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Course: American Museum of Natural History > Unit 3
Lesson 1: Evolution: the basics (American Museum of Natural History)- Introducing Darwin and natural selection
- Charles Darwin's evidence for evolution
- Glossary
- Evolution: a paleontologist's perspective
- Phylogenetic trees
- What is a Tree of Life?
- The science of speciation – molecular adaptation in vampire bats
- Quiz: Evolution by natural selection
- Exploration Questions: Evolution by natural selection
- Answers to Exploration Questions: Evolution by natural selection
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What is a Tree of Life?
A phylogenetic tree, also known as a cladogram, is a diagram that proposes how different types of living things are related. If you follow the lines connecting any two groups on a tree, you'll get an idea of how closely related they are. Tree of Life diagrams are phylogenetic trees that propose what are the evolutionary relationships for all species of life. Different software programs allow scientists to build Trees of Life in different arrangements so they can better understand how species are related.
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Video transcript
Cladograms, or tree of life diagrams, show
evolutionary relationships among species. This circular tree of life was made by comparing
the DNA sequences of species. The names of species living today are around
the outside of this tree. By tracing the lines from each until they
meet, you can find the common ancestor of two species. Straighten out the circle, and you'll see
a more traditional tree of life diagram. It gets crowded when you show a lot of species,
like the 479 shown here. Bending the tree into a circle makes more
room to add species. The same 479 are displayed here in a circular
format. Software also allows scientists to travel
through a tree of life, so they may visualize it in three dimensions. Species that are closely related are clustered
together and distantly related species are farther apart. Each of these trees shows only a small portion
of the millions of species that have been identified on Earth. Millions more remain to be discovered.