evolution by means of natural selection. evolution by natural selection: 5 keys 1.variation...
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Evolution by means of Evolution by means of Natural SelectionNatural Selection
Evolution by Natural Selection:Evolution by Natural Selection:5 KEYS5 KEYS
1.1. VARIATIONVARIATION• Variation is inherent in populations of Variation is inherent in populations of
organisms (members of a population are not organisms (members of a population are not all the same).all the same).
• This Variation is This Variation is HeritableHeritable – able to be – able to be passed from generation to generation.passed from generation to generation.
Elaphe obsoletaElaphe obsoleta
2.2. More offspring are born than surviveMore offspring are born than survive..• Differential reproduction and survival.Differential reproduction and survival.• ““Survive” = Live long enough to reproduce.Survive” = Live long enough to reproduce.
Evolution by Natural Selection:Evolution by Natural Selection:5 KEYS5 KEYS
3.3. Differences occur between surviving Differences occur between surviving offspring and those not survivingoffspring and those not surviving..
• Advantageous VarationsAdvantageous Varations = Certain = Certain characteristics found in surviving offspring that characteristics found in surviving offspring that afford them a survival advantage.afford them a survival advantage.
• Sometimes called “Sometimes called “AdaptationsAdaptations” (but this implies ” (but this implies a goal, and Natural selection is NOT goal-a goal, and Natural selection is NOT goal-oriented).oriented).
Evolution by Natural Selection:Evolution by Natural Selection:5 KEYS5 KEYS
4.4. More individuals with advantageous More individuals with advantageous adaptations occur in succeeding adaptations occur in succeeding generations of organismsgenerations of organisms..
• Their variations are beneficial, therefore they Their variations are beneficial, therefore they survive & reproduce.survive & reproduce.
• Individuals without beneficial variation do not Individuals without beneficial variation do not survive to reproductive age.survive to reproductive age.
• IndividualsIndividuals
Evolution by Natural Selection:Evolution by Natural Selection:5 KEYS5 KEYS
5.5. Results in a population that is well-Results in a population that is well-adapted to its environmentadapted to its environment..
• PopulationPopulation as a whole is becomes fitted to as a whole is becomes fitted to its particular environment.its particular environment.
Evolution by Natural Selection:Evolution by Natural Selection:5 KEYS5 KEYS
NATURAL SELECTIONNATURAL SELECTION
• This takes a long timeThis takes a long time – many generations. – many generations.– Earth is old (We now know the Earth is roughly Earth is old (We now know the Earth is roughly
4.5 Billion Years Old!).4.5 Billion Years Old!).
NATURAL SELECTIONNATURAL SELECTION
• Variation is essentialVariation is essential– Previously viewed as imperfection…Previously viewed as imperfection…– Now viewed as the Now viewed as the raw materialraw material on which on which
evolution occurs.evolution occurs.– We now know that GENES (Alleles) are We now know that GENES (Alleles) are
responsible for variation:responsible for variation:• Crossing Over (Meiosis)Crossing Over (Meiosis)• Independent Assortment (Meiosis)Independent Assortment (Meiosis)• OogenesisOogenesis• FertilizationFertilization• MutationMutation
NATURAL SELECTIONNATURAL SELECTION• ““Struggle for ExistenceStruggle for Existence””
– Limited Resources are available for a Limited Resources are available for a population, leading to population, leading to CompetitionCompetition..• Some survive, some don’tSome survive, some don’t• Sometimes this is randomSometimes this is random
– The “Struggle” is for the resources, not as The “Struggle” is for the resources, not as much direct competition between individuals. much direct competition between individuals.
• ““Survival of the FittestSurvival of the Fittest””– The most The most FITFIT organisms survive & reproduce. organisms survive & reproduce.– FitnessFitness = how well an organism = how well an organism fitsfits into its into its
environmentenvironment• Securing resourcesSecuring resources• Avoiding predatorsAvoiding predators• Finding foodFinding food
– What determines What determines FitnessFitness??• Varies with organism, but ultimately….Varies with organism, but ultimately….ENVIRONMENTENVIRONMENT• This is always This is always changingchanging – what is most fit one month, – what is most fit one month,
may not be the next.may not be the next.
NATURAL SELECTIONNATURAL SELECTION
• EnvironmentEnvironment is important! is important!– In In Artificial SelectionArtificial Selection, humans select for , humans select for
survival & reproduction.survival & reproduction.– In In Natural SelectionNatural Selection, “nature” selects for , “nature” selects for
survival & reproduction.survival & reproduction.• HabitatHabitat• ClimateClimate• Food & Shelter AvailabilityFood & Shelter Availability• Etc.Etc.
NATURAL SELECTIONNATURAL SELECTION
• Not goal-orientedNot goal-oriented, no particular goal., no particular goal.– Environmental conditions are always Environmental conditions are always
changing.changing.– Organisms’ needs are always changing.Organisms’ needs are always changing.– Genotype is heritable, not phenotype. Genotype is heritable, not phenotype.
NATURAL SELECTIONNATURAL SELECTION
• Populations Evolve, NOT individualsPopulations Evolve, NOT individuals..– PopulationsPopulations: Groups of individuals belonging : Groups of individuals belonging
to the same species and occupying the same to the same species and occupying the same given area, and being similar in form, given area, and being similar in form, behavior, and physiology.behavior, and physiology.
– Inheritance of acquired characteristics by Inheritance of acquired characteristics by IndividualsIndividuals (Lamarck) does NOT occur. (Lamarck) does NOT occur.
NATURAL SELECTIONNATURAL SELECTION
• ““AdaptationAdaptation””– Traits are sometimes referred to as either Traits are sometimes referred to as either
“Adaptive” or not.“Adaptive” or not.– ““Adaptive” traits are those that accumulate in Adaptive” traits are those that accumulate in
each succeeding generation (due to each succeeding generation (due to differential reproduction).differential reproduction).
– This is somewhat arguable …why?This is somewhat arguable …why?
NATURAL SELECTIONNATURAL SELECTION
EVIDENCE for Common DescentEVIDENCE for Common Descent
Bacterial CapsulesBacterial Capsules
1. 1. Direct observationDirect observation..
Evidence for EvolutionEvidence for Evolution(Common Descent)(Common Descent)
2.2. Fossil RecordFossil Record– History of life recorded in fossils.History of life recorded in fossils.
• Bones, plants, shells, insects, etc.Bones, plants, shells, insects, etc.
– Many fossils offer evidence for Many fossils offer evidence for transitionstransitions..
– Special Creation predicts no historical pattern of Special Creation predicts no historical pattern of change -- the same organisms today as before.change -- the same organisms today as before.
(Transition of the Ancient Reptilian Pelvis to Early Modern Birds)(Sequential evolution of the lower foreleg of horses)
3.3. BiogeographyBiogeography– Different organisms with similar adaptations found in Different organisms with similar adaptations found in
similar environments, but in very distant locations.similar environments, but in very distant locations.– Adaptive RadiationAdaptive Radiation
• Slight adaptations to slightly different environments in the Slight adaptations to slightly different environments in the same basic geographic area.same basic geographic area.
– Special Creation predicts perfectly-adapted organisms Special Creation predicts perfectly-adapted organisms occupying suitable habitats, despite geography.occupying suitable habitats, despite geography.
Evidence for EvolutionEvidence for Evolution(Common Descent)(Common Descent)
EmuEmu
RheaRhea
OstrichOstrich
4.4. Comparative AnatomyComparative Anatomy– Similarities in organisms’ internal structures, Similarities in organisms’ internal structures,
despite their functions.despite their functions.– Homologous StructuresHomologous Structures– Vestigial StructuresVestigial Structures
– Special Creation predicts no similarity in structure if Special Creation predicts no similarity in structure if used for different functions & no such thing as a used for different functions & no such thing as a structure with no function.structure with no function.
Evidence for EvolutionEvidence for Evolution(Common Descent)(Common Descent)
5.5. Comparative EmbryologyComparative Embryology– Similarity of different organisms during early Similarity of different organisms during early
(neo-natal, pre-birth) development.(neo-natal, pre-birth) development.
Evidence for EvolutionEvidence for Evolution(Common Descent)(Common Descent)
6.6. Comparative BiochemistryComparative Biochemistry– Similarities and differences in chemicals:Similarities and differences in chemicals:
• Nucleotide Sequences (DNA, RNA)Nucleotide Sequences (DNA, RNA)
• Amino Acid Sequences (Proteins) Amino Acid Sequences (Proteins)
Evidence for EvolutionEvidence for Evolution(Common Descent)(Common Descent)
The Theory of EvolutionThe Theory of Evolution
• Populations of Populations of organisms have the organisms have the capacity to change over capacity to change over time, generally in time, generally in response to changes in response to changes in their supporting their supporting environment. environment.