1. 15.1: New Species Evolve Vocabulary Objectives:
Biological Species concept
Macroevolution
Speciation
Reproductive Isolation
Geographic Isolation
Adaptive Radiation
Punctuated Equilibrium
Objectives:
Describe the biological species concept.
Distinguish b/w micro and macroevolution.
List types of reproductive barriers b/w species.
Explain how geographic isolation and adaptive radiation contribute to species diversity.
Summarize models for the tempo of speciation.

2. When do new species evolve?

3. Evolution of Human Species

6. Hominids
Humans
Neanderthal

7. Most Recent Common Ancestor
Homo heidelbergenesis, ka (thousands)
Homosapiens and Neanderthal evolve from

8. Homo erectus m.y.a
Homo Habilis m.y.a
Australopithicus, 3.2 m.y.a
“Lucy”

9. SPECIATION = formation of new species.
Species = a group of organisms that breed with one another and produce fertile offspring.
The gene pools of two populations must become separated.
When the members of two populations cannot interbreed and produce fertile offspring, reproductive isolation has occurred and speciation will result.

11. Micro vs. Macroevolution
Change allele frequencies W/IN A POPULATION.
Small changes fr. generation to generation
Result: What species look like can change over time.
*Does NOT change branches on EVOLUTIONARY TREE
Large scale changes in biological record (fossils)
Origin of new species
Extinction of species
Evolution of new features (backbones, wings, etc)
Result: Increase in # of species
*Changes branches on EVOLUTIONARY Tree

12. Speciation: Reproductive Barriers
Species separate when they cannot interbreed.
Reproductive Isolation: Condition that keeps 2 species from interbreeding
1. Timing Issues: 2 species have diff. Breeding seasons
2. Behavior: Different courtship or mating behaviors
3. Habitat: Surface water v. deep water
4. Not anatomically compatable

13. Speciation: Geographic Barriers
Species separate when they cannot interbreed.
Geographic Isolation: Separation of populations by barriers like mountains
Over time isolated populations change through microevolution (natural selection acting on variations to produce adaptations)

14. Divergent v. Convergent Evolution
One species gives rise to many species
Also known as adaptive radiation
Many species with common ancestor
Many homologous structures
Convergent
Similar looking species that do not have a common ancestor
Similar behavior and appearance due to environmental similarities
Many analogous structures

15. Divergent Evolution (Adaptive)

16. Convergent Evolution (Adaptive)

17. Coevolution: The evolution of one species is directly influenced by the evolution of another

18. Gradualism v. Punctuated Equilibrium
Rate of Speciation
Two Models
Gradualism v. Punctuated Equilibrium

19. Punctuated Equilibrium
Slow background evolution (stasis) is interrupted by rapid bursts of change
Rapid/Abrupt bursts of change usually occur after a mass extinction
Abrupt : w/in a few thousand years
Seen in fossil record after mass extinctions.

20. Speciation in Darwin's Finches20

21. Speciation of Darwin’s Finches
founding of a new population
geographic isolation
changes in new population's gene pool
reproductive isolation
ecological competition

22. STEP 1: Founders Arrive
A few finches, “species A”, travel from S. America to one of the Galápagos Islands.
There, they survive and reproduce.
Speciation in the Galápagos finches occurred by founding of new populations, geographic isolation, gene pool changes, reproductive isolation, and ecological competition. Small groups of finches moved from one island to another, became reproductively isolated, and evolved into new species. 22

23. STEP 2: Geographic Isolation
Some birds from species A cross to a second island.
The two populations no longer share a gene pool.
Speciation in the Galápagos finches occurred by founding of new populations, geographic isolation, gene pool changes, reproductive isolation, and ecological competition. Small groups of finches moved from one island to another, became reproductively isolated, and evolved into new species. 23

24. STEP 3: Changes in the Gene Pool
Seed sizes on the second island favor birds with large beaks.
The population on the second island evolves into population “B”, with larger beaks.
Speciation in the Galápagos finches occurred by founding of new populations, geographic isolation, gene pool changes, reproductive isolation, and ecological competition. Small groups of finches moved from one island to another, became reproductively isolated, and evolved into new species. 24

25. STEP 4: Reproductive Isolation
If population B birds cross back to the first island, they will not mate with birds from population A.
Populations A and B are separate species. 25

26. STEP 5: Ecological Competition
As species A and B compete for available seeds on the first island, they continue to evolve in a way that increases the differences between them.
A new species—C—may evolve. 26