Speciation Formation of Species SPECIES = grp. of organisms that look alike & interbreed to produce fertile offspring Subspecies-(they can be broken down into subspecies-distinct from each other, but can interbreed-usually don’t) SPECIATION = to form a new species• need isolation from gene pool!! (Ex: Finches on Galapagos) A new species has formed: • produce fertile offspring • Offspring develop completely offspring live to reproductive age 3 Isolation Mechanisms 1. Geographic isolation = population separated by physical barriersEx: island formation, a canyon/river forms 2. Behavioral isolation = differ in courtship rituals or don’t respond to mating signals Ex: Birds using different songs to attract mates 3. Temporal isolation = species reproduce at different times of the yearEx: organisms mate in autumn vs. spring Rates of Speciation – Two Hypotheses: 1. Gradualism – speciation occurs through a SLOW change of adaptations2. Punctuated Equilibrium – speciation occurs in BURSTS w/ long periods of no change in between * Fossil evidence for both but remember not everything is fossilized!