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Current time:0:00Total duration:2:44

Video transcript

Let’s talk tree basics. An evolutionary phylogenetic tree is a depiction of how different species are related to each other. We’ll start with just one branch, which represents a single species. Like cushion sea stars… or… human beings. The top of that branch contains all the individual organisms of that species. So, all people. Or all cushion sea stars. If we travel along a branch, back in time: You come to common ancestors of species when two branches come together. Now, let’s roll time forward instead. This split point represents the evolutionary moment when a common ancestor species diverged into two distinct species – a process called speciation. As time goes on, you get more splitting, more species, and more biodiversity. Until you get a tree that looks something like this. It’s a hierarchical arrangement of how those organisms originated, and who they are more closely related to. A tree isn’t a literal timeline, but it does show the passing of time. More ancient branches occur deeper in the tree, and more recent splits occur closer to the tips. For each puzzle in this Lab, you’ll be organizing a collection of species into a tree. Start by using the magnifying glass to learn about the organisms. Explore the species screens and the comparison screen to track down the characteristics, or traits, that different groups of species have in common. Now, not all traits are useful for analyzing evolutionary relationships. But not to worry—we’ve made sure to give you mostly informative ones. After you’ve gathered the information you need, build your tree by dragging species icons, and then traits, into the center of the screen. In general, the more closely related the species, the more traits they share. Deeper branch points connect species that are more distantly related and have fewer traits in common. When you position a trait, that location on the tree corresponds to the common ancestor where that trait first arose. Earn up to two leaves in every puzzle—one for completing the tree, and one for getting the quiz question right. The more leaves you get, the more complex you can make your fractal tree, which tracks your progress through the lab. After you finish each puzzle—you’ll unlock the next one, or open up a whole new mission—and you’ll discover something about the living world pulsing all around you.