Download Allele Frequency Lab: Variation in a Pumpkin Species

Allele Frequency Lab: Variation in a Pumpkin Species
Standard: SB5.d Relate natural selection to changes in organisms.
Essential Questions: What is the role of natural selection in speciation?
Objective: To observe how selective forces “Natural Selection” can change allele frequencies in a
population and cause evolution to occur.
Introduction: Allele frequency refers to how often an allele occurs in a population. Allele frequencies can
change in a population over time, depending on the ‘selective forces’ shaping that population.
Predation, food availability, and disease are all examples of selective forces. Evolution occurs when
allele frequencies change in a population!
In this lab, you will be determining the allele frequency of length in a pumpkin seed population.
Procedure:
1. Count out 50 Pumpkin seeds.
2. Measure their length in millimeters.
3. Place them in size groups on your paper. Usually, you will need to form a group of pumpkin seeds in
each of the following size categories: Under 12mm, 12 mm, 13 mm, 14 mm, 15 mm, 16 mm, 17 mm, 18
mm, 19 mm, 20 mm, 21mm, and over 21 mm.
Your sheet of notebook paper can be used as a temporary pumpkin seed holder to hold them in groups,
like this:
12 mm
13mm
14mm
15mm
16mm
17mm
18mm
19mm
20mm
21mm
Under 12mm
Over 21 mm
4. Once you have divided seeds into groups, COUNT and RECORD how many seeds fit into each size
group. LEAVE THE SEEDS LATING IN EACH GROUP. DON’T CLEAR YOUR PAPER!!!!!
5. Then carry the seeds to the front of the room and place the seeds into their appropriate sorting tubes.
6. As the other students do the same, you will notice a HISTOGRAM (Bar Graph) forming at the front of
the room.
7. Enter your data onto the class spread sheet so it can be projected for the class to record.
Analysis Questions:
1. Make a BAR GRAPH on graph paper of the data that was accumulated by the entire class. This
graph should be titled “FREQUENCY DISTRIBUTION of PUMPKIN SEEDS”
2. Explain what CAUSES the pumpkin seeds to be so many different sizes? Use the words natural
selection, fitness, and adaptations in your explanation.
3. Explain why some seed sizes (12mm) are rare while other seed sizes (17mm) may be more
common.