Question

Introduction The Island of Daphne Major, one of several islands that make up the archipelago of islands off the coast of Ecuador, supports a population of ground finches, Geospiza fortis. Finches are small songbirds with chunky beaks which they use to crack open seeds from various shrubs and trees on the island. These seeds make up most of the finch diet. Biologists have been studying this population for over 30 years. Each year, biologists capture individual finches and take several measurements of finch characters, including the total depth of the beak (a measure of the beak from the top of the upper beak to the bottom of the lower beak). After three years of collecting data (1974-1976), biologists arrived to the island in 1977 to find it had experienced a severe drought. Rainfall that year was 20% of normal average rainfall. Consequently, small, softer seeds became scarce, as they did not survive these dry conditions. Large, drought-resistant seeds survived in greater numbers. Biologists noted that finches with smaller beaks could eat small seeds, but not large ones. Birds with thicker beaks had an easier time eating large seeds, but not smaller ones. The 1977 drought provided an opportunity to observe whether natural selection operated in this population of finches. Table 1 summarizes some of the data collected from 1974-1981.
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Answer 1

This question is composed of 8 sub-parts. Since you haven't mentioned the specific sub-parts, as per Chegg guidelines, I am answering the first 4 sub-parts.

a) The biologist have been studying the finch beak depth over the years. A drought led to a decrease in the number of soft seeds and an increase in the hard seeds. The larger beaked words had an ease at processing the available large seeds. A natural assumption from this observation would be to expect the natural selection to be underplay. Since the small beak words have a survival disadvantage over the large beak birds, they would be selected out and the population of large beak birds would increase. This can be studied from the data collected by the scientists.

b) The increase in the average bird beak depth would be expected. This pertains to the directional evolution model wherein the population mean changes in a particular direction based on the driving force. Hence the alternate hypothesis would be to expect an increase in the mean beak depth with time.

c) The data can be visualized to study the validation of the hypothesis. Since we are interested to know if the beak depth increases after drought, we are interested to check for the variation of the beak depth with time. A line plot can be plotted with the average beak depth (mm) as a function of time in years. This appears as shown below:

d) With the data not in hand, graphical representation of the data can be easiest for a person to interpret the variation/trend. As can be seen from the figure, the mean beak depth has undergone variation with time between the years 1974-1981. There has been a sudden spike in the beak depth after 1977, that correlates with the drought of 1977 and our hypothesis. Hence based on this data, we can say that the birds with larger beak depth are preferred as compared to the ones with small beak due to their higher fitness capability in the post-drought island with larger seeds.