Jube's Fast Plant Mini Lab

Fast Plant Lab Report

The purpose of this lab was to see how selective pressures may affect average leaf lengths. The proposed null hypothesis was that there will be no significant difference between the average leaf lengths of the parent population and the average leaf lengths of F1 generation. We tested this by selecting against shorter leaf lengths. (The data collected can be seen in Table 4).

 

The parent generation had a sample size of fifty-seven plants. The average height of the leaves was 8.84 mm. Furthermore, the median was 8.5 mm. Some plants had leaves less than 8.5mm and greater than 8.5 mm, but they were all within range of 8.84mm. Standard deviation is a measure of variation. The parent generation had a standard deviation of 3.39. This was due to the fact that there were differences in leaf lengths within the population. As shown in the histogram in figure 1, the leaves that were between 4 and 10 mm had the greatest frequencies.  After 10mm, we see a decrease in frequency. These leaves represent the outliers. Furthermore, the standard error for the parent population was .45 which could've also accounted for the inconsistency of the data in the histogram. In addition, confidence intervals were calculated to see how're reliable the estimate of the mean is. The confidence interval for the parent population had an upper limit of 9.7 and a lower limit of 7.9.

                                 Figure 1

The survivors of the parent generation had a sample size of eight plants. There was selection to ensure that all survivors had leaf lengths of 12 mm or longer. The average length of the leaves was 13.88 mm. The mean was 13.75 mm. Therefore, some plants had leaves less that 13.75 mm and some plants had leaves that were greater than 13.75 mm. However, they all fell within the range 13.75 mm. In essence, there was a significant difference in the average leaf length the compared to the parent population. On average, the plants of the survivor generation had leaf lengths about 5.04 mm greater than than that of the parent population. To add, the survivors had a standard deviation of 1.26. As a result, there was a bell shaped curve in the graph due to the differences in the frequency of the average leaf lengths. The standard error of the survivor population was .45. Confidence intervals also allowed for further evaluation of the acquired data. Essentially, the survivor generation had a 95% confidence interval of 12.98 for the lower limit and 14.78 for the upper limit. These intervals don't overlap with the confidence intervals calculated in the parent population. Therefore, we can be at least 95% sure that there is a statistical difference between the average leaf lengths of both generations. When compared to the parent generation, the results vary greatly. The survivor generation has lower frequency rates than that of the parent population, and it is apparent that the shape of the survivor population data is not as skewed.

                             

 Figure 2

The offspring of the survivors (F1 generation) had a sample size of thirty- three plants. The average leaf height was 6.46 mm. The mean height was 6.33. Thus, some plants had leaves with lengths less that 6.33 mm while other plants had a height greater than 6.33 mm. The F1 generation had a standard deviation of 1.81. The heights were not evenly distributed. To add, the standard error was .31. Since the standard error of the mean is such a minute number, most of the calculated leaf lengths were about about average although there were a few outliers. The outliers were the leaves with lengths from 3-4.5 mm and 9-12 mm. However, most of the leaf lengths which ranged from 4.5-9 mm were centered around the average leaf length of 6.46 mm. Essentially, the leaf lengths of the F1 generation are very different from the initial leaf lengths of the parent generation. The F1 generation had a 95% confidence interval of 5.83 for the lower limit and 7.09 for the upper limit. Since these confidence intervals don't overlap with the confidence intervals of the survival population, we can conclude that there is indeed a statistical difference between the average leaf lengths of the survival and F1 generation. Hence, there’s a statistical difference between the average lengths of the parent population and F1 generation.

                               Figure 3

                   Table 4

Conclusion

The proposed hypothesis can be rejected because there was a statistical difference between the average leaf lengths. As recorded in table 4, there’s a significant difference between the average leaf length in the parent generation when compared to the F1 generation. To add, the standard deviations also helped to reject the null hypothesis because they showed varied measures of differences within each population. Each successive generation after the parent population had specific traits, and ultimately it became evident that the parent population greatly differed from the F1 population.  These results were unexpected because I figured that the plants would just grow to their typical length no matter what the circumstances were due to their genome sequence. However, that was not the case in this experiment.

Some limitations to this experiment includes the fact that the class did not check on the plants very often. Hence, they may not have gotten enough water. As a result, they would not have been able to flourish to their maximum capability. In the real world, plants grow to be a wide assortment of various shapes and sizes. Leaf lengths vary greatly in the real world. We can conclude that leaf lengths occur at random as they are affected by environmental pressures and conditions.

Experimental Evaluation:

The confidence intervals calculated do not overlap at any point. My calculations of the 95% confidence intervals upper and lower limits made me 95% sure that there’s a statistical difference between the average leaf lengths of the parent generation and F1 generation. I feel that my group could have used less seeds because many of them died off during the experiment. Therefore, it may have been more efficient to give the seeds more room to grow from the beginning. Also, I feel that if the class had kept a closer eye on the fast plants, we would have been able to make more observations. Furthermore, the room that the plants were placed in may have had an effect on their growth. If we could have regulated the temperature of the room throughout the experiment, there would be more accurate results because each generation would have lived under the same exact conditions. Nevertheless, I still feel confident in the results obtained from this experiment.