Question

Peter and Rosemary Grant's work on the Galapagos finches showed that

A) Darwin's postulate of inheritance can be proven with the discovery of genes

B) Darwin's postulate of fitness is not supported

C) Darwin's postulate of variation is not supported as each island contained only one type of finch

D) Darwin's postulate of struggle was demonstrated by a drought causing finch populations to plummet

Answer 1

Peter and Rosemary Grant's work on the Galapagos finches showed that

A) Darwin's postulate of inheritance can be proven with the discovery of genes

This is because Darwin proposed his theory of natural selection without the knowledge of the sources of variation in the populationa. After Mendel's laws were discovered and genetic variation was shown to be generated by mutation, Darwinism and Mendelism were used as a framework of neo- Darwinism.

According to this theory, although mutation is recognised as the ultimate source of genetic variation, natural selection is given the dominant role in shaping the genetic makeup of population and in the process of gene substitution.

The ground finches inhabiting the Galápagos Islands comprised several species with a unique beak shape. The species on the islands had a graded series of beak sizes and shapes with very small differences between the most similar. Darwin observed that these finches closely resembled another finch species on the mainland of South America. Darwin imagined that the island species might be modified from one of the original mainland species. Upon further study, he realized that the varied beaks of each finch helped the birds acquire a specific type of food. For example, seed-eating finches had stronger, thicker beaks for breaking seeds, while insect-eating finches had spear-like beaks for stabbing their prey.

Wallace and Darwin observed similar patterns in other organisms and independently developed the same explanation for how and why such changes could take place.

Darwin called this mechanism natural selection. Natural selection, also known as “survival of the fittest,” is the more prolific reproduction of individuals with favorable traits that survive environmental change because of those traits. This leads to evolutionary change, the trait becoming predominant within a population.

Natural selection, Darwin argued, was an inevitable outcome of three principles that operated in nature.

First, most characteristics of organisms are inherited, or passed from parent to offspring, although how traits were inherited was unknown.

Second, more offspring are produced than are able to survive. The capacity for reproduction in all organisms outstrips the availability of resources to support their numbers. Thus, there is competition for those resources in each generation. Both Darwin and Wallace were influenced by an essay written by economist Thomas Malthus who discussed this principle in relation to human populations.

Third, Darwin and Wallace reasoned that offspring with the inherited characteristics that allow them to best compete for limited resources will survive and have more offspring than those individuals with variations that are less able to compete. Because characteristics are inherited, these traits will be better represented in the next generation. This will lead to change in populations over successive generations in a process that Darwin called descent with modification.

Ultimately, natural selection leads to greater adaptation of the population to its local environment; it is the only mechanism known for adaptive evolution.