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Chapter 16 Evolution of Populations Section 16-3 The Process of Speciation 16-3 The Process of Speciation Speciation The Formation of New Species Species A Group of Organisms That Breed With One Another And Produce Fertile Offspring Individuals In The Same Species Share A Common Gene Pool

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chapter 16 evolution of populations

Chapter 16Evolution of Populations

Section 16-3The Process of Speciation

16 3 the process of speciation
16-3 The Process of Speciation
  • Speciation
    • The Formation of New Species
  • Species
    • A Group of Organisms That Breed With One Another And Produce Fertile Offspring
    • Individuals In The Same Species Share A Common Gene Pool
isolating mechanisms
Isolating Mechanisms

Key Concept:

As New Species Evolve, Populations Become More Reproductively Isolated From Each Other

isolating mechanisms4
Isolating Mechanisms

ReproductiveIsolation

  • When Members Of Two Populations Cannot Interbreed And Produce Fertile Offspring
    • The Populations Have Separate Gene Pools
reproductive isolation
Reproductive Isolation

Can Occur Through:

  • Behavioral Isolation
  • Geographic Isolation
  • Temporal Isolation
behavioral isolation
Behavioral Isolation

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

  • Behavior Differences e.g.
    • Different Courtship Rituals
    • Other Types of Behavior
      • Courtship Songs
      • Courtship Behavior
      • Sleep/Wake Cycles, etc.
behavioral isolation7
Behavioral Isolation

Populations May Share Overlapping Territories

Eastern Meadowlark

WesternMeadowlark

Each Species Has Separate Mating Song

geographic isolation
Geographic Isolation

Populations Are Separated By Geographic Barriers e.g.

Rivers

Mountains

Bodies of Water

Deserts

geographic isolation9
Geographic Isolation
  • Grand Canyon Squirrels
    • Colorado River Formation Of The Grand Canyon Separated Populations Of Abert Squirrels About 10,000 Years Ago.
    • Separate species – The Kaibab Squirrel Developed
slide10

Kaibab

Abert

temporal isolation
Temporal Isolation

Two Or More Species Reproduce At Separate Times

  • Three species of Orchids Each Release Pollen On Different Days
  • Frogs in same pond breed in different months
testing natural selection in nature
Testing Natural Selection In Nature
  • Galapagos Finches
    • Darwin’s Radiation Theory Proven By Peter & Rosemary Grant of Princeton University
    • Required
      • Variation
      • Beak Size Must Change Fitness
testing natural selection in nature13
Testing Natural Selection In Nature

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

  • Inheritable Variation Must Be Present In Current Population
  • Variations Must Produce Enough Differences In Fitness That Natural Selection Will Occur
variation
Variation

On A Single Island Grant’s Mapped:

Populations

Breeding Success

Wing, Leg, Beak Length

Beak Depth & Color

Feather Colors

Bird Mass

They Verified Genetic Variation

natural selection
Natural Selection

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

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

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

Most died of starvation!

rapid evolution
Rapid Evolution

They Were Able To Document Several Incidences of Rapid Evolution On Daphne Major Over Several Decades

speciation in darwin s finches
Speciation In Darwin’s Finches

Key Concept

Speciation In The Galapagos Finches Occurred By Founding Of A New Population, Geographic Isolation, Changes In The New Populations Gene Pool, Reproductive Isolation, And Ecological Competition