1. Dichotomous Keys

2. What is a dichotomous key?
A tool that allows the user to determine the identity of things in the natural world
Keys consist of a series of choices that lead the user to the correct name of a given item

3. What does dichotomous mean?
Di = two
Dichotomous = divided into two parts
Therefore, there are always two choices in each step

4. When using a dichotomous key
Always read both choices
Be sure you understand the meaning of the terms involved. Do Not Guess.
Since living things are always somewhat variable, do not base your conclusion on a single observation. Study several specimens to be sure your specimen is typical.
If the choice is not clear, for whatever reason, try both divisions. If you end up with two possible answers, read descriptions of the two choices to help you decide.

5. Let’s try it! Using your dichotomous key, identify the following organisms
Musca domestica Hippodamia convergens
Melanoplus differentialis Austrocordulia leonardi

6. 1. a. wings covered by an exoskeleton ……go to step 2
b. wings not covered by an exoskeleton …go to step 3
2. a. body has a round shape ……….ladybug
b. body has an elongated shape …grasshopper
3. a. wings point out from the side of the body …dragonfly
b. wings point to the posterior of the body …housefly

7. Let’s try it! Using your dichotomous key, identify the following organisms
Musca domestica Hippodamia convergens
housefly ladybug
Melanoplus differentialis Austrocordulia leonardi
grasshopper dragonfly

8. Listen to the screaming mouse
The strange names under each of the organisms identified are called the scientific names.
They are typically written in Latin and are a combination of the genus and species names of the organism