.VISUAL SKILLS Based on the tree below, which statement is cor...

Question

.VISUAL SKILLS Based on the tree below, which statement is correct? (A)Lizards and goats form a sister group. (B)Salamanders are a sister group to the group containing liz-ards, goats, and humans. (C)Salamanders are more closely related to lizards than to humans. (D)Goats and humans are the only sister group shown in this tree.

Accepted Answer

Hi everyone. Let's look at our next question based on a given tree diagram, which of the following statements is true. And when we look over our answer choices, there are questions about whether species are closely related or more closely related to one species versus another. So if we're evaluating how closely related species are based on philo genetic tree, what we want to look at is how recent is there common ancestor? So bearing that in mind, let's look at our answer choices here. Our first choice a says humans are closely related to elephants. So here's our human, here's our elephant and we traced back to find their closest and most recent common ancestor. Well, to do that, we've got to go all the way back to the beginning of our tree here. So we can pretty safely say that these two are not closely related because you have to go all the way back to the top of our given philo genetics tree. Now, given that they're both mammals, if we had a bigger tree that had protest on it or something, we might not be able to say they are not closely related. But we're supposed to look at the given tree diagram. So based on this, they are not closely related. So let's look next at choice B cows are more closely related to pigs than whales. So let's find our cow and our pig and find their most recent common ancestor right there and then with a different color. Well, look at the relationship between the cow and the whale and we see it, their most common ancestor is more recent than the common ancestor of the cow and the pig so that is an incorrect answer. And this is also a good example when we're looking at telegenic trees that we can't always use our intuition about which animals are more closely related. You think a cow and a pig, you know they both got four legs. Um They're both you know farm animals I guess if you're thinking it that way. Um But when we look at the actual genomes of these species, we see based on common DNA sequences that the common ancestor of the cow and the whale is more recent than the common ancestor of the cow and the pig. The cow and the wheel are more closely related. So our intuition can actually lead us astray in these sorts of relatedness questions that would be based on things like convergent or divergent evolution. Which would mean you could have um similar shared shared D. N. A. But the animals evolved to be very different, fill a genetically and vice versa. Now let's look at choice see of our markings here for that last problem. Leave them. I see, says hedgehogs, hedgehog Are closely related to aardvarks. So again let's find our common ancestor here between the two and we see that like humans and elephants are most recent common ancestor all the way up at the top of the tree. So we would not say based on this tree that they're closely related. So it's eliminate choice. See well now we're down to choice D. Humans are closely related to chimpanzees and when we look at them sure enough, our most recent common ancestor is right there, the next branch up, so that would be our correct answer. Human D humans are closely related to chimpanzees in this case that matches with our intuition. Um We tend to know that humans and chimpanzees are closely related, but as we noticed in the whale and pig problem, that is not always the case. So something to be careful of these kind of problems. See you in the next video.

Key Concepts

Phylogenetic Trees

Sister Groups

Cladistics

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