Mechanisms of Microevolution (adapted from: http://evolution. berkeley Three (3) examples of mechanisms that contribute to Microevolutionary change. Mutation Migration (emigration and/or immigration) Predation ALL of the above produce VARIATION in populations. VARIATION is the “fuel” for NATURAL SELECTION

EXAMPLE: Beetle Color You are observing a population of beetles Over time, you observe 2 changes in the beetle population An increase in the frequency brown beetles A 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 observations The gene that makes beetles brown has increased in frequency in the population The gene that makes beetles green has decreased.

Example: Beetle Color (3) Any combination of the Microevolutionary Mechanisms might be responsible for the observed changed in the frequency of green and brown beetles

Contributing Microevolutionary Mechanisms Mutation as the source of observed variation in beetle color Some "green genes" randomly mutated to "brown genes“ Since any particular mutation is rare, this process alone cannot account for a big change in gene frequency over one generation but can account for big changes of multiple generations.

Contributing Microevolutionary Mechanisms (2) Migration (or Gene Flow) (Ref: Invasive species) Some beetles with brown genes immigrated from another population, OR Some beetles carrying green genes emigrated.

Contributing Microevolutionary Mechanisms (3) Predation (Ref: Kettlewell) Beetles with brown genes escaped predation (being eaten by a bird) and survived to reproduce more frequently than beetles with green genes So more brown genes got into the next generation.