Bio - Ch.22: The Origin of Species

Microevolution

1. Changes within a single gene pool

Macroevolution

1. Evolutionary change above the species lvl

2. Cumulative effects of speciation over long periods of time

Species

1. Population or group of populations whose members have the potential to interbreed in nature and produce viable, fertile offspring

2. Reproductively compatible

1. Reproductive isolation

1. Barrier that prevent members of species from produce viable, fertile hybrids

1. Prezygotic barriers

1. Impede mating/fertilization

2. Types:

   1. Habitat isolation

   2. Temporal isolation

   3. Behavioral isolation

   4. Mechanical isolation

   5. Gametic isolation

1. Postzygotic barriers

1. Prevent hybrid zygote from developing into viable adult

2. Types

   1. Reduced hybrid viability

   2. Reduced hybrid fertility

   3. Hybrid breakdown

1. Allopatric speciation

1. Geographically isolated populations

   1. Caused by geologic events/processes

   2. Evolves by natural selection and genetic drift

2. Ex squirrels on N/S rims of Grand Canyon

1. Sympatric speciation

1. Overlapping populations within home range

2. Gene flow between subpopulations blocked by

   1. Polyploidy

   2. Sexual selection

   3. Habitat differentiation

3. Ex polyploidy in crops (oats, cotton, potatoes, wheat)

Autopolyploid

1. Extra sets of chromosomes

2. Failure of cell division (2n->4n)

3. Ex. strawberries are 4n,6n,8n, 10n (decaploid)

Allopolyploid

1. 2 species produce a hybrid

2. Species A (2n=6) + Species B (2n=4) -> Hybrid (2n=10)

1. Hybrid zones

1. Incomplete reproductive barriers

2. Possible outcomes

   1. Reinforcement: decrease in gene flow

   2. Fusion: increase gene flow 

   3. Stability: same

Gradualism

1. Common ancestor

2. Slow, constant change

1. Punctuated equilibrium

1. Eldridge and gould

2. Long period of stasis punctuated by short bursts of significant change