Understanding Phylogenies (2 of 2)

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A clade is a grouping that includes a common ancestor and all the descendents (living and extinct) of that ancestor. Using a phylogeny, it is easy to tell if a group of lineages forms a clade. Imagine clipping a single branch off the phylogeny—all of the organisms on that pruned branch make up a clade.

Clades are nested within one another—they form a nested hierarchy. A clade may include many thousands of species or just a few. Some examples of clades at different levels are marked on the phylogenies below. Notice how clades are nested within larger clades.

So far, we’ve said that the tips of a phylogeny represent descendent lineages. Depending on how many branches of the tree you are including however, the descendents at the tips might be different populations of a species, different species, or different clades, each composed of many species.

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Phylogenetic starbursts

Teach this!
•  Lesson plans for teaching phylogeny
•  Lesson plans for teaching common ancestry

 
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Trees, Not Ladders


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Spanish translation of Understanding Evolution For Teachers from the Spanish Society of Evolutionary Biology.