Dichotomous key
Does it have legs?
No: does it have a shell?
Yes: snail
No: does it have feelers?
Yes: slug
No: earthworm
Yes: does it have six legs?
Yes: insect
No: does it have eight legs?
Yes: spider
No: two pairs of legs on each segment?
Yes: millipede
No: centipede
Make a dichotomous key
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What a dichotomous key is
“A single-access key (also called dichotomous key, sequential key, analytical key, or pathway key) is an identification key where the sequence and structure of identification steps is fixed by the author of the key.”
Types of decision tree
When to use a dichotomous key
Science
Name a living thing by answering yes or no at each step until one name is left.
Nature
Take it outside: turn over a log and use the key to name the minibeasts you find.
Sorting
Each question splits the group in two, until every animal ends up on its own.
How to make a dichotomous key
- 1First questionDoes it have legs?
- 2Yes or noDoes it have legs?No: does it have a shell?Yes: does it have six legs?
- 3Keep askingDoes it have legs?No: does it have a shell?Yes: snailNo: does it have feelers?Yes: slugNo: earthwormYes: does it have six legs?Yes: insectNo: does it have eight legs?Yes: spiderNo: two pairs of legs on each segment?Yes: millipedeNo: centipede
Helpful resources
Questions
- Why is it called dichotomous?
If the entire key consists of exactly two choices at each branching point, the key is called dichotomous.
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