Our example here says, answer the following questions using the tree below, and well, here's the tree. So it's, our tree. Let's introduce you to the organisms. We have the ostrich, the rhea, the tinamou, the cassowary, the emu, and the kiwi.
The ostrich and the rhea and the cassowary and the emu, those are all large flightless birds. The kiwi is a sort of small flightless bird that lives in New Zealand, and the tinamou, that's actually a group of bird species that live in South America. All right. That's not really relevant to any questions we want to answer though. So let's go through our questions.
First, it says, a) which organism is most closely related to the emu? All right. Well, here's the emu. Take a look at the tree. What's most closely related to the emu?
Well, remember to answer these questions. What's most closely related? You follow the branches back to find the nodes. And the deeper in the tree, the farther back in time or the closer to the top of the tree, the more recent. So as I follow this branch back from the emu, this is its sort of most recent node, the most recent splitting event in that population, and I can follow that node up and it shows me that it's most closely related to the cassowary.
So I'm going to write the cassowary here. Alright. Next, we have is a Tinamou more closely related to a kiwi or a rhea? So here's the Tinamou. Here's the rhea and here's the kiwi.
Take a look at the tree and tell me what you think. All right. Well, when I look at this, I'm kind of instantly tempted to say the rhea because, well, you look here, they're sort of close to each other on the screen or on the paper. But remember, we have to find where these nodes meet, and I follow this branch back to a common node. That's the common node here with the kiwi, and I have to go deeper in the tree to find that common node with the rhea.
So more recently, I'm trying to not go as deep in the tree. So both the kiwi and the tinamou come out of this node here. So the Tinamou is going to be more closely related to the kiwi. Alright, next it says which bird or birds is the ostrich most closely related to? Alright, well here's the ostrich.
Take a quick look. Which birds is it most closely related to? Well, as I look, when I follow this back and I find this is the most recent node that the ostrich sort of branches out of and I look, well, everything else comes out of that node. So that's really a bit of a trick question. The ostrich is going to be equally related to all other birds on this tree.
So I'll write that equally related to all other birds. Birds with an r. Birds on the tree. Alright. Next, we have which bird or birds would you expect to share the most traits with the Tinamou?
Alright. Again, here are those birds. The Tinamou. Which things would you think have the most in common? Well, I would think that things that share a more common ancestor, a more recent common ancestor with the Tinamou would share traits because those traits would have been present in that common ancestor.
So I'm going to say what's most closely related to the Tinamou. I'm going to follow this back. Here's its, the last node that the Tinamou branches off from. What else comes out of that node? Well, the Emu and the Cassowary.
So the Emu and the Cassowary, those are both equally related to the Tinamou. I would think that they share a lot of traits with that, and with the Tinamou. Alright, so I'm going to say the Cassowary and the emu. All right. Next, we have e.
Circle all the descendants of the bird that lived at node a. Right. Here's the, here is node a. So what birds are descendants of the organisms that lived at that time? I'm just going to follow the branches that come out of node A.
Right? So coming out here. Well, that leads to all those and coming out this way that leads to the rhea. So it's really just going to be all of these birds here. I'll circle in there.
Those are all the descendants of the birds that lived at node a. And our final one here. Put a star on the node of the tree that represents the most recent common ancestor of the cassowary and the kiwi. Alright. Take a look.
Where do you think you should put that star? Well, I trace my nodes back. The kiwi back to this node right here. The cassowary also can trace its lineage back to that node. That's the last, that's the most recent place where those two branches meet.
So I'm going to put a star there, and with that, we've answered all the questions and I'll see you in the next video.