New Critters: How Do I Do That?

How Do I Construct A Diagram That Uses "Shared Derived Characteristics?"

The Jason Project has asked you to construct a diagram that will graphically illustrate the relationships between six new critters they discovered in the Rain Forest. How do you do that? What are the steps you should take?

Before actually working with the critters themselves, it might be a good idea to practice with something else. Let's pretend these geometric shapes are critters:

The first thing we need to do is identify our critters. Scientists use a system called "binomial nomenclature" to assign a two-part, latinized name to living things. Humans, for instance, are Homo sapiens. We don't need to be that fancy with the geometric shapes. We can use numbers, letters, or names to identify the shapes.


A	B	C	D	E

The shapes are identified! Now what?

Constructing a data matrix

Before we can determine how these shapes might be related to each other, we have to find out a little bit more about them by observing how they are alike, and how they are different, from one another. One of the first things an Evolutionary Biologist does is set up a table called a "data matrix." After observing the organisms, the Evolutionary Biologist assigns "characters" and "character states" to describe the structures they find on the organism.

In comparing cats and dogs, for instance, a character might be "claws;" the two character states might be "retractable" and "non-retractable." Other characters might be "tail," with character states like "curly," "straight," "short," "long." Look at all the geometric shapes. How are they the same? How are they different? What characters and character states can you come up with for the geometric shapes?

Example Character: Color

Character States for 'Color':

Pink
Blue
Red

Data Matrix

Name	Color	Character	Character	Character
A	Blue
B	Blue
C	Pink
D	Red
E	Red

Can you come up with more characters, and the character states for those characters? Once you think that you are done, you can go on to How to build a cladogram.

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