OBJECTIVES: Students will:
Construct a simple key that places every donut in its own
category according to its properties.
Identify each donut according to the key.
6 distinctly different donuts (for a group of 6)
6 sandwich bags
1 blank dichotomous key per person
Before class: Put each donut in its own baggie.
1. Ask students if they know what classification is and if they have done it or not (most will not know). Then ask them if they know what organization is (more affirmative responses). Ask them how they might organize their clothes (examples – shirts and pants, by color, by season, etc). On the board, draw an example of a dichotomous key that shows how their clothes may be organized. Discuss that objects have properties or features that we use when we organize them.
2. Briefly review what a property is. Hold up one donut and
orally list properties that might pertain such as shape,
size, color, coating, etc.
3. Put students into groups of six.
4. Have each person pick a donut and put their name on the
baggie in permanent marker. Then have the group lay all of
the donuts out in front of them and name one property they
can use to divide the donuts into two piles.
5. Make one pile 'that which has the
property' and the other one 'that which doesn't'. For
example in this group of donuts: round and not round.
Fill in 1A and 1B on the dichotomous key as
1A not round
Next take either group and divide it again by one property.
For example take the not round into twist or no twist. Fill
in 2A and 2B on the dichotomous key/
2A not round twist
2B not round not twist
As soon as you've gone as far as necessary to identify an
individual donut then name whose it is.
Continue until all donuts have their own individual
category. Students must name all the characteristics to
"key out" their donut before they can have it to eat.
Sample Donut Key
1A not round
2A not round, twisted
2B not round, not twisted
3A round, no hole
3B round, hole
4A round, hole, choc. iced
4B round, hole, not choc. iced
5A round, hole, choc. iced, ruffled
5B round, hole, choc. iced, not ruffled
** Note **
Any property may be used to make each new classification.
There are many right answers as long as each division is
made according to just one property and states it in terms
of that property; for instance:
Green --- Not Green
Afterwards, discuss with the class how each group classified their donuts. Look at the properties that each group chose to use in their key. Point out how using different features may have caused groups to organize their donuts in different ways and that it is important for scientists to agree to use the same features so that they do not overlap.