What is a Dichotomous Key?
• S7L1. Students will investigate the diversity of living
organisms and how they can be compared
scientifically.
• a. Demonstrate the process for the development of a
dichotomous key.
• b. Classify organisms based on physical
characteristics using a dichotomous key of the six
kingdom system (archaebacteria, eubacteria,
protists, fungi, plants, and animals).
What is a Dichotomous key?
• Used to help identify known specimen
• Work by asking yes or no questions whose
answers lead the reader to the correct taxa for
the organism
• Each step has 2 choices
• Uses scientific names that are the same in
every country
Dichotomous Keys
1a. Organism has 4 legs
Go to # 2
1b. Organism has more than 4 legs
Go to # 20
2a. Organism has a tail
Go to # 3
2b. Organism has no tail
Go to # 35
3a. Organism has stripes
Bengal Tiger
3b. Organism has no stripes
African Lion
Dichotomous Key
• Try this one:
1a. Organism walks on all 4 legs (quadruped)
2
1b. Organism walks on 2 legs (biped)
8
2a. Organism has visible fur
3
2b. Organism has no visible fur
20
3a. Organism lives in warm climates
7
3b. Organism lives in cold climates
4
4a. Organism has brown or black fur
Ursus americanus
4b. Organism has white fur
Ursus maritimus
Taxonomy, Classification, and Dichotomous
Keys
Help! Scientists have discovered quite a few new creatures on planet
Pamishan. They need your help to identify and classify them. Use the
dichotomous key on the next page to identify these creatures.
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The creature has a large wide head............................go to 2
The creature has a small narrow head..........................go to 11
It has 3 eyes ................................................go to 3
It has 2 eyes ................................................go to 7
There is a star in the middle of its chest....................go to 4
There is no star in the middle of its chest ..................go to 6
The creature has hair spikes .................................Broadus hairus
The creature has no hair spikes...............................go to 5
The bottom of the creature is arch-shaped ....................Broadus archus
The bottom of the creature is M-shaped .......................Broadus emmus
The creature has an arch-shaped bottom .......................Broadus plainus
The creature has an M-shaped bottom...........................Broadus tritops
The creature has hairy spikes ................................go to 8
The creature has no spikes....................................go to 10
There is a star in the middle of its body ....................Broadus hairystarus
The is no star in the middle of its body .....................go to 9
The creature has an arch shaped bottom .......................Broadus hairyemmus
The creature has an M shaped bottum ..........................Broadus kiferus
The body is symmetrical ......................................Broadus walter
The body is not symmetrical...................................Broadus anderson
The creatrue has no antennae .................................go to 12
The creature has antennae ....................................go to 14
There are spikes on the face .................................Narrowus wolfus
There are no spikes on the face ..............................go to 13
The creature has no spike anywhere ...........................Narrowus blankus
There are spikes on the right leg ............................Narrowus starboardus
The creature has 2 eyes.......................................go to 15
The creature has 1 eye........................................Narrowus cyclops
The creature has a mouth......................................go to 16
The creature has no mouth.....................................go to 17
There are spikes on the left leg .............................Narrowus portus
There are no spikes at all ...................................Narrowus plainus
The creature has spikes ......................................go to 18
The creature has no spikes ...................................Narrowus georginia
There are spikes on the head .................................go to 19
There are spikes on the right leg.............................Narrowus montanian
There are spikes covering the face ...........................Narrowus beardus
There are spikes only on the outside edge of head ............Narrowus fuzzus
What is a Dichotomous Key?
• What is the purpose of a dichotomous key?
• How do you read a dichotomous key?
• Each step has _______ choices
• What name is assigned to the new organism?