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Macroevolution: Evolution of New Species Species: a group of organisms that can interbreed & produce fertile offspring Speciation: the evolution of new species (by genetic change or change in form) - occurs when members of similar populations no longer interbreed Methods of Speciation: Reproductive Isolation: occurs when formerly interbreeding organisms can no longer mate & produce fertile offspring o Genetic Isolation – genetic differences are too great to breed successfully o Geographic Isolation - occurs when physical barriers divide a population & prevent interbreeding Beetles in Grassland Become Green Beetles in Woody Habitat Become Brown o Behavioral Isolation – mating behaviors or mating seasons don’t allow for mating o Polyploidy – any species with extra sets of chromosomes (common in plants) Polyploids can interbreed or self-fertilize, forming separate species o Hybridization – When two closely related species attempt to mate Typically results in sterile offspring, but can sometimes lead to new successful species Speed of Speciation (Macroevolution): Gradualism: the idea that species originate through a slow, gradual change of adaptations over long periods of time Punctuated Equilibrium: the idea that species can remain stable for long periods until environmental changes cause many new species to appear. o Environmental changes lead to rapid changes in a populations gene pool o Speciation occurs in 10,000 years or less Patterns of Macroevolution Divergent Evolution (Adaptive Radiation): species diverge, or become increasingly distinct from an ancestral species o Often occurs when populations adapt to use different niches o Example: Darwin’s Finches / Hawaiian Honeycreepers Convergent Evolution: The process by which unrelated species become similar as they adapt to similar environments. o Example: Emu (Australia), Ostrich (Africa), Rhea (South America) Coevolution: Organisms that live in close association develop adaptations to one another’s existence. o Example: moth and orchid (mutualism) Extinction: When all members of a species die off or fail to reproduce o o o o Scientists estimate that 99% of all species that ever lived on Earth have become extinct Many cases of extinction are the result of environmental change When the environment changes, species that were well adapted can become poorly adapted If the environment changes faster than a species can adapt, extinction can result