Download common descent with modification

Biology
A Guide to the Natural World
Chapter 16 • Lecture Outline
An Introduction to Evolution: Charles Darwin,
Evolutionary Thought, and the Evidence of Evolution
Fifth Edition
David Krogh
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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 through which
traits that confer a reproductive advantage
to individual organisms grow more common
in populations of organisms over successive
generations.
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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 16.2
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 16.3
Darwin and the Theory of
Evolution
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Figure 16.4
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 16.6
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 Russel 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 Darwin: Accepted, Doubted,
and Vindicated
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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 16.9
Descent with Modification Is
Accepted
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Figure 16.8
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 16.10
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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16.7 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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16.8 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 16.11
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 16.12
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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5. Evidence from Gene
Modification
• Fifth, variations found in the DNA
sequences of various organisms are
consistent with evolutionary theory.
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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
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moth
yeast
Figure 16.13
6. Experimental Evidence
• And sixth, experimental demonstrations of
evolution have been carried out in the
laboratory and in nature.
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