in this video, we're going to begin our introduction to arcadia. And so the term arcadia is actually a plural term and the singular form is actually are key in. And so these are referring to organisms and one of the three domains of life. And again recall from our previous lesson videos that the three domains of life are bacteria. Archaea and you Kariya. And so arcadia is one of the major domains of life and so like bacteria. Archaea also have a pro carry attic cell structure which makes RK approach chariots along with bacteria. And for that reason many students mistakenly believe that bacteria and archaea are identical because they're both pro carry its. But that is not the case at all. It turns out that bacteria and archaea are as different from each other as they are from eukaryotes. And so there are still many differences between bacteria and archaea, although they are both categorized as pro curios. For example, archaea have unique ribosomes, RNA or our RNA sequences that significantly differ from the ribs. OMA RNA sequences of bacteria and you Kariya, also, Archaea have cell walls that lack the molecule Pepto Glicken. Whereas recall from our previous lesson videos that bacteria have cell walls made of peptidoglycan and peptidoglycan is really a molecule that is unique to bacteria and archaea lack peptidoglycan. And so those are just some of the major differences between bacteria and archaea. But there are also other differences as well. Now our care are well known for growing in extreme environments and those that do are known as extremophiles because they can survive in extremely, extremely salty environments or extremely hot environments or environments that have extremely high pressures and things of that nature. However, although many arcade do grow in extreme environments and are extremophiles, there are some are cave that can grow in modern environments as well and so they can be found in soils and they can even be part of the human microbiota as well. And so if we take a look at our image down below, notice again, on the left hand side, we're showing you a little snippet of our map of the lesson of the microbial world. And again, we're focusing in on the pro carry its. We already talked about bacteria and in this video we're focusing on the arcadia. And so you can once again see that both bacteria and archaea are classified as pro corrodes. And again, although they're both classified as pro carry its meaning that they're going to be uni cellular and that they're not going to have a nucleus. Um they have some similarities but they still have many differences, bacteria and archaea are not identical. And so over here, on the right hand side we're showing you some examples of archaea. Some are going to be extremophiles in a way where they can grow an extremely salty environments such as halo cuadrado. Um walls by I uh and this is known as the salt square. And so you can see that it has this square like arrangement uh that uh it takes up and again it is able to grow an extremely salty environments Down below. We have some archaea that are capable of growing in extremely hot environments such as pilo pyro lotus few mari which is known as the fire lobe of the chimney. We also have pyro caucus furio sis which is known as the furious fireball. And then we have thermal caucus gamma tolerance which is known as the Ball of Fire. And so these are examples of Arcade that can grow in extremely hot environments. And so again, this here is just our brief introduction to Arquette, and we'll be able to talk more about Arquette as we move forward in our course. But for now, this year concludes our introduction, and we'll be able to get some practice applying these concepts as we move forward, so I'll see you all in our next video.