1. AP Biology Crosby High School
The Origin of Species
AP Biology
Crosby High School

2. Reproductive Isolation
Prezygotic Barriers:
Habitat Isolation: Parasites in different hosts
Behavioral Isolation: Generally courtship rituals
Temporal Isolation: Different time, day, season, or year
Mechanical Isolation: Square peg, round hole
Gametic Isolation: Gamete recognition doesn’t match

3. Reproductive Isolation (cont.)
Postzygotic Barriers:
Reduced Hybrid Viability: Embryo may abort due to genetic incompatibility
Reduced Hybrid Fertility: Hybrid can not backbreed due to sterility
Hybrid Breakdown: May produce one generation of viable and fertile offspring, but future generations are not

4. Classifying a Species
Biological Species: emphasizes reproductive isolation
Ecological Species: Species defined by ecological niche
Pluralistic Species: Reproductive or niche
Morphological Species: Unique set of structural features
Geneological Species: Unique genetic history

5. Allopatric Speciation
Conditions
Separated by a geographical feature
Changes must prevent interbreeding
Ring Species
California Salamanders more distant to the south
Adaptive Radiation
Diversely adapted species from common ancestor

6. Evolution of Reproductive Barriers
Prezygotic:
Two populations of D. melanogaster
Starch vs. Maltose for generations
Maltose females only breed with maltose males

7. Sympatric Speciation Polyploid Speciation in Plants
2n  4n
4n can self pollinate or mate with other 4n
Oats, cotton, potatoes, tabacco, wheat
Sympatric Speciation in Animals
Pundamilia pundamilia vs. Pundamilia nyererei
Normal light vs. monochromatic orange

8. Evolutionary Time
“Although each species must have passed through numerous transitional stages, it is probable that the periods during which each underwent modification, though many and long as measured by years, have been short in comparison with the periods during which each remained in an unchanged condition.”
-Charles Darwin

9. Punctuated Equilibrium
Evolution occurs so rapidly that there is no fossil record

10. Eye Development Pigmented Cells Eyecup Pinhole camera-type
Eye w/ Primitive lens
Complex Camera-type

11. Exaptations Develop for one purpose, but later end up serving another
Birds
Honeycombed bones
Original: light for agility
Present: light for flight
Feathers
Original: Display for mating
Present: flight

12. Evo - Devo
Allometric Growth: Growth rates create proportioning for each species
Heterochrony: Evolutionary change in rate or timing of developmental events
Paedomorphosis: Rate of reproductive development accelerates compared to somatic
Homeotic genes: Determine placement and spatial organization of body parts
Hox genes

13. Evolutionary Trends Evolution is not goal oriented Horse Evolution
Equus is only surviving genus of the tree
Not all adaptive radiations lead to same result
Parahippus: Grazers
Miohippus: Browsers
Species Selection: Species that endure the longest and reproduce the most set the trend for macroevolution

14. Equus Evolution

15. Sympatric Speciation

16. Ring Species

17. Adaptive Radiation