1. the formation of new species
SPECIATION
the formation of new species

2. Speciation follows the results of DIVERGENT (branching) EVOLUTION

3. Phylogenetic Tree for all living things
Time >present
Nodes indicate most recent common ancestor of two branches

4. What is a SPECIES?
Biological Species Concept: A group of naturally or potentially interbreeding organisms that can produce fertile offspring.

5. How Do New Species Form?
Take 2 minutes to think about how it might happen…

6. Steps of Speciation: Reproductive isolation of two populations
Allopatric speciation – due to a geographic barrier that prevents gene flow
Squirrels and the Grand Canyon
Birds and the Rocky Mountains
Galapagos Finches separated from the mainland
Sympatric speciation – two populations in same place, but behavior or niche prevents interbreeding
Cichlid Fish
Polyploidy in plants

7. Genetic barriers to reproduction arise.
2) Genetic divergence
The gene pools become more and more different due to selection and/or drift.
Genetic barriers to reproduction arise.
The two populations are no longer able to interbreed, due to genetic differences in habitat preference, mating behavior, or physical compatibility.
Now there are two separate species!

8. What can make a population reproductively isolated?
Pre-zygotic isolating mechanisms (before the zygote is formed)
Geographic isolation
Habitat isolation
Behavioral isolation
Temporal isolation
Mechanical isolation
Chemical isolation

9. Post-zygotic isolating mechanisms
Hybrid inviability (zygote or offspring dies)
Hybrid inferiority (hybrid is weak and sickly)
Hybrid sterility (offspring can’t reproduce)

10. Ring Species

11. Ligers and tigons and geeps (oh my!)

12. Speciation results in PATTERNS in EVOLUTION:
Adaptive radiation
Stasis
Gradualism
Punctuated equilibrium

13. How can we describe the RATE OF EVOLUTIONARY CHANGE?
Two opposing theories:
Gradualism – slow and steady change.
Punctuated equilibrium – change is relatively rapid, interspersed with periods of stasis

14. Gradualism vs. Punctuated equilibrium

16. Punctuated equilibrium happens when…
The environment changes quickly
A barrier arises quickly
One mutation enables a large shift in the population
Evidence: fossils, experiments

17. A long period of little or no
Evolutionary STASIS
A long period of little or no
evolutionary change

18. The development of many species from a common ancestor
ADAPTIVE RADIATION
The development of many species from a common ancestor

19. Adaptive radiation may result from: 1
Adaptive radiation may result from: 1. New Environments with diverse habitats

20. …especially on islands Fruit fly evolution in Hawaii

21. Galapagos finches

22. 2. New traits that then diversify
Example: Flowering plants – once flowers emerged as a strategy, it worked so well in so many different niches that flowering plants diversified greatly.

23. 3. New Communities of Organisms
Example 1: One new organism allows other to diversify – e.g. flowering plants and insects
Example 2: Extinction of one group allows diversification of another – e.g. dinosaurs and mammals

24. Phylogenetic Tree for all living things
Time >present
Nodes indicate most recent common ancestor of two branches