Evolution of Populations

1
Evolution of Populations

• The Process of Speciation

2
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

3
Isolating Mechanisms

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

4
Isolating Mechanisms

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

5
Reproductive Isolation

• Can Occur Through
• Behavioral Isolation
• Geographic Isolation
• Temporal Isolation

6
Behavioral Isolation

• Two or More Populations Are Capable of
  Interbreeding But Dont Due To
• Behavior Differences e.g.
• Different Courtship Rituals
• Other Types of Behavior
• Courtship Songs
• Courtship Behavior
• Sleep/Wake Cycles, etc.

7
Behavioral Isolation
Populations May Share Overlapping Territories
Eastern Meadowlark
Western Meadowlark
Each Species Has Separate Mating Song
8
Geographic Isolation

• Populations Are Separated By Geographic Barriers
  e.g.
• Rivers
• Mountains
• Bodies of Water
• Deserts

9
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

10
Kaibab
Abert
11
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

12
Testing Natural Selection In Nature

• Galapagos Finches
• Darwins Radiation Theory Proven By Peter
  Rosemary Grant of Princeton University
• Required
• Variation
• Beak Size Must Change Fitness

13
Testing Natural Selection In Nature

• Grants Realized Darwins 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

14
Variation

• On A Single Island The Grants Mapped
• Populations
• Breeding Success
• Wing, Leg, Beak Length
• Beak Depth Color
• Feather Colors
• Bird Mass
• They Verified Genetic Variation

15
Natural Selection

• The Grant's studied finches on Daphne Major,a
  small island (800 sq. yd)
• In 1977 island had only 2mm of raininstead of
  normal 130mm...
• The drought resulted in a loss of84 of medium
  ground finch population.
• Most died of starvation!

16
(No Transcript)
17
Rapid Evolution

• They Were Able To DocumentSeveral Incidences of
  Rapid Evolution On Daphne MajorOver Several
  Decades

18
Speciation In Darwins 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

19
Speciation In Darwins Finches
20
Speciation In Darwins Finches
21
Speciation In Darwins Finches
22
Speciation In Darwins Finches
A B Dont Mate
23
Speciation In Darwins Finches
24
Speciation In Darwins Finches