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Cladistics

The Basics

The human brain loves to group things, including the various forms of life we see on the planet. This grouping helps us to predict behavior, structure, function, etc.. of organisms. There are different methods for grouping organisms depending upon the purpose of the individual doing the grouping. You may, for example, be looking at organisms that fly and that do not fly. Classically in biology, life overall has been grouped according to the Linnaean Classification system and its multiple kingdoms.(e.g. animal, plant, fungi, protists, archaea, eubacteria) Another way to group life is according to evolutionary ancestry. This produces a tree-diagram like the one below.

Image courtesy of http://evolution.berkeley.edu
Image courtesy of http://evolution.berkeley.edu


The Details

Evolution and Patterns - Go to this site to get a background on evolutionary patterns and how they are represented with trees. Continue clicking 'next' and read until you get to the end of the "Patterns" section. It ends with 'Important events in the history of life' and before you get to 'Mechanisms'.
Evolutionary Trees - Go to this site to learn more about how to read and construct trees.
Misconceptions About Evolutionary Trees - Go to this site and scroll down to the section titled, "Misconceptions about evolutionary trees" and explore the topics listed in that section to be sure you avoid the common mistakes when reading a cladogram.

Lesson Activity

Build a Cladogram - Go to this site to complete an interactive and build your own cladogram.
What did T.rex taste like? - Complete this activity to determine what T. rex probably tasted like and practice your ability to make and interpret cladograms.

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