Sandy C - Evolution/ Polygenic Traits

Population Study (Sandy Combs)

Lesson Plan: High School Biology

Chapter 15 and 16  Evolution

Objectives: Students will understand

1)    how data is collected and organized

2)    that some sort of statistical analysis must be performed on the data in order to gain understanding from it. Students calculate the mean

3)    how to create a graph from their data representing all their variables

4)    how to read the graph and gain knowledge from it

5)    how to draw conclusions from their results

California State Standards: Evolution

7.a The frequency of an allele in a gene pool of a population depends on many factors and may be stable or unstable over time. As a basis for understanding this concept: a. Students know why natural selection acts on the phenotype rather than the genotype of an organism.

7.d Students know variation within a species increases the likelihood that at least some members of a species will survive under changed environmental conditions.

8.a Evolution is the result of genetic changes that occur in constantly changing environments. As a basis for understanding this concept: a. Students know how natural selection determines the differential survival of groups of organisms.

 8.b Students know a great diversity of species increases the chance that at least some organisms survive major changes in the environment.

8.c Students know the effects of genetic drift on the diversity of organisms in a population.


2 meter sticks

2 rulers




Students understand the concepts of polygenic traits, populations, genetic drift, directional selection, stabilizing selection, and disruptive selection.


The purpose of this lab is to give students an opportunity to form a hypothesis, collect data, make sense of their data by calculating a mean, organizing their results by creating a graph to help visually interpret the data, and making conclusions about their hypothesis based on their data. From this study students will write a report with the following components: Introduction and hypothesis, procedures, results, conclusions, discussion.


This study will collect data on the height of each member of the class. Data for females will be collected separately from males. A mean for both males and females will be calculated from the data. A bar graph will be created from the data representing all heights in the class .



1)    each meter stick is taped vertically to the wall one meter above the floor

2)    students are divided into groups of three

3)    students are given the directions and instructed to formulate and record a hypothesis regarding the outcome of this study

4)    Each group will measure all members height and record the data

5)    Each member of the group will have their height measured, will measure the height of another group member, and will record the height of a group member.

6)    Each group will record their data on their own data sheet and on the combined class data table.

The combined class data table is vertically divided into boxes of 5 cm increments beginning with the height of the shortest person in the class
1)    and continuing through the height of the tallest person in the class. Horizontally divided for each group to enter their data, and a bottom row to total the tallies.

2)    Each group will make tally marks in the boxes corresponding to the height in cm for each member of their group.

3)    All tally marks for each height and for each group will be counted and recorded.

4)    As the class data table is completed all students will record the class data.

5)    Groups will work together to calculate mean heights for male and females, and create one bar graph representing all the class data.


1)    Is height a polygenic trait or a single gene trait? How do you know?

2)    Why does the graph have two peaks?
3)  Does this graph show disruptive selection? why or why not?

4)    If the population was experiencing directional selection how would that be expressed on the graph?

5)    Create a scenario in which directional selection would affect height.

6)    Explain why the characteristic of height might experience stabilizing selection?
Norman Herr,
Mar 31, 2011, 12:01 PM