| SALE TODAY: Learn Piano on iOS bit.ly Adjunct Professor Mary Poffenroth teaches various topics in biology in a series of Mahalo-produced videos. In this installment, Professor Poffenroth explains natural selection. She makes the point that evolution is a process affecting populations of organisms, not individuals. Professor Poffenroth explains how mutations are chance events, not willed by the organism. Natural selection is the process by which organisms that possess certain traits tend to survive longer and produce more offspring than organisms that lack these traits. Over many generations, those traits that confer fitness (that is, comparative success at survival and reproduction) are likely to increase in frequency in the population. Since environmental conditions are always in flux, it is not always possible to predict beforehand which traits will confer a survival advantage. A trait that enhances fitness in one environment can decrease fitness if the environment changes or if the population migrates to a new environment. bioweb.cs.earlham.edu The Darwinian theory of random mutation as the engine of natural selection replaced the earlier Lamarckian theory of inheritance of acquired traits. In Lamarck's theory, organisms were thought to be capable of evolving by force of will, intentionally modifying their behavior, then passing these modifications on to their offspring. In Darwin's theory, the variations are chance mutations over which the organisms have no ... |
