1. Speciation

2. Factors such as natural selection and genetic drift (chance events) can change the relative frequencies of alleles in a population.
Speciation: the formation of a new species

3. The "Steps" in a speciation event:
Step 1:  gene flow between two populations is interrupted
(populations become genetically isolated from each other)

4. The "Steps" in a speciation event:
Step 2:  genetic differences gradually accumulate between the two populations
(populations diverge genetically)

5. The "Steps" in a speciation event:
Step 3:  reproductive isolation evolves as a consequence of this divergence
(a reproductive isolating mechanism evolves)

6. The "Steps" in a speciation event:
Step 1:  gene flow between two populations is interrupted
(populations become genetically isolated from each other)
Step 2:  genetic differences gradually accumulate between the two populations
(populations diverge genetically)
Step 3:  reproductive isolation evolves as a consequence of this divergence
(a reproductive isolating mechanism evolves)

7. Reproductive isolation: When the members of two populations cannot interbreed and produce fertile offspring
Includes: behavioral, geographic, and temporal

8. Behavioral isolation: occurs when two populations are capable of interbreeding but have differences in courtship rituals or other reproductive strategies that involve behavior.
Ex. Easter vs. Western meadowlarks, use different songs to attract mates

9. Temporal Isolation: in which two ore more species reproduce at different times.
Ex. Three similar flower, release pollen at different times of the day.

10. Geographic isolation: two populations are separated by geographic barriers such as rivers, mountains, or bodies of water.
Ex separation of river