Chapter 21, Problem 43A

Summary Introduction

To describe:

The things that Darwin saw that led him to hypothesize that species evolve.

Introduction:

Evolution is the term that describes the cumulative changes in groups of organisms through time. Almost everyone in the past believed that animals and plants were unchanging. Darwin’s book Origin of species demonstrated how natural selection might operate. The book provided evidence for evolution to have occurred in the earth. Darwin’s theory of natural selection is part of the larger theory of evolution.

Explanation of Solution

Darwin spent five years collecting biological and geological specimens abroad the ship Beagle, whose mission was to survey the coast of South America. Over the course of the ship's five year voyage, Darwin collected many rocks, fossils, plants and animals. In Galapagos Islands, he noticed that different islands seemed to have slightly different variety of animals. On his return, he began reconsidering his observations. Almost every specimen that he collected were new to European scientists. Darwin proposed that through small changes in ancestral species, new species could slowly emerge. He further researched pigeon breeding to better understand that. While thinking about artificial selection, Darwin realized that some competitors in the natural world would be better equipped for survival than others. He called this as natural selection. It has four fundamental principles which explain how a population's traits change over time. First, individuals of a population show variation. Second, variations can be inherited. Thirdly, organisms have more offspring than can survive on the resources available. Fourth, mutations that improve reproductive success would have a better chance of passing on. Darwin hypothesized that natural selection could change a population enough to create a new species, given enough time.

Conclusion

The variation in the animal species in different islands that closely resembled each other led Darwin to hypothesize that species evolve over time.