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Dichotomous Key Notes
Note: The word dichotomous means “divided into two parts”. A dichotomous key is a tool that provides the reader with two statements (choices) that describes characteristics about items or living organisms. These statements help the reader to classify and identify the items.
Key Ideas for reading a dichotomous key:
- Always read the descriptions given in the two statements thoroughly.
- Make sure you understand all the words in the statement. If not, look the word up in a dictionary.
- Examine all the chas inracteristic the pictures for the items or living organisms.
- Decide which choice best represents the description given in the statement.
- When all items have been identified, recheck the answers.
Dichotomous Key Example
- a. Body of shell with whorl appearance (turns of the spiral shell)………go to #2
b. Body of shell with no whorl appearance………………………………go to #4
- a. Has pointed needle-like spines……………………................................go to #3
b. Has curved horn-like spines………………………................................Kiener Whelk
- a. Raised closely spaced longitudinal ribs on body………………………Giant Atlantic Murex
b. Raised widely spaced vertical ribs on body……………………………Lightning Whelk
- a. ear-shaped pattern………………………………………………………go to #5
b. no ear-shaped pattern…………………………………………………...go to #6
- a white with shiny appearance on shell…………………………………….White Baby's Ear
b.gray to tan with shiny appearance on shell………………………………Atlantic Moon Snail
- a. opening with slit-like tooth appearance………………………………….Atlantic Deer Cowrie
b. opening with non slit-like tooth appearance……………………………..go to #7
- a. gray to tan appearance on shell…………………………………………..Lettered Oliven
b. brown and white pattern appearance on shell………………………..Marble Cone shell
Answers:
- Atlantic Moon Snail
- Giant Atlantic Murex
- Marble Cone Shell
- Lightening Whelk
- Atlantic Deer Cowrie
- White Baby’s Ear
- Lettered Olive
- Kiener Whelk
Try Another Dichotomous Key for Practice!
Wacky People Key
1a Two feet |
2 |
1b Some other number of feet |
3 |
2a Does not look at all human |
4 |
2b Looks a lot like a human |
5 |
3a One leg |
6 |
3b Three or four legs |
7 |
4a Fly-like |
Mosk Cara |
4b Not fly-like |
8 |
5a Seems to be a girl |
Rita Nita |
5b Not a girl |
9 |
6a Leg is curled , two feet |
Ru-ela.Brella |
6b Leg is straight, one foot |
Giggles |
7a Three legs |
10 |
7b Four legs |
11 |
8a Has webbed feet |
Hex Oculate |
8b Clawed feet |
12 |
9a Curly hair, no toes |
Lugio Wirum |
9b Wiggly looking mouth, three toes on feet |
C. Nile |
10a Very long nose, open mouth |
Elle E. Funk |
10b Some other appearance |
13 |
11a Has duck bill, two pinchers |
Tri D. Duckt |
11b No arms or pinchers |
14 |
12a Has ears, tail, and beak |
Grif Leon |
12b Four eyes on stalks |
Eggur Ondy |
13a One eye, webbed feet |
Cue Kide |
13b Four stalked eyes, four pinchers |
Quadrumenox |
14a Three toed feet, nose like a flower |
Tunia petalos |
14b Spider-like, has spots |
Patterned mulywumpus |
Adapted from Vivian Johnson at HotChalk, Inc.
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