Chapter 22: Descent With Modification A Darwinian View
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Transcript 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
Taxonomy
Paleontology
Cuvier
Study of fossils
Gradualism
Linnaeus- group organisms based on similar
structures
Change is slow but continuous
Lamarck’s Theory
First to include gradualism
Use & disuse
Inheritance of acquired characteristics
Natural Selection
Population CAN change over generations if
individuals with better adaptations leave more
offspring
Evolutionary adaptation
Inherited characteristics that enable survival and
reproduction in a certain environment
Evolution
Change in genetic composition of a population over
time
Descent with modification (Darwin’s term)
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
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
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
Environment does not create change- it
selects for individuals who already
possess beneficial adaptation
Examples of natural selection at
work
Guppy sexual maturation age & predatory
pressure
Drug resistant HIV
Insecticide resistance in insects
Evidence
Fossil record
Homology
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)