The traditional tree of life (shown above) presents the three dom...

Question

The traditional tree of life (shown above) presents the three domains as distinct, monophyletic lineages. However, other hypotheses propose different views on the relationships among the Archaea, Bacteria, and Eukarya. In particular, the two-domain hypothesis—or eocyte hypothesis—is emerging as a well-supported alternative to the three-domain hypothesis. The eocyte hypothesis, illustrated below, suggests that eukaryotes evolved from eocytes (also known as the Crenarchaeota—a major lineage of the Archaea). Resolving the relationships among these ancient lineages is difficult, but it has profound implications on our understanding of the origin of eukaryotic cells. Other hypotheses for the tree of life present the Archaea as the ancestors to all other organisms. Sketch a phylogenetic tree that presents Bacteria and Eukarya as more closely related to each other than to Archaea, and that has Archaea as a sister group to Bacteria and Eukarya.

Accepted Answer

Hi everyone. Welcome back. Let's look at our next problem. It says which of the following villa genetic trees accurately illustrates the divergence of bacteria and Archaea from a common ancestor while also demonstrating that you care area are more closely related to archaea than to bacteria. So we're going to evaluate the four choices here and I'll scroll down to show us all of them fill a genetic trees to see which accurately illustrates these two pieces of information were given. So I'm just going to drop them down here to help us kind of sort them out from the whole question. So we see that we want a tree that shows that bacteria and arcadia have a common ancestor and we want to show that you carry A and arcadia are close learn more closely related groups then UK Area and bacteria. So again those are the two things we're looking for a tree to illustrate. So we'll start with choice a here first looking for a common ancestor for bacteria and Archaea. Here's our K. And our bacteria and we do see that the two of them in this tree descend from a common ancestor. So that part is on this tree. Then let's look at the second part and I'm gonna use a different color for this says that UK UK area and archaea are more closely related. So here's UK area and here's archaea are more closely related than you carry A. And bacteria. But when we look at this tree it shows a relationship where bacteria and UK area have descended from a common ancestor that split off of arcadia earlier. So in this tree, bacteria is more closely related to UK area. So it's not our answer. So we're gonna eliminate choice A. Now I'm gonna go ahead and scroll down so we can see our other answer choices. And you can see we still got our information that we're looking for from the question there to refer to. So let's look at answer choice B. So first we're looking to bacteria. Archaea descend from a common ancestor and we can see that Yes, this tree does illustrate that you can see that right there. Now let's switch to our blue and we're looking for the relationship of you carry an arc area. RK Excuse me. So there they are you carry in arcadia and indeed we see that in this tree they are descended from a common ancestor that split off earlier from bacteria. So in this tree indeed you carry A. And archaea are more closely related to each other than you carry A. And bacteria. So we're going to assume the choice B is our correct answer. I'm going to circle it but we'll just check out the other trees to make sure none of them illustrates this better. So let's move onto Choice B. Again. We look for bacteria and archaea and see yes represents a common ancestor. Let's look at part two here. So we're looking for UK area and Arcadia. But here what we see is that it shows you carry a descending from arcadia shows arcadia splitting off from bacteria as they descend from a common ancestor but then you carry a descending later from arcadia and being more closely related to other archaea here. So this tree does not it's not as good an illustration of what our problem is asking us to look for as Choice B. So we're gonna go ahead, eliminate C. And then finally we're gonna look down here at Choice D. Here's archaea and bacteria. But instead of showing them descending from a common ancestor, this tree shows archaea descending from bacteria. So Choice D. Is not our answer. So we're going to confirm that the best illustration of these relationships is Choice B. As this best illustrates the divergence of bacteria and archaea from a common ancestor. While also demonstrating that you carry A. Are more closely related to archaea than to bacteria. See you in the next video

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