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Natural Selection of Leaf Thickness on Planet Eorthe, Galaxy Tlaloc

A Carolina Essentials™ Activity

Overview

In this introductory activity, students graph and analyze data, observing trends and change over time. The data set consists of leaf thickness measurements taken 4 times during a growing season and the number of fruits produced by plants with each thickness of leaf. The graphical data visualization can be the lead-in to more advanced statistical analysis for comparing differences among groups. With the data provided, students see a shift in the number of plants for each thickness—the thick-leafed plants increase in number and produce more fruit. Students are asked to use the data to make an argument for natural selection in the plants grown on Eorthe.

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Teacher Notes
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Student Worksheet
Grade & Discipline
9-12

Life Science, Physical Science, Earth Science. Recommended for grades 9-12.

Time Requirements
Prep10-15 min
Activity30-40 min

Teacher Prep time: 10-15 min
Student time: 30-40 min

Safety Requirements

No PPE is required for the activity.

Overview

In this introductory activity, students graph and analyze data, observing trends and change over time. The data set consists of leaf thickness measurements taken 4 times during a growing season and the number of fruits produced by plants with each thickness of leaf. The graphical data visualization can be the lead-in to more advanced statistical analysis for comparing differences among groups. With the data provided, students see a shift in the number of plants for each thickness—the thick-leafed plants increase in number and produce more fruit. Students are asked to use the data to make an argument for natural selection in the plants grown on Eorthe.

Save & Print
Teacher Notes
Save & Print
Student Worksheet

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

  1. Use data to explain if natural selection may be taking place.
  2. 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.

Student

Teacher

  1. Student: 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.
  1. Teacher: Students may graph by hand on graph paper or use a graphing program such as excel or graphing calculators.
  1. Calculate the average number of plants of each variety per 1000 plant random sample for each year.
  1. 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.
  1. Your teacher may direct you to calculate summary, descriptive statistics for each variety of plant.
  1. 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
  1. Discuss the shape of the lines on both graphs and let students briefly interpret what the graphs indicate about changes in population variation
  1. Calculate the average number of fruits for each variety per 1000 plant random sample for each year.
  1. 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.
  1. Your teacher may direct you to calculate summary, descriptive statistics for each variety of plant.

Data and Observations

Plant Data

Number of XR-45 Plants/1000 Plant Random Sample by Leaf Thickness (mm)
Year Season Leaf Thickness <0.5mm Leaf Thickness 0.5-1.0mm Leaf Thickness >1.0mm
3030 Spring 1 320 342 338
  Spring 2 315 344 341
  Summer 1 316 338 346
  Summer 2 303 335 362
3031 Spring 1 302 331 367
  Spring 2 299 331 370
  Summer 1 299 330 371
  Summer 2 283 332 385
3032 Spring 1 282 329 389
  Spring 2 280 300 420
  Summer 1 280 298 422
  Summer 2 260 287 453
3033 Spring 1 258 288 454
  Spring 2 255 287 458
  Summer 1 254 288 458
  Summer 2 250 287 463
XR-45 Leaf Thickness and Number of Fruit (1000 plant random sample)
Year Season Average Number of Fruit/Plant (Thin leaf) Average Number of Fruit/Plant (Moderate leaf) Average Number of Fruit/Plant (Thick leaf)
3030 Summer 1 12 14 18
3030 Summer 2 14 14 17
3031 Summer 1 9 14 19
3031 Summer 2 9 13 19
3032 Summer 1 9 12 20
3032 Summer 2 7 13 18
3033 Summer 1 4 10 19
3033 Summer 2 3 8 21

Graphing Results



Analysis & Discussion

  1. What is the percent abundance of each variety of XR-45 at spring 1 of 3030, at summer 2 of 3030, 3031, 3032, 3033?

    Year <0.5mm 0.5-1.0mm >1.0mm
    Spring 1 3030 32% 34% 34%
    Summer 2 3030 30% 34% 36%
    Summer 2 3031 28% 33% 39%
    Summer 2 3032 26% 29% 45%
    Summer 2 3033 25% 29% 46%
  2. 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.

  3. 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.

  4. 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.

  5. 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.

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