Variation in peanut weight, leaf length, forearm length and Coquina shells Lab Purpose: The purpose is to investigate variation in four populations, peanuts (weight), leaves (length), forearms (length) and Coquina shells, to demonstrate whether the variation is a normal distribution (makes a bell curve).
Another purpose of the investigation is to learn about the effects of variation on natural selection. Hypothesis: If measurements of features of three populations are graphed as histograms, then those histograms will form a bell curve, because they all fit the description of normal distribution. Results and Calculations: – See the spreadsheet listing the group data (all of the populations except for the shells) – See the bar graphs (all populations except for the shells) – See spreadsheet for mean, median and mode of the forearms, leaves and peanuts. – Observations of the Coquina shells: vary in color (white, blue, red, purple, yellow, orange, gray and brown), out of all of the pairs one of the two shells has a small hole near the top of the shell, discolored ridges, all of the shells have the same basic shape, they come in pairs. (Also see the diagram sheet of the Coquina Shell).
Discussion: A population is the number of one species in a single place. During the “Variation in a Population Lab” four different populations were studied, they were: Coquina Shells (coquina varriabilis), peanuts, tree leaves and human forearms. Our data formed bell curves. A bell curve is a hill shaped curve (graph) called normal distribution, the average value falls at the summit. The peanut weights ranged from 0. 6-4.
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4 (g).
The mode (weight which occurs the most number of times during our research) for the peanut weight is 2. 6 g. (it occurred 97 times).
The mean (average) is 2. 4 g.
The median (value in the middle) is the same, 2. 4 g. The graph (See: Class Peanut Weight Graph) has a Bell Curve (normal distribution) in one way, it is hill shaped, but not in another, the summit was not the Mean (average), it nearly appears to be symmetrical (proportioned on both sides, in this case left and right), but in fact it is asymmetrical (disproportional on either side).
The summit of the curve is the mass of 2. 6 g, but the mean of the total data is 2. 4 g.
The curve seems to be on target, except for three minor exceptions: there were abnormally few at 1. 6 g (or abnormally many at 1. 4 g, either one would make the curve more consistent).
Another exception is that there are abnormally few at 3.
2 (If there were anywhere between 50 and 39 peanuts at that weight the curve would be more consistent).
The last and biggest exception is that there are abnormally few at 2. 4 g and abnormally many at 2. 6 g. If the two amounts at 2.
4 and 2. 6 grams had been reversed the curve would have made more sense because the summit would have been the mean or average (See: Bell Curve definition above).
The tree leaf lengths ranged from 3-18 (cm).
The mode for the leaf length is 9 (it occurred 23 times).
The mean is 9.
81 g. which rounds up to 10 g. And the median is 9 g. The graph (See: Class Leaf Weight Graph) has a bell curve because it is hill shaped, barring a few exceptions, and the summit is the same as the median, which is different from the class peanut weight graph.
The exceptions which keep the graph from almost being symmetrical and make it asymmetrical are that there are abnormally many 4 cm leaves, 9 (if there were 2 or 3 the graph would be consistent with the bell curve).
There was only one 14 cm leaf, it appears as a gap in the data because it’s surrounding data (13 cm leaves, and 15 cm leaves) does not fit in the bell curve form to it. The forearm lengths range from 21-30 (cm).
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The mode for the forearm length is 27 cm (it occurs 16 times).
The mean is 27 cm as well, and the median is also 27 cm. The graph mainly has the bell curve pattern, the summit is the same as the median, but the one main abnormality which makes it particularly asymmetrical is that there are 16, 27 cm forearms which falls out of the pattern because there are only 12 of each 26 and 28 cm forearms.
The main similarity that all three graphs and sets of data have is that they all have the bell curve look, they are all hill shaped. They all have the correct summit (being equal to the median), with the exception of the peanut graph. Although, the Class Peanut Graph was the most symmetrical, it never really jumped around except for a minor unexpected decrease at the 3. 4 g value. The leaves had the largest range, 15.
The Forearms had the second largest range, 9. The Peanuts had the smallest range by far, 3. 8. One reason that the leaves had such a large range is because it was the only data which people could select which leaf (peanut or forearm in the other cases) and naturally the people measuring were trying to get the best range of data possible, so they measured the smallest and largest leaves on their respective trees.
Other populations that might show a bell curve if graphed could be, beetles (all the same species), people in class (height), or blades of grass on the front lawn (height).
The four populations that were studied each vary in a way. The forearms vary in length, the leaves also vary in length and the peanuts vary in weight. Populations with more variation are more likely to be more successful because of natural selection (Johnson and Raven 1067) and genetic drift (Johnson and Raven 1064).
Natural selection, Darwin’s theory says that populations change in response to their environment.
Populations which are better adapted to their environment can live more easily and reproduce more than those populations which are not suited to the environment. Populations with more variations are more likely to be successful because if there is more variation there is more possibility to adjust to the environment. Conclusion:.
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