1. According to the phylogenetic tree, which organisms are...

1. According to the phylogenetic tree, which organisms are the least related to each other evolutionarily? Arachnata Arthropoda Trilobita Chelicerata Crustacea Mandibulata Myriapoda Insecta Trilobita and Insecta Insecta and Myriapoda Insecta and Crustacea Trilobita and Chelicerata Crustacea and Myriapoda

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00:01 So we have a phylogenetic tree and we want to know which organisms are the least related to each other.

00:06 Okay, i'm going to start by drawing the tree because it'll be easier to explain what's going on.

00:14 So we have some of it looks like this.

00:19 Okay, so we have the trilobites over here.

00:22 We have the chalcerata.

00:26 We have the crustacea, the myrioposa, and the insects.

00:31 Okay.

00:32 Okay.

00:33 So, which of these groups are least related to each other? so we have trilobiter and insecta, insecta amyropodia, insectin, crustacea, trilobiter and chalicerata, crustacea, myropoda.

00:47 Okay, how do we work this out? so i'll start at the bottom, crustacea and myropoda.

00:54 To do this, we go to the tree and we follow their ancestry, like so, and we see where they meet.

01:03 I may meet here.

01:04 So this is the most recent common ancestor of these two groups.

01:08 So i'll mark that with an e.

01:10 And we're looking for the one that's the furthest back, because those are going to be the least related.

01:16 The further back, their common ancestor, the less related they are.

01:20 Looking at d, we have the therilarylobytes and the trilisterata.

01:24 So if i follow these back, they meet here.

01:30 So we'll put a d here...

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