Download 16-2 The Process of Speciation

16-3 The Process of
Speciation
Interactive pgs. 404-410
What is speciation?
 It
is the formation of a new species
 A species is a group of organisms that can
breed with one another and produce fertile
offspring.
 Different species have different gene pools
(groups of alleles)
How to become reproductively isolated…
(cannot interbreed)

Behavior Isolation



Geographic Isolation



Capable of interbreeding but different courting rituals
Eastern and Western meadowlarks have different songs
Separation by geographic barriers : rivers or mountains
Natural selection works separately on each group
Temporal Isolation

Reproduction during different times of the year
Behavioral Isolation:
Different Mating Calls
Geographic Isolation:
Separated by a Boundary
Temporal Isolation: Reproduce during different times of the year
Peter and Rosemary Grant’s Research on
the Galapagos Finches
 Tested
2 Hypotheses
 There
must be inheritable variation in beak size
and shape
 The difference in beaks must produce
differences in fitness leading to nat. selection
 Studied
the medium ground finch on
Daphne Major (one of the islands)
 They
caught and measured almost every
medium ground finch on the island
What they found…
 Variation
 Many
different characteristics showed bell
shaped distribution of polygenic traits
 Natural
Selection
 Beak
shape determined survival during a
drought.
 Largest beaks most likely to survive
 Rapid
 As
Evolution
food supply changed so did the fluctuation of
beak size over a period of a few decades
Speciation in Darwin’s Finches

1. Founders Arrive


2. Separation of Populations


A few birds (B) cross back to island 1 and cannot mate with original
population
5. Ecological Competition



Population on the new island evolves due to different environmental
conditions (species B)
4. Reproductive Isolation


Some birds cross to another island & become isolated
3. Changes in the Gene Pool


From South America and populate an island (species A)
Species A and B compete for food and resources.
Species C may evolve
6. Continued Evolution

Process continues leading to the formation of 13 different species
of finches
Founders Arrive
Separation of Populations
Changes in the Gene Pool