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Chapter 23-24 - Populations and Species Notes

Chapter 23-24 - Populations and Species Notes - CHAPTER 23...

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CHAPTER 23 & 24 POPULATIONS AND SPECIES POPULATION-  localized  group  of individuals  capable  of interbreeding GENE POOL - All the  alleles  in a population SPECIES=  = group  of organisms  that can  interbreed  with one  another  and  produce  viable  fertile  offspring        Different  species  can’t produce  fertile  offspring      EX: Horse  X donkey    mule;    lion  X tiger    liger WHAT PREVENTS INTERBREEDING AND KEEPS SPECIES SEPARATE? 1) REPRODUCTIVE BARRIERS: PREZYGOTIC BARRIERS  – Impede mating or hinder fertilization POSTZYGOTIC BARRIERS - After mating 2) GEOGRAPHIC BARRIERS  Gene  pool  of a population  is separated/split  Ex: Island,  lake,  mountain  top,  retreating  water,  fire  separating  populations  of grasslands,         seed  blown  to new  region  by  storm,  lake  drying  up  Allows  change  in gene  pool  provided  that each  population  has  selection  taking  place REPRODUCTIVE/GEOGRAPHIC BARRIERS    can  lead  to  SPECIATION : formation  of new  species  too  many  c hanges   make  interbreeding  impossible MACROEVOLUTION (fish    amphibians;  dinosaurs    birds)     •  change  above  species  level    HABITAT ISOLATION “COMPETITIVE EXCLUSION PRINCIPLE”      = each  species  occupies  a specific  niche May  not contact  each  other  even  if live  in same  area MECHANICAL ISOLATION Size  and  shape  of reproductive  organs   anatomically  incompatible GAMETIC/GENETIC ISOLATION  = gametes  are  incompatible Sperm  can’t survive  in female  reproductive  tract        OR  not recognized  by  egg  receptors TEMPORAL ISOLATION  Breed  during  different  times  of day,   seasons,  or different  years  
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