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The Origin of Species                        Mom, Dad…                        There’s something                        you...
So…what is a species?Biological species concept population whose members can interbreed &  produce viable, fertile offsp...
How and why do new species originate?Species are created by a series of evolutionary processes   populations become isol...
PRE-reproduction barriers     Obstacles to mating or to fertilization if mating occurs     Theses obstacles help to make...
Ammospermophilus sppGeographic isolation Species occur in different areas    physical barrier    allopatric speciation ...
Ecological isolation   Species occur in same region, but occupy different    habitats so rarely encounter each other     ...
Temporal isolation     Species that breed during different times of day,      different seasons, or different years canno...
sympatric speciationBehavioral isolationUnique behavioral patterns & rituals isolate species identifies members of speci...
sympatric speciationMechanical isolation: PlantsMorphological differences can prevent successful mating  reproductive is...
Mechanical isolation: AnimalsFor many insects, male & female sex organs of closely related species do not fit together, p...
Gametic isolation                          sympatric speciationSperm of one species may not be able to fertilize eggs of ...
Sometimes, it is possible to breedtwo related, but different speciesHybridization: Creation of an offspring (hybrid) from...
POST-reproduction barriers These barriers prevent hybrid offspring from developing  into a viable, fertile adult    redu...
sympatric speciation   Reduced hybrid viability  Genes of different parent species may interact & impair the   hybrid’s d...
Reduced hybrid fertility    Even if hybrids are vigorous/viable     they may be sterile      chromosomes of parents may ...
sympatric speciation    Hybrid breakdown     Hybrids may be fertile & viable in first generation, but when      they mate...
Rate of SpeciationCurrent debate: Does speciation happen gradually or rapidly  Gradualism     Charles Darwin     Charl...
GradualismGradual divergence over long spans of time   assume that big changes occur    as the accumulation of many    s...
Punctuated EquilibriumRate of speciation is not constant   rapid bursts of change   long periods of little or no    cha...
Evolution is not goal-orientedAn evolutionary trend does not mean thatevolution is goal-oriented.Surviving speciesdo not r...
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Implications of variation adaptation and natural selection

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Implications of variation adaptation and natural selection

  1. 1. The Origin of Species Mom, Dad… There’s something you need to know… I’m a MAMMAL!
  2. 2. So…what is a species?Biological species concept population whose members can interbreed & produce viable, fertile offspring reproductively compatible Distinct species: songs & behaviors are different enough to prevent interbreeding Eastern Meadowlark Western Meadowlark
  3. 3. How and why do new species originate?Species are created by a series of evolutionary processes  populations become isolated/separated  geographically isolated  reproductively isolated  isolated populations evolve independentlyIsolation  allopatric  geographic separation/isolation  sympatric  still live in same area  Must be isolated by other means rather than geographic isolation
  4. 4. PRE-reproduction barriers Obstacles to mating or to fertilization if mating occurs Theses obstacles help to make new speciesgeographic isolation ecological isolation temporal isolationbehavioral isolation mechanical isolation gametic isolation
  5. 5. Ammospermophilus sppGeographic isolation Species occur in different areas  physical barrier  allopatric speciation  “other country”  Creation of new species due to physical barriers Harris’s antelope squirrel inhabits the canyon’s south rim (L). Just a few miles away on the north rim (R) lives the closely related white-tailed antelope squirrel
  6. 6. Ecological isolation Species occur in same region, but occupy different habitats so rarely encounter each other reproductively isolated 2 species of garter snake, Thamnophis, occur in same area, but one lives in water & other is terrestriallions & tigers couldhybridize/mate, butthey live in differenthabitats: lions in grasslands tigers in rainforest
  7. 7. Temporal isolation Species that breed during different times of day, different seasons, or different years cannot mix gametes reproductive isolation sympatric speciation  “same country”  Occupy same habitat, but are reproductively isolatedEastern spotted skunk(L) & western spottedskunk (R) overlap inrange but eastern matesin late winter & westernmates in late summer
  8. 8. sympatric speciationBehavioral isolationUnique behavioral patterns & rituals isolate species identifies members of species attract mates of same species   courtship rituals, mating calls  reproductive isolation Blue footed boobies mate only after a courtship display unique to their species
  9. 9. sympatric speciationMechanical isolation: PlantsMorphological differences can prevent successful mating reproductive isolation Even in closely related species of plants, the flowers often have distinct appearances that attract different pollinators. These 2 species of monkey flower differ greatly in shape & color, therefore cross-pollination does not happen.
  10. 10. Mechanical isolation: AnimalsFor many insects, male & female sex organs of closely related species do not fit together, preventing sperm transfer  lack of “fit” between sexual organs: a big issue for insects with different shaped genitals! Damsel fly penises
  11. 11. Gametic isolation sympatric speciationSperm of one species may not be able to fertilize eggs of another species mechanisms  biochemical barrier so sperm cannot penetrate egg or sperm cannot survive in female reproductive tract Sea urchins release sperm & eggs into surrounding waters where they fuse & form zygotes. Gametes of different species— red & purple —are unable to fuse.
  12. 12. Sometimes, it is possible to breedtwo related, but different speciesHybridization: Creation of an offspring (hybrid) from parents of different species  Resultant hybrid may/may not be viable (functional)  Resultant hybrid may/may not be sterile (not fertile)Hybrids are usually weaker and less “fit” than either parent  These pressures prevent species from interbreeding/hybridizing
  13. 13. POST-reproduction barriers These barriers prevent hybrid offspring from developing into a viable, fertile adult  reduced hybrid viability (offspring is small and weak)  reduced hybrid fertility (offspring is healthy, but sterile)  hybrid breakdown (offspring is healthy and fertile, but next generation is small and weak) zebroid
  14. 14. sympatric speciation Reduced hybrid viability Genes of different parent species may interact & impair the hybrid’s developmentSpecies of salamander genus,Ensatina, may interbreed, butmost hybrids do not completedevelopment & those that do arefrail.
  15. 15. Reduced hybrid fertility Even if hybrids are vigorous/viable they may be sterile chromosomes of parents may differ in number or structure & meiosis in hybrids may fail to produce normal gametes Mules are vigorous, but sterileHorses have 64 Donkeys have 62chromosomes chromosomes(32 pairs) Mules have 63 chromosomes! (31 pairs)
  16. 16. sympatric speciation Hybrid breakdown Hybrids may be fertile & viable in first generation, but when they mate offspring are feeble or sterileIn strains of cultivated rice,hybrids are vigorous butplants in next generation aresmall & sterile, so why wouldthese species even hybridizein the first place…there is noreason to…On path to separate species.
  17. 17. Rate of SpeciationCurrent debate: Does speciation happen gradually or rapidly  Gradualism  Charles Darwin  Charles Lyell  Punctuated equilibrium  Stephen Jay Gould  Niles Eldredge Niles Eldredge Curator American Museum of Natural History
  18. 18. GradualismGradual divergence over long spans of time  assume that big changes occur as the accumulation of many small ones
  19. 19. Punctuated EquilibriumRate of speciation is not constant  rapid bursts of change  long periods of little or no change  species undergo rapid change when they 1st bud from parent population Time
  20. 20. Evolution is not goal-orientedAn evolutionary trend does not mean thatevolution is goal-oriented.Surviving speciesdo not representthe peak ofperfection. Thereis compromise & Evolution is not the survival of the fittest. Rather it is therandom chance survival of the just goodinvolved as well enough.Remember that forhumans as well!
  21. 21. Any Questions??

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