Notes: How to Read a Dichotomous Key
Georgia Performance Standard
 S7L1
o Students will investigate the diversity of living organisms and how they can be compared
scientifically
 S7L1a
o Demonstrate the process for development of a dichotomous key.
Essential Questions
1. What is binomial nomenclature?
2. How are scientific names written?
3. Why do scientists use scientific names?
4. What is a field guide?
5. What is a dichotomous key?
6. How do scientists use dichotomous keys to identify organisms?
Tools For Identifying Organisms
(You do not have to copy this slide)
 Scientists around the world use two main tools to identify organisms…
1. Field Guides
2. Dichotomous Keys
 Our standard for 7th grade focuses on teaching students how to make and use
dichotomous keys.
Field Guides – paste your copy onto page 43 of your notebook
EQ#4 - What is a field guide? (Copy onto page 42 of your notebook)
(Textbook reference page 25)
1. A field guide is a tool that scientists can use to identify species from around the world.
2. Most field guides contain
3. Illustrations or photographs of organisms
4. Information about where each organism lives
5. General descriptions of each species
Dichotomous Keys – paste your copy onto page 45 of your notebook
EQ#5 - What is a dichotomous key?
(Textbook reference page 26)
1. A dichotomous key is a tool that allows the user to determine the identity of items in the
natural world, such as trees, wildflowers, mammals, reptiles, rocks, fish, and much more.
2. Dichotomous means “divided into two parts”.
3. Dichotomous keys always give two descriptive choices in each step to help a person
identify an organism.
EQ#6 - How do scientists use dichotomous keys to identify organisms? (Copy onto pages 44 of
your notebook)
1. Refer to the pictures provided. If no pictures, rely on prior knowledge.
2. Start by reading both descriptive choices at step 1, even if the descriptive choice seems to
be logical.
3. Follow the direction at the end each descriptive choice to lead you to the next step.
4. If the descriptive choice is not clear, try both directions again.
5. If you end up with two possible answers, reread the descriptive choices again to help you
decide.
6. Repeat these process until you have identified all of the organisms.
Now let’s look at a sample…
1. Using a Dichotomous Key
2. Practice Work – USE PENCIL - Independent Practice Dichotomous Keys
a. Smiley Faces – We will check this one in class, glue it onto page 47 of your
notebook
b. Norns – I will collect this one as your exit ticket today