post 2 - Biological evolution definitions 1 Descent with...

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Biological evolution definitions : 1) Descent with modification through selection. 2) Adaptive changes in successive, related forms through time. 3) Any change in gene frequencies in populations. Populations: groups of organisms within a species that interbreed frequently and thus individuals share many genes. Basic Darwinian framework as we understand it today: A. Individuals within populations vary in terms of genetic information (genotype). This produces variation in the structure (phenotype) and behavior of individuals and is inherited across generations. Most of this genetic variation is random (e.g. mutations), and accidental or random . B. Organisms produce far more offspring than can possibly survive. C. Natural selection by the environment (everything external to the individual) is the most important mechanism (like giant sieve) that non-randomly favors the survival and reproduction of some individuals as opposed to others, given variations in inherited phenotype and behavior. Some individuals (those not selected against) contribute more genetic information to the next generation than others, and hence the genetic makeup of the population, and eventually whole species, changes. We call this long-term process adaptation. Selection directly works on are inheritable biological structures and behaviors, and ultimately on the genetic information responsible for them. Besides what Darwin called “natural selection” there are other mechanisms of evolution that include genetic drift , which can particularly alter the genetic frequencies of small populations, and sexual selection , in which mating preferences condition genetic change.
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