Name _____________________________________________________________
Date ____________
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.
2. 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.
3. 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)
0 -5 mm
6 -10 mm
11 – 15 mm
16 – 20 mm
Frequency
4. Questions: Answer the following questions:
a. Calculate the range of variation in your experiment. The range is the difference
between the largest and the smallest measurements.
b. Look at your bar graph, which length frequency was the most common for your
sunflower seed samples?
c. What does the range of length measurements for the sunflower seeds indicate?
d. How do you think a graph of data from the entire class would be different from
your graph of data?
5. 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.
6. Claim and Evidence Writing Prompts: Use the following prompts to help you
construct your lab conclusion, What I Learned.
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


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 Learned statement.
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.
7. 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.