3 Domains of Life

by Jason Amores Sumpter
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So from our last lesson video, we know that there are eight categories of life used to classify all living organisms, and the most inclusive of those eight categories is the domain. But really, there are three domains of life, and that's the focus of this video. So once again, the broadest and the most inclusive categories of life are the three domains, which we have numbered down below. And so the first domain of life is domain bacteria. The second domain of life is domain archaea, and the third and final domain of life is domain. You carry a now domain bacteria and domain. Archaea can be grouped together because they both consists of what are known as pro carry Ah, tick cells. Now, later, in our course, we'll talk Maura about these pro carry attic cells. But for now, what you guys should know is that these pro carry attic cells lack an Oregon l called the nucleus. Now the you carry a domain. On the other hand, these consists of eukaryotic cells, and once again, we'll talk more about Eukaryotic cells later in our course. But for now, you should know that eukaryotic cells will actually contain a nucleus, so you could think of them. Pretty much is being the opposite as pro carry attic cells which lack the nucleus. Now, if you take a look at our image down below, what you'll notice is we're showing you the three domains here. Domain, bacteria, domain, archaea and domain. You carry a and this portion right here of the image scientists will refer to as a filo genetic tree. But for our purposes here in this video, you can just think of it as the tree of life. And it's showing us where all organisms, all living organisms off, where they fought and how they could be categorized. And so on this horizontal axis here, what we have is time and so the further to the left you are on the axis, the further in the past you are. And as you make your way towards the right of the image, you make your way towards the present. And so in today's present time, there are these three domains domain bacteria, archaea, and you carry A. However, if you go way back into the past, there is evidence that suggests that all life came from a common ancestor and this is just a theory, so it can never be proven true. But there is lots of evidence that supports this idea. And so what you'll notice is that the theory shows that life came from a single common ancestor. But over time, as we make our way to the right, notice that through natural selection and evolution, these three different branches of life came to exist. The three different domains. Now, once again, domain, bacteria and domain archaea can be grouped together, which is why we have these brackets around them. And they could be grouped together because they both consists of pro carry attic cells, so they could be called pro carry outs. And, as we mentioned up above, pro carry attic cells lack and Oregon L called a nucleus. But also pro carry attic cells are uni cellular, meaning that they're on Lee made up of just one single cell. Whereas down here, what you'll notice is with the domain. You Kariya. This is where humans fall like ourselves, and these are going to be consisted of eukaryotic cells, so they're referred to as eukaryotes as well. Now eukaryotes, although you may think of humans as being multi cellular. Uh, eukaryotes can either be uni cellular or multi cellular, and so it includes all multi cellular organisms that you can think of, but it also includes some uni cellular organisms as well. And so that's something important to keep in mind. But once again later in our course will talk even mawr about these prokaryotes and eukaryotes. For now, you should focus on the three domains of life domain, bacteria, domain, archaea and domain You Correa. And so this here concludes our introduction to the three domains of life. And as we move forward in our course, we'll be able to get a little bit of practice with this idea. So I'll see you guys in our next video.