Question

In order to build a longitudinal dataset, data of adult finches Geospiza fortis living on one of the Galapagos islands were collected. The beak shape data collected between 1971 - 2001 are shown in the graph. Study the graph and select the correct statement.

A. The fluctuating direction in the beak shape is most probably due to change in the environment.
B. The graph as a whole does not indicate an evolutionary change in the beak shape as the time interval is too small and evolution requires thousands of years to occur.
C. The graph indicates that the beak shape may lead to convergent evolution in the finches of Galapagos islands.
D. The change in any phenotypic character requires the selection to alter the expression of the target number of genes in a coordinated fashion. Hence it is unlikely that change in the beak shape depicted in the graph is a result of evolution.

Answer 1

By reading the graph, one can observe that the pointiness of the beak increased between 1970 and 1980 but saw a steep decrement till the year 1983. 1984 onwards, the pointiness has only increased or remained constant.

Complete answer: The variety in beak shape is most probably due to the changes in the environment which has led to natural selection and changes in gene flow among species. The graph clearly indicates evolutionary change. It has been depicted that evolution can occur with an astonishing speed. As fast as those resulting from an artificial selection that was collected. The selection here of finches was a strong one and the populations evolved in a matter of just a few generations. The Galapagos finches proved as an excellent example of adaptive radiation. It is considered that a stock of ancestral finches migrated to the islands from the mainland and then in the absence of extensive competition, evolved to fill the voids of many empty ecological niches. There is also a change in the phenotypic character which can be attributed to the alteration in the expression of one to several genes relating to the physiology of the beak. Thus, the change in the shape of the beak can be attributed to evolution.
So, the correct answer is option A.

Note: Evolution is an inevitable law of nature. Every organism undergoes evolution in order to adapt to the surrounding. The surroundings or the environment thus plays a major role in determining the parts of the body of the organism which will get modified or will get eliminated. Humans today evolved from primates. Birds evolved from dinosaurs.