An Educator's Reference Desk Lesson Plan
Date: May 1994
Grade Level(s): 3, 4, 5, 6
Subject(s):
This activity is the product of consistent requests received on Family Science evaluations for donuts to be served at the classes! Since we had done one entire evening class sorting, classifying and constructing dichotomous keys, it became a natural review and culmination activity for our Family Science program. It's also a big hit in the classroom!
PURPOSE:
This is the clearest and easiest road to understanding construction of a dichotomous Key that I have found.
OBJECTIVE(s):
Learners will:
Prerequisite Skills:
MATERIALS:
ACTIVITIES AND PROCEDURES:
Before class:
Best Shot:
Have each person pick a donut and put their
name on the baggie in a permanent felt pen. Then have the group lay all the donuts out in front of
them and name one property they can use to divide the donuts into two piles. For the sake of clarity
make one pile 'that which has the property' and the other one 'that which doesn't'. For example in
this group of donuts:
File in 1a and 1b on the dichotomous key as:
1a - not round
1b - round
Next take either group and divide it again by one property. For example,
take the not round into twist or no twist:
Sample Donut Key:
1a - not round
1b - round
2a - not round, twisted (Shirley's)
2b - not round, not twisted (Michael's)
3a - round, no hole (John's)
3b - round, hole
4a - round, hole, choc. iced
4b - round, hole, not choc. iced (Sheila's)
5a - round, hole, choc. iced, ruffled (Paul's)
5b - round, hole, choc. iced, not ruffled (Katie's)
** 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
Have fun and enjoy your donuts!
TYING IT ALL TOGETHER:
Family Science available form N.W. Equals Portland, OR has a good unit on constructing and understanding dichotomous keys.
Useful Internet Resource:
* Dichotomous
Key for Trees
http://oregonstate.edu/trees/dk/start.html