Natural Selection Mr. Modafferi. Do Now Define Natural Selection.
The Genetical Theory of Natural Selection
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Transcript of The Genetical Theory of Natural Selection
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The Genetical Theory of Natural Selection
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Where natural selection occurs
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Fundamental patterns of intraspecific natural selection
Disruptive
Rare
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Carnivores
• Consume nutritionally-rich prey.• Problems involve capture
• Some prey defensive signals:• Aposomatic coloring - Warning colors.• Mullerian mimicry: Signal shared among
several species of noxious organisms.• Batesian mimicry: Edible species uses same
signal as a noxious species.• Crypticity: camouflage
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Camouflage and directional selection
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Directional selectionBiston betularia
Pre-pollution control
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Original habitatPost pollution control
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Directional selection
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Disruptive selectionBlack-bellied seedcracker (an African finch)Multiple-niche polymorphism
Bimodal distribution
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Black-bellied seedcracker
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Balancing selectionPolymorphismMaintained because intermediate expression of a continuous character is favored by NSor by hetorozygote advantage
Genetic variation at beta-hemoglobin locus
Polymorphic in response to malarial organism
Two selectors: malaria and sickle-cell anemia
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Uta stansburianaSide-blotched lizardPolymorphism: males
Color and behaviordetermined by levels ofprolactin and testosteronein early development.
Fixed for life.
1. Large territories,many females2. Small territories,one female.3. Non-territorial,sneak copulations from1.
Morph frequencies shiftbetween generations depending on success ofa particular tactic.
Polymorphic mating strategies
1.
2.
3.
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Batesian mimicry
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Müllerian mimicryMicrurus eryxanthus: Western coral snakeAposematic colorationProblem: how established?
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A mimetic system
Batesian and MüllerianMimicry
Aposematic coloration
Parallel geographic variation
Micrurus 6 species. Highly venomousFixed front fangsNeotropicalElapidae
Pliocercus 1 or 2 species.Mildly venomousFixed rear fangsColubridae
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Does aposematic coloration work?Plasticine models
Forest floor: on white paper and on forest floor
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Experiment carried outin natural habitat
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Resemblance does nothave to be perfect to confer protection
Significantdifferences
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• Is avoidance of aposematic coloration innate?• Naïve motmots (Neotropical birds)• Caged birds presented with:
– 1. coral snake models– 2. models of natural prey species.
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A famous Müllerian mimicrycomplex.
Each species withsubspecies defined bycolor pattern and geography.
What happens at subspecificboundaries?
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Phenotypic plasticity: environmentally induced variationoperating on common genetic background.
Geometrid mothNemoria arizonaria
Water CrowfootRanunculus aquatilis
Phenology: relationshipbetween climate andthe timing of ecologicalevents.