Download Chapter 22: Descent With Modification A Darwinian View

Chapter 22: Descent With
Modification
A Darwinian View of Life
On the Origin of Species by Means of
Natural Selection by Charles Darwin
 Attempts to create a family tree for all
life on Earth
Mechanism=
natural selection
Groundwork for Darwin’s Theory
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Taxonomy
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Paleontology
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Cuvier
Study of fossils
Gradualism
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Linnaeus- group organisms based on similar
structures
Change is slow but continuous
Lamarck’s Theory
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First to include gradualism
Use & disuse
Inheritance of acquired characteristics
Natural Selection
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Population CAN change over generations if
individuals with better adaptations leave more
offspring
Evolutionary adaptation
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Inherited characteristics that enable survival and
reproduction in a certain environment
Evolution
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Change in genetic composition of a population over
time
Descent with modification (Darwin’s term)
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All organisms are related through descent with an ancestral
organism
Modifications in species a result of inhabiting different
environments
Natural selection

Requirements
Resources are limited

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Struggle for existence
Individuals with heritable traits better suited
to environment leave more offspring
Population gradually evolves to exhibit higher
number of individuals with beneficial trait
Natural Selection
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INDIVIDUALS DO NOT EVOLVEPOPULATIONS CAN!!!!
Environment determines which traits are
favored

Biogeography- similarities found among
species in similar ecological niches
Convergence- unrelated species in similar niches
have similar adaptations
 Divergence- related species in different ecological
niches have dissimilar adaptations
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Environment does not create change- it
selects for individuals who already
possess beneficial adaptation
Examples of natural selection at
work
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Guppy sexual maturation age & predatory
pressure
Drug resistant HIV
Insecticide resistance in insects
Evidence
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Fossil record
Homology
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related species have similar underlying traits
that MAY be used for different functions
Homologous structures
Comparative embryology
Vestigial structures (remnant structures)
Molecular similarities (DNA, protein)