Mechanisms of Microevolution(adapted from: http://evolution.berkeley.edu/evolibrary/article/0_0_0/evo_39)
Three (3) examples of mechanisms that contribute toMicroevolutionarychange.MutationMigration (emigration and/or immigration)PredationALL of the above produce VARIATION in populations.VARIATION is the “fuel” for NATURAL SELECTION
EXAMPLE: Beetle Color
You are observing a population of beetlesOver time, you observe 2 changes in the beetlepopulationAn increase in the frequency brown beetlesA decrease in the frequency of green beetles in the beetle population.
Example: Beetle Color (2)
As genes determine characteristics, you generate 2 related hypotheses based on your observationsThe gene that makes beetles brown has increased in frequency in the populationThe gene that makes beetles green has decreased.
Any combination of theMicroevolutionaryMechanismsmight be responsible for the observed changed in the frequency of green and brown beetles
Example: Beetle Color (3)
Mutationas the source of observed variation in beetlecolorSome "green genes" randomly mutated to "browngenes“Since any particular mutation is rare, this process alone cannot account for a big changeingenefrequency overonegeneration but can account for big changes of multiple generations.
Migration(orGene Flow)(Ref: Invasive species)Some beetles with brown genes immigrated from another population,ORSomebeetles carrying green genes emigrated.
Predation(Ref:Kettlewell)Beetles with brown genes escaped predation (being eaten by a bird) and survived to reproduce more frequently than beetles with greengenesSomore brown genes got into the next generation.