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Four processes drive microevolution mutation: random changes in the ______________________________molecules that serve as the ultimate source of genetic variation; natural selection: the process by which some individuals of a population have genetically based characteristics that cause them to ____________ & _________________________________than other individuals; Four processes drive microevolution (Cont.): • gene flow: the movement of ____________ between populations (____________________ into or out of a region); genetic drift: change in genetic composition that results by ______________, especially in __________ ____________________ . Example: Cheetahs, low genetic diversity Divergent Evolution and Speciation Divergent evolution is the accumulation _____________ ___________________ between populations due to being ________________________________. Divergence can lead to ____________ (development of a new species) if there are enough ___________so that the diverged populations can no ________________________ offspring. Divergent Evolution and Speciation new species typically evolve by two processes: geographic isolation – ancestral population is separated into distinct regional populations with different ______________________________; reproductive isolation – evolutionary changes in each population that prevent ____________________ when populations come into contact. Continental Drift Continental drift (due to plate tectonics), the slow movement of continents, has played a major role in both _______________________ and ________________________ . Gradualism versus Punctuated Equilibrium • Gradualism is the idea that the Earth and its species have _____________, over a long period of time, changed. Punctuated Equilibrium is the idea that species have changed ____________ (due to dramatic ______________________________) in short bursts followed by long periods of little change. This is seen in the fossil record Most scientists believe species have changed due to both of these concepts.
