NAME:
DATE:
BIOLOGY LAB
SECTION:
MINI LAB: USING AND CONSTRUCTING DICHOTOMOUS KEYS
CLASSIFICATION TECHNIQUES
QUESTION:
How do scientists use and make dichotomous keys?
INTRODUCTION:
1) Who developed the classification system that scientists use today to classify and group
organisms according to their inherited traits?
2) What is taxonomy? Why is it essential to biology?
Background Information: A dichotomous key uses pairs of contrasting, descriptive statements
to lead to the identification of an organism or object. It uses the principle of forced choice – the
reader must make a decision at certain points that narrow the path down towards a particular
answer. Field guides often use dichotomous keys to identify organisms.
OBJECTIVES:
In this exercise you will:
 Use a dichotomous key to identify leaves
 Construct a dichotomous identification key
MATERIALS:
 Pencil
 Paper
 Shoes
 Masking tape
 Marker
PROCEDURE:
PART A
1. Take off your shoes. (Yeah! Plug your nose!!!) Use masking tape to label each shoe
with your name.
2. Place your shoes into a right and a left pile.
3. Divide the entire class into two or four groups – making sure each group take entirely the
right shoes or the left shoes.
4. Each group should begin by discussing the appearance of the shoes. List and write down
some common and uncommon characteristics that you notice in the shoes.
5. Choose a partner within your group. One member of the pair will be a recorder and the
other will be a shoe manipulator. The actions and decisions of the entire group will help
guide you.
6. You should start by dividing the shoes into two main groups based on their physical
characteristics. For example, you could divide them into a group of male shoes and
female shoes or sneakers and sandals.
7. Then, divide each of those groups into two more groups. Continue dividing each group
into two until each sneaker has been identified or narrowed down to one owner.
8. The recorder will now have each shoe identified in their notes. Use this information to
make a dichotomous key that can be used to identify the owner of each shoe.
9. After pairs from both groups have completed their keys, exchange keys with a member of
the opposite group.
10. Pick a shoe and use the other group’s key to identify the owner of the shoe.
11. Record if the other group’s key correctly identified the shoe’s owner in the results.
12. Repeat this step one more time and identify another shoe.
13. Return the key to the other group so corrections can be made if needed.
14. Staple your key to your results section. Each pair should turn in one section of results.
PART B – PAGES 462-463
1. Use the dichotomous key in your class textbook to identify the tree leaves. Begin with
the paired descriptions 1a and 1b, and follow the directions. Proceed through the list of
paired descriptions until you identify the leaf in question.
2. Label each leaf in the results section.
NAME(S):
DATE:
BIOLOGY
SECTION:
RESULTS:
PART B: Leaf Identification
I.
__________________________
II.
__________________________
III.
__________________________
IV.
__________________________
V.
__________________________
VI.
__________________________
VII.
__________________________
PART A: Dichotomous Key Construction – Staple your key to this sheet
TRIAL ONE: CIRCLE ONE: Did your group correctly identify the shoe? Yes or No
TRIAL TWO: CIRCLE ONE: Did your group correctly identify the shoe? Yes or No
ANALYSIS
1. What other characteristics might be used to identify leaves with a dichotomous key?
2. Were you able to identify the shoes using the other group’s key? Why or why not?
3. How was it helpful to discuss the shoe characteristics with your group members before
you started?
4. Does a dichotomous key begin with general descriptions and then proceed to more
specific descriptions, or vice versa? Explain your answer using examples from the key
that your group made.
5. Are dichotomous keys based on a phylogenetic or morphological approach to
classification? Explain your answer.
CONCLUSION:
List the characteristics that might be used to identify birds using a dichotomous key.
Labs Due: _____________________
PER PAIRED GROUP:
- Results answers
- Full page dichotomous key
- Analysis and Conclusion answers