Pepered Moth Lab
The purpose of the lab was to determine if the changes in the population of light-colored moths and malonic moths post-industrial revolution was a result of natural selection through the melonic moth's ability to avoid predation because of better fitness. In order to determine if the changes in population density were attributed to natural selection one would look for an increase in population for each subsequent generation for the moth that possesses the selective advantage. Such as for the pre-industrial simulation the light moth’s population increased because of its ability to avoid predation because of camouflage. The method needed to complete this investigation would be placing fifteen malonic and fifteen light-coloured moths on a sheet of paper then having an individual act as the predator attempting to remove as many moths as possible over a quantized time.
The simulation would have to be completed for three trials representing each generation then repeated again utilizing a different colored paper, the papers used should be white, intermediate (cream) and black. Observations were made and the results were that the species of moth which possessed a selective advantage was in fact better suited for the environment and therefore able to avoid predation and experience thriving numbers. These results were standard for the light paper and intermediate paper although the black paper did not follow suit as a result of the melonic moths not in fact being fully dark. The experiment demonstrates that natural selection can be attributed to the diminishing number of light-coloured moths following the industrial revolution and H. B.
Kettlewell, an English physician with an interest in butterfly and moth collecting, decided to study the unexplained color variations of the peppered moth. Kettlewell focused his study on a trend observed in Manchester England from 1845 to 1890 where the population of peppered mouths once made of gray-colored organisms inevitably was replaced with a darker almost black counterpart. Kettlewell hypothesized that a change in pollution found in industrial areas had provided the dark moths with a selective advantage over their peppered counterparts. This selective advantage, which increased the dark moth’s fitness, was the result of layers of soot altering the color of barks of which the moths would reside.
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Therefore making the dark moths less susceptible to predation as a result of being better suited to the environment. Kettlewell focused his study on industrial Melanism, which is used to describe the adaption of the population by the darkening of its individuals in response to pollution, especially during the time of the industrial revolution. The industrial revolution was a period from the 18th to the 19th century where major changes in agriculture, manufacturing, mining, transport and technology effected the world through the introduction of coal-powered machinery. The above-noted adaption is directly linked to Charles Darwin’s Theory of Natural Selection. Natural Selection is the reproduction of organisms best suited, possessing a selective advantage, to thrive in their environment.
A selective advantage is a genetic advantage of one organism over its competitors that causes it to be favored in survival and reproduction rates over time. The purpose of this investigation is to determine if the extinction of light-coloured (peppered moths) post industrial revolution was a result of natural selection due to the melonic moth’s selective advantage in soot-covered foliage.The hypothesis for this investigation is the appearance of individuals is the quintessential influence of affecting the likelihood of predation. The influence natural selection has on the survival of the organism is exponential, the better suited the individual is for their environment the greater their fitness will be. Materials and Method Prior to beginning the experiment three tables were constructed in order to record the data observed for each simulation and trial (generation).
Table 1 was titled simulation 1 (white paper) and each trial represented a subsequent generation. The table consisted of four columns; number of melonic moths, number of light coloured moths, percentage malonic and percentage light. Two other tables were constructed in the same manner one titled simulation 2 and the other simulation 3. In a group one student acted as the predator and the other as the timer. The predator faced away from the page while the timer randomly placed 15 white and 15 melonic moths on the page.On the timers command the predator turned around and removed as many moths as possible in a four-second period. Time was calculated using a stopwatch.
The removed moths were considered dead and replaced in the next trial generation by the antagonist color (if a melonic moth was removed it was replaced with a white one for always a total of. The timer then recorded the observed data onto the chart (number of remaining moths). This process was repeated for each simulation (different coloured tree bark) for three trials each totaling 9 attempts. The experimental design for this experiment was as followed. The independent variable was the number of moths that were spread on the sheet, always thirty. The dependent variable was the actions of the predatory which were influenced by the type of environment for that particular simulation. The control for this experiment was the cream-coloured paper because it provided an environment to which no selective advantage was gained by either species of moth.
Image of the Melonic moth and the Peppered moth The pre-industrial Revolution era reveals that through each generation the number of white moths increase as the melonic moths decrease Early Industrial revolution the change in colour of population for the moths appears to be unaffected, experiencing a sustained growth Post Industrial Revolution the graph displays that the number of moth distribution becomes stagnate following an increase in the percentage of light. DiscussionThe results of simulation 1 (pre industrial) coincided with the theory that since the environment was cohesive to camouflaging the lighter moth they possessed a selective advantage and thus were able to avoid predation.
Through natural selection, one can see that each generation the amount of light moths increased while the melonic decreased one can infer that the lighter moths selectively mated with other white moths in order to avoid predation and successfully reproduce. The early industrial revolution period, simulation two (cream coloured) acted as the control for the experiment providing no selective advantage toward either species of moth. Each generation followed very slight fluctuation is the percentage thus supporting the hypothesis that the reason for the growth of specific species in an environment is correlated to their ability to thrive through natural selection. Simulation three the dark bark Post-industrial simulation did not follow the expected pattern.
Each generation found that there was an increase in the percentage of light-coloured moths despite the fact that they possess no advantage in their fitness. The reason why this experimental error occurred can be attributed to several experimental flaws. The moths being used were not in fact light vs dark, for this investigation, there were light moths and peppered moths. Since the “dark” moth was actually peppered, it possessed no true selective advantage in terms of camouflage on the dark bark sheet. Other significant errors include the random spreading by which the moths were spread on the sheet. Since grouping was inevitable the results may have been varied because of high densities of specific moths in certain areas.Also the timing mechanism was not accurate enough to stop the predator at exactly four seconds so fluctuations in time may have been allotted to extra moths or less moths being removed.
One must also take into consideration that it is human intuition to overcome a proverbial challenge, in this investigation case the predator was expected not to be able to remove the better-suited moths with ease so one might have self-consciously attempted to prove otherwise.Based upon the achieved results according to the data natural selection did occur because in simulation one each generation possessed an increase in the number of light moths and the natural depletion of melonic moths which were in fact not fit for the environment. The purpose of utilize an intermediate colour background was to act as a control allowing comparable results for when there is no selective advantage. These results support the theory of natural selection because when neither moth were better suited to the environment both became susceptible to predation.Possible improvements in the design of this experiment would be as follows.
For the difference in moth colouration to truly be cohesive to that of the paper upon which they lay, also a better suited timing mechanism would be a system pre tuned to set a alarm at the passing of four seconds. Another potential improvement to the experiment would be to have someone with no knowledge of natural selection and Ketllewell’s theory of melaism to act as the predator to avoid any intuition of proving the theories incorrect. Regardless of the slight error found within the post industrial revolution simulation the evidence obtained supports the hypothesis that changes in the population of the different species of moths are in fact a result of natural selection through the ability to avoid predation in their environment.
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Pepered Moth Lab. (2018, Dec 19). Retrieved from https://phdessay.com/pepered-moth-lab/
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