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CHAPTER 13
How Populations Evolve
PowerPoint® Lectures for
Essential Biology, Third Edition
– Neil Campbell, Jane Reece, and Eric Simon
Essential Biology with Physiology, Second Edition
– Neil Campbell, Jane Reece, and Eric Simon
Lectures by Chris C. Romero
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Figure 13.1
Charles Darwin and The Origin of Species
• Charles Darwin’s On the Origin of Species by
Means of Natural
• Two concepts: “descent with modification” and
natural selection.
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• The basic idea of natural selection is that:
- Success in reproduction leads to an accumulation
of favored traits in the population over generations
- Darwin based this off of:
- Species tend to produce excessive numbers of
offspring (only a small percentage will survive)
- The variation among individuals of a population
Example: The evolution of pesticide resistance in
hundreds of insect species
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Figure 13.2
• The Darwinian revolution in its historical context
1831-36: Darwin travels around the world on the
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
1858: The Origin of Species is published
Grand Canyon
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• Jean Baptiste Lamarck was a French naturalist who
suggested that the best explanation for the
relationship of fossils to current organisms was that
life evolves.
• He explained evolution as a process of adaption.
(evolutionary adaption)
• He also proposed that acquired characteristics are
inherited.
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The Voyage of the Beagle
• Darwin sailed from Great Britain on the Beagle in
December 1831.
• Main mission: chart poorly known stretches of the
South American coastline.
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Figure 13.4
• On his journey on the Beagle, Darwin
– Collected thousands of specimens.
– Observed various adaptations in organisms.
– The plants and animals living in temperate
regions of South America seemed more closely
related to species living in tropical regions of that
continent than to species living in temperate
regions of Europe.
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• Darwin was intrigued by the geographic
distribution of organisms on the Galapagos Islands.
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Figure 13.5
Descent with Modification
• Darwin made two main points in The Origin of
Species:
•
Descent of diverse species from common
ancestors.
•
Natural Selection as the mechanism of Evolution
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Figure 13.6
Evidence of Evolution
• Fossils
• Biogeography
• Comparative Anatomy
• Comparative Embryology
• Molecular Biology
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The Fossil Record
• Over millions of years, deposit piles up and
compress older sediments.
• If organisms that have been swept into the water
die, could be compressed too and may leave
imprints into the rock.
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Figure 13.7
Figure 13.8
Comparative Anatomy
• Comparison of body structures between different
species.
• Certain anatomical similarities show signs of
evolutionary history.
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• Homology: similarity due to common ancestry.
• Arms, forelegs, flippers, and wings of different
mammals are variations on a anatomical themes
that has become adapted to different functions.
Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings
Figure 13.11
Comparative Embryology
• Comparative Embryology- The comparison of
structures that appear during the development of
different organisms
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Figure 13.12
Molecular Biology
Molecular Biology says:
• If two species have genes with nucleotide
sequences that match closely, they might have been
inherited from a common ancestor.
• The greater the number of sequence differences,
the less likely the share a common ancestor.
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Figure 13.13
Natural Selection
• Darwin studied finches that lived on different
Galapagos islands and concluded that:
• The finches began to differ from one another
because they adapted to their environment.
o Different beak shapes (adapted to specific foods).
o Might become dissimilar enough to be classified
as different species.
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Figure 13.14
Natural Selection in Action
• Examples of natural selection include
– The evolution of pesticide resistance in hundreds
of insect species: a pesticide does not create
resistant individuals, but selects for resistant
insects that were already present in the
population.
– The development of antibiotic-resistant bacteria:
doctors have recently documented an increase in
drug-resistant strains of HIV.
Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings
Genetic Variation in Populations
• An individual’s genome is reflected in their
appearance and temperament. Some things cannot
be seen.
• Not all variation is heritable. Phenotype is made up
of the genotype and environmental influences.
• Polymorphic: when a population includes two or
more forms of a phenotypic characteristic.
• Mutations and sexual recombination produce
genetic variation.
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Sources of Genetic Variation
• Mutations: a mutation in a gene may substitute one
nucleotide for another, but the change will be
harmless if it does not affect the function of the
protein the DNA encodes.
• Sexual recombination: plants and animals depend
on sexual recombination for the genetic variation
that makes adaption possible. The two sexual
processes of meiosis and random fertilization
shuffle alleles and deal them out to offspring in
fresh combinations.
Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings