Download Charles Robert Darwin (1809

Chapter 15: Darwin’s
Theory of Evolution
Charles Robert Darwin (1809-1882)
“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.
Evolutionary Theory: A collection of facts,
observations, and hypotheses about the process
by which modern organisms have descended from
ancient ones.
15-1: The Puzzle of Life’s Diversity
► 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
 Many different ways of reproducing and surviving
 Life seemed well suited for the environment
 Some fossils resembled modern life forms, some had no
resemblance
► 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
15-2: Ideas that Shaped Darwin’s
Thinking
► Darwin’s
voyage occurred during one of the most
exciting periods in the history of Western science
► Explorers were traveling the globe, and great
thinkers were beginning to challenge established
views about the natural world
► At this time, most Europeans believed:
 Life was created in its complexity and has remained
fixed (or unchanging) since this time
 The Earth was about 10,000 years old and also
relatively unchanging
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
Geological Influence
►
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On the voyage of the Beagle,
Darwin read the writings of
geologist Charles Lyell (1833)
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
A Mechanism for Change
►
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►
►
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 200page 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 On The Origin of Species
by Means of Natural Selection