Dichotomous Key Lab
Lab Directions
Read through all the directions before beginning. Submit your lab report according to the
directions and grading rubric below.
Overview: Classification systems are usually based on structural similarities, at
least initially. Let’s pretend that scientists have recently discovered some new
monster-like animals, and you get to name them! Create a dichotomous key to
help identify them. You will not be submitting a full lab report, but rather a table,
your key and answers to thought-provoking pre-lab and discussion questions.
Directions:
1. Name each organism. Record this in a Data Table.
2. Study the organisms on the last page and note their similarities and differences. Create a
dichotomous key that could be used to identify each of the 10 bizarre animals shown below. Be
sure it fits the rules below.
3. Test out your key to be sure it works for each organism before submitting your work!
Rules for Constructing Useful Dichotomous Keys
When constructing your own dichotomous keys to classify things, it’s best to start by
dividing them up into groups of similar characteristics. When you are ready to write
out your key, remember to follow these rules:
1. Use traits that anyone can observe with the naked eye (or an available tool.)
2. Use traits that are unambiguous - the organism either always has the trait or it
does not have the trait. Avoid seasonal characteristics or locations/habitats.)
3. Descriptions are based on either/or alternative statements describing the
organism's features.
4. Only one of the statements describes the organism being keyed.
5. Use quantitative measurements rather than terms such as “big” or “little.”
6. You should end up with one less couplet than the number of organisms used in the
key. If you have 6 organisms, you will end up with 5 couplets.
Dichotomous Key Lab 1 of 3
Example:
1a Organism has horns ... go to 2
1b Organism does NOT have horns ... go to 3
(continues…)
Discussion Questions:
Answer each question in thoughtful, detailed and complete sentences.
1. What are the benefits of classifying organisms?
2. What errors or difficulties can a scientist run into when trying to create a key that is accurate?
3. Are there instances where closely related species of organisms might not be best identified
with a dichotomous key? Explain your answer.
Grading:
The following criteria will be used to evaluate your lab:
Criteria
Points Possible
Results
Data Table (10)
● Proper Title
● Each organism is identified by a name (A = name, B = name, etc.)
10
Results
Key (60)
● Digitally produced
● Proper format (number/letter couplets)
● Proper number of couplets
● Couplets are opposites or unambiguous
● All organisms are present in key
● Key works for all organisms
60
Discussion Questions
● 10 points per question
● Answered in complete sentences
30
TOTAL
100
Dichotomous Key Lab 2 of 3
Monsters
Dichotomous Key Lab 3 of 3