Download History of Evolution

What is a species?
Development of Evolution
Theory
History of Evolutionary Thought
• Early biological thought didn’t include
evolution
• Creationism
– Organisms remain fixed and unchanged
• 427-347 B.C. – Plato
• 384-322 B.C. – Aristotle – Scala Naturae
(ladder of Nature) – categorized
organisms into a linear hierarchy
• Until 1700’s creationism was unchallenged
• We need to define what a species is to
understand evolution, the mechanisms,
and diversity
• Species – basic unit of taxonomic
classification; population of closely related
and similar. In sexually reproducing
organisms, the similar organisms must be
able to breed and produce viable, fertile
offspring
New Evidence Eroded View of
Creationism
• New lands
– revealed diversity of life
– Africa, Asia, Americas
– Many different species; some closely resembled each
other
• Fossil Discoveries
– Fossils – remains of dead organisms (in rock,
petrified bones and wood, shells, impressions of body
forms
– showed life changed over time
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2. skin impression
3. bones
1. eggs in nest
(a)
(b)
(c)
4. fossilized feces
(coprolites)
5. footprint
Nonevolutionary explanations for
fossils
• Catastrophism
– Georges Cuvier (1769-1832)
• Proposed a vast # of species was created and
successive catastrophes produced layers of rock
and destroyed many species, fossilizing them
– Problem: some organisms that survived should have
shown up in fossils because some would have died; the
majority of fossils are extinct species
– Louis Agassiz (1807-1873)
• Proposed there were new creations after each
catastrophe
Speculations Life Did Evolve
• Original creation produced a small # of
founding species and later species
evolved through natural processes
– Georges Louis LeClerc (Comte de Buffon)
(1707-1788)
– Problem: couldn’t prove a mechanism and
also no one thought the earth was old enough
to allow time for producing a new species
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Geological Evidence – Earth is Old
• Uniformitarianism
– View of geologists Thomas Hutton and
Charles Lyell
– Earth developed gradually through natural
processes that occur over long periods of time
• Examples – river flooding, volcanoes, geologic
shift
Darwin and natural selection
PrePre-Darwin Biologists Proposed
Mechanisms for Evolution
• Jean Baptiste Lamarck (1744-1829)
• Hypothesized that organisms evolved through
the inheritance of acquired characteristics
– Proposed that all organisms have an innate drive for
perfection
– Example: Giraffes
– Problem: Acquired characteristics cannot be inherited
• Though he was wrong, Lamarck’s evolution
ideas influenced later biologists
The Voyage of the Beagle
1831 - 1836
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Darwin’s Voyage
Galapagos islands
• Volcanic archipelago- geologically young.
• Several groups of closely related species
found nowhere else.
• Mockingbirds, Finches, giant tortoisesdistinct types on the different islands
• Diversification (adaptive radiation) from
mainland ancestors
14 Varieties of finches
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Darwin and Wallace Proposed a
Mechanism of Evolution
• 1858 – Charles Darwin and Alfred Russel
Wallace came up with the mechanism for
evolution
• Worked separately
• 1859 – Darwin published On the Origin of
Species by Means of Natural Selection
How Does Natural Selection Work?
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Overproduction
Struggle for existence
Variation
Survival of fittest
Origin of a new species
Important Points Underlying
Evolutionary Change
• Variations that natural selection works on are
produced by chance mutations
– Mutations that produce traits occur spontaneously
and are made common or rare by natural selection
• Natural selection selects organisms that are
best adapted to a particular environment
– Conditions change in environments so the best at
one point may not survive at another time
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