# Natural Selection of Leaf Thickness on Planet Eorthe, Galaxy Tlaloc

## A Carolina Essentials™ Activity

##### Total Time: 40-55 mins

Prep: 10-15 mins | Activity: 30-40 mins

## 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.

## Phenomenon

These are examples of leaves. How can they be used as evidence for adaptation among plants?

## 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 & Engineering Practices

Analyzing and Interpreting Data

### Disciplinary Core Ideas

LS4.B: Natural Selection

Patterns

## 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 Procedures

1. 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.
2. Calculate the average number of plants of each variety per 1000 plant random sample for each year.
3. Your teacher may direct you to calculate summary, descriptive statistics for each variety of plant.
4. 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
5. Calculate the average number of fruits for each variety per 1000 plant random sample for each year.
6. Your teacher may direct you to calculate summary, descriptive statistics for each variety of plant.

### Teacher Preparation and Tips

1. Students may graph by hand on graph paper or use a graphing program such as excel or graphing calculators.
2. 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. Discuss the shape of the lines on both graphs and let students briefly interpret what the graphs indicate about changes in population variation
2. 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.

Plant Data

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?

1. 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.

2. 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.

3. 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.

4. 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.

### The Evolution and Survival of the Galápagos Medium Ground Finch

*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.