 40m
- 3. Water1h 26m
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- Monohybrid Crosses16m
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- Review of the Lac Operon & Trp Operon11m
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- Eukaryotic Post-Transcriptional Regulation28m
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- Introduction to Community Ecology2m
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36. Plant Reproduction
Flowers
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