WEEK 1: CHAPTER 13 HOW POPULATIONS EVOLVE

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• WEEK 1 CHAPTER 13 - HOW POPULATIONS EVOLVE
• CHARLES DARWIN AND HIS THEORY OF
  EVOLUTIONNATURAL SELECTION    SPECIES PRODUCE
  EXCESSIVE NUMBER OF OFFSPRING    LIMITED NUMBER
  OF RESOURCES    COMPETITION FOR RESOURCES   
  ONLY THE MOST FIT SURVIVESURVIVAL OF THE
  FITTESTDESCENT WITH MODIFICATIONS
•  

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• LAMARCKINHERITANCE OF ACQUIRED CHARACTERISTICS
• FOSSILSSTUDY OF FOSSILS USED TO EXPLAIN AND
  DOCUMENT EVOLUTION
• OTHER EVIDENCE FOR EVOLUTIONBIOGEOGRAPHYCOMPARAT
  IVE ANATOMYMOLECULAR BIOLOGYLOOK AT THIS SITE
  WWW.NCBI.NLM.NIH TO FIND DNA AND
  PROTEIN SEQUENCES FOR VARIOUS ORGANISMS

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• POPULATION GENETICSPOPULATIONSSPECIESGENE
  POOLDOMINANT AND RECESSIVE GENESHOMOZYGOUS AND
  RECESSIVEYOU MAY NEED TO REVIEW SOME TERMS YOU
  LEARNED IN BIOL1111LOOK AT THE SECTION ON
  MENDELIAN GENETICS
• OTHER TERMS  GENE FLOW, GENETIC DRIFT, THE
  FOUNDER EFFECTGENOTYPE FREQUENCYALLELE
  FREQUENCYHARDY-WEINBERGp q 1p2 2pq q2
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• CALCULATIONS - YOU WILL HAVE SOME HOMEWORK AND
  OR/QUIZ WHERE YOU WILL NEED TO FIGURE OUT SOME
  PROBLEMS RELATED TO THE GENOTYPE AND ALLELE
  FREQUENCY
• GENETIC VARIATION DUE TO MUTATIONSDUPLICATIONSIN
  VERSIONSDELETIONS
• GENETIC VARIATION DUE TO SEXUAL
  RECOMBINATIONDIPLOIDY AND BALANCING SELECTION
  PRESERVE VARIATION
• REPRODUCTIVE FITNESS
• NATURAL SELECTION ALTERS VARIATIONSTABILIZING
  SELECTIONDIRECTIONAL SELECTIONDISRUPTIVE
  SELECTION

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• HOW POPULATIONS EVOLVE
• CHARLES DARWIN DISCUSSED THE THEORIES OF
• NATURAL SELECTION AND SURVIVAL OF THE FITTEST
• SOME ANIMALS HAVE FEATURES THAT HELP THEM
• SURVIVE IN THEIR ENVIRONMENTS
• EVOLUTIONARY ADAPATATIONS
• EXAMPLE IN BOOK BIRD CALLED A BOOBY
• LARGE WEBBED FIT CAN WALK FAST
• BODY SHAPE
• LARGE TAIL
• SPECIALIZED GLANDS HELP ANIMALS STAY AFLOAT AND
  MANAGE SALT ITAKE
• ALL THESE FEATURES EVOLUTIONARY ADAPTATIONS
  THEY HELP THE ANIMAL SURVIVE AND REPRODUCE
• TODAY WE WILL DISCUSS THE PROCESS BY WHICH
  ANIMALS DEVELOP EVOLUTIONARY ADAPTATIONS

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• DARWIN LIVING SPECIES HAVE ARISEN FROM EARLIER
  LIFE FORMS
• SPECIES CHANGE OVER TIME
• PRIOR SCIENTISTS BELIEVED THAT SPECIES ARE FIXED,
  UNCHANGING AND PERMANENT
• LAMARCK DIFFERENT FROM DARWIN
• -AN INDIVIDUAL DEVELOPS CERTAIN TRAITS THAT IT
  PASSES ON TO ITS OFFSPRING
• - INHERITANCE OF ACQUIRED CHARACTERISTICS
• -ANCESTORS OF GIRAFFES HAD LENGTHENED THEIR
  NECKS BY STRETCHING HIGHER AND HIGHER INTO
  LEAVES TO REACH LEAVES
• -SPECIES EVLOLVE AS A RESULT OF INTERACTING WITH
  THEIR ENVIRONMENT

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• DARWIN WENT ON A ROUND-THE-WORLD SEA VOYAGE
• THE EARTH WAS CONSTANTLY CHANGING
• PUBLISHED A BOOK ENTITLED ON THE ORIGIN OF THE
  SPECIES BY MEANS OF NATURAL SELECTION
• DISCUSSES HIS THEORY OF NATURAL SELECTION AND HOW
  EVOLUTION OCCURS
• DESCENT WITH MODIFICATIONS
• -AN ANCESTRAL SPECIES COULD DIVERSIFY INTO MANY
  DESCENDANT SPECIES BY THE ACCUMULATION OF
  ADAPTATIONS TO VARIOUS ENVIRONMENTS

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• DARWIN - ALL SPECIES TEND TO PRODUCE EXCESS
  NUMBER OF OFFSPRING
• POPULATIONS GROW FASTER THAN THE SUPPLY OF FOOD
  AND OTHER RESOURCES CAN KEEP UP
• COMPETITION FOR RESOURCES
• ONLY SOME OFFSPRING SURVIVE IN EACH GENERATION
• INDIVIDUALS IN A POPULATION VARY IN MANY TRAITS
• THESE TRAITS ARE INHERITED PASSED FROM ONE
  GENERATION TO THE NEXT

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• EVERY ENVIRONMENT HAS A LIMITED SUPPLY OF
  RESOURCES
• SURVIVAL DEPENDS ON THE SPECIFIC TRAITS THAT WERE
  INHERITED FROM THEIR PARENTS
• INDIVIDUALS WHOSE CHARACTERISTICS ADAPT THEM BEST
  TO THEIR ENVIRONMENTS ARE MOST LIKELY TO SURVIVE
  AND REPRODUCE
• THESE INDIVIDUALS LEAVE MORE OFFSPRING
• NATURAL SELECTION CAN MODIFY SPECIFIES
  CONSIDERABLE OVER THOUSANDS OF GENERATIONS

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DIVERSITY OF DIFFERENT BREEDS OF DOGS A SINGLE
SPECIES
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• FOSSILS
• IMPRINTS OR REMAINS OF ORGANISMS THAT LIVED IN
  THE PAST
• SCIENTISTS OBSERVED SIMILARITIES BETWEEN FOSSILS
  AND LIVING ORGANISMS
• FOSSILS DOCUMENT THE CHANGES THAT
• LIFE HAS UNDERGONE OVER TIME
• LIFE EVOLVES
• PALEONTOLOGIST SCIENTISTS WHO STUDY FOSSILS

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• THE FOSSIL RECORD THE ORDERED ARRAY IN WHICH
  FOSSILS APPEAR WITHINS LAYERS OF SEDIMENTARY ROCK
  EVIDENCE OF EVOLUTION
• ROCK FORMS IN STRATA OR LAYERS
• YOUNGER STRATA ARE ON TOP OF OLDER ONES
• THE AGE OF THE FOSSILS CAN BE DETERMINED BY THE
  LAYERS

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• DIFFERENT ORGANISMS APPEARED AT DIFFERENT TIMES
• OLDEST FOSSILS FROM 3.5 BILLION YEARS AGO
• PROKARYOTES ANCESTORS OF ALL LIFE
• THEN, EUKARYOTES
• AMPHIBIANS
• REPTILES
• MAMMALS
• BIRDS
• WE FIND SIGNS IN THE FOSSIL RECORD OF LINKAGE
  BETWEEN ANCIENT EXTINCT ORGANISMS AND SPECIES
  LIVING TODAY

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EXAMPLES OF FOSSILSSKULL FROM ONE OF OUR EARLY
RELATIVES WHO LIVED 1.5 MILLION YEARS AGO

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• BOY STANDING IN
• A 150 MILLION YEAR AGO DINOSAUR TRACK

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• EVIDENCE THAT REINFORCES THE FOSSIL RECORD OF
  EVOLUTION
• BIOGEOGRAPHY GEOGRAPHIC DISTRIBUTION OF SPECIES
• SPECIES IN ONE AREA MAY RESEMBLE SPECIES IN A
  DIFFERENT GEOGRAPHICAL AREA EVOLUTION
• COMPARATIVE ANATOMY COMPARISON OF BODY
  STRUCTURES IN DIFFERENT SPECIES
• HOMOLOGY SIMILARITY IN CHARACTERISTICS THAT
  RESULT FROM COMMON ANCESTORY
• HOMOLOGOUS STRUCTURES FEATURES THAT OFTEN HAVE
  DIFFERENT FUNCTIONS BUT ARE STRUCTURALLY SIMILAR
  BECAUSE OF COMMON ANCESTORY
• EVOLUTION ANCESTRAL STRUCTURES THAT ORIGINALLY
  FUNCTIONED IN ONE CAPACITY BECAME MODIFIED AS
  THEY TAKE ON NEW FUNCTIONS

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EXAMPLES OF HOMOLOGOUS STRUCTURESVERTEBRATE
FORELIMBS
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• ANOTHER EXAMPLE OF HOMOLOGOUS STRUCTURES
• VESTIGIAL ORGANS DO NOT HAVE ANY IMPORTANT
  FUNCTION TODAY
• REMNANTS OF STRUCUTRES THAT SERVED IMPORTANT
  FUNCTIONS IN THE ORGANISMS ANCESTORS
• THE ORGANISM CAN LIVE WITHOUT IT TODAY
• WHAT ARE SOME IMPORTANT VESTIGIAL ORGANS IN
  HUMANS?

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• APPENDIX
• GALL BLADDER
• THESE STRUCTURES CAN BE REMOVED AND THE PERSON
  CAN LIVE A NORMAL LIFE

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• COMPARATIVE EMBRYOLOGY
• COMPARISON OF EARLIER STAGES OF DEVELOPMENT
• MOLECULAR BIOLOGY
• COMPARE DNA SEQUENCES BETWEEN DIFFERENT ORGANISMS
• HEREDITY COMES FROM THE DNA
• IF TWO SPECIES HAVE DNA WITH SEQUENCES THAT MATCH
  CLOSELY, BIOLOGISTS CONCLUDE THAT THESE SEQUENCES
  MUST HAVE BEEN INHERITED FROM A COMMON ANCESTOR
• THE GREATER THE SEQUENCE DIFFERENCE, THE LESS
  LIKELY THAT THERE IS A COMMON ANCESTOR

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• DNA ENCODES FOR PROTEINS
• WE CAN ALSO COMPARE SIMILARITIES IN PROTEIN
  SEQUENCES

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• WWW.NCBI.NLM.NIH.GOV
• LOOK AT NUCLEOTIDES FOR DNA SEQUENCES OF
  DIFFERENT ORGANISMS
• LOOK AT PROTEINS FOR THE PROTEIN STRUCTURES OF
  DIFFERENT ORGANISMS
• LOOK AT TAXONOMY TO FIND INFORMATION ON DIFFERENT
  ORGANISMS

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• EXAMPLES OF NATURAL SELECTION
• USE OF PESTICIDES SELECT FOR PESTICIDE
  RESISTANT INSECTS
• INITIALLY, A LARGE NUMBER OF INSECTS KILLED WITH
  PESTICIDES, A SMALL PERCENT OF INSECTS THAT ARE
  PESTICIDE RESISTANT SURVIVE
• IF YOU SPRAY AGAIN, THERE ARE NOW MORE PESTICIDE
  RESISTANT INSECTS, SO THAT THE NUMBER THAT WILL
  SURVIVE WILL BE GREATER

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EXAMPLE OF NATURAL SELECTION IN ACTION
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• NATURAL SELECTION IS A EDITING RATHER THAN A
  CREATIVE MECHANISM
• IT SELECTS FOR RESISTANT INSECTS IT DOES NOT
  CREATE THEM
• IT DEPENDS ON TIME AND PLACE THE ENVIRONMENT
• SIGNIFICANT EVOLUTIONARY CHANGE CAN OCCUR OVER A
  SHORT PERIOD OF TIME

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MICROEVOLUTION

• THE PROCESS WHEREBY CHANGES IN THE ALLELE
  FREQUENCIES ARE BROUGHT ABOUT BY GENETIC DRIFT,
  GENETIC FLOW, MUTATION AND NATURAL SELECTION

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• POPULATIONS ARE THE UNITS OF EVOLUTION
• POPULATION A GROUP OF INDIVIDUALS OF THE SAME
  SPECIES LIVING IN THE SAME PLACE AT THE SAME TIME
• SPECIES A GROUP OF ORGANISMS THAT CAN BREED
  WITH EACH OTHER AND PRODUCE FERTILE OFFSPRING
• IT IS POPULATIONS THAT EVOLVE
• POPULATIONS CHANGE OVER GENERATIONS
• POPULATION GENETICS STUDY HOW POPULATIONS
  CHANGE GENETICALLY OVER TIME DARWIN AND MENDEL

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• GENE POOL ALL OF THE GENES IN A POPULATION AT A
  GIVEN TIME
• THE GENE POOL REMAINS CONSTANT OVER THE
  GENERATIONS UNLESS ACTED UPON BY OUTSIDE AGENTS
  HARDY-WEINBERG PRINCIPLE
• DOMINANT GENE W
• RECESSIVE GENE w
• THESE ARE DIFFERENT EXAMPLES OF ALLELES
• THE DIFFERENT FORMS OF THE GENE
• GENOTYPES WW, Ww AND ww

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• ALSO REMEMBER
• HOMOZYGOUS DOMINANT WW
• HOMOZYGOUS RECESSIVE ww
• HETEROZYGOUS Ww

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• GENOTYPE FREQUENCY
• THE NUMBER OF ANIMALS WITH A PARTICULAR GENOTYPE
  (2 ALLELES)/THE TOTAL NUMBER OF ANIMALS
• ALLELE FREQUENCY
• THE NUMBER OF ANIMALS WITH ONE SPECIFIC
  ALLELE/TOTAL NUMBER OF ANIMALS

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HOW DO WE CALCULATE GENOTYPE AND ALLELE
FREQUENCIES?

• THE FREQUENCY OF W FREQUENCY OF W IN WW AND IN
  Ww ANIMALS
• THE FREQUENCY OF w FREQUENCY OF w IN Ww AND IN
  ww ANIMALS

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• p q 1
• p THE FREQUENCY OF THE DOMINANT ALLELE
• q THE FREQUENCY OF THE RECESSIVE ALLELE
• p2 2pq q2 1
• p2 THE FREQUENCY OF HOMOZYGOUS DOMINANT ANIMALS
  WW
• 2pq THE FREQUENCY OF HETEROZYGOUS ANIMALS
• q2 THE FREQUENCY OF HOMOZYGOUS RECESSIVE
  ANIMALS

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• FROM GENERATION TO GENERATION, THE GENE POOL
  REMAINS CONSTANT HARDY-WEINBERG EQUILIBRIUM
• THE POPULATION IS VERY LARGE
• THERE IS NO GENE FLOW NO MOVEMENT IN OR OUT OF
  THE POPULATION
• MUTATIONS DO NOT ALTER THE GENE POOL
• MATING IS RANDOM
• ALL INDIVIDUALS ARE EQUAL IN REPRODUCTIVE SUCCESS
• THESE CONDITIONS ARE NOT USUALLY MET

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• EVOLUTION IS CAUSED BY
• NATURAL SELECTION
• GENE FLOW THE MOVEMENT OF NEW ALLELES INTO A
  POPULATION DUE TO INDIVIDUALS ENTERING OR LEAVING
  A POPULATION
• GENETIC DRIFT
• CHANGE IN THE GENE POOL DUE TO CHANCE
• IF THE POULATION IS SMALL, THE GENE FREQUENCIES
  MAY NOT ADEQUATELY REPRESENT WHAT WILL BE SEEN IN
  THE NEXT GENERATION
• CAN CAUSE REDUCED GENETIC VARIATION

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• GENETIC DRIFT CAN OCCUR DUE TO THE BOTTLENECK
  EFFECT ANY EVENT THAT DRAMATICALLY REDUCES
  POULATION SIZE
• EARTHQUAKES, FLOODS, FIRE
• ONLY A SMALL NUMBER OF INDIVIDUALS MAY SURVIVE
• GENETIC DRIFT CAN OCCUR DUE TO THE FOUNDER EFFECT
• A SMALL NUMBER OF INDIVIDUALS MAY LEAVE THE
  POPULATION AND MOVE TO A NEW LOCATION
• THE GENE FREQUENCY WILL BE DIFFERENT FROM THE
  LARGER POPULATION

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• ARE THERE GROUPS OF PEOPLE IN THE WORLD WHERE
  ONLY SMALL NUMBERS OF PEOPLE BREED WITH EACH
  OTHER?

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CERTAIN ETHNIC GROUPS TEND TO MARRY AND BREED
WITHIN THEIR OWN GROUP THIS DECREASES THE
GENETIC VARIABILITY THERE ARE ONLY A SMALL
NUMBER OF GENES THERE MAY BE AN INCREASED
INCIDENCE OF CERTAIN DISEASES
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• MUTATION IS THE ULTIMATE SOURCE OF RAW MATERIAL
  FOR EVOLUTION
• CHANGES IN THE SEQUENCE OF DNA CAN CREATE NEW
  ALLELES
• ONLY MUTATIONS IN CELLS THAT PRODUCE GAMETES CAN
  BE PASSED TO OFFSPRING AND POTENTIALLY AFFECT A
  POPULATIONS GENE POOL
• THERE ARE DIFFERENT TYPES OF MUTATIONS
• DUPLICATIONS
• INVERSIONS
• DELETING DNA
• GENE SEQUENCE IS ALTERED

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DUPLICATION
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INVERSIONA LINEAR STRETCH OF DNA ISREVERSED
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• DELETIONS
• LOSS OF A PIECE OF DNA
• MOST ARE LETHAL OR CAUSE SERIOUS
• PROBLEMS

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SHUFFLING ALLELES BY SEXUAL RECOMBINATION ALSO
CREATES GENETIC VARIATION
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• DIPLOIDY AND BALALANCING SELECTION PRESERVE
  VARIATION
• MOST EUKARYOTES ARE DIPLOID THERE ARE TWO COPIES
  FOR EACH GENE ONE FROM THE FATHER AND ONE FROM
  THE MOTHER
• BEING DIPLOID HELPS PREVENT POPULATIONS FROM
  BECOMING GENETICALLY UNIFORM

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• BALANCING SELECTION OCCURS WHEN NATURAL SELECTION
  MAINTAINS STABLE FREQUENCIES OF TWO OR MORE
  PHENOTYPE FORMS IN A POPULATION
• MAY BE THE RESULT OF HETEROZYGOTE ADVANTAGE
• THOSE INDIVIDUALS WITH TWO ALLELES HAVE AN
  ADVANTAGE OVER THOSE WITH ONLY ONE ALLELE
• THE TWO ALLELES WILL THEN BE MAINTAINED
• EXAMPLE PROTECTION FROM MALARIA BY HAVING THE
  ALLELE FOR SICKLE CELL ANEMIA

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SOME GENETIC VARIATIONS HAVE NO IMPACT ON
REPRODUCTIVE SUCCESS

• EXAMPLE HUMAN FINGERPRINTS
• NEUTRAL VARIATION GENETIC VARIATION THAT
  PROVIDES NO APPARENT SELECTIVE ADVANTAGE

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• FITNESS CONTRIBUTION THAT AN INDIVIDUAL MAKES
  TO THE GENE POOL OF THE NEXT GENERATION RELATIVE
  TO THE CONTRIBUTIONS OF OTHER INDIVIDUALS
• THE FITTEST INDIVIDUALS ARE THOSE THAT PRODUCE
  THE LARGEST NUMBER OF VIABLE, FERTILE OFFSPRING
  AND PASS ON THE MOST GENES TO THE NEXT GENERATION

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• NATURAL SELECTION ALTERS VARIATION BY
• STABILIZING SELECTION FAVORS INTERMEDIATE
  VARIANTS
• DIRECTIONAL SELECTION ACTS AGAINST INDIVIDUALS
  AT ONE OF THE PHENOTYPIC EXTREMES
• DISRUPTIVE SELECTION FAVORS INDIVIDUALS AT BOTH
  EXTREMES OF A PHENOTYPIC RANGE

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NATURAL SELECTION CAN ALTER VARIATION IN A
POPULATION IN THREE WAYS