Dichotomous key

A dichotomous key is chart which allows you to identify a specific organism, based on its characteristics.

The best way to explain a dichotomous key is to see one.

The chart to the right is a dichotomous key.

The goal is to ask a series of questions where there is only 2 possible answers, and continue until you find your organism.

For example in the image to the right. If we see a Duck but are unsure of its name, we can follow the chart.

Does is have feathers? If yes, does it swim? If yes then it is a duck.

Dichotomous keys can become extremely specific, however they all operate on the same system.

Try and create a dichotomous key  for the following 7 organisms.  

Once you have completed the above try to create a Dichotomous key for the 8 organisms bellow.  

Plant cell

Bacteria B

Bacteria A

Human cheek cell

Sperm cell

Bacteria C

Bacteriophage

Mushroom cell

To the left is another dichotomous key. Scroll over the yes or no answers to find the organism.  

Year 9 iGSCE - Biology

We can also make a dichotomous key into a table instead of a chart.

This is shown in the table to the right.