Chapter 9: Mechanisms of Evolution and their effect on Populations Flashcards
gene flow
the net movement of alleles from one population to another due to the migration of individuals
non-random mating
mating among individuals on the basis of mate selection for a particular phenotype or due to inbreeding
genetic drift
the change in frequencies of alleles due to change events in a breeding population
founder effect
a change in a gene pool that occurs when few individuals start a new isolated population
bottleneck effect
changes in gene distribution that result from a rapid decrease in population size
stabilizing selection
natural selection that favours intermediate phenotypes and acts against extreme variants
directional selection
natural selection that favours the phenotypes at one extreme over another, resulting in the distribution curve of phenotypes shifting in the direction of that extreme
disruptive (diversifying) selection
natural selection that favours the extremes of a range of phenotypes rather than intermediate phenotypes; can result in the elimination of intermediate phenotypes
sexual selection
natural selection for mating based on competition between males and choices made by females
speciation
the forming of a new species from an existing species
pre-zygotic isolating mechanism
a barrier that either impedes mating between species or prevents fertilization of the eggs if individuals from different species attempt to mate
post-zygotic isolating mechanism
a barrier that prevents hybrid zygotes from developing into viable, fertile individuals (think mules)
sympatric specialisation
speciation in which populations within the same geographical areas diverge and become reproductively isolated
allopatric speciation
speciation in which a population is split into two or more isolated groups by a geographical barrier
ecological niche
the ecological role and physical distribution of a species in its environment
