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Origin of Biological Diversity
Formation of a Species
Evolution: A Remodeling Process
Lifes History
Modern Taxonomy
Life Begins
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Formation of a Species
A. Speciation
B. Causes of Speciation
C. Adaptive Radiation
D. Punctuated Equilibrium
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A. Speciation
1. Biological Species Concept:(Ernst Mayr) a group ofinterbreeding organismsthat can produce healthy,fertile offspring
2. Speciation, the origin of newspecies can arise by:
a. separation by a barrier
b. two groups live indifferent environments
for thousands of years_
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c. individuals with favorabletraits survive andreproduce
d. in time each group maybecome a different
species_
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B. Causes of Speciation
1. Geographic isolation is thephysical separation of apopulation (allopatricspeciation)
a. mountain, ocean_
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B. Causes of Speciation
2. Reproductive isolation is dueto the inability of twospecies to breed (sympatricspeciation)
a. Prezygotic isolation
before fertilization(temporal, behavioral,habitat)
b. Postzygotic isolation after fertilization (hybridinviability, hybrid sterility,
hybrid breakdown)_
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C.Adaptive Radiation
1. Adaptive radiation producesdiverse species adapted todiverse environments allfrom one common ancestor
(Darwins finches)_
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D. Punctuated Equilibrium
1. Darwin proposed thatevolution occurred at aconstant, gradual rate(gradualism)
2. Eldredge and Gould proposed
that evolution progresseswith little change,punctuated by rare, shorttimes with increaseddiversification (punctuatedequilibrium)_
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THE END
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Evolution: A Remodeling Process
A. Refine Existing Adaptations
B. Adapting Existing Structures
C. Types of Selection
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A. Refine Existing Adaptations
1. Complicated structures haveevolved from the gradualrefinement of simplerstructures (eyes)
2. Co-evolution one species can
influence the evolution ofanother species and viceversa (finches and beetles)_
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B.Adapting Existing Structures
1. Pre-existing structures thatevolved as adaptations forcertain functions can laterfulfill other functions
a. convergent evolution_
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C.Types of Selection
1. Directional Selection - onephenotype is favored overanother (giraffe neck)_
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C.Types of Selection
2. Stabilizing Selection -extreme phenotypes areselected against (humanbirth weight)_
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C.Types of Selection
3. Disruptive Selection(diversifying selection) favors individuals at eitherextreme phenotype
(seed size)_
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D. Other Notable Scientists
1. Alfred Wallace-
British Naturalist
Studied Flora and Fauna ofmany islands
Came up with a theory ofNatural Selectionindependent of CharlesDarwin_
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2. Charles Lyell-
Scottish Geologist
Uniformitarianism Thepresent is the key to thepast_
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3. Thomas Malthus
Population Growth Apopulation grows faster thanits food supply_
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4. Ernst Haeckel
Otogeny recapitulatesphylogeny
(embryonic developmentalstages look like adult
evolutionary ancestors)Better to say otogenyrecapitulates ancestralotogeny_
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D. Miscellaneous
Red-Queen Hypothesis aspecies must continue toevolve simply to maintaincurrent fitness
Non-evolutionist TheoryScala-naturae great chainof being
Definitions
Homology study of similarstructures (due to sharedancestry)
Morphology study of overallform or shape
Physiology study of function inliving organisms
Aggregate - collection
Fitness success of passingones genes to the next
generationAssortive mating selecting
similar mates
Selective mating choosing onebest trait_
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THE END
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A. Refine Existing Adaptations
1. Complicated structures haveevolved from the gradualrefinement of simplerstructures
a. eyes and flowers_
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C.Adaptive Radiation
1. Adaptive radiation producesdiverse species adapted todiverse environments allfrom one common ancestor
a. Darwins finches
b. genetic drift_
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