Sara's Fast Plant Mini Lab Report

The Effects of Artificial Selection on Fast Plants

Calculations & Statistical Analysis:

Figure 1:

For this experiment we measured all of the individual leaf lengths for each plant and calculated the average leaf length for each plant. A histogram of the average leaf length of all the plants  was created with a sample size of 57(figure 1).  The graph is not a bell curve shape but, instead is skewed.  The histogram shows that most of the plants have an average leaf length from 4mm to 10mm. The histogram also shows that there were a few plants that had extremely high leaf lengths of 18mm and 20mm. With the average leave lengths mostly being below 10 mm caused for the skew shape of the graph (Figure 1).  The average  length of the parent population is 8.84 mm and the median is 8.5 mm. The SEM was about .45 and a standard deviation of about 3.39 which, would have caused the the histogram to appear skewed.   The 95% CI is 7.94 to 9.74 which, would have contributed to the histogram to be skewed due to the spread of the data(Figure 1). 



Figure 2: 
  As a class we decided to select for plants with an average leaf length of 12 mm or higher therefore, we cut the plants who did not fit that criteria. We ended up with 8 plants as survivors after the selection (shown in Figure 2). The graph is not a bell curve just like the graph of the population before the selection (Figure 1 and 2).  The shape changed due to the change in the data. The mean of the data is 13.88mm and the median is 13.75mm which, would have caused the graph to shift.  The standard deviation is 1.26 which, shows that there was not much of a fluctuation in the data in Figure 2. However, the P generation had a higher standard deviation which, shows that there was more spread of data (as shown in Figure 1). The SEM was 0.45 and there was a 95% CI of 12.98 to 14.78.  This 95% CI of the survivors was not significantly than the 95% CI of the P generation since the two do not overlap each other (Figures 1and 2).

Figure 3: 
The last set of data collected was the average leaf length for all of the plants in the next generation.  This data was collected on Day 9 after planting of the first generation of offspring of the survivors. We did the same thing we did the other two times we had collected data which, was measure all the leaves per plant and then average the length of those leaves.  Then those values were graphed in a histogram.   This histogram is more of a bell curve shape but, slightly more to the left side.That would be because there were more plants with average leaf lengths that were lower. The mean of the average leaf lengths is about 6.5mm and the median of the the data is 6.3mm (Figure 3).  The histogram shows that most of the plants had an average leaf length from 6 mm to 7.5 mm ( Figure 3). There were only few that had an average leaf length from 10.5 mm to 12mm.  There was a standard deviation of about 1.81 with a SEM of about 0.31.  Compared to the survivors (Figure 2) the standard deviation for the F1 generation is higher which shows that there was more of a spread of data because there are more plants that were planted.  The 95% CI is 5.83 to 7.09 and it doesn’t overlap the 95% CI of the survivors (Figure 2) which, means that they are not significantly close to each other.  The F1 95% CI does overlap the P generation (Figure 1) a little which, means that they are significantly close to each other.







   Discussion:
Conclusion:
The experiment conducted relates to the evolution domain in the course and specifically with artificial selection.  By doing this lab I was able to see that artificial selection sometimes doesn’t always mean that the trait selected for is not necessarily a gene that is passed down from generation to generation rather it is a random trait. That is based off the evidence shown in the F1 generation (figure 3) with the mean being lower than the survivors after the selection (figure 2).  Also with the 95% CI not overlapping it showed that they were not significantly close.  If the trait was able to be passed down the two 95% CI should overlap due to the fact that the points in the F1 generation would be higher since the average leaf length would be higher. Also that the lengths would be similar to those of their parents since that is where the trait came from.  As shown in Figure 3 the average leaf lengths of the plants are mainly low and few are 12mm or higher unlike the average leaf lengths in Figure 2.   Therefore, based on that data the results did not turn out the way I had hypothesized.   Some limitations in the experiment could have lead to the results to be different from expected.  One limitation would be keeping the plants 10 cm from the light that was provided.  We used textbooks to regulate the distance but, once the plants grew and one textbook was removed it was hard to keep the plants at the right distance.  Reason being that by removing the last textbook would make the plants too far away from the light and the textbook kept the plants a little too close as well.

Experimental Evaluation: 
However, errors could have altered the outcome of the experiment.  For instance, we might not have measured the plants on the wrong day from what the experiment called for.  This could be due to there not being enough time in class to do so or forgetting or the 9th day which the leaves were suppose to be measured fell on a weekend.  That would lead to the leaves being able to grow a little longer which, made the averages bigger.   Another error would be the measurements of the leaves could be off and the math done for the averages could have been wrong as well which, would have lead to altered data.  Therefore, leads to different results.  Lastly, when cutting the plants that didn’t have an average leaf length of 12mm or higher could have been a source of error because too many could have been cut which, leads to a different amount of survivors.  The fact that no one had recorded the number of survivors is an error because when doing final calculations knowing the exact number of survivors would have lead to more accurate results.  If this experiment was done over then the math would have been done twice to ensure accuracy and the measuring could be done by two people as well for the same reason.  The cutting of the plants would have also be done more carefully by making sure that the right ones are being cut by double checking the data collected. Then recording the number of the survivors in order to have the correct amount in order to have more accurate calculations in the end.  Lastly, in regards on keeping track on what day of the experiment we were on would be done better in order to make measurements and steps are done at the right time in order to make sure that more accurate data could be collected.