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Chapter 16.3:
The Process of Speciation
Speciation The formation of new species
Because a population of individuals has a shared gene pool, a genetic change that occurs in one individual can spread through the population as that individual and its offspring reproduce
Reproductive Isolation As new species evolve, populations become
reproductively isolated from each other
Reproductive isolation occurs when members of two populations cannot interbreed and produce fertile offspring
– Can develop by behavioral isolation, temporal isolation, and temporal isolation
Behavioral Isolation Occurs when two populations are
capable of interbreeding but have differences in courtship rituals or other reproductive strategies that involve behavior
Geographic Isolation Occurs when two populations are
separated by geographic barriers such as rivers, mountains, or bodies of water– Temporary geographic features does not
guarantee isolation– Geographic features may isolate some
species but not others
Temporal Isolation Occurs when two or more species
reproduce at different times
Darwin’s Finches Darwin hypothesized that the finches
he found on the Galapagos Islands descended from a common ancestor– He proposed that natural selection
shaped the beaks of different bird populations as they adapted to eat different foods
Darwin’s Hypothesis Proven
Speciation in the Galapagos finches occurred by founding of a new population, geographic isolation, changes in the new population’s gene pool, reproductive isolation, and ecological competition