Download Mechanisms of Microevolution (adapted from: http://evolution

Mechanisms of Microevolution
(adapted from: http://evolution.berkeley.edu/evolibrary/article/0_0_0/evo_39)
• Three (3) examples of mechanism 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 allele
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.