Okay, so this video is about alternation of generations. Those are some words they have to do with reproduction in plants, also animals sometimes. In order to figure out what those words mean, here are some more words. These words are about genetics. You've got diploid, think two, die, and haploid think half, right? So that's a little misleading. What it means to be haploid is that you have half the amount of genetic information that you would have if you were diploid. If you were diploid, you have twice the amount that you would have if you were haploid, right? So haploid means that you've got one copy of all of your genes, and diploid means you've got two copies of every single gene in your genome. You and me, and most of the insects in plants and animals you see around you, were all diploid. We've got two copies of each gene. But ferns, ferns are special. They say that ferns have alternation of generations because you can find two unique multicellular body types that ferns have. Ready for some more words? Okay. The two kinds of bodies that ferns can have are either going to be a sporophyte or a gamete fight. Sporophytes make spores. Gamete fights make gametes. What do you know? There are some ferns sporophytes behind me. Let me show you them. So this is a fern sporophyte. Sporophytes are diploid, meaning they've got two copies of the genetic information. These are the leaves of the sporophyte. This is what you typically think of when you think of a fern. And down here, you can see the spores. Ferns have a number of different ways of growing their spores. In this species, what you can see is that the spores are all located on the bottom four fronds of the fern. So you've got this one stem and it's got a lot of different fronds. And four of them have been devoted completely to spore manufacturing. So here, all those little dots are spores capable of making a new fern, a fern gamete fight, a new kind of fern body. Other ferns will have the spores growing on the underside of each of these fronds, rather than dedicating entire ferns to spores. It depends on the species. Okay, so that was a brief tour of a sporophyte. Here's another sporophyte in my hair. To reiterate, the sporophyte is the body of what we typically think of as the fern. And the sporophyte makes spores. Sporeophytes are diploid, and in order to make spores, they undergo a process called meiosis. In meiosis, diploid cells cut their genes in half, producing half-loid cells, and those cells develop into spores. The next step in this story is what happens to the spores. So the spores get released, and they fall on the ground, and they develop into a gamete fight, a creature that makes gametes. So the gamete fights are really, really tiny. I'm going to put a picture on the screen, because I won't be able to find one on the forest floor. They're about the size of your thumb now. But you know, that's still like a multi-cellular creature. You can see it with the naked eye. It's got a fully developed body. It's not just a single cell. So the gamete fight is this little half-loid plant that grows on the forest floor. Half-loid fern plant. It's a fern. It just doesn't look anything like a fern. And it grows on the forest floor, and it releases gametes. Eggs and sperm. And when it rains, those eggs and sperm swim through the water droplets, and they find each other, and then they fuse. Fertilization. From this fused, fertilized creature grows a new fern, a new sporophyte. So this is what alternation of generations means. It means you've got two distinct body types that alternate from one another. Sporophytes make gamete fights, gamete fights make sporophytes. They're all the same creature. You would call them all ferns. They're the same species. They just have radically different body plants. Some bodies are diploid, some bodies are haploid, and they give rise to one another. This might sound strange, but it really isn't. Actually, all multicellular creatures undergo alternation of generations. It's pretty crazy. With ferns, it's particularly notable because you get two unique multicellular bodies. But it happens to every creature, you and me and the trees and the bees and all of them. So I'm a male human, right? And that means that I make sperm. So here you've got alternation of generations. I'm diploid. I've got two copies of each gene. And in my gonads, I have a process called meiosis occurs where those genes split in half and make the sperm. So the sperm are a unique phenotype of humans, right? You could say that sperm are human. They're not anything else, right? Eggs are human, even though they're unicellular creatures, they're still human. So in humans and other animals, you also get alternation of generations. It's just going from haploid to diploid to haploid to diploid. You also go from multicellular to unicellular to multicellular to unicellular. So it's not as big and flourishing because one of the generations is always housed inside the other generations' body, right? Spurman eggs never leave a human body and go develop a baby out in the woods somewhere, like ferns do. Okay, so why am I telling you all this? What's the big deal? The big deal is that what we think of as a self or an individual is actually very fluid. And it's not contingent on the kind of body that you have. Ferns go from one kind of body to another back to the first, back to the second in this crazy meandering path of life, right? But the line of continuity of selfhood, of individuality, it's still the same fern the entire time. It's just metamorphosing over and over and over again. So what that shows more abstractly is that who we are is not necessarily tied to our physical bodies. Instead, it's the information that makes us up and that information can be translated and interpreted in many different ways to make many different humans, many different ferns, all the same kind of self. Part of me is in the screen right now. That's cool. Bye.