Transcript Darwin and the Theory of Evolution

BIOLOGY
A GUIDE TO THE NATURAL WORLD
FOURTH EDITION
DAVID KROGH
An Introduction to Evolution:
Charles Darwin, Evolutionary Thought,
and the Evidence of Evolution
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16.1 Evolution and Its Core Principles
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Common Descent with Modification
• Within the theory of evolution, a key principle
is that of common descent with modification.
• This principle describes the process by which
species of living things can undergo
modification over time, with such change
sometimes resulting in the formation of new,
separate species.
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Common Descent with Modification
• All species on Earth have descended from other
species, and a single, common ancestor lies at
the base of the evolutionary tree.
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Natural Selection
• A second key principle in the theory of
evolution concerns natural selection.
• Natural selection is a process in which the
differential adaptation of individual organisms
to their environment selects those traits that will
be passed on with greater frequency from one
generation to the next.
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Importance of Evolution as a Concept
•
The theory of evolution has an importance
beyond the domain of biology. Through it,
human beings have become aware that:
1. They are descended from other varieties of living
things.
2. The organisms that populate the living world are
not fixed entities, but instead are constantly
undergoing modification.
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16.2 Charles Darwin and
the Theory of Evolution
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Darwin and the Theory of Evolution
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Figure 16.1
Darwin and the Theory of Evolution
• Charles Darwin deserves primary credit for the
theory of evolution.
• Darwin developed existing ideas about descent
with modification while providing a large body
of evidence in support of them.
• He was the first to perceive natural selection as
the primary process that drives evolution.
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Darwin and the Theory of Evolution
• Darwin’s insights were inspired by the research
he carried out during a five-year voyage he took
around the world on the ship HMS Beagle,
beginning in 1831.
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Darwin and the Theory of Evolution
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Figure 16.2
Darwin and the Theory of Evolution
Dec. 1831Oct. 1836
North
America
Europe
Asia
Africa
Sept. 1835
Galapagos
Islands
equator
South
America
July 1834
April 1832
Australia
Jan. 1836
Falkland Islands
March 1833
March 1834
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Figure 16.3
16.3 Evolutionary Thinking before Darwin
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Evolutionary Thinking Before Darwin
• Some of Darwin’s ideas can be traced to the
work of Charles Lyell, who noted the dynamic
geological nature of the Earth.
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Evolutionary Thinking Before Darwin
• Also important were Jean-Baptiste de Lamark
and Georges Cuvier.
• Lamark noted the possibility of descent with
modification.
• Cuvier noted the extinction of some species on
Earth and the appearance of others within
different time-frames.
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Evolutionary Thinking Before Darwin
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Figure 16.5
16.4 Darwin’s Insights Following the
Beagle’s Voyage
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Darwin’s Insights
• Darwin understood descent with modification
for several years before he comprehended that
natural selection was the most important
process driving it.
• It was his reading of a work by Malthus on
limits to population growth that sparked his
realization about natural selection.
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16.5 Alfred Russel Wallace
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Alfred Russell Wallace
• English naturalist Alfred Russel Wallace is the
co-discoverer of natural selection as the
principal process underlying evolution.
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16.6 Descent with Modification Is Accepted
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Descent with Modification is Accepted
• Descent with modification was accepted by
most scientists not long after publication of
Darwin’s On the Origin of Species by Means of
Natural Selection in 1859.
• Scientists accepted it because it explained so
many facets of the living world.
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Descent with Modification is Accepted
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Figure 16.8
Descent with Modification is Accepted
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Figure 16.7
Descent with Modification is Accepted
Pharyngeal slits exist in these five vertebrate animals . . .
pharyngeal
slits
sea lamprey
pond turtle
chicken
domestic cat
human being
. . . evidence that all five evolved from a common ancestor
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Figure 16.9
16.7 Darwin Doubted: The Controversy
over Natural Selection
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Controversy over Natural Selection
• The hypothesis that natural selection is the most
important process underlying evolution was not
generally accepted until the middle of the
twentieth century.
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Controversy over Natural Selection
• Its acceptance hinged on a modern synthesis in
the theory of evolution that brought together
lines of evidence from genetics, the fossil
record, and the distribution of organisms
throughout the world.
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16.8 Opposition to the Theory of Evolution
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Opposition to the Theory of Evolution
• Even today, the theory of evolution is regularly
challenged as being unproven or simply wrong.
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Opposition to the Theory of Evolution
• One factor leading to the appearance of a
“scientific debate” over evolution is confusion
about the meaning of the word theory.
• Though the average person may equate
“theory” with speculation, in science a theory is
a general set of principles supported by a lot of
evidence that explains some aspect of the
natural world.
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16.9 The Evidence for Evolution
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The Evidence for Evolution
• Six lines of evidence are consistent with the
theory of evolution.
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1. Radiometric Dating
• First, radiometric dating has confirmed the
immense age of the Earth—an age that is
consistent with the long periods of time
scientists believe it has taken species to evolve.
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2. Fossils
• Second, around the globe, fossils from the same
evolutionary periods are consistently found
together in geologic strata.
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2. Fossils
• Moreover, there is excellent agreement between
the relative ages assigned to fossils by
evolutionary theory and the absolute ages
assigned to them by radiometric dating.
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2. Fossils
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Figure 16.10
3. Comparative Morphology and
Embryology
• Third, the theory of evolution explains the
common occurrence of homologous physical
structures in different organisms.
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3. Comparative Morphology and
Embryology
whale
cat
bat
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gorilla
Figure 16.11
4. Evidence from Biogeography
• Fourth, island biogeography—the geographic
distribution of species on Earth’s islands—is
explained by the theory of evolution.
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4. Evidence from Biogeography
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Figure 16.13
5. Evidence from Gene Modification
• Fifth, variations found in the DNA sequences of
various organisms are consistent with
evolutionary theory.
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5. Evidence from Gene Modification
Number of DNA nucleotide base differences in the cytochrome c oxidase gene
Large number of
base differences
between humans
and yeast
66
36
31
20
17
Small number of
base differences
between humans
and pigs
13
human
pig
duck snake
tuna
moth
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yeast
Figure 16.14
6. Experimental Evidence
• And sixth, experimental demonstrations of
evolution have been carried out in the
laboratory and in nature.
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Principles of Evolution
PLAY
Animation 16.1: Principles of Evolution
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