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Variation Lab –How Patterns of Variation Relate To Evolution

Purpose– In this lab you will investigate variations in mealworms, peanuts, and humans and how they relate to the survival of a species. To do this, you will measure the length of mealworms, the length of the inside nut (cotyledon) of peanuts, and the length of your hand spread from the tip of your thumb to your little finger. You will, then, graph the data and analyze your results.

Definitions –

Variation –

Gene Pool –

Population –

Evolution –

Materials (per group of 3 students)–

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-meter stick or ruler

-five mealworms in a Petri dish

-five peanuts in a shell

-graph paper

-colored pencils

-calculator

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Predictions –

Predict the shape of the graph of the variation of each of the traits that you are measuring. For each trait, explain why you expect to see your predicted shape.

Procedure –

  1. Obtain five mealworms in a Petri dish from the back of the room.
  2. Using a metric ruler, measure (in mm) the length of each mealworm.
  3. Record your measurements on the chart below and on the class data chart at the front of the room.

Mealworm / 1 / 2 / 3 / 4 / 5
Length of mealworm (mm)
  1. Obtain five peanuts in a shell from the back of the room.
  2. Crack each peanut open and, using a metric ruler, measure (in mm) thelength of theinside nut (cotyledon).
  3. Record your measurements on the chart below and on the class data chart at the front of the room.

Peanut / 1 / 2 / 3 / 4 / 5 / 6 / 7 / 8 / 9 / 10
Length of inside nut (mm)
  1. Using a metric ruler, measure (in cm) the length of your hand spread apart from your thumb to your little finger.
  2. Record your measurements on the chart below and on the class data chart at the front of the room.

Hand / 1 / 2 / 3
Length of
hand spread (cm)
  1. Follow the instructions below to make a histogram of each of the data sets the class has collected. (i.e. length of mealworm)
  1. Answer the questions at the end of the lab that analyze the data.

Class Data–

Length of mealworm (mm)
Number of Students
Length of inside nut (mm)
Number of Students
Length of hand spread (cm)
Number of Students

Graphing Instructions–

  1. On your sheet of graph paper, treat the horizontal axis as your x-axis and the vertical axis as the y-axis. Label the x-axis (independent variable) and the y-axis (relative frequency).
  2. Set up your values on each axis. To do this, list your minimum and maximum measurements below and your range for each bar.

Minimummeasurement–

Maximum measurement –

Range for each bar –

  1. Draw a bar for each range of values that shows how many organisms have a trait that measures within that range. Repeat this for all ranges of measurements.

Conclusions –

  1. How do the actual shapes of your graphs compare to your predictions? Be specific in the similarities and differences.
  1. Think about how the data was collected for this lab. Looking at each of the graphs, what effect does sample size have on the shape of the graph and the validity of the information? Are there any reasons why the data in this lab may not give us a perfect bell shaped curve, even though it may exist in the entire population. What flaws in the procedure may give us incorrect data?
  1. For each population (mealworms, peanuts, humans), how might each maximum measurement help the organism survive in its natural environment?

Mealworm –

Peanut –

Human –

  1. For each population (mealworms, peanuts, humans), how might each minimum measurement help the organism survive in its natural environment?

Mealworm –

Peanut –

Human –

  1. What general statement can you make about the gene pool for each of the populations you studied?
  1. A new population of birds has migrated into the mealworm’s natural environment. These birds have a new favorite meal – a big, juicy mealworm. Over time, how might these birds affect the gene pool for the length trait in this population of mealworms? How long will it take for any changes in the population’s average length to be noticed?
  1. How do patterns of variation relate to evolution? Explain how variation in a population leads to a change in the relative frequencies of alleles, and could lead to the formation of a new species. (A complete answer should be at least a paragraph in length.)

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