Activity: Recognizing Variation in a Population

Goals: To measure a selected variation within a species.

Background Information: One of the points in Darwin’s theory of evolution is that

variations are found among individuals in a species. A variation is the appearance of an inherited trait that makes an individual different from other members of the same species. Variations can be small, such as the differences in the form of human hairlines, or large, such as an albino deer or a fruit without seeds. Variations are important in populations of organisms. If enough variations occur in a population as it produces new offspring, a new species may evolve from the existing species. It may take hundreds, thousands, or even millions of generations for a new species to evolve. Variations must exist in a population for evolution to take place.

Materials: sunflower seeds, metric ruler

Procedure:

  1. What I Know:Write two sentences about what you already know about variations that exist in a population.
  1. Complete the following tasks:
  • Use a ruler to measure the length of 10 randomly selected sunflower seeds. Measure the length of the sunflower seeds in millimeters (mm).
  • Record each measurement on your data table.
  • Use the data totals to complete the frequency chart.
  • Use the information from the frequency chart to create a bar graph.
  1. What I Observed: Summarize your data using the frequency chart provided. Use this information to make a bar graph of the frequencies. Place the number of seeds on the y-axis and the frequency range on the x-axis.

Data Table: Measure the length of 10 random sunflower seeds in millimeters (mm) and record the lengths on the table below.You and your partner can each measure 5 sunflower seeds for this part and share the results.

Length of Sunflower Seed (mm)
1
2
3
4
5
6
7
8
9
10

Frequency Chart: Ask your group members (the students at your table) to share the information from their data table on seed length to complete the frequency chart below.

Length (mm) / Frequency
0 -5 mm
6 -10 mm
11 – 15 mm
16 – 20 mm

  1. Questions: Answer the following questions:
  1. Calculate the range of variation in your experiment. The range is the difference between the largest and the smallest measurements.
  1. Look at your bar graph, which length frequency was the most common for your sunflower seed samples?
  1. What does the range of length measurements for the sunflower seeds indicate?
  1. How do you think a graph of data from the entire class would be different from your graph of data?
  1. What I Wonder: Write a question that states describes what you still may wonder or may still want to know about the topic of variations in a population.
  1. Claim and Evidence Writing Prompts: Use the following prompts to help you construct your lab conclusion, What I Learned.
  • Goal: State the goal of this lesson.

The goal of this lesson is…

  • Claim: What did you learn from the activity that satisfies the goal of this lesson? This is an I Learnedstatement.

I learned that…

  • Evidence: How can you prove from your observations that you learned what you claim? This can be a general statement that you will explain in detail in your explanation.

I know this because….

  • Explanation: Use specific data from your observations to support your claim and describe the evidence. Use details to support your claim.
  • Concluding Statement: Reword the goal and either add information you learned about the topic from your text book, class discussions, and/ or personal research OR you can extend the statement by adding a relevant question.
  1. What I Learned: Write at least a one paragraph summary of what you learned from completing this activity. Use the Claims and Evidence Writing Prompts to help you compose your summary.