Charles Robert Darwin (1809-1882) Chapter 14, Section 1 “nothing in biology makes sense except in the light of evolution”-Theodosius Dobzhansky

Evolution On the grandest scale, is all the changes that have transformed life over time. Essentially, it is the biological history of life on Earth.

Ideas that set the Stage for Darwin There were 2 prevailing ideas about life on Earth: Life was created in its complexity and has remained fixed (or unchanging) since this time The Earth was believed to be about 10,000 years old and also relatively unchanging However, these ideas were challenged as explorers traveled and observed the incredible diversity of life (past and present) and the nature of Earth’s geological processes

Early Influences George Buffon (mid-1700s): French naturalist; collected fossils and noticed similarities and differences; suggests Earth is older than 10,000yrs James Hutton (1785): English Geologist; suggest geological forces that shape Earth’s surface are slow and require long periods of time (Earth must be millions of years old) Jean Baptiste Lamarck (1809): French naturalist; Explains Buffon’s observations by making a hypothesis that life evolves through the inheritance of acquired characteristics

Lamarck’s Hypothesis

The Voyage In 1831, a 22-yr-old Darwin set sail on the HMS Beagle on a 5 year cruise around the world As a naturalist, he studied the geology, plants, and animals encountered on the voyage

Darwin’s Observations He observed an immense amount of diversity in the South American plants, animals, and fossils Some fossils resembled modern life forms, some had no resemblance Life seemed well suited for the environment The Galapagos Islands- islands had similar life forms but varied in climate and vegetation Darwin inferred that the species on the different islands had once been part of the same mainland species

The Galapagos Tortoises

Geological Influence On the voyage of the Beagle, Darwin read the writings of geologist Charles Lyell Lyell proposed that the geological processes that shape the Earth’s surface today (erosion, deposition, earthquakes, etc.) are the same processes that shaped the Earth in the past Encouraged explaining the past in terms of observable present day processes Darwin personally witnessed an earthquake in the Andes Mtns and observed marine fossils move centimeters above the water line He realized that slow, gradual processes could cause enormous change over vast periods of time

A Mechanism for Change When Darwin returned to England, he could no longer accept the idea of unchanging life He began contemplating a mechanism for evolutionary change In 1838, he read the work of Thomas Malthus (an economist who wrote an essay on human populations) Malthus suggested that human warfare, famine, and disease would limit the growth of the population

Darwin Publishes His Ideas In 1844, Darwin wrote a 200-page essay that outlined his idea, but did not publish it in fear of controversy and doubt Instead he spent the next decade collecting evidence to support his idea Darwin received an essay from a young naturalist, Alfred Wallace, in 1858 proposing the same idea for evolutionary change with similar evidence In 1859, Darwin published his book The Origin of Species by Means of Natural Selection

Darwin’s Two Main Ideas Natural Selection His mechanism for evolutionary change Organisms with inherited traits best suited for the environment will survive and reproduce more often Descent with Modification The species living on Earth today descended from common ancestral species This is the most controversial part of his publication because it is often misunderstood and its religious conflict