Download PPT

History of Evolutionary Thought
What was the view of the world and nature before Darwin?
1. Static Universe
The universe didn’t change through time
Problem - Fossil Evidence
What was the view of the world and nature before Darwin?
1. Static Universe
2. Earth Centred Universe
Galileo - showed that this was wrong
What was the view of the world and nature before Darwin?
1. Static Universe
2. Earth Centred Universe
3. Great Chain of Being
Problem - how do you incorporate new species?
What was the view of the world and nature before Darwin?
1.
2.
3.
4.
Static Universe
Earth Centred Universe
Great Chain of Being
Argument from Design
Each species was designed for a specific purpose
Problem:
How did this ‘traditional’ view (or Natural Theology)
apply to Biology?
1. Argument from Design
The design of all organisms showed that
there was an intelligent and benevolent Creator
BUT….
How do disease
organisms fit into
this scheme ?
Ebola
How did this ‘traditional’ view (or Natural Theology)
apply to Biology?
1. Argument from Design
The design of all organisms showed that
there was an intelligent and benevolent Creator
OR….
Why did some
species go
extinct?
How did this ‘traditional’ view (or Natural Theology)
apply to Biology?
1. Argument from Design
2. Relationship between Species
(Great Chain of Being)
BUT ..
vulnerable to
extinction
How did this ‘traditional’ view (or Natural Theology)
apply to Biology?
1. Argument from Design
2. Relationship between Species
3. Fixed Species and Relationships
How do you incorporate new species?
General Summary:
The world/universe was designed by
a benevolent Creator to function perfectly
and its form and function were fixed
through all time.
But Evolution is about change
What were the pre-Darwinian ideas of change through time?
Pre-Darwinian Ideas of Organic Change
1. Georges Louis Leclerc, Comte de Buffon (1707-1788)
Species - a distinct group maintained by
reproduction
Local
Conditions
Ancestor
Time
Different
species
Pre-Darwinian Ideas of Organic Change
1.
2.
Georges Louis Leclerc, Comte de Buffon (1707-1788)
Jean-Baptiste Lamarck (1744-1829)
Pre-Darwinian Ideas of Organic Change
1.
2.
Georges Louis Leclerc, Comte de Buffon (1707-1788)
Jean-Baptiste Lamarck (1744-1829)
Lamarck’s ideas:
1. Spontaneous generation
Pre-Darwinian Ideas of Organic Change
1.
2.
Georges Louis Leclerc, Comte de Buffon (1707-1788)
Jean-Baptiste Lamarck (1744-1829)
Lamarck’s ideas:
1. Spontaneous generation
2. Ascent up the scale of nature
Different species
Complexity
of the
organism
Time
Pre-Darwinian Ideas of Organic Change
1.
2.
Georges Louis Leclerc, Comte de Buffon (1707-1788)
Jean-Baptiste Lamarck (1744-1829)
Lamarck’s ideas:
1. Spontaneous generation
2. Ascent up the scale of nature
3. Acquired characteristics
Originators of Modern Theories of Natural Selection
Charles Darwin
Alfred Russell Wallace
Voyage of HMS Beagle
Darwin’s Finches - Geospiza
Galapagos tortoise - Geochelone
Contributing Elements to Darwin’s theory
1. Charles Lyell (1797 - 1875)
Gradualism (Uniformitarianism)
All change through time can
be explained by processes at
work today
No need to invoke catastrophic
events
Contributing Elements to Darwin’s theory
1. Charles Lyell (1797 - 1875)
2. Thomas Malthus (1766 - 1834)
Populations of organism will grow
faster than their food supply
Population
Number
Food supply
Time
Contributing Elements to Darwin’s theory
1. Charles Lyell (1797 - 1875)
2. Thomas Malthus (1766 - 1834)
3. Plant and Animal Breeders
-showed that the form of a
species could be changed
over time
Logic of Darwin’s
Theory of Natural Selection
(or Descent with Modification)
Observation
1.
All organic populations
can exponentially.
2.
In spite of Obs. 1, they
don’t.
3.
All members of a
species are not the
same.
4.
Differences in
individuals are passed
to their offspring.
Deduction
1.
There is some kind
of struggle for
existence.
2.
Some members of a
species are better
equipped to survive and
reproduce than others.
This differential reproduction/survival is
natural selection