Download Descent With Modification

Descent With Modification
Charles Darwin
Traditional Views
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Earth is several thousand years old
Forms remain unchanged
Species composition remains unchanged
Adaptation interpreted as genius design
Evolutionary Adaptation
• Accumulation of inherited characteristics
that increase fitness
Lamarck
• Recognized examples of evolution taking
place
• Incorrect mechanism
– Use and Disuse
– Inheritance of acquired
characteristics
The Groundwork for Darwin’s Idea
• Fossils
• Geology
Gradualism vs. Catastrophism
• Catastrophism-Each boundary between
fossil layers represents a natural disaster
– Floods, droughts, fires
• Gradualism- change is a slow process of
accumulated traits
• Uniformitarianism- Geologic features can
be explained by current events
• Grand Canyon/ Green River
Darwin’s Influences
• Medical School
• HMS Beagle
A Revolutionary Theory
• On the Origin of Species by Means of
Natural Selection- 1859
– Many species alive today are descendants of
species that lived many years ago
– Populations change when some individuals
are more fit than others
Adaptation
• Could the accumulation of traits lead to
new species?
Descent with Modification
• All living things
descended from one
ancestral organism
• As populations moved
into new habitats they
were changed by the
new conditions
• Species that appear
similar have a more
recent common
ancestor
• Most branches are
dead ends  most
species that have
ever lived are now
extinct
Darwin’s observations
• Variation within population
• Overproduction of offspring
• Most offspring don’t survive
• Different phenotypes
lead to different
reproductive success
Artificial Selection
Natural Selection
• Over production leads to competition for
resources
• Survival (successful competition) depends
on inherited traits
• Only those with the most useful traits will
survive to reproduce
• Offspring will more closely resemble
successful individuals
A Unifying Theory
• Theory of natural selection explains a wide
range of phenomena
– Predator prey relationships
– Camouflage
– Similarities in DNA and protein sequences
– Fossil record
– Antibacterial resistance
Cichlid fish
Drug resistant TB
• Drug regimen
completion is rare
• Surviving bacteria
are the most resistant
• Rebuild population
• Multiple drug resistant
strains of disease
Homologies
• Molecular homologies
• Embryology
• Homologous structures
– Vestigial organs
Homologous structures
Vestigial structures
Biogeography
• Closely related species are found in the
same areas
– Australian marsupials
• Island species are
related to mainland species
• Similar environments
select for similar traits
– Sugar glider and flying squirrel
Fossil Record
• Transitional species
link ancient and
modern forms
Theories
• Theory= a hypothesis that has stood up to
testing, skepticism and extensive
observations
• “There is grandeur in this view of life…”
On the Origin of the Species