Darwin’s Theory of Evolution

Key Terms Evolution = change over time Theory = a well-supported testable explanation Fossils = preserved remains of ancient organisms

Charles Darwin Made observations and collected data as the naturalist aboard the HMS Beagle’s voyage around the world beginning in 1831, shortly after his completion of college. These observations provided the foundation for his hypothesis about the way life changes over time.

Darwin’s Observations Darwin noted that the plants and animals of particular environments were adapted to fit that environment. Plants and animals were different based on the continent they inhabited. Besides the great diversity of living species, the fossil record showed an even greater diversity had previously existed. The Galapagos Islands displayed variation of species based on the climate of each particular island. (Tortoises and finches)

Darwin and the Galapagos Islands

Age of Earth Hutton and Lyell helped scientists recognize that Earth is many millions of years old, and the processes that changed Earth in the past are the same processes that operate in the present. Their work in 1785 and 1833, respectively, provided the time span for Darwin’s hypothesis on evolution to take place.

Lamarck’s Hypothesis In 1809, Lamarck proposed that by selective use and disuse of organs, organisms acquired or lost certain traits during their lifetime. These traits could then be passed on to their offspring. Over time, this process led to change in a species. We now understand this hypothesis was wrong on many levels, but he was one of the first to recognize organisms are adapted for the environment in order to survive.

Thomas Malthus Malthus provided a hypothesis that if human population continued to grow unchecked, sooner or later there would be insufficient living space and food for everyone. The forces working against growth were war, famine, and disease. The key resources were food and space.

Artificial vs. Natural Selection In artificial selection, nature provides variation and humans selected the variations they found useful. (Farmers and dog breeders) In natural selection, or survival of the fittest as Darwin referred to it, over time the inherited characteristics of a population changes. These changes increase the fitness of a species to its environment. Those individuals in a species that are most fit will survive to reproduce and pass on their genes.

Darwin’s Evidence The fossil record Geographic distribution of living species Homologous body structures Similarities in embryology