Reference no: EM133261432

How to make a simple dichotomous key for taxonomic identification

Dichotomous keys are based on the use of pairs of contrasting statements. That is, the pairs of statements are designed so that if a characteristic isn't described by one statement, it must be included in the contrasting statement (mutually exclusive). By setting up pairs of contrasting statements, you can set up a working key that leads the user to the correct identification. For example statement if 1a may be "organism does not have feet", then statement 1b would be "organism does have feet". Continue to break a group down by characteristics one at a time until you reach the correct classification. Then you continue with the next group.

Things to Remember:

1) Keep the descriptions simple.

2) Work with one sub-group at a time.

3) Make sure your number correspond to your descriptions!

Dichotomous Key for your specimens. This must include all 10 species. Randomly pick 10 species to work on. Please include Genus and Species names (binomial name) for each organism.

Analysis (see last page)

Part A:

Steps

1. Use the most general traits that can be used to divide organisms up into two categories. These two categories will become 1a and 1b. Example:

1a.............................. Go to 2

1b.............................. Go to 3

2. The second step (2a and 2b) needs to consist of a pair of statements that will allow for the identification of one organism (2b should ID one organism).

3. Every statement after the second should allow for the identification of one or two organisms.

4. The last pair of statements (ex. 5a and 5b) should identify two organisms.

5. There should be one less step then the total number of organisms to be identified in your key (if you have 6 organisms, you should have 5 paired statements to identify them all).

6. The more similarities the group of organisms has, the more difficult it is to develop the key. Try to choose characteristics that are different to make classifying the organisms easier.

Part B:

Questions

1. What is the purpose of a dichotomous key (not just this key, but any key)?

2. Why is a dichotomous key called a dichotomous key?

3. Is it possible to create more than one dichotomous key for classifying and identifying the same group of objects? Explain.

4. When two people use the same dichotomous key to identify the same object, is it possible (should it be possible) for them to have different final answers?

5. Why are classification and identification important?