Actually, in the below senario there is Natural Selection and it is = working. Since those organisms are now maladapted, and declining to = extinction Natural Selection is selecting them for extinction. =20 Natural Selection selects against unfit organisms, not for fit ones. = This is much different from selecting for the most fit organisms. This = is particularly important because it is this selection against = maladapted individuals that maintains diversity within a population. If = Natural selection selected for a particular genome, the entire = population would rapidly become homogeneous. The heterogeneity dictates = that the population has many different characteristics, some of which = are ideally adapted to the current climatic/habitat conditions, others = are only marginally adapted to this optima. As the climates change or = habitats success, dominance of different traits shifts do to = differential selection pressure across a continuum of from least to most = adapted. The least adapted will decline, possibly becoming extirpated. = The most adapted will proliferate and dominate. Another shift in optima = occurs and the population traits shift in response. =20 =20 This is not unlike a place of employment. People who can't do the job = are fired. But there is wide variation in the ability of employees to = do the same job. Some of these receive raises and promotions due to = their ability to excel while others are demoted or do not receive = raises. This array of employees remains employed and functioning in the = workplace, they all reproduce! =20 =20 To learn more about this interesting relationship it would be good to = get yourself a copy of Dawkin's "The Selfish Gene." In my opinion, it = is the best evolution book out there (still) because anyone can grasp = what is written. My genetics class is required to read this! =20 =20 I hope that answers your question and if you need clarification, feel = free to send an email!=20 =20 VISIT HERPETOLOGICAL CONSERVATION AND BIOLOGY www.herpconbio.org = <http://www.herpconbio.org>=20 A New Journal Published in Partnership with Partners in Amphibian and = Reptile Conservation and the World Congress of Herpetology. =20 Malcolm L. McCallum Assistant Professor Department of Biological Sciences Texas A&M University Texarkana 2600 Robison Rd. Texarkana, TX 75501 O: 1-903-223-3134 H: 1-903-791-3843 Homepage: https://www.eagle.tamut.edu/faculty/mmccallum/index.html =20
________________________________ From: Ecological Society of America: grants, jobs, news on behalf of Kim = van der Linde Sent: Sat 7/8/2006 11:36 PM To: [email protected] Subject: Maldaptation, Extinction and Natural selection Hi all, I am having an interesing discussion at the moment about Natural selection. The context is a single population of individuals that, due to changes in the environment, are now maladapted and the population is reducing in size. Based on the often used definition of differential reproduction, when there is not much to differentiate with, there is no longer differential selection, and as such, no natural selection. However, they are maladapted, so unfit to survive. Any opinions about this nice contradiction? Cheers, Kim -- http://www.kimvdlinde.com
