BIOL 1001 Lecture Notes - Lecture 9: Sewall Wright, Allele, Sickle-Cell Disease
15 Jan 2016
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Even though there would be gains in typing efficiency there are far too many steps to go through: the intervening steps. Normal distribution: if individuals in the tails have lower fitness , then the distribution won"t move left / right i. e. no directional selection / no disruptive selection, individuals around the mean have the highest fitness. Fitness landscape model: sewall wright, intervening generations which has lower fitness. So, they cannot escape a to get to b because they have to go downhill through generations of lower fitness first: phylogenetic inertia. Phylogenetic inertia: vestigial structures, imperfect structures, heterozygote advantage, natural selection reduction, pleiotropy, fitness trade-of, 1. Genes from the past are influencing present phenotypes. If they are not too costly to make then there will not be strong selective pressure to eliminate them: 2. Evolution can only modify existing structures & functions can produce less than perfect results. E. g. vertebrates & cephalopods developed eyes in separate.
