The Evolution of a Theory
Darwin and Evolution
Outline
• History of Evolutionary Thought
• Darwin’s Theory of Evolution
– Occurrence of Descent
– Biogeography
• Natural Selection and Adaptation
• The Evidence of Evolution
– Fossil
– Biogeographical
– Anatomical
– Biochemical
Scientific view prior to Darwin
• strongly tied to religion, in fact, its purpose
was to verify religious dogma.
Some guiding ideas in science
• Special creation of the fixity of all species
• The Scala Naturae
Mid-Eighteenth Century
• Taxonomy -- important
endeavor during mid-eighteenth
century.
–Linnaeus
–Count Buffon.
Late Eighteenth Century
• Cuvier --comparative anatomy
Founded Paleontology
• Proposed Catastrophism
Natural Theology
• The Rev. William Paley –
looking for perfection
• precursor to scientific
creationism
• Precursor to ID?
Life’s a Struggle
• The Rev. Thomas Malthus – life is a
struggle. Populations limited by:
–Drought
–Famine
–Pestilence
–War?
Late Eighteenth Century
•Lamarck was first biologist to believe
evolution occurs and to link diversity with
environmental adaptation.
–Concluded more complex organisms
are descended from less complex
organisms.
PROPOSED:
Inheritance of Acquired Characteristics
Darwin’s Theory of Evolution
• The theory of evolution is also called
descent with modification.
• Darwin’s Influences:
– Charles Lyell
• Uniformitarianism
– Thomas Malthus
– Reverend Paley
Galapagos Islands-Darwin’s Lab
Galápagos Tortoises and Finches
Driving Force of Evolution?
NATURAL SELECTION
–Preconditions
• Heritable variation
• Struggle for resources
• Variations in fitness
–Consequences
• Population better adapted to local
environment
Artificial Selection
Preconditions
• Organisms Have Variations
• Organisms Struggle to Exist
• Organisms Differ in Fitness
Result
• Populations Become Adapted
What is the evidence for evolution?
• Fossil
• Biogeographical
• Anatomical
• Embryological
• Biochemical
Evolution of the Horse
Biogeography
Comparative Anatomy
Comparative Anatomy 2
• Homologous Structures are
anatomically similar
• Analogous Structures serve the
same function
• Vestigial Structures
Comparative Embryology
Biochemical Evidence
Models of Evolution
Summary
• History of Evolutionary Thought
• Darwin’s Theory of Evolution
– Occurrence of Descent
– Biogeography
• Natural Selection and Adaptation
• The Evidence of Evolution
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Fossil
Biogeographical
Anatomical
Embryological
Biochemical