1. Speciation Notes pg __

2. Speciation Speciation = formation of new species
Species = group of organisms that breed with one another and produce fertile offspring in nature (share a common gene pool)

3. Speciation can happen in two modes
Modes of speciation:
Sympatric: new species develop in same geographic region
Sym= same
Allopatric: new species develop in separate regions
allo= other

4. Isolation isn’t always bad…
As new species evolve, populations become reproductively isolated from each other: When 2 populations cant breed and produce fertile offspring, resulting in separate gene pools
Behavioral isolation: Capable of breeding, but have different courtship rituals or behaviors
Geographic isolation: Separate by geographic barriers
Temporal isolation: Reproduce at different times

5. Geographic Isolation (allopatric)
Two populations are separated by geographic barriers. Over time different pressures result in distinct species
Rivers, mountains, bodies of water, glaciers, deserts

7. Behavioral Isolation
Differences in the behavior of two populations prevent mating
Because there is no gene exchange between populations, evolution occurs
Behaviors:
Mating rituals
Mate preference
Mate calling

8. Temporal Isolation (sympatric)
Two or more populations are separated by the time of year/day that reproduction occurs
Nocturnal vs Diurnal mating
Seasonal mating differences

10. Speciation can happen at two different rates
Gradualism: Evolution occurs slowly, gradually and continuously
Punctuated Equilibrium: Species remain unchanged for long periods of time. During certain events, species undergo rapid evolution.
Both of the processes above have likely happened

11. Speciation of Darwin’s Finches
Speciation in the Galapagos finches occurred by:
Founding a new population: A small population of finches migrates to a different island
Geographic isolation: Finches don’t usually fly over open water, so stayed on own island (separate gene pool)
Changes in the new population’s gene pool: Adapted to new environment (directional selection) to be more fit
Reproductive isolation: Differences in phenotypes and mating rituals may turn different finches off to one another
Ecological competition: Similar finches compete, so individuals that are most different from each other have the highest fitness, because less competition.
Continued Evolution: Process repeats and over many generations, it produced the 13 different finch species