Question

In the late 1970's, the Galapagos Islands experienced a severe drought that sharply reduced the finch population living there. It was discovered that only finches with large, thick beaks survived the drought as they subsisted on cactus, which are drought tolerant plants.
In the early 1980's, the Galapagos Islands underwent an El Nino event that led to higher annual levels of precipitation than normal. This climate event occurred just a few years after the drought. The increase in rainfall led to a dramatic increase in growth of seed-producing plants, which led to an abundance of foods for seed-eating finches, which have small, short beaks.
The increase in rainfall also decreased the availability of cactuses on the islands. Which of the following would you predict occurred in the finch population as a result of the second change in climate?

• A. The variety present in the finch population did not change due to changes in climate.
• B. The population of short-beaked finches increased while the population of large beaked birds decreased.
• C. The large-beaked finches increased in number while the short-beaked finches decreased in number.
• D. The number of finches of each type both decreased due to the change in climate.
• E. The large-beaked finches hybridized with the short-beaked finches.

Answer 1

Answer: (B)

The population of short-beaked finches increased while the population of large beaked birds decreased.

The finches show the case of natural selection. According to Darwin's concept of natural selection, as a struggle for existence, only those organisms could survive which have favourable variation to adapt with the environmental conditions. In other words, struggle for existence results in survival of the fittest which means that natural selection tends to favour those organisms which are most fit to survive with the reproductive age in a particular environment and to produce offspring.

Hence, as result of second change in the environment, short beaked finches will predominate as they will be able to survive but the population of long beaked finches will decline a they won't be able to adapt to the change in environment.

So, the correct answer is 'The population of short-beaked finches increased while the population of large beaked birds decreased'.