BIOL300 Laboratory Lab 5.1 - Analysis and Discussion: Ceratopteris Experiment Initial Understanding 1) What is the name of the substance that Ceratopteris spores secrete into the environment and what effect does it have on developing gametophytes? Recall that each spore has the genetic ability to develop into either a male or a hermaphrodite. Results Name: 2) How do we expect the concentration of the secreted substance to vary among the treatments? Why? 3) With reference to the Excel sheet of student data, complete Table 1. Table 1. Results from analysis of raw class data by treatment type. Treatment Expected number of (%) Observed mean number of gametophytes per plate gametophytes per plate. Recall that the original 100% stock solution of spores contained 2.77 spores/μL and 75 μL was applied to each plate Observed minimum and maximum number of gametophytes per plate 3.13 6.25 25 100 Lab Section: Estimated density of mean number of gametophytes per plate (60 mm diameter), expressed as gametophytes/cm² Lab 6.1 Page 1 of 2 Observed mean proportion of hermaphrodites in the gametophyte population, expressed as a decimal number, (e.g. 0.67) 4) Averages (Table 1) are a notoriously poor way of looking at a range of data values because they obscure variation in the original observations that may be scientifically meaningful. Using Excel, create a scatterplot graph of the observed gametophyte density (gametophytes/cm²) (X-axis) against the proportion of hermaphrodites (Y-axis) for each student observation. Describe the general trend of the data. 5) Using the statistical functions in Excel, provide the slope of this line (SLOPE=) and its R² value (RSQ=) as estimated from the X & Y values specified in Question 4. BIOL300 Laboratory Name: Discussion 6) The Polka Dot mutation is also known to cause weakened walls of the spore, which are more likely to break during the plating process and kill the gametophyte before it sprouts. Use a Chi-Square test to determine if there is a statistically significant departure in the expected 1:1 ratio of Wildtype to Polka Dot genotypes among our surviving hermaphrodites. Use the Chi-Square Goodness of Fit Calculator at http://www.socscistatistics.com/tests/Default.aspx). Row 1 and Row 2 are labeled by genotype, Column 1 and Column 2 report Observed and Expected values. Test Statistic p-value Lab Section: Is this significant at the 0.05 level? 7) Assuming there was 100% spore germination, how accurate were students in their ability to pipette the expected number of spores for each treatment? Explain and defend your explanation using results from Table 1. 8) Each spore has the ability to develop into either a male or a hermaphrodite, so why is there a density dependent trend? In your answer, described how the observed proportion of hermaphrodites changes as a function of gametophyte density and what may have caused this trend. 9) What advantage could there be to individual gametophytes that produce the hormone? 10) Was there difference in the survivorship between the two genotypes (wild type and polka dot), at least among the hermaphrodites? Lab 6.1 Page 2 of 2