1. Human Traits - Lesson Plan
Day 1 - Introduction
- Pose the following scenario to your students: “An exchange student from England is coming to stay with your family for a month. You go to the airport to pick her up and need to describe yourself to her so that she can find you in the crowd at the airport. In 2-3 sentences, how would you describe yourself?” Solicit volunteers to describe themselves.
- After 5 or 6 students have shared, draw attention to some of the general categories of responses. Note how some descriptors are biologically based (eye color, ethnicity, hair color, height, etc.), whereas others are environmental (clothing, accessories, dyed hair, etc.). In this class, we will focus on the biological descriptors.
- Go over the vocabulary. “Characteristics” are the general category of descriptions (height, eye color, etc.) whereas “traits” are the precise description of an individual’s characteristics (5’2”, blue eyes, etc.).
- Pass out the human traits survey. Read the instructions together, then answer any questions about the survey.
- Allow students to work individually or in pairs to survey their traits.
- Completion of the survey for individuals not in your classes should take place as homework that evening.
Day 2 – Collect and organize data
- Give each student a sheet with 12 sticky dots.
- Have students write the name (or initials) of each person they surveyed on the dots. Each person surveyed should end up with 4 dots total. If using multi-colored dots, each person should have their name on a dot of each color.
- Describe to the students how a histogram is constructed with the range of possible traits on the x axis and the number of people in a given category on the y axis. Show students how to add their dots to the charts, making sure they understand how the dots stack one on top of the other.
- Describe to the students how to add a tally mark to the summary table beside the traits for themselves and the people they surveyed.
- Allow students time to add their information to the graphs and tables.
- If you have multiple classes, you may want to postpone the analysis and discussion part below until after all classes have added their information to the tables.
Day 3 – Analyze data
- This is the opportunity for your students to look at the tables and graphs and look for patterns the different kinds of traits. Before you begin, make sure students know how to find an average, median, range, outlier and percentage. Use a few examples to help them with the statistics.
- Either as a class or in small teams, summarize the data – you may wish to have students create a summary table, pie chart, histogram or other graph in their lab notebook. What was the average broad jump distance? What was the range? Were there any outliers? What percentage of people were blue eyed? What percentage had freckles?
- Look for patterns. Do the 4 histograms look the same in shape (they should all form a bell curve distribution)? What would histograms look like for the yes/no/multiple choice traits? What would the histograms look like for other traits that were not surveyed like height, age, favorite color, hair length, test scores, etc.?
- What is the source of all these differences between people (genes and environment)? Discuss the contribution of genetics (nature) versus environment (nurture). With broad jump distance as an example, how much is determined by genetics and how much is determined by environment like practice?
- From here, there are many different ways to take the discussion:
- Discuss the difference between the traits measured in centimeters versus the yes/no/multiple choice traits. How many possible outcomes were there for traits measured in centimeters? If the yes/no/multiple choice traits were plotted on a histogram, what would the histogram look like? What is the biological difference between these 2 categories (traits measured in centimeters depend on many genes while yes/no/multiple choice traits depend on a small number of genes)?
- Discuss the evolutionary advantage of different traits. Is there an advantage to having a broad hand span? Is there an advantage to having a small hand span?
- Lead the discussion into a description of basic Mendelian genetics. For each of the yes/no traits, one trait is dominant and the other is recessive (see Making Babies lab for additional information). Eye color and hair color are more complicated because they are determined by multiple genes. Hair texture is more complicated because it is determined by codominance. Discuss how each person has 2 genes for each trait, one from mom and one from dad. The combination of these genes is what determines your traits.