Chigozie's Wisconsin Fast Plant Mini Lab Report

Name:  Chigozie Amonu

The Effect of Artificial Selection on the Average Leaf Length of Wisconsin Fast Plants

Results:

The question that we attempted to answer in this lab was, “Does selection for average leaf length influence F1 phenotypes?” The null hypothesis for this lab was, “There is no significant difference between the mean of the P Generation (Pre-Selection) and the mean of the F1 Generation”. We gathered data in order to answer this question and reject, or fail to reject, this null hypothesis.

Calculations & Statistical Analysis:

Figure 1:  

We planted the P generation on Day 1 of this experiment, and on Day 9 we took measurements of the leaves of all 57 plants and averaged the leaf length of each plant. The histogram below (Figure 1) shows the distribution of the average leaf length in the P Generation of the plants. The mean of the average leaf lengths was 8.84 mm, and the median was 8.5 mm. These values were similar, so we could assume that the data was normally distributed. The calculated SEM was 0.45. The lower limit of the 95% Confidence Interval was 7.94 mm, and the upper limit of the 95% Confidence Interval was 9.74 mm. There was not a definite bell curve to the data that we collected, as seen in the histogram. We later used this data to conclude what we would manipulate during our artificial selection.

Figure 2:

After we gathered the data from the pre-selection P Generation, the class collaboratively decided to select for leaf lengths of 12 mm or greater. The leaves that did not meet this criteria were cut off. After this selection, 8 plants remained. This histogram (Figure 2) displays the data that we collected from the survivors of our artificial selection. We selected for leaf lengths of 12 mm or higher. Only 8 plants were left after this selection. The mean of these average leaf lengths was 13.88 mm, and the median was 13.75 mm. These values were similar, so we could assume that the data was normally distributed. The calculated SEM was 0.45 mm. The lower limit of the 95% Confidence Interval was 12.98 mm, and the upper limit of the 95% Confidence Interval was 14.78 mm. This histogram also does not display a bell curve with the data that we collected. After collecting this data, we expected the F1 Generation to have phenotypes similar to this post-selection P Generation since we purposely selected for a certain range of leaf lengths.

Figure 3:

After the post-selection P Generation fully grew and created seed pods, we planted the seeds from this group of plants. We then collected data from the offspring. This graph shows the average leaf length of the F1 plants. There were 33 plants in the generation. The mean of the average leaf lengths of the F1 plants was 6.46 mm, and the median was 6.33 mm. These values were similar, so we could assume that the data was normally distributed. The calculated SEM was 0.31 mm. The lower limit of the 95% Confidence Interval was 5.83 mm, and the upper limit of the 95% Confidence Interval was 7.09 mm. This graph is also in more of a bell curve, and the curve is shifted slightly to the left.

Table 1:

This data table shows the descriptive data that was collected during this experiment from the pre-selection P Generation, the post-selection P Generation, and the F1 Generation. Shown below is the sample size, mean, median, standard deviation, SEM, and the lower and upper limits of the 95% Confidence Interval.

DESCRIPTIVE STATISTICS - AVG. LEAF LENGTH OF WISCONSIN FAST PLANTS (mm)
	P Generation	P Generation - Survivors	F1 Generation
Sample Size (n)	57	8	33
Mean	8.839181287	13.88	6.462121212
Median	8.5	13.75	6.333333333
Standard deviation	3.39196426	1.26	1.80735
SEM	0.4492766416	0.45	0.3146201419
95% CI Lower Limit	7.940628004	12.98	5.832880928

Discussion:

Conclusions:

In this lab, we attempted to perform directional selection. This selection would easily be seen in the histograms as the curves in the histograms would shift to the left or right. However, the 95% confidence intervals of the pre-selection P Generation do not overlap with the 95% confidence intervals of the F1 Generation. This allowed us to reject our null hypothesis, “There is no significant difference between the mean of the P Generation (Pre-Selection) and the mean of the F1 Generation”. There is a significant difference between the mean of the pre-selection P Generation and the F1 Generation. Overall, the artificial selection for average leaf length did not affect the F1 Generation.

Experimental Evaluation:

This experiment was carried out with a few errors that could have affected our data that we collected, and as a result our entire conclusion. There were different individuals measuring the leaves of the plants, so the different strategies of measuring could have created incorrect measurements. Also, some measurements and calculations were rushed due to lack of time, so errors could have been made in that aspect. One other error could have occurred from the lack of recording in some areas. For example, the number of survivors from the P Generation was only recorded by one individual, so if that record was wrong, then the whole lab is possibly thrown off. In spite of the possible errors, I am overall satisfied with the conclusion that we received from the lab.