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Evolution
MRS. BARROW
Learning Objectives
1.25 Student is able to describe a model that
represents evolution with in a population
1.26 Student is able to evaluate given data sets that
illustrate evolution as an ongoing process
Prior Beliefs
Aristotle (384-322 BC) : Time allowed more complex life- forms to develop
Theology : Old testament, Divine Creation
Taxonomy ( Linnaeus 1707-1778) : Blended complexity with creationism
(intelligent design)
Gradualism (Hutton 1726-1796) : Changes took place slowly
Lamarck (1744-1829) : Use and disuse, acquired characteristics
Catastrophism (Cuvier 1769- 1832) : Destruction of organisms and evolution of
replacements
Uniformitarianism (Lyell 1797- 1875) : Same process as in the past
Hutton Vs. Lyell
Lamarckian Vs. Darwinian Evolution
Darwinian evolution posits
organism genetic
adaptation to
environments, though it is
actually Lamarck who first
conceived of such a
concept
Difference?
Darwin had a
population
emphasis
Historical context
Charles Darwin (1809-1882)
HMS Beagle (1831-1836)
Darwin
Developed the basis his theory based on his observations of
the principles of botany, geology, and zoology while on a
five year research voyage
He gained great insights while visiting the Pacific Islands,
Galapagos Archipelago, and South America
He was afraid to share his work so he waited to publish until
he heard of another scientist, Wallace, who was developing
a theory similar to his own
Wallace
Independently developed a
theory of evolution by
natural selection
Terms to know:
Evolution:
Descent with modification
Natural Selection:
Individuals with certain heritable traits leave more offspring
Evolutionary Adaptation:
Characteristics that enhance survival
Evolution: Descent with Modification
Evolution: Premises
1. Struggle for survival
◦ Competition between individuals
◦ Over production (Malthus)
Evolution: Premises
2. Variations Exist
Evolution: Premises
3. Many Variations are heritable
Evolution by Natural Selection
1.
Natural selection is the differential reproductive success of among individuals
2.
Variations exist; some represent adaptive traits that increase reproductive success
3.
Many of these are heritable
4.
Over time, this can increase the adaptation of organisms to their environment
5.
Environmental changes may result in adaptation of a species to these new conditions.
Natural Selection: Diversity derived from wild mustard
Adaptation: the result of natural selection
*The result of natural selection is adaptation
Adaptation – heritable trait that increase an organism’s likelihood
of surviving and reproducing in its environment
Example: Desert animals exhibit extraordinary adaptations, both
physical and behavioral, to their environment
"In the struggle for survival, the fittest win out
at the expense of their rivals because they
succeed in adapting themselves best to their
environment."
-Charles Darwin, The Origin of Species
Adaptation
Adaptation: Camouflage
Not an adaptation
Artificial Selection (Not the same)
Breeding plants and
animals for specific
traits
Darwin was a fan of
fancy pigeons
Fitness
1. Individual organisms are selected
2. Populations evolve!
Remember, individuals live or die. They do not evolve!
Evidence for evolution
Evolution is supported by an overwhelming
amount of scientific evidence
Let’s take a look at some direct observations of
evolutionary change . . .
How does selection drive changes in a population?
Paul Muller discovered DDT in 1939.
Nobel Prize 1948
By 1945, 3m pounds of DDT
produced/year!
Examples of Selection provide evidence
of Evolution . . .
Examples of Natural Selection
30-60 generations later . . .
14% heavier; average age at maturity higher
More examples….
Salmon
◦ 80% mortality
◦ Evolving to be smaller and more torpedo-shaped
◦ Population is 30% smaller over 50 years
The Peppered Moth
Biston betularia
Evolution of drug resistance
A drug does not create a resistant pathogen
It selects for existing resistant pathogens
And so with evolution:
Evolution does not create novel life forms
Nature selects from existing variants
Need more evidence?
Viruses
Bacteria Resistance
The Red Queen Hypothesis
Forewarned is forearmed . . .
A. Biogeography
Closely related species tend
to be found in the
same region
Pangea, Laurasia and
Gondwanaland
What is the significance of Biogeography?
The geographical distribution of species only makes sense in
light of evolutionary past
What are specific examples?
Marsupial Mammals in Australia
Finches in Galapagos
Fruit flies in Hawaii
Convergent Evolution
So how can disjunct regions have
species that appear similar,
though are not closely related?
Different geographic regions,
different mammalian “brands”
CONVERGENT EVOLUTION
Same problem, same solution
B. Vestigial Organs
C. Comparative Embryology
D. Homologous Structures:
Similar Anatomy(relatedness)
Different Functions (adaptation)
NOT EVIDENCE FOR EVOLUTION
Analogous Structures:
Similar Functions (adaptation)
Different Anatomy (lack relatedness)
E. Comparative Biochemistry
Molecular Data and the
Evolutionary Relationships of
Vertebrates
Evidence Summary
A.
B.
C.
D.
E.
F.
G.
Direct Observations of Evolutionary Change
Biogeography
Vestigial Organs
Comparative Embryology
Homologies
Comparative Biochemistry
Molecular Biology
Natural Selection Review
A. Product is adaptation of populations to their
environment
B. Does not “create” options
C. Is an Editing Process
Natural Selection Premises Review
A. Variation must exist
A. Variation must lead to differential
reproductive success
A. Variation must be heritable.
Descent with Modification
Evidence of Biblical Flood? (Theology)
Some people think that the Grand Canyon is evidence of the great flood told in the story of
Noah in the bible. I’ll leave it up to you to decide what you believe on this one.