Transcript Chapter 2 the Development of Evolutionary Theory

Chapter 2
The Development of
Evolutionary Theory
Chapter Outline
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Brief History of Evolutionary Thought
Natural Selection in Action
Constraints on Nineteenth-Century
Evolutionary Theory
Opposition to Evolution
Evolution
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A change in the genetic structure of a
population.
Also refers to the appearance of a new
species.
Often controversial, some religious views hold
that evolutionary statements run counter to
biblical teachings.
Evolution Is a Theory
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The theory has been supported by a mounting
body of genetic evidence.
The theory has stood the test of time.
The theory stands today as the most
fundamental unifying force in biological
science.
Pre-scientific View
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In the middle ages, the predominant world was
stasis, the world was fixed and unchanging.
The great chain of being held that life was
arranged from simplest to 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 - God’s design.
The Scientific Revolution
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Discovery of the new world challenged
fundamental views about the planet.
Exposure to new plants and animals increased
awareness of biological diversity.
The Scientific Revolution
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Copernicus challenged the idea that the earth
was the center of the universe.
Galileo’s work supported the idea that the
universe was a place of motion.
Keppler, Descartes and Newton established
the laws of physics, motion and gravity.
The Path to Natural Selection
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John Ray provided first definition of the
concept of species and genus.
Carolus Linnaeus developed system of
classification and the basis for taxonomy.
Comte de Buffon stressed the importance of
change in the universe and the environment as
an agent of change.
The Path to Natural Selection
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John Baptiste Lamack was the first scientist to
produce an explanation for the evolutionary process.
Georges Cuvier introduced the concept of extinction
and the theory of catastrophism.
Charles Lyell developed the theory of
uniformitarianism.
Thomas Malthus wrote about relationship between
food supply and population increase.
Charles Darwin (1809-1882)
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Ideas were formed while serving as a naturalist
on the voyage of the HMS beagle.
Darwin saw the importance of biological
variation within a species.
Recognized the importance of sexual
reproduction in increasing variation.
By 1844, Darwin had complete the work that
he would publish fifteen years later.
Alfred Russell Wallace
(1823-1913)
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A naturalist who worked in South America and
Southeast Asia.
Suggested species descended from other
species and new species were influenced by
environmental factors.
Presented paper on evolution and natural
selection to the Linnean Society of London
jointly with Darwin.
Processes of Natural Selection
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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.
Processes of Natural Selection
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Individuals that possess favorable traits or
variations are more likely to survive and
produce offspring.
Environmental context determines whether a
trait is beneficial.
Traits are inherited and passed on to the next
generation.
Processes of Natural Selection
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Variations accumulate over long periods of
time, so 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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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.