Chapter 2
Development of Evolutionary Theory
Brief History of Evolutionary Thought
 Natural Selection in Action
 Constraints on Nineteenth-Century
Evolutionary Theory
 Opposition to Evolution
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Evolution
A change in the genetic structure of a
population. Also refers to the
appearance of a new species.
Pre-scientific View
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Predominant world view throughout the middle ages
was stasis, the idea that the world was fixed and
unchanging. Also called Fixity of Species.
The Great Chain of Being held that life was arranged
from the simplest to the most complex.
It was believed that the earth was “full” and nothing
new could be added.
The world was seen as the result of a grand design that is, God’s design. Also called Teleology.
The Scientific Revolution
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The discovery of the new world challenged
fundamental views about the planet.
Exposure to new plants and animals increased the
awareness of biological diversity.
Copernicus challenged the idea that the earth was the
center of the universe.
Galileo’s work further supported the idea that the
universe was a place of motion rather than fixity and
solidified use of scientific method in research.
Keppler, Descartes and Newton established the laws
(theories?) of physics, motion and gravity.
The Path to Natural Selection
 John
Ray provided the first definition of the
concept of species and genus (groups of
interbreeding organisms and related such
groups).
 Carolus Linnaeus developed a system of
classification and laid the basis for taxonomy
and binomial nomenclature used today.
 Comte de Buffon stressed the importance of
change in the universe and recognized the
environment as an agent of change.
The Path to Natural Selection
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John Baptiste Lamarck was the first scientist to
produce an explanation for the evolutionary
process, called Use-Disuse or Inheritance of
Acquired Characteristics
Georges Cuvier introduced the concept of
extinction and the theory of catastrophism.
Charles Lyell developed the theories of
uniformitarianism and deep time.
Thomas Malthus wrote about the relationship
between food supplies and population increase.
Charles Darwin (1809-1882)
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Many of Darwin’s ideas were formed while serving as a
naturalist on the voyage of the HMS beagle.
Darwin saw that biological variation within a species
was critically important.
Darwin recognized the importance of sexual
reproduction in increasing variation.
By 1844, Darwin had complete the work that he would
publish fifteen years later.
Darwin’s Finches
Alfred Russell Wallace (1823-1913)
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Wallace was a naturalist who worked in South America
and Southeast Asia.
Wallace published an article suggesting that species
were descended from other species and new species
were influenced by environmental factors.
The coincidental development of evolution by natural
selection by both Darwin and Wallace was resolved
with the joint presentation of their papers to the
Linnean Society of London.
Processes of Natural Selection
1.
2.
3.
4.
Species can produce offspring at a faster rate than
food supplies increase.
There is biological variation within all species.
In each generation, more individuals are produced
than can survive.
Individuals that possess favorable traits or variations
are more likely to survive and produce offspring than
those who do not.
Processes of Natural Selection
5.
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8.
The environmental context determines whether or
not a trait is beneficial.
Traits are inherited and passed on to the next
generation.
Over long periods of time, variations accumulate so
that later generations may be distinct from ancestral
ones.
As populations respond to pressures over time, they
may become distinct species, descended from a
common ancestor.
Evolutionary Change
Through Natural Selection
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2.
3.
A trait must be inherited to have importance
in natural selection.
Natural selection cannot occur without
variation in inherited characteristics.
Fitness is a relative measure that will change
as the environment changes. See Peppered
Moths for an example of this in action.
Peppered Moths &
Industrial Melanism
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Until the mid-nineteenth century, peppered moths,
Biston betularia, had mostly light-colored wings.
Later, darker individuals became predominant.
Industrial smog helped turn tree trunks dark.
Contrasting colors between trunk color and moth
color led to differential predation by birds.
Mutations and chance continued to create or
permit survival of SOME lighter moths, though.
As pollution controls increased, frequencies
reversed again.
Peppered Moths
Challenges to Darwin
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Evolution not solidly demonstrated
There are no fossil intermediates
Intelligent design
Evolution violates Second Law of
Thermodynamics
Proteins too improbable
Natural selection does not imply evolution
Irreducible complexity argument