Forces of Evolutionary Change, Part II

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Mechanisms of Evolution
GENETIC DRIFT &
NATURAL SELECTION
Five Factors Drive Evolution
 Mutation
Venom-like proteins
first appeared about 200 million years ago
Venoms
evolved from other proteins
Venoms
were recruited from other functions
I. Natural Selection
Green mamba is arboreal
Its venom is most effective
against birds.
Black mamba is terrestrial
Its venom is most
effective against
mammals.
OVERPRODUCTION
HERITABLE VARIABILITY
COMPETITION
DIFFERENTIAL REPRODUCTION
II. GENETIC DRIFT
 The smaller the population, the less genetic
variety it has.
 In a very small population, alleles can be lost
from one generation to the next, simply by
random chance.
 When a population evolves only because of
this type of random sampling error,
GENETIC DRIFT is taking place.
FOUNDER EFFECT
BOTTLENECK EFFECT
AND IN 4.5 BILLION YEARS…
 The diversity of life on earth around us evolved.
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