Transcript C15-Theory of Evolution Pp. 392

C15-Theory of Evolution Pp.
392- 419
Sharp
Honors Biology
Contents
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15-1
Natural Selection and
the Evidence for
Evolution
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15-2
Mechanisms of
Evolution
Theory of Evolution
Charles Darwin (1809-1882) English
scientist whose observations as a young
man of 22 aboard the HMS Beagle were
the basis for his theory of evolution.
 Five-year scientific journey as naturalist
took him around the world collecting
specimens and fossils.
 On the Galapagos Islands, the many
species suggested change
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Theory of Evolution
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On the Galapagos Islands, the many
species suggested the possibility of
change over time; however, he had no
explanation of how this occurred.
Theory of Evolution
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Darwin continued his
studies for another 20
years.
Read economist Thomas
Malthus ideas regarding
survival of the fittest &
adapted it.
Conducted pigeon
breeding experiments with
artificial selection.
His study at Down House
Darwin Explains Natural Selection
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Natural Selection is a
mechanism for change in
populations. It occurs when
organisms with favorable
variations survive,
reproduce, and pass on
their variations to offspring.
Seen here, Galapagos
finch species varied by
nesting site, beak size, and
eating habits.
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Soon Alfred Russel Wallace
wrote Darwin a letter
expressing similar thoughts.
In 1859, Darwin published
On the Origin of the
Species by Means of
Natural Selection.
His ideas have become the
basic unifying theme of
modern biology.
Evidence Since Darwin
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Structural Adaptation
Homologous structures
Comparative Embryology
Molecular Record (DNA)
Physiological Change i.e.
antibiotic resistance
Fossil Evidence
Biochemistry
Adaptations: Evidence for Evolution
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Any variation that aids an organisms chance of survival in its
environment.
Structural adaptations arise over time.
Mimicry enables one species to resemble another.
Camouflage enable species to blend with background
Adaptation: Physiological
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Some adaptations develop
rapidly.
Bacteria develop resistance
to antibiotics by changing
their metabolic processes.
Also observed with pests
and weeds responding to
insecticides and herbicides.
Other Evidence for Evolution
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Fossils
As the fossil record
becomes more complete,
the sequences of evolution
become more clear.
Anatomy: Homologous Structures
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Homologous Structures
Anatomy: Homologous Structures
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The bones of each forelimb
are modified for function,
but they are arranged
similarly.
Analogous Structures are
similar in function but do
not have a common
evolutionary relationship.
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Add
your
conclusions
here.
Conclusion
Anatomy: Vestigial Structures
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A body structure that no
longer serves its original
purpose.
Human ear muscles?
Appendix?
Whale hip bones?
Blind Cavefish?
Embryology
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An embryo is the earliest
stage of development of a
plant or animal.
Shared features in the
young embryo suggest
evolution from a distant
common ancestor.
Fish
Bird
Turtle
Dog
Biochemistry
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Can you fill in the missing
sequences?
Nearly all organisms share
DNA, ATP, and many
enzymes such as
cytochrome c.
Organisms that are
biochemically similar have
more amino acid sequences
in common.
Used to interpret
evolutionary relationships
btw species.
15-2 Mechanisms of Evolution
15-2 Mechanisms of Evolution
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Population Genetics and
Evolution
Populations, not individuals,
evolve!
Genes determine traits of
an individual; those who
survive and reproduce
determine allelic
frequency.
Mechanisms of Evolution
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The gene pool changes
over generations as natural
selection affects the allelic
frequency.
A population in genetic
equilibrium is not
evolving…the allelic
frequency stays the same.
One mechanism for change
is mutation.
Mechanisms of Evolution
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Genetic Drift alteration of
allelic frequencies by
chance events.
Genetic drift can greatly
affect small populations
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Distinctive species of
Galapagos
Amish in Lancaster, PA
Mechanisms of Evolution
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Gene Flow when
individuals leave or enter a
population
Mutation, genetic drift and
gene flow can greatly
affect a small, isolated
population.
Natural selection is usually
the most significant factor
in causing changes.
Mechanisms of Evolution
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Natural Selection acts on
variations in 3 ways:
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Stabilizing- favors average
individuals
Directional- favors one of
the extreme variations
Disruptive- selects for either
extreme variation
See p. 408 for examples.
Evolution of Species
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Speciation of Cichlids
Define Species
The evolution of a new
species is a process called
speciation which occurs
when members of similar
populations no longer
interbreed to produce
fertile offspring.
Physical Barriers Prevent Interbreeding
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Geographic Isolation
Volcanoes
Continental drift
Mountain formation
Island
Regional varieties due to
reduced gene flow &
geographic distance
Reproductive Isolation
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Formerly interbreeding
organisms can no longer
mate & produce fertile
offspring.
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Conspicuous differences in floral
morphology are partly responsible for
reproductive isolation between two
sympatric species of monkeyflower,
due to their effect on visitation of the
flowers by different pollinators.
(Bumblebees or hummingbirds)
Genetic material changes
preventing fertilization.
Behavioral ex. Fall vs.
summer mating
Change in Chromosome Numbers
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Polyploidy results when an individual or species have
multiple sets of chromosomes.
Often occurs in plants due to mistakes in mitosis or meiosis or
during hybridization.
Polyploid speciation takes only one generation.
Speciation Rates
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Gradualism slow, steady
rate with small adaptive
changes accumulating
gradually
Punctuated equilibrium
(1972) Eldredge & Gould speciation occurs rapidly in
quick bursts with long
periods of equilibrium
between
Patterns of Evolution
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Adaptive Radiation
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Hawaiian honeycreepers
Ancestral species evolved
to fit diverse habitats
Occupy own various
niche
Divergent Evolution
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Similar species diverge
becoming increasingly
distinct
Patterns of Evolution
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Convergent Evolution – unrelated species occupy similar environments
in different parts of the world.
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Share similar environmental pressures & similar natural selection
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See anteaters shown above.
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Another example- N. & S. American & African cacti