Kimbrough_Lab Activity Footsteps in Time Spring

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University of Kansas *

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102

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Biology

Date

Feb 20, 2024

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pdf

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Uploaded by PresidentExplorationHippopotamus35

Lab Activity BIOL 102 Lab Activity – Tracing Footsteps in Time Data analysis and Conclusions Learning Objectives ● Explain how current biometric data of a species can be used to estimate traits of extinct species. ● Explain how anatomical features and the fossil record are used to support the theory of evolution. ● Create a scatter plot and a “best fit line.” Summary: ● In this lab, you will study the relationship between foot length and height of modern humans. Applying this relationship to footprints left by ancient hominids, we will estimate their height. Can we accurately predict their height or have modern humans evolved and the relationship between foot length and height changed? Materials Needed for Lab Ruler Calculator / Computer Photographic diagram of Laetoli Footprints (Appendix) Source Footsteps in Time. Evolution & the Nature of Science Institutes) www.indiana.edu/~ensiweb Masao, T. et al. 2016. New footprints from Laetoli (Tanzania) provide evidence for marked body size variation in early hominins. eLi. 2016;5:e19568. 1 Tracing Footsteps in Time Spring 2024-1

Lab Activity BIOL 102 Results and Analysis YOU NEED TO COMBINE YOUR DATA WITH THE CLASS DATA FOR THIS PORTION OF THE LAB Step 1. Navigate to the assignment in Canvas. Download the Excel file and open the class data sheet. Step 2. Save the Excel file to your computer. Add your data from the pre-lab to the Excel file. Step 3. Use all data for data analysis when completing activities below. Activity 1 – Graphing Foot Length and Height Data Using the data from the Excel Data sheet, make a scatter plot. See example graph below. For “how to guides” on creating scatter plots and adding trendlines, see the resources in the How to Guides Module in Canvas. 1. The x-axis is foot length. 2. The y-axis is height. 3. Add a trendline or “best-fit” line to your scatter plot. Be sure to extend the trendline beyond the data set. 4. Make sure to label the x-axis, the y-axis and give your graph a descriptive title. 5. Insert your graphs in the Assignment – Exit Ticket section of this document. You may use your preferred graphing software (Excel, Numbers, Google Sheets, or Chart tool in MS Word) to create your bar graphs. You may also draw them by hand on paper and submit photos of your graphs. 2 Tracing Footsteps in Time Spring 2024-1

Lab Activity BIOL 102 Activity 2 – Calculating the Percent Error To test whether foot length can be used to predict height we will calculate the percent error. Percent errors indicate how big our errors are when we measure something in an analysis process. Smaller percent errors indicate that we are close to the accepted or original value. For example, a 1% error indicates that we got very close to the accepted value, while 48% means that we were quite a long way off from the true value. If the experimental value is equal to the accepted value, the percent error is equal to 0. The smaller the percent error, the closer the estimate is to the actual value. Measurement errors are mostly unavoidable: equipment can be imprecise, hands can shake, or your instruments just might not have the capability to measure accurately. Percent error will let you know how badly these unavoidable errors affected your results. The percent error is calculated using the equation below. If the experimental value is less than the accepted value, the error is negative. If the experimental value is larger than the accepted value, the error is positive. Often, percent error is reported as the absolute value of the difference to avoid confusion of a negative error. % Error = |Estimated – Actual| * 100 Actual 1. Using your own foot length measurement and your graph, estimate your height. To find your estimated height follow these steps: (also see the example for height and femur length in Pre-lab): Step 1 . On the x-axis for foot length, find your foot length. Step 2 . Move vertically up towards the trendline. 3 Tracing Footsteps in Time Spring 2024-1

Lab Activity BIOL 102 Step 3 . Once on the trendline, move horizontally towards the y-axis for height. Step 4. The value on the y-axis is your estimated height. 2. Record your estimated height in Assignment – Exit Ticket section of the document. Activity 3 – Estimating the Height of Individuals of Fossilized Footprints. To determine if our modern footprint and height data can be used to estimate the height of the individuals that made the Laetoli footprints, we are going to measure the lengths of the footprints that were discovered at the Laetoli site. We will want to measure the length of the footprints, in the same manner that we measured our footprints, from the heel to the big toe. The photographic diagram of one of the footprints for individual G1 is in Figure 1. The remaining photographic diagrams of the fossilized footprints are in the Appendix, located at the end of the document. When looking at this image, we can make out a footprint – think of the footprints that you leave when walking in sand on the beach. In this figure, the gradient of colors represents the depth of the footprint. If we think back to the footprint in the sand, our footprints are deeper in the sand where most of our weight is when our foot hits the ground. In this figure, the red orange shading, marked as high, indicates the surface of the soil; the dark blue, marked as low, indicates a deeper impression in the soil. 1. Using the photographic diagram of the Laetoli Footprints as shown in Figure 3, we will determine the length of the foot from the heel to the big toe the footprint for the individual (G1-34). From this Figure you will determine the foot length for G1-34. NOTE: The scale in these images is in mm. You will need to convert to cm. Figure 1. Steps and examples to calculate the length of a footprint using photographic diagrams. 4 Tracing Footsteps in Time Spring 2024-1

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