In this video, we're gonna recap the classification categories of life. And so taxonomy is the name of the branch science that classifies, identifies, and properly names all living organisms. And there are actually 8 biological classification categories used to identify all life. And you guys have talked about these categories in your previous bio courses, so we're just gonna do a quick review here. And in our example, we have a vertical representation and a horizontal representation of the 8 categories. And to refresh your memories, these 8 categories include domain, kingdom, phylum, class, order, family, genus, and species. And in parentheses, we have the plural version of these categories. And notice that domain at the very top has the largest broadest bar, which means it is the most inclusive and all living organisms fall under it. Now, as you move down in categories, the bars get smaller, which means the categories get less and less inclusive and less organisms fall under it until you get to the least inclusive category, species, which only includes one type of organism. And so you can see that over here on the right where domain is the most inclusive category and species is the least inclusive category. And there's an acronym to help you guys remember the categories in order from most inclusive to least inclusive, and that acronym is Dear King Philip Came Over for Great Soup. And so we have an image of King Philip here and the delicious looking soup soup that he came over for. So if you can remember that dear King Philip came over for great soup, you can remember the order of these categories from most inclusive to least inclusive. Inclusive. And so in our next video, what we're gonna do is talk about a particular category, the domains of life. So I'll see you guys in that video.
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concept
Domains of Life
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So we already know from our previous bio courses that there are 3 domains of life, bacteria, archaea, and eukarya. And bacteria and archaea are grouped together as single cell celled prokaryotic organisms, and that's because they lack a membrane bound nucleus. And bacteria are theorized to most closely resemble the very first cells because there are less divergences in the evolutionary tree, which is built by comparing the DNA sequences of many different organisms. Now archaea include organisms such as halophiles and thermophiles, which live under intense conditions. Halophiles live under high salt conditions, whereas thermophiles live under high temperature conditions. Now, we already learned that eukarya are cells that contain a membrane bound nucleus, and this includes all multicellular organisms as well as the single celled protists. Now, in our example below, we have an evolutionary tree. And notice that on our timescale over here on the far right on the present, we have the three domains of life which represent all living organisms our in time, bacteria encounter less divergences than archaea and eukarya do. And so for that reason, bacteria are theorized to most closely resemble the very first cells. And bacteria and archaea, they are grouped together as single celled prokaryotic organisms, which lack a membrane bound nucleus, whereas eukarya include the eukaryotic organisms that do have a membrane bound nucleus. And so, humans and ostriches are both multi cellular organisms, so they both fall under the eukarya domain. And notice that when we compare the biological classifications, class, they start to fall under different categories of life. Now, in our biochemistry class, we're gonna be mainly focusing on eukaryotic organisms. However, recall from our previous videos that the biochemical unity of life states that all living organisms have a resemblance at the biochemical level. And so things that we learn about eukaryotic organisms are gonna also be able to, apply to prokaryotic organisms. And so in our next video, what we're gonna do is directly compare prokaryotic organisms with eukaryotic organisms, and I'll see you guys in that video.
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Prokaryotic vs. Eukaryotic Cells
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So as you guys already know, prokaryotic and eukaryotic cells are the broadest and the most distinct groupings of all life, so it's important to be able to compare and contrast. And so in our example below, we have a Venn diagram, where on the left we have prokaryotic cells, the right we have eukaryotic cells, and in the middle, we have characteristics of both. And so we're actually gonna start with the characteristics of both. And so both prokaryotic and eukaryotic cells contain cell membranes. And recall that all cells have cell membranes. They both also have structures known as ribosomes, which we'll do a refresher on in some of our later videos, and they display all eight characteristics of life and contain all 4 major macromolecules that we talked about in our previous videos, and those are proteins, nucleic acids, carbohydrates, carbohydrates, and lipids. And so to contrast prokaryotic and eukaryotic cells, we already know that prokaryotic cells do have a nucleus whereas eukaryotic cells contain a nucleus. Now, prokaryotic cells tend to be smaller, less complex and only unicellular organisms and their diameters only range from 1 to about 5 micro meters. Now, in comparison, eukaryotic cells are larger, more complex, and they can be either unicellular or multicellular. And their diameters range from 10 to about a 100 micrometers. So eukaryotic cells are double the size all the way up to a 100 times the size of a prokaryotic cell. So that's much much larger. And so as you guys already know, you prokaryotic cells tend to have circular DNA and they do not contain membrane bound organelles, whereas eukaryotic cells have linear DNA and they do contain membrane bound organelles. Prokaryotic cells divide by a process known as binary fission, whereas eukaryotic cells divide by a process known as, that's right, mitosis. And so although both prokaryotic cells and eukaryotic cells contain ribosomes, their ribosomes differ from one another. And eukaryotic cell cells have larger a d s ribosomes, whereas prokaryotic cells have smaller 70 s ribosomes. And we'll talk more about that in some of our later videos. Now there are a lot more similarities and differences between prokaryotic and eukaryotic cells. However, this is a good summary that I want you guys to know as we move forward in our course. And so this concludes our compare and contrast, and I'll see you guys in the practice videos.
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Problem
Problem
Which of the following are correctly listed from least inclusive to most inclusive?
A
Domain → Kingdom →Phylum →Class →Order
B
Domain → Kingdom → Class →Phylum →Order
C
Species → Genus → Family → Order →Class
D
Species → Genus → Family → Class →Order
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Problem
Problem
Which of the following statements is generally considered true for both prokaryotes and eukaryotes?