The Mystery of the Galapagos Finches (Essay Sample)

In the year 1977, a drought occurred on one of the smaller islands in the Galapagos, Daphne Major. The drought lasted from January 1976 to July 1978, hence no rain fell for those 18 months. The island's vegetation severely disappeared, and subsequently smaller seeds became more scarce. The Galapagos is a cluster of islands 600 miles from the mainland of Ecuador that supports a modest number of species, including thirteen species of finches found in various combinations on the different islands. The great diversity of the islands led the Finches to evolve in many ways to survive. With the great drought on Daphne Major, the finches’ capability to access an ​​adequate amount of seeds was greatly impacted. The medium-ground finches that lived on the island had to compete for food and their survival, resulting in over 80% of the medium-ground finches dying.  Due to the drought, there was a relationship between the finches and the reduction of the number of seeds on the island. According to data recorded before the drought on Daphne Major, there were 751 finches inhabiting the island.

The beak depths of the finches recorded on the island ranged from 5.8 mm to 13.8 mm and the mean beak depth of the finches was 9.2 mm. Before the drought, there were recorded to be about 10.5 g/m2 of seeds on the island. However, during the drought on the island Daphne Major, 89 finches inhabited the island. The beak depth data ranged from 6.8 mm to 11.4 mm and the mean beak depth was 10 mm. After the drought occurred on the island, there was around 3 g/m2 of seeds left for the finches to compete for. During the drought, the lack of rain caused the abundance of seeds to minimize for the finches, impacting the population as a whole.

According to the data collected from the drought on Daphne Major, some trends were found within the data. One trend found was that the mean of the finches’ beak depth increased after the drought. Before the drought, the mean was 9.2 mm and after the drought, the mean was 10 mm. In this short amount of time, .8 mm is a substantial amount of increase It can be inferred that due to the drought, the weaker finches, those with smaller beaks, were picked off and the strongest or the fittest were selected for. A second trend found in the data was that the range of beak depths decreased after drought. Before the drought, the beak depths ranged from 5.8 mm to 13.8 and after the drought, they ranged from 6.8 mm to 11.4. If this data were to be put into a graph, this would be considered to be stabilizing, therefore the most selected trait would be those closest to the mean. The final trend that was found within the data was that the population of finches decreased as seed abundance also decreased. Finches rely on the seeds on the island as their main source of food, so, when their food source becomes scarce and much harder to obtain, the population as a whole will decrease in size. When observing the data, however, some outliers were also found within the data. In figure one, one of the beak depths was recorded as 13.8 mm which is an observable abnormality in the graph. The closest measurement to 13.8 mm is 12.2 mm. If this data was removed from the graph, the data would be changed as a whole. The second outlier that was observed within the data was in figure two, where one of the beak depths was recorded as 6.8 mm. This measurement is relatively far away from the mean of the graph, which was 10 mm. With this piece of data being removed from the experiment, the data could be more accurate when comparing beak sizes from before and after the drought. The drought on Daphne major affected the population of finches because their ability to obtain their main source of food, seeds, was corrupted by the lack of rainfall. Through natural selection and evolution, the finches were able to better adapt to their environment and the fittest were able to survive and pass on genes to future generations.