Chapter 15: Darwin’s Theory of Evolution

15.1 The Puzzle of Life’s Diversity Why do scientists use a classification system? To organize many diverse organisms (biological diversity) What is a theory? A well-supported ,testable explanation of phenomena that have occurred in the natural world. What is evolution? Change over time; process by which modern organisms have descended from ancient organisms Theories can only be supported or disproven. (i.e. was the hypothesis supported or not supported; scientific method)

15.1 Voyage of the Beagle Charles Darwin: British scientist who made a significant contribution to the understanding of evolution; traveled with a sailing crew around the world on the H.M.S. Beagle Key Concept: During his travels, Darwin made numerous observations and collected evidence that led him to propose a revolutionary hypothesis about the way life changes over time.

15.1 Darwin’s Observations Key concept: Darwin observed that the characteristics of many animals and plants varied noticeably among the different islands of the Galápagos. Patterns of diversity: plants and animals “matched” their environments Fossils of ancient organisms sometimes resembled living organisms (Fig. 15-2) Characteristics of animals on the Galápagos varied from island to island due to climate change (Fig. 15-3)

15.2 Ideas That Shaped Darwin’s Thinking Darwin’s voyage occurred during a time of great change in the perspective of the natural world. At the time, many people believed that the world was only several thousand years old. Key Concept: 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.

15.2 Ideas That Shaped Darwin’s Thinking James Hutton and Geological Change Hutton proposed the rock formations occur over millions of years at a very slow rate (Fig. 15-6) Charles Lyell’s Principles of Geology Darwin received a copy of Lyell’s book before his voyage on the Beagle. Lyell proposed that processes that currently shape Earth must be used to explain processes that shaped Earth in the past. Darwin concluded that if Earth takes many years to change, so should life on Earth.

15.2 Ideas That Shaped Darwin’s Thinking Key Concept: Lamarck proposed that by selective use or 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.

15.2 Ideas That Shaped Darwin’s Thinking Jean-Baptiste Lamarck’s Evolution Hypotheses (c.1809) Tendency toward perfection: all organisms have an innate tendency toward complexity and perfection (i.e. fiddler crabs, Fig. 15-7) Use and disuse: Organs that are not used will decrease in size over generations and finally disappear. Inheritance of acquired traits: these changes are passed on to future generations (i.e. body builders will have children with big muscles too)

15.2 Ideas That Shaped Darwin’s Thinking Key Concept: Malthus reasoned that if the human population continued to grow unchecked, sooner or later there would be insufficient living space and food for everyone. Thomas Malthus and Population Growth English economist who stated that war, famine and disease are the only factors working against population growth