General Biology

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27. Protists

Protist Life Cycles

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Alteration of Generations

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Hi. In this video, we're gonna look at a few ways that you carry attic life cycles can play out. We'll see these ideas come up again when we take a look at the various lineages of protests and also when we look at plants and animals as well as fungi later on. Now, we've already talked about alteration of generations briefly when we were talking about, uh, sexual life cycles and we mentioned alteration of generations in connection to plants. But it actually, uh, plays out in protests as well. And basically, the way that alteration of generations works is that, uh, in the course of the life cycle of these organisms, uh, there will be a hap Lloyd and deployed stage, and both of these will be multi cell or we'll have a multi cellular component, I should say so. Looking at our image here, you can see here we have our hap Lloyd phase, and down here we have our deployed phase. Now, the half Lloyd multi cellular stage is known as the Gumede. A fight and you can see we have our Amiga fights right here. And these are going to produce our GAM eats our gametes will get together and fertilization occurs and we form a Zygo. Now the zygote will undergo mitosis and form the spore. A fight, right? That spore fight is the deployed multicellular stage. And this is what is going thio undergo my, oh, sis and produce spores. Spores are a unit of a sexual reproduction. They're generally hap Lloyd and uni Cellular, and we'll see that spore fights. They're gonna produce spores. These spores will undergo mitosis to form those comida fights that we started off talking about. And, of course, those Gumede a fights will then produce gametes and the cycle continues. And we continually alter between generations the media fight and the horror fight generation. So we'll see this again when we talk about various protests. And also when we talk about plants Now, what's kind of cool about alteration of generations is in some species thesis poor fight and Jamie to fight are structurally different. They look different. Um, you know, they have, you know, distinctly different structures. And we call these hetero more fic basically meaning different shape, right? Different form. Uh huh. Now, in some species, the spore Fighting committee fight will actually look the same. Even though, of course, in you know, the spore fight, the cells are all deployed and in the army to fight. The cells are all hap Lloyd. Pretty crazy. I know these organisms are called Isom or thick or same form Pretty cool. And you can see here we have two images. Both of these air, actually brown algae. So these air both protests both types of brown algae. This one over here is is a more FIC, though. So both the spore fight and give me to fight Gonna look like that. And this one over here is hetero, more fic. And this is, you know, different type of brown algae. You don't really need to worry about the, you know, names or anything about these types of brown algae. Just an example of how you know two organisms that air from sort of like the same lineage, right? These air, both types of brown algae, how they can use thes two different types of strategies. With that, let's flip the page
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Haploid and Diploid Dominant Life Cycles

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not all you Kerasiotes undergo in alteration of generations. Some have life cycles that are either dominated by a deployed or hap Lloyd phase. And in the hap Lloyd dominant life cycle, what we'll see is the zygote is the Onley part of the life cycle that is deployed right. The zygote is gonna form from the fusion of GAM. It's like normal. And then it's gonna undergo my Asus and it's going to reform. Hap Lloyd cells and thes life cycles can be experienced by Eunice cellular organisms or multi cellular organisms. That's what's meant by individuals or more cells. Now these Hap Lloyd cells will reproduce a sexually, so they're gonna, uh, reproduce through mitosis and cell division, and they can also form GAM eats right also through my toe, sis. And again those gametes will fuse to form the zygote, and then the zygote will undergo my oasis. So, um, basically, the dominant part of the life cycle of these organisms is hap Lloyd, now in a deployed dominant life cycle, which is what humans are like. So use that as your basis of comparison in the deployed dominant life cycle. Basically, the Onley hap Lloyd cells are the gametes and thes. They're gonna be formed by some type of mature cell that's gonna undergo my Oh, sis, um, you know, this is like sperm and egg formation. So these are going these cells, they're gonna undergo my Asus form, those gametes and those gametes Arthuis, Onley, hap Lloyd, part of this organism's life cycle, and they will fuse together to form a zygote, and then the individual, which is all going to be deployed now Ah, you know, the difference between these two life cycles is that in the hap Lloyd dominant life cycle, it's the zygote itself that's going to undergo my Asus to produce, um, to produce the, uh Well, in the case of that, it's gonna be right. Our little hap Lloyd cells. They're not actually the gametes. But the point is, the zygote undergoes my Asus directly, whereas in a deployed dominant life cycle, the zygote will undergo might assis to form the organism. And then certain mature cells in that organism will will be the ones that undergo my oh, sis, to you form gam. It's so the zygote does not undergo bio sis. With that, uh, let's conclude this video