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Name: ______________________
Using a Dichotomous Key:
A dichotomous key is a method for determining the identity of something (like the
name of a butterfly, a plant, a mineral, or a rock) by going through a series of choices
that leads the user to the correct name of the item. Dichotomous means "divided in
two parts".
At each step of the process of using the key, the user is given two choices; each
alternative leads to another question until the item is identified. (It's like playing 20
questions.)
For example, a question in a dichotomous key for trees might be something like, "Are
the leaves flat or needle-like?" If the answer was "needle-like," then the next question
might be something like, "Are the needles in a bunch or are they spread along the
branch?" Eventually, when enough questions have been answered, the identity of the
tree is revealed.
Classroom Activity:
As a simple example, you can construct a dichotomous key to identify people (or
another group of items) in a classroom, using questions based on gender, hair
length/color, glasses (or not), clothing color, etc.
Question 1: Is the person male or female?
Question 2: Does the person wear glasses or not?
Question 3: Is the person wearing blue jeans or not?
The end of each branch of the key should be a person's name.
A dichotomous key will have enough questions to identify each member of the group.
To test it, you can identify each person in the group by going through the key and seeing
if the right name comes up.
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Creating a Dichotomous Key
Part 1: Making Observations
There are many different “unidentified objects” located at the front of the room. Write down as
many qualitative observations as you can about each unidentified object in the table below.
Describe each object in as much detail as possible.
Unidentified
Object
A
B
C
D
E
F
Qualitative Observations
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Part 2: Creating Scientific Names
Create a “scientific name” for each object using a noun and an adjective (for example, Aching
toes or Comfy flats). Make sure you following the proper procedure for scientific naming:
The 1st word (genus) should be capitalized, and the 2nd name (species) should be
lowercase.
Unidentified
Object
“Scientific Name”
A
B
C
D
Part 3: Identifying Similar Characteristics
How many differences can you find between the objects? How many different ways can you
split them into groups? Fill in the following blanks. The first example is done for you.
Laces vs. No Laces
_________________________________ vs. ___________________________________
_________________________________ vs. ___________________________________
_________________________________ vs. ___________________________________
_________________________________ vs. ___________________________________
_________________________________ vs. ___________________________________
_________________________________ vs. ___________________________________
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Part 4: Creating a Dichotomous Key
Create a dichotomous key for the shoes in the space below.
Statement
1 The object has laces.
The object does not have laces.
2
3
4
5
6
Instruction
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Questions:
1. Were there any shoes that were hard to classify? Why?
________________________________________________
________________________________________________
________________________________________________
2. What were some of the common characteristics that you used to
classify the shoes?
________________________________________________
________________________________________________
________________________________________________
3. Is there more than one way you could have classified the shoes?
________________________________________________
________________________________________________
________________________________________________
4. How does classifying shoes relate to science?
________________________________________________
________________________________________________
________________________________________________
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Dichotomous Key Lab:
1. Has pointed ears ............................... go to 3
Has rounded ears ....................................go to 2
2. Has no tail .................................... Kentuckyus
Has tail .................................................. Dakotus
3. Ears point upward ............................ go to 5
Ears point downward ..............go to 4
4. Engages in waving behavior ............... Dallus
Has hairy tufts on ears ....................Californius
5. Engages in waving behavior ........ WalaWala
Does not engage in waving behavior ......go to 6
6. Has hair on head .................. Beverlus
Has no hair on head (may have ear tufts)
……………go to 7
7. Has a tail ............................................. Yorkio
Has no tail, aggressive ............................ Rajus
Norns belong to the
genus Norno and can be
divided into eight
species that are
generally located in
specific regions of the
world. Use the
dichotomous key to
identify the norns below.
Write their complete
scientific name (genus +
species) in the blank.
8
2.
1.
4.
6.
1.
3.
5.
7.
1.
8.
1.
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Creating a Dichotomous Key:
You are an alien taxonomist. Your job is to classify the aliens found on the
planet Bizarro-World. You have noted that there are two main groups of
organisms on this planet: a group of humanoid like organisms that live on
the land, and a group of fish like organisms that live in the water. The fish
like organisms are photosynthetic and get their food from Bizarro-Sun, the
humanoids eat the fish-like organisms. Create a dichotomous key which will
classify this entire group of creatures. The aliens on Bizarro-World are
pictured below.
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Does the alien
look like a
humanoid?
YES
NO