Classification

Activity One: Red and Yellow Squares, Triangles, and Circles

Each of you has been given 12 pieces of paper.

Divide the papers into two groups. What characteristic did you use to divide them?

1.

2.

Put your papers back into one group. Divide them into three. What were the three characteristics used to separate them?

1.

2.

3.

Put your papers back into one group. Divide them into six groups. What are the characteristics used to separate them?

1.

2.

3.

4.

5.

6.

If you would make a graph for the data it might look like the following:

_____ _____ _____ _____ _____ _____ ................_____ _____ _____ _____ _____ _____

Write the name of each unique object at the end of the path that identifies it.

You identified 12 objects. Another way to represent this is with a dichotomous key.

Below is a dichotomous key for this set of objects. It divides the objects into pairs, the first pair is red and yellow (1A and 1B). Depending on the color of the object to identify the next number is chosen from the one that describes the object (2 or 7). Continue the procedure until the object is identified.

Use a large red circle and follow it on the key:

1 A Red paper (2)
1B Yellow paper (7)
2A Circle (3)
2B Non circle (4)
3A Large red circle
3B Small red circle
4A Square (5)
4B Triangle (6)
5A Large red square
5B Small red square
6A Large red triangle
6B Small red triangle
7A Circle (8)
7B Non circle (9)
8A Large yellow circle
8B Small yellow circle
9A Square (10)
9B Triangle (11)
10A Large yellow square
10B Small yellow square
11A Large yellow triangle
11B Small yellow triangle

Note that when something is "keyed down", it is identified. It has been classified completely when you reach the boldface print.

  Try to identify several pieces of paper on the key, such as a small yellow triangle, until you know how to use it easily.

Activity Two: What's the Object

In a small container are a number of objects which can be graphed the same way as the bits of colored paper. Fill in the graph below:

The objects can also be identified with a dichotomous key. Have a partner select one object from the container, without you seeing what it is, and ask your partner questions to identify the object.

1A     Object made of metal (2)
1B     Object not made of metal (5)

2A    Shaft mostly smooth (3)

2B    Shaft with deep grooves on it) (4)

3A    TWO INCHES OR LONGER NAIL

3B    LESS THAN TWO INCHES BRAD OR TACK
4A    + ON TOP PHILLIPS SCREW
4B    ONE SLIT ON TOP SCREW
5A    Match (6)
5B    Toothpick (7)
6A    WOODEN SHAFT WOODEN MATCH
6B    PAPER SHAFT PAPER MATCH

7A    ROUND SHAFT, POINTED AT BOTH ENDS ROUND TOOTHPICK

7B    FLAT SHAFT, POINTED and ROUNDED on each END. FLAT TOOTHPICK

Now key out a paper match.

Keys are useful in the identification of plants and animals. Your teacher can give you keys to identify: deciduous trees, evergreen trees, insects or other objects.

Activity Three: Making Your Own Key

To really understand a key you should make one for yourself. Try one for animals like: pigeon, rattlesnake, rabbit, goldfish, earthworm and butterfly.

First, you might want to record the similarities and differences of the animals in a chart.
After you have collected enough data you can make a graph. Here is one started for you.

or a chart might help:

  pigeon rattlesnake rabbit goldfish worm butterfly
wings            
scales            
feathers            
warm blooded            
cold blooded            
backbone            
fur            
live totally under water            
             

Now complete the dichotomous key:

1A     Animals without a backbone (2)

1B     Animals with a backbone

2A     With legs - BUTTERFLY
2B     Without legs -
3A
3B
4A
4B
5A
5B
6A
6B
7A
7B

Now that you understand how to make a graph or a dichotomous key you can use them to help sort, classify, or identify objects.

See examples - leaf identification chart dichotomous leaf identification chart coniferous

Robert Sweetland's Notes ©