Foothill High School Science Department Evolution of Populations The Process of Speciation

Foothill High School Science DepartmentFoothill High School Science Department

Evolution of PopulationsEvolution of Populations

The Process of SpeciationThe Process of Speciation


The Process of SpeciationThe Process of Speciation

• SpeciationSpeciation– The Formation of New SpeciesThe Formation of New Species

• SpeciesSpecies– A Group of Organisms That Breed With A Group of Organisms That Breed With

One Another And Produce Fertile OffspringOne Another And Produce Fertile Offspring– Individuals In The Same Species Share A Individuals In The Same Species Share A

Common Gene PoolCommon Gene Pool


Isolating MechanismsIsolating Mechanisms

Key ConceptKey Concept:–As New Species Evolve,As New Species Evolve,• Populations Become More Populations Become More

Reproductively Isolated From Reproductively Isolated From Each OtherEach Other


Isolating MechanismsIsolating Mechanisms

ReproductiveReproductive IsolationIsolation–When Members Of Two Populations When Members Of Two Populations

Cannot Interbreed And Produce Cannot Interbreed And Produce Fertile OffspringFertile Offspring• The Populations Have Separate Gene The Populations Have Separate Gene

PoolsPools


Reproductive IsolationReproductive Isolation

Can Occur ThroughCan Occur Through:1.1. Behavioral IsolationBehavioral Isolation2.2. Geographic IsolationGeographic Isolation3.3. Temporal IsolationTemporal Isolation


Behavioral IsolationBehavioral Isolation

Two or More Populations Are Capable of Two or More Populations Are Capable of Interbreeding But Don’t Due To:Interbreeding But Don’t Due To:

• Behavior Differences e.g.Behavior Differences e.g.–Different Courtship RitualsDifferent Courtship Rituals–Other Types of BehaviorOther Types of Behavior• Courtship SongsCourtship Songs• Courtship BehaviorCourtship Behavior• Sleep/Wake Cycles, etc.Sleep/Wake Cycles, etc.


Easte

rn

Mead

ow

lark

Each Species Has Each Species Has Separate Mating SongSeparate Mating Song

West

ern

M

eadow

lark

Behavioral IsolationBehavioral IsolationPopulations May Share Populations May Share Overlapping TerritoriesOverlapping Territories


Geographic IsolationGeographic Isolation

Populations Are Separated By Populations Are Separated By Geographic Barriers e.g.Geographic Barriers e.g.

RiversRiversMountainsMountains

Bodies of WaterBodies of WaterDesertsDeserts


Geographic IsolationGeographic Isolation

• Grand Canyon SquirrelsGrand Canyon Squirrels– Colorado River Formation Of Colorado River Formation Of

The Grand Canyon Separated The Grand Canyon Separated Populations Of Abert Squirrels Populations Of Abert Squirrels About 10,000 Years Ago.About 10,000 Years Ago.

– Separate species – The Kaibab Separate species – The Kaibab Squirrel DevelopedSquirrel Developed


Kaibab

Abert


Temporal IsolationTemporal Isolation

Two Or More Species Reproduce At Two Or More Species Reproduce At Separate TimesSeparate Times

–Three species of Orchids Each Release Three species of Orchids Each Release Pollen On Different DaysPollen On Different Days–Frogs in same pond breed in different Frogs in same pond breed in different

monthsmonths


Testing Natural Selection In NatureTesting Natural Selection In Nature

• Galapagos FinchesGalapagos Finches– Darwin’s Radiation Theory Darwin’s Radiation Theory

Proven By Peter & Proven By Peter & Rosemary Grant of Rosemary Grant of Princeton UniversityPrinceton University

– RequiredRequired• VariationVariation• Beak Size Must Change Beak Size Must Change

FitnessFitness


Testing Natural Selection In NatureTesting Natural Selection In Nature

Grants Realized Darwin’s Hypothesis Grants Realized Darwin’s Hypothesis Relied On Two Testable Relied On Two Testable

Assumptions:Assumptions:1.1. Inheritable Variation Must Be Present Inheritable Variation Must Be Present

In Current PopulationIn Current Population2.2. Variations Must Produce Enough Variations Must Produce Enough

Differences In Fitness That Natural Differences In Fitness That Natural Selection Will OccurSelection Will Occur


VariationVariation

On A Single Island The Grant’s Mapped:On A Single Island The Grant’s Mapped:PopulationsPopulations

Breeding SuccessBreeding SuccessWing, Leg, Beak LengthWing, Leg, Beak Length

Beak Depth & ColorBeak Depth & ColorFeather ColorsFeather Colors

Bird MassBird MassThey Verified Genetic VariationThey Verified Genetic Variation


Natural SelectionNatural Selection

The Grant's studied finches on Daphne Major,The Grant's studied finches on Daphne Major,a small island (800 sq. yd)a small island (800 sq. yd)

In 1977 island had only 2mm of rainIn 1977 island had only 2mm of raininstead of normal 130mm... instead of normal 130mm...

The drought resulted in a loss ofThe drought resulted in a loss of84% of medium ground finch population.84% of medium ground finch population.

Most died of starvation!Most died of starvation!



Rapid EvolutionRapid Evolution

They Were Able To DocumentThey Were Able To DocumentSeveral Incidences of Rapid Several Incidences of Rapid Evolution On Daphne MajorEvolution On Daphne Major

Over Several DecadesOver Several Decades


Speciation In Darwin’s FinchesSpeciation In Darwin’s Finches

Key ConceptKey ConceptSpeciation In The Galapagos Finches Speciation In The Galapagos Finches

Occurred By Founding Of A New Occurred By Founding Of A New Population, Geographic Isolation, Changes Population, Geographic Isolation, Changes In The New Populations Gene Pool, In The New Populations Gene Pool, Reproductive Isolation, And Ecological Reproductive Isolation, And Ecological CompetitionCompetition









A & B Don’t Mate





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Foothill High School Science Department Evolution of Populations The Process of Speciation