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Unformatted text preview: t different continents, islands, � Postmating Gametes mortality / sperm cannot reach or fertilize egg
Zygote mortality / fertilisation occurs, but zygote fails to develop
Hybrid sterility / hybrid survives (viable) but is sterile and cannot reproduce (no meiosis)
Hybrid inviability / F1 hybrid has reduced viability: incomplete development Allopatric speciation (geographical isolation) Physical barrier (H2O, mountains, dessert) divides a population
Two different environments (abiotic, biotic)
Genetic drift changes genotype and phenotype
Two populations evolve separately
Reproductively isolated / 2 distinct species Sympatric speciation (reproductive isolation) Genetic isolation by mutation / reproductively isolated / but inhibit same habitat
Drift can cause further divergence between isolated gene pools
Hybridisation in plants
o Offspring produced from parents of two different species
o Chromosomal number doubles / polyploidy
o New species is reproductively isolated by a postmating mechanisms
Can only reproduce with other polyploids, backcrosses with (2n) parents are sterile...
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This document was uploaded on 02/28/2014 for the course BLG 144 at Ryerson.
- Summer '10