1. Macroevolution & Speciation
Biology Honors

2. Review: Adaptation
Any heritable characteristic that increases an organism’s ability to survive and reproduce in its environment
ORGANISMS CANNOT ADAPT TO THEIR ENVIRONMENT
They are born that way or die!

3. Review: Microevolution
Focuses on the change in genetic frequencies for a trait in the population over time.

4. Macroevolution
Accumulation of genetic changes over time leads to speciation
Formation of a new species

5. What is a species? A population or group of populations,
whose members have the potential to interbreed with one another in nature
to produce viable, fertile offspring,
but who cannot successfully interbreed with members of other species

6. Mechanisms for Macroevolution
Requires reproductive isolation
Pre-zygotic barriers
Barriers prior to reproduction
Post-zygotic barriers
Barriers after reproduction

7. Pre-Zygotic Barrier: Temporal Isolation
Populations breed during different times

8. Pre-Zygotic Barrier: Behavioral Isolation
Populations respond to different mating cues
Blue footed booby dance

9. Pre-Zygotic Barrier: Habitat Isolation
Populations are geographically separated

10. Pre-Zygotic Barrier: Mechanical Isolation
Reproductive parts are incompatible
Ex: Pollinators and plants

11. Pre-Zygotic Barrier: Gametic Isolation
Gametes of different species don’t recognize each other and join
Ex: Ocean organisms

12. Post-Zygotic Barriers
Hybrid Inviability
Zygote forms but doesn’t develop
Hybrid Sterility
Hybrid offspring is not fertile
Hybrid Breakdown
Hybrid may be fertile but subsequent generations are not

13. Types of Speciation Allopatric speciation
Formation of new species due to geographic isolation
Each group undergoes natural selection within its own area
animation

14. Types of Speciation Sympatric speciation
Formation of a new species within a population
Could be a result of behavioral or temporal isolation
Ex: hawthorn/apple trees & apple maggot fly
Flies normally lay eggs in hawthorn tree fruit
Apples trees introduced, some laid eggs there

15. Crash Course – Speciation

16. Convergent Evolution Parallel evolution:
Similar environments produce similar species

17. Convergent Evolution Analogous structures
Similar structures without evolutionary relationships
Ex: bats, birds, and butterflies all have wings

18. Evolutionary Pace Gradualism Punctuated equilibrium
Each new species evolves continuously over long spans of time
The large phenotypic difference we see is largely due to the accumulation of many small genetic changes  
Punctuated equilibrium
Species have a long period where they remain unchanged , punctuated by a short phase of rapid changes