Natural Selection of Leaf Thickness on Planet Eorthe, Galaxy Tlaloc
Life Science, Physical Science, Earth Science. Recommended for grades 9-12.
Teacher Prep time: 10-15 min
Student time: 30-40 min
No PPE is required for the activity.
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Phenomenon
These are examples of leaves. How can they be used as evidence for adaptation among plants?
Essential Question
How can data be used to support an argument that natural selection is occurring in an organism?
Activity Objectives
- Use data to explain if natural selection may be taking place.
- Use data to argue that adaptations in the plants are taking place since their arrival on Eorthe.
Next Generation Science Standards* (NGSS)
HS-LS4-3. Apply concepts of statistics and probability to support explanations that organisms with an advantageous heritable trait tend to increase in proportion to organisms lacking this trait.
Science and Engineering Practices
Analyzing and Interpreting Data
- Apply concepts of statistics and probability (including determining function fits to data, slope, intercept, and correlation coefficient for linear fits) to scientific and engineering questions and problems, using digital tools when feasible.
Disciplinary Core Ideas
LS4.B: Natural Selection
- Natural selections occurs only if there is both (1) variation in the genetic information between organisms in a population and (2) variation in the expression of that genetic information-that is, trait variation- that leads to differences in performance among individuals.
- The traits that positively affect survival are more likely to be reproduced, and thus are more common in the population.
LS4.C: Adaptation
- Differential survival and reproduction of organisms in a population that have an advantageous heritable trait leads to an increase in the proportion of individuals in future generations that have the trait and to a decrease in the proportion of individuals that do not.
- Adaptation also means that the distribution of traits in a population can change when conditions change.
Crosscutting Concepts
Patterns
- Different patterns may be observed at each of the scales at which a system is studied and can provide evidence for causality in explanations of phenomena.
Safety Procedures and Precautions
No PPE is required for the activity.
Teacher Preparation and Disposal
Copy the student pages or upload to a class webpage.
- Graph the information for numbers of plants according to leaf thickness. Time should be on the x axis and should include year and season. Color or symbol code the 3 plant variations.
- Students may graph by hand on graph paper or use a graphing program such as excel or graphing calculators.
- Calculate the average number of plants of each variety per 1000 plant random sample for each year.
- Depending on the level of students and time available, students should at least calculate averages/mean but additional descriptive statistics may be assigned at your discretion.
- Your teacher may direct you to calculate summary, descriptive statistics for each variety of plant.
- Graph the information for numbers of fruit produced by leaf variation. Time should be on the x axis and should include year and season. Color or symbol code the 3 plant variations
- Discuss the shape of the lines on both graphs and let students briefly interpret what the graphs indicate about changes in population variation
- Calculate the average number of fruits for each variety per 1000 plant random sample for each year.
- Depending on the level of students and time available, students should at least calculate averages/mean but additional descriptive statistics may be assigned at your discretion.
- Your teacher may direct you to calculate summary, descriptive statistics for each variety of plant.
Data and Observations
Plant Data
Graphing Results
Analysis & Discussion
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What is the percent abundance of each variety of XR-45 at spring 1 of 3030, at summer 2 of 3030, 3031, 3032, 3033?
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Use the data, statistics, and graph to explain the trend in abundance of each variation in leaf thickness within the 1000 plant samples.
Student answers will vary, but all students should explain the increase in population for the thick leaf variation of XR-45 and the decrease in the other 2 varieties. Student answers must contain the numeric values they calculated.
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Use the data, statistics, and graph to explain the trend in abundance of fruit for each leaf thickness variation within the 1000 plant samples.
Student answers will vary and must contain numerical support for their statements. The thick leaf plant is producing more fruit and the other 2 varieties are showing fruit reduction at about the same rate.
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Explain the difference in fruit production among the 3 variations of plant leaf thickness that could lead to increased survival.
The plant variety with the thicker leaf produces more fruit. By producing more fruit, the plant produces more seeds, which increases the probability of survival for that variety. The evidence supports this because there is an increasing number of the thick leaf variety every year.
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Use your data to explain if natural selection and adaptation may be taking place in the plants since being transplanted to Eorthe.
Student answers will vary and must contain numerical support for their statements. Natural selection and adaptation are probably taking place on Eorthe.
Environmental changes that affect the growth of XR-45 seem to be impacting the proportion of plants with thicker leaves. The data show_______________ . When two sets of rainy seasons (spring) are followed by a dry season (summer), conditions appear to favor the plant variety that can retain water in its leaves, as evidenced by _______________.
In turn, those plants can produce more fruit because there is adequate water stored in the leaf. More fruit production from the thick-leafed variety of XR-45 means that those genes will be passed on. This fits the definition of natural selection and adaptation.
*Next Generation Science Standards® is a registered trademark of Achieve. Neither Achieve nor the lead states and partners that developed the Next Generation Science Standards were involved in the production of, and do not endorse, these products.
