1. 1 Origin of Species Chapter 24

2. 2 What you need to know! The difference between microevolution and macroevolution. The biological concept of species. Prezygotic and postzygotic barriers that maintain reproductive isolation in natural populations. How allopatric and sympatric speciation are similar and different. How an autopolyploid or an allopolyploid chromosomal change can lead to sympatric speciation. How punctuated equilibrium and gradualism describe two different tempos of speciation. The difference between microevolution and macroevolution. The biological concept of species. Prezygotic and postzygotic barriers that maintain reproductive isolation in natural populations. How allopatric and sympatric speciation are similar and different. How an autopolyploid or an allopolyploid chromosomal change can lead to sympatric speciation. How punctuated equilibrium and gradualism describe two different tempos of speciation.

3. 3 Species A population (or group of populations) who can mate and produce fertile offspring Speciation: One species transforms into another A Population transforms over time as adaptations add up in its gene pool (microevolution) Macroevolution: is major developmental changes spawning new branches of species –the evolution of the spinal cord: vertebrates –the evolution of feathers: birds A population (or group of populations) who can mate and produce fertile offspring Speciation: One species transforms into another A Population transforms over time as adaptations add up in its gene pool (microevolution) Macroevolution: is major developmental changes spawning new branches of species –the evolution of the spinal cord: vertebrates –the evolution of feathers: birds

4. 4 Adaptations A genetic change that makes an organism better suited to their environment Natural selection facilitates adaptation Special adaptations: Mimicry: mimicking another organism that is potentially dangerous Camouflage: blending in with the environment A genetic change that makes an organism better suited to their environment Natural selection facilitates adaptation Special adaptations: Mimicry: mimicking another organism that is potentially dangerous Camouflage: blending in with the environment

5. 5 Reproductive Isolation Prezygotic (prevent mating and/or hinder fertilization): 1.Habitat isolation: don’t share a habitat 2.Behavioral isolation: different mating practices 3.Temporal isolation: sex at different times of day or year 4.Mechanical isolation: not physically possible 5.Gametic isolation: sperm cannot fertilize egg Prezygotic (prevent mating and/or hinder fertilization): 1.Habitat isolation: don’t share a habitat 2.Behavioral isolation: different mating practices 3.Temporal isolation: sex at different times of day or year 4.Mechanical isolation: not physically possible 5.Gametic isolation: sperm cannot fertilize egg

6. 6 Reproductive Isolation Postzygotic (fertilized eggs don’t develop into fertile adults): 1.Reduced hybrid viability: genetic incompatibility terminates pregnancy 2.Reduced hybrid fertility: viable offspring that cannot reproduce (mule) 3.Hybrid breakdown: viable offspring that grow and reproduce but their offspring are weak or sterile Postzygotic (fertilized eggs don’t develop into fertile adults): 1.Reduced hybrid viability: genetic incompatibility terminates pregnancy 2.Reduced hybrid fertility: viable offspring that cannot reproduce (mule) 3.Hybrid breakdown: viable offspring that grow and reproduce but their offspring are weak or sterile

7. 7 Speciation Allopatric Speciation random mating becomes impossible due to geographic isolation (rivers, canyons, mountains) New species evolve on the fringes of large ancestral populations Sympatric Speciation Sudden mutation within a population leads to new species Polyploidy plants mutate by altering chromosome number in a non-disjunction error Allopatric Speciation random mating becomes impossible due to geographic isolation (rivers, canyons, mountains) New species evolve on the fringes of large ancestral populations Sympatric Speciation Sudden mutation within a population leads to new species Polyploidy plants mutate by altering chromosome number in a non-disjunction error

8. 8 Adaptive Radiation Colonization of new habitat –New habitats usually vary from the original habitat Example Darwin’s Finches Colonization of new habitat –New habitats usually vary from the original habitat Example Darwin’s Finches

9. 9 Rate of Change Species that change slowly are K (carrying capacity) – selected –elephants Species that change quickly are r (growth rate) – selected –Bacteria Gradualism: species descended from a common ancestor and gradually diverge Punctuated equilibrium: period of apparent stasis followed by rapid change Species that change slowly are K (carrying capacity) – selected –elephants Species that change quickly are r (growth rate) – selected –Bacteria Gradualism: species descended from a common ancestor and gradually diverge Punctuated equilibrium: period of apparent stasis followed by rapid change