1. Chapter 24 ~ The Origin of Species Chapter 24 ~ The Origin of Species

2. Macroevolution: the origin of new taxonomic groups (change above species level) Microevolution: changes in a specific gene pool Speciation: the origin of new species Speciation: the origin of new species 1- Anagenesis (phyletic evolution): accumulation of heritable changes 1- Anagenesis (phyletic evolution): accumulation of heritable changes 2- Cladogenesis (branching evolution): budding of new species from a parent species that continues to exist (basis of biological diversity) Speciation: the origin of new species Speciation: the origin of new species 1- Anagenesis (phyletic evolution): accumulation of heritable changes 1- Anagenesis (phyletic evolution): accumulation of heritable changes 2- Cladogenesis (branching evolution): budding of new species from a parent species that continues to exist (basis of biological diversity)

3. What is a species? Biological species concept (Mayr): a population or group of populations whose members have the potential to interbreed and produce viable, fertile offspring (genetic exchange is possible and that is genetically isolated from other populations)Biological species concept (Mayr): a population or group of populations whose members have the potential to interbreed and produce viable, fertile offspring (genetic exchange is possible and that is genetically isolated from other populations) Usually cannot interbreed with members of other speciesUsually cannot interbreed with members of other species Biological species concept (Mayr): a population or group of populations whose members have the potential to interbreed and produce viable, fertile offspring (genetic exchange is possible and that is genetically isolated from other populations)Biological species concept (Mayr): a population or group of populations whose members have the potential to interbreed and produce viable, fertile offspring (genetic exchange is possible and that is genetically isolated from other populations) Usually cannot interbreed with members of other speciesUsually cannot interbreed with members of other species

4. SpeciesSpecies Gene flow continues through generations Gene flow continues through generations Reproductively united - results in change slowly through time Reproductively united - results in change slowly through time Reproductively isolation - results in speciation Reproductively isolation - results in speciation Gene flow continues through generations Gene flow continues through generations Reproductively united - results in change slowly through time Reproductively united - results in change slowly through time Reproductively isolation - results in speciation Reproductively isolation - results in speciation

5. Reproductive Isolation (isolation of gene pools) (Prezygotic Barriers) Habitat -occupation of different niche (snakes; water/terrestrial)Habitat -occupation of different niche (snakes; water/terrestrial) Behavioral usually used during sexual selection (fireflies; mate signaling)Behavioral usually used during sexual selection (fireflies; mate signaling) Temporal - different timeTemporal - different time ex) - salmon; seasonal mating)ex) - salmon; seasonal mating) Mechanical - Size/shape of organs]Mechanical - Size/shape of organs] ex- flowers; pollination anatomyex- flowers; pollination anatomy Gametic - gametes are incompatibleGametic - gametes are incompatible ex. - frogs; egg coat receptorsex. - frogs; egg coat receptors Habitat -occupation of different niche (snakes; water/terrestrial)Habitat -occupation of different niche (snakes; water/terrestrial) Behavioral usually used during sexual selection (fireflies; mate signaling)Behavioral usually used during sexual selection (fireflies; mate signaling) Temporal - different timeTemporal - different time ex) - salmon; seasonal mating)ex) - salmon; seasonal mating) Mechanical - Size/shape of organs]Mechanical - Size/shape of organs] ex- flowers; pollination anatomyex- flowers; pollination anatomy Gametic - gametes are incompatibleGametic - gametes are incompatible ex. - frogs; egg coat receptorsex. - frogs; egg coat receptors Prezygotic barriers: impede mating between species or hinder the fertilization of the ova Prezygotic barriers: impede mating between species or hinder the fertilization of the ova - Usually enough to prevent mating between species - Usually enough to prevent mating between species

6. Reproductive Isolation - If you are really determined Postzygotic barriers: fertilization occurs, but the hybrid zygote does not develop into a viable, fertile adultPostzygotic barriers: fertilization occurs, but the hybrid zygote does not develop into a viable, fertile adult Reinforce Pre-mating factorsReinforce Pre-mating factors Reduced hybrid viability (frogs; zygotes fail to develop or reach sexual maturity)Reduced hybrid viability (frogs; zygotes fail to develop or reach sexual maturity) Reduced hybrid fertility (mule; horse x donkey; cannot backbreed)Reduced hybrid fertility (mule; horse x donkey; cannot backbreed) Hybrid breakdown (cotton; 2nd generation hybrids are sterile)Hybrid breakdown (cotton; 2nd generation hybrids are sterile) Postzygotic barriers: fertilization occurs, but the hybrid zygote does not develop into a viable, fertile adultPostzygotic barriers: fertilization occurs, but the hybrid zygote does not develop into a viable, fertile adult Reinforce Pre-mating factorsReinforce Pre-mating factors Reduced hybrid viability (frogs; zygotes fail to develop or reach sexual maturity)Reduced hybrid viability (frogs; zygotes fail to develop or reach sexual maturity) Reduced hybrid fertility (mule; horse x donkey; cannot backbreed)Reduced hybrid fertility (mule; horse x donkey; cannot backbreed) Hybrid breakdown (cotton; 2nd generation hybrids are sterile)Hybrid breakdown (cotton; 2nd generation hybrids are sterile)

7. Modes of speciation (based on how gene flow is interrupted) Allopatric: populations segregated by a geographical barrier; can result in adaptive radiation (island species)Allopatric: populations segregated by a geographical barrier; can result in adaptive radiation (island species) –Geographical Barriers –Adaptive Radiation Allopatric: populations segregated by a geographical barrier; can result in adaptive radiation (island species)Allopatric: populations segregated by a geographical barrier; can result in adaptive radiation (island species) –Geographical Barriers –Adaptive Radiation

8. Geographical Barriers Geographical Barriers After separation genetic drift may occur- divergence of populations gene pool (that is microevolution) New species are then formed. The subset of the population may under-represent the main population. (May occur along outer edges of large population that form the fringes of the parent population.) As increase in population occurs, genetic drift increases the difference between the original and new population. May be experiencing environmental/selective pressures different from the main group. After separation genetic drift may occur- divergence of populations gene pool (that is microevolution) New species are then formed. The subset of the population may under-represent the main population. (May occur along outer edges of large population that form the fringes of the parent population.) As increase in population occurs, genetic drift increases the difference between the original and new population. May be experiencing environmental/selective pressures different from the main group.

9. Adaptive Radiation

10. Modes of speciation (based on how gene flow is interrupted) Sympatric: reproductively isolated subpopulation in the midst of its parent population (change in genome)Sympatric: reproductively isolated subpopulation in the midst of its parent population (change in genome) polyploidy (in plants) - caused by failure to separate in cell divisionpolyploidy (in plants) - caused by failure to separate in cell division Autopolyploid - more than 2 sets of chromosomesAutopolyploid - more than 2 sets of chromosomes Allopolyploid- (hybrid that became fertile)Allopolyploid- (hybrid that became fertile) Sympatric: reproductively isolated subpopulation in the midst of its parent population (change in genome)Sympatric: reproductively isolated subpopulation in the midst of its parent population (change in genome) polyploidy (in plants) - caused by failure to separate in cell divisionpolyploidy (in plants) - caused by failure to separate in cell division Autopolyploid - more than 2 sets of chromosomesAutopolyploid - more than 2 sets of chromosomes Allopolyploid- (hybrid that became fertile)Allopolyploid- (hybrid that became fertile)

11. How fast does speciation occur? (Macroevolution) Tempo of speciation:Tempo of speciation: Two Schools of ThoughtTwo Schools of Thought Gradualism - evolution proceeds slowly at a constant rateGradualism - evolution proceeds slowly at a constant rate Darwin was a gradualist Darwin was a gradualist populations slowly diverge populations slowly diverge appearance of species in the fossil record appearance of species in the fossil record Tempo of speciation:Tempo of speciation: Two Schools of ThoughtTwo Schools of Thought Gradualism - evolution proceeds slowly at a constant rateGradualism - evolution proceeds slowly at a constant rate Darwin was a gradualist Darwin was a gradualist populations slowly diverge populations slowly diverge appearance of species in the fossil record appearance of species in the fossil record

12. Punctuated equilibria Niles Eldredge and Stephen Jay Gould (1972) Niles Eldredge and Stephen Jay Gould (1972) thousands of years!) is involved in speciation. Most of species existence is spent in stasis (w/o change or in equilibrium) and a very small amount of time (tens of thousands of years!) is involved in speciation. changes are brought about by rapid changes in the environment such as a mass extinction of species with few survivors. (Founders/bottleneck). changes are brought about by rapid changes in the environment such as a mass extinction of species with few survivors. (Founders/bottleneck). helped explain the non-gradual appearance of species in the fossil record helped explain the non-gradual appearance of species in the fossil record Niles Eldredge and Stephen Jay Gould (1972) Niles Eldredge and Stephen Jay Gould (1972) thousands of years!) is involved in speciation. Most of species existence is spent in stasis (w/o change or in equilibrium) and a very small amount of time (tens of thousands of years!) is involved in speciation. changes are brought about by rapid changes in the environment such as a mass extinction of species with few survivors. (Founders/bottleneck). changes are brought about by rapid changes in the environment such as a mass extinction of species with few survivors. (Founders/bottleneck). helped explain the non-gradual appearance of species in the fossil record helped explain the non-gradual appearance of species in the fossil record

13. Which follows which school of thought?

14. Evolution is not Goal Oriented How could a new species result?