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Patterns of Evolution Sec 17-4 Microevolution • Refers to small-scale evolutionary patterns that occur in a population over short periods of time, such as generations • Change in genes of populations Examples of Microevolution • Natural Selection • Migration • Mate Choice • Mutation • Genetic Drift Natural Selection and Migration • As you have learned, natural selection can cause an increase or decrease in certain alleles in a population • Migration: is the movement of individuals into, out of, or between populations • Population: a group of organisms of the same species that live in a specific geographical area Mate Choice • If parents are paired up randomly in a population a random assortment of traits will be passed on to the next generation • If parents are limited or selective in their choice of mates, a limited set of traits will be passed on (artificial selection) • Larger male iguanas on the Galapagos islands are more favorable Mutation and Genetic Drift • Mutation- any change in DNA • Mutation can change the numbers and types of alleles from one generation to the next • However changes are rare • Genetic Drift: the random change in allele frequency in a population Macroevolution • Refers to large scale evolutionary patterns and processes that occur over long periods of time • Includes – – – – – – Extinction Adaptive radiation Convergent evolution Coevolution Punctuated equilibrium Changes in developmental genes Extinction • If all members of a lineage die off or simply fail to reproduce, the lineage is said to be extinct Natural selection did not allow them to evolve to new environments Mass Extinctions • Periods of time when entire ecosystems were destroyed – Causes collapse of food chains and food webs – Extinction was due to environments collapsing rather than natural selection • Ice ages, asteroids,… • Large loss of life leaves many holes for new organisms to evolve into Adaptive Radiation • The evolution of several different species from one common species – EX: Darwin’s 13 finches all evolved from one common species of finch • A side effect is that these radiations can produce unrelated organisms that look similar Convergent Evolution • When unrelated organisms come to resemble one another Due to natural selection working on the raw materials of organisms that live in similar environments • EX: fish and sea mammals – All adapt a streamlined figure, appendages to move through water,… Coevolution • Organisms that are closely connected to one another by ecological interactions may evolve together When one organism changes, the other organism will change as well • Example: Pollination Gradualism/Punctuated Equilibrium • Gradualism is the idea that evolution occurs slowly and steadily over time • Punctuated equilibrium is the idea that long, stable periods of “organism equilibrium” are interrupted by brief periods of rapid change Gradualism Punctuated Equilibrium