Scientific Method Assessment Story
Please read the story below and then answer the following questions to the best of your ability. The questions are in the format of a short essay.
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Background
In the country of Southlandia, there is an abundance of beetles, Dynastes hercules (the Hercules beetle). These beetles are easily identified by their whitish coloring and prominent horns. In 1950, a candy company, MMMMDelicious, was established and specialized in blue-covered chocolates that became very popular in the country. However, this industry caused extensive blue pigment air pollution. Over time, cities that housed MMMMDelicious factories became covered in blue dust. In 1957, Dr. Curtis Peregrine, of Southlandia University, was the first to identify an unusual Hercules beetle at an MMMMDelicious factory in the city of Candyville that had excessive blue coloration. He named this beetle Dynastes hercules azularia or Blue Hercules beetle. Dr. Peregrine continued to monitor and collect beetles all over the country, and by the mid-1960s, it was recorded that Blue Hercules beetles, ( azularia), outnumbered (90% in some areas) the natural whitish ones, now named Dynastes hercules alba, or White Hercules Beetle.
There were conflicting ideas among the country’s scientists as to the biological basis of this industrial cyanoleucism (blue coloration caused by pollution) found in the Hercules beetles. Ideas such as vegetation shift, temperature effects, solar radiation, disease, genetic drift, and protection (such as camouflage) were put forward as possible reasons for the development of this new blue beetle. Dr. A. B. Pluma of Southlandia State College was the first to come up with natural selection as an explanation, hypothesizing that birds were selecting non-blue beetles. To experimentally investigate the issue, Dr. Pluma was recruited in 1966 by the Southlandia Department of Natural Resources.
About the Hercules beetle
Hercules beetles are normally found crawling in leaf litter on the forest floor. Their normal predators are birds and foraging mammals. Hercules beetles primarily feed on small insects and worms. Their life cycle is that of complete metamorphosis where the larvae (grubs) overwinter in the soil. The distribution of the Hercules beetle is throughout the country of Southlandia. The original form, alba, is whiteish grey with black speckles on the elytra (outer wings). The color was perfectly camouflaged in newly fallen leaf litter. The new form, azularia, is blue with black spots.
The Experiment
The main experiment, called mark-release-recapture, started in the summer of 1967 and lasted for three years. This experiment consisted of two phases.
1. First phase
A heavily polluted site was chosen for its intact forest, presence of predators, and robust population of beetles. Dr. Pluma captured all three types of beetles and marked individual beetles underneath their elytra with paint so that he would be able to identify them later after recapture. He captured beetles for 2 weeks and caught a total of 630, of which 470 were azularia and 160 were alba. Dr. Pluma and his team marked each beetle with paint and then released them from the point of capture. Within two days the team returned to the collection area to collect beetles. A total of 149 beetles were recaptured, out of which azularia was 87% and alba was 13%. Thus, the survival values of the captured and marked beetles were 8.72%, and 1.28%, respectively. These data indicate that blue beetles ( azularia) had the best survival advantage in the blue, polluted environment.
2. Second phase
For the second phase, a similar mark-release-recapture experiment was conducted but this time in both polluted and clean environments. Dr. Pluma’s team captured, marked, and released 800 Hercules beetles into an unpolluted environment (400 azularia and 400 alba). After 11 days his team returned to recapture marked beetles. His team recaptured 73.7% of the marked alba beetles, and 4.7% of the marked azularia. Immediately after completion, Dr. Pluma and his team headed back to a polluted area and repeated the experiment. This time 82% of the marked azularia beetles and only 2% of the marked alba beetles were recaptured in the polluted environment.
To directly study bird predation on the beetles, Dr. Pluma placed White and Blue Hercules beetles on the forest floor of a heavily polluted forest within a specific area where he could observe them. He then recorded the number of times a bird found a beetle and recorded what color beetle was picked up. He found that in a polluted forest, birds were twice as likely to eat a White Hercules beetle over a Blue Hercules beetle. He repeated this experiment in a non-polluted forest and found that birds were 2.8 times more likely to select a White Hercules beetle over the Blue Hercules beetle.
Please answer these 4 questions:
1. What observations did scientists make that made them want to study this system?
2. What was their hypothesis?
3. What were the results of their studies?
4. Did the results support the hypothesis or not? Why?
