Transcript The Origin of Species

Chapter 22
Descent with Modification: A
Darwinian View of Life
PowerPoint Lectures for
Biology, Seventh Edition
Neil Campbell and Jane Reece
Lectures by Chris Romero
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Overview: Darwin Introduces a Revolutionary
Theory
• A new era of biology began on November 24,
1859, the day Charles Darwin published On the
Origin of Species by Means of Natural Selection
• The Origin of Species focused biologists’ attention
on the great diversity of organisms
Video: Galápagos Marine Iguana
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Darwin made two major points in his book:
– Many current species are descendants of
ancestral species
– Natural selection is a mechanism for this
evolutionary process
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Concept 22.1: The Darwinian revolution challenged traditional
views of a young Earth inhabited by unchanging species
• To understand why Darwin’s ideas were
revolutionary, we must examine them in relation to
other Western ideas about Earth and its life
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LE 22-2
Linnaeus (classification)
Hutton (gradual geologic change)
Lamarck (species can change)
Malthus (population limits)
Cuvier (fossils, extinction)
Lyell (modern geology)
Darwin (evolution, natural selection)
Mendel (inheritance)
Wallace (evolution, natural selection)
American Revolution
U.S. Civil War
French Revolution
1850
1900
1750
1800
1795 Hutton proposes his theory of gradualism.
1798 Malthus publishes “Essay on the Principle of Population.”
1809 Lamarck publishes his theory of evolution.
1830 Lyell publishes Principles of Geology.
1831–1936 Darwin travels around the world on HMS Beagle.
1837 Darwin begins his notebooks on the origin of species.
1844 Darwin writes his essay on the origin of species.
1858 Wallace sends his theory to Darwin.
1859 The Origin of Species is published.
1865 Mendel publishes inheritance papers.
Resistance to the Idea of Evolution
• The Origin of Species
– Shook the deepest roots of Western culture
– Challenged a worldview that had been
prevalent for centuries
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The Scale of Nature and Classification of Species
• The Greek philosopher Aristotle viewed species
as fixed and unchanging
• The Old Testament holds that species were
individually designed by God and therefore perfect
• Carolus Linnaeus interpreted organismal
adaptations as evidence that the Creator had
designed each species for a specific purpose
• Linnaeus was a founder of taxonomy, the branch
of biology concerned with classifying organisms
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Fossils, Cuvier, and Catastrophism
• The study of fossils helped to lay the groundwork
for Darwin’s ideas
• Fossils are remains or traces of organisms from
the past, usually found in sedimentary rock, which
appears in layers or strata
Video: Grand Canyon
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Paleontology, the study of fossils, was largely
developed by French scientist Georges Cuvier
• Cuvier advocated catastrophism, speculating that
each boundary between strata represents a
catastrophe
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Theories of Gradualism
• Gradualism is the idea that profound change can
take place through the cumulative effect of slow
but continuous processes
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• Geologists Hutton and Lyell perceived that
changes in Earth’s surface can result from slow
continuous actions still operating today
• This view strongly influenced Darwin’s thinking
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Lamarck’s Theory of Evolution
• Lamarck hypothesized that species evolve
through use and disuse and the inheritance of
acquired traits
• The mechanisms he proposed are unsupported by
evidence
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Concept 22.2: In The Origin of Species, Darwin
proposed that species change through natural selection
• As the 19th century dawned, it was generally
believed that species had remained unchanged
since their creation
• However, a few doubts about the permanence of
species were beginning to arise
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Darwin’s Research
• As a boy and into adulthood, Charles Darwin had
a consuming interest in nature
• After receiving his B.A. degree, he was accepted
on board the HMS Beagle, which was embarking
on a voyage around the world
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The Voyage of the Beagle
• During his travels on the Beagle, Darwin collected
specimens of South American plants and animals
• He observed adaptations of plants and animals
that inhabited many diverse environments
• His interest in geographic distribution of species
was kindled by a stop at the Galápagos Islands
near the equator west of South America
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LE 22-5
England
EUROPE
NORTH
AMERICA
PACIFIC
OCEAN
ATLANTIC
OCEAN
AFRICA
Galápagos
Islands
HMS Beagle in port
Equator
SOUTH
AMERICA
Darwin in 1840,
after his return
AUSTRALIA
Cape of
Good Hope
Tasmania
Cape Horn
Tierra del Fuego
New
Zealand
Video: Albatross Courtship Ritual
Video: Blue-footed Boobies Courtship Ritual
Video: Galápagos Island Overview
Video: Galápagos Sea Lion
Video: Soaring Hawk
Video: Galápagos Tortoise
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Darwin’s Focus on Adaptation
• In reassessing his observations, Darwin perceived
adaptation to the environment and the origin of
new species as closely related processes
• From studies made years after Darwin’s voyage,
biologists have concluded that this is indeed what
happened to the Galápagos finches
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LE 22-6
Cactus eater. The long,
sharp beak of the
cactus ground finch
(Geospiza scandens)
helps it tear and eat
cactus flowers and
pulp.
Seed eater. The large
ground finch (Geospiza
magnirostris) has a large
beak adapted for cracking
seeds that fall from plants
to the ground.
Insect eater. The green warbler finch
(Certhidea olivacea) used its narrow,
pointed beak to grasp insects.
• In 1844, Darwin wrote an essay on the origin of
species and natural selection but did not introduce
his theory publicly, anticipating an uproar
• In June 1858, Darwin received a manuscript from
Alfred Russell Wallace, who had developed a
theory of natural selection similar to Darwin’s
• Darwin quickly finished The Origin of Species and
published it the next year
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The Origin of Species
• Darwin developed two main ideas:
– Evolution explains life’s unity and diversity
– Natural selection is a cause of adaptive
evolution
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Descent with Modification
• The phrase descent with modification summarized
Darwin’s perception of the unity of life
• The phrase refers to the view that all organisms
are related through descent from an ancestor that
lived in the remote past
• In the Darwinian view, the history of life is like a
tree with branches representing life’s diversity
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LE 22-7
Sirenia
Hyracoidea (Manatees
(Hyraxes) and relatives)
0
10,000
2
5.5
24
34
Elephas Loxodonta Loxodonta
cyclotis
maximus africana
(Africa)
(Africa)
(Asia)
Natural Selection and Adaptation
• Evolutionary biologist Ernst Mayr has dissected
the logic of Darwin’s theory into three inferences
based on five observations
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• Observation #1: For any species, population sizes
would increase exponentially if all individuals that
are born reproduced successfully
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Observation #2: Populations tend to be stable in
size, except for seasonal fluctuations
• Observation #3: Resources are limited
• Inference #1: Production of more individuals than
the environment can support leads to a struggle
for existence among individuals of a population,
with only a fraction of their offspring surviving
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings