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

2. 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.

3. 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

4. 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

5. Lamarck’s Hypothesis

6. 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

7. 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

8. The Galapagos Tortoises

9. 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

10. 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

11. 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

12. 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