PSYC 385 Lecture Notes - Lecture 8: Niche Construction, Genetic Drift, Directional Selection

• School: Simon Fraser University
• Department: Psychology
• Course: PSYC 385
• Professor: Timothy Racine

Document Summary

If you"re interested in the genes that support a particular phenotype, as something becomes more representative in a member o f a species, until it becomes universal, then there"s no variation b/c everyone has the same thing. But there"s some form of selection that keep variation in a population. Ni(cid:272)he (cid:272)o(cid:374)st(cid:396)u(cid:272)tio(cid:374) is a(cid:374) e(cid:454)(cid:272)eptio(cid:374) that (cid:272)a(cid:374) o(cid:272)(cid:272)u(cid:396) (cid:894)eg: (cid:271)ea(cid:448)e(cid:396)s(cid:895) so does(cid:374)"t (cid:373)ea(cid:374) that (cid:374)i(cid:272)he (cid:272)o(cid:374)st(cid:396)u(cid:272)tio(cid:374) al(cid:449)a(cid:455)s o(cid:272)(cid:272)u(cid:396)s. If (cid:455)ou ha(cid:448)e a phe(cid:374)ot(cid:455)pe that o(cid:272)(cid:272)u(cid:396)s o(cid:374) a (cid:374)o(cid:374)(cid:272)oded (cid:396)egio(cid:374), this does(cid:374)"t (cid:373)atte(cid:396) it"s the p(cid:396)i(cid:374)(cid:272)iple of ge(cid:374)eti(cid:272) d(cid:396)ift=sele(cid:272)ti(cid:448)el(cid:455) neutral/no change in phenotypejust change in population . Is why drift is useful in estimate human descent/molecular time. Genes increase in population, vs being fixed=part of the genotype=no genetic variation. Stabilizing selection: acts against both extremes in a distribution to keep pop. Opti(cid:373)al phe(cid:374)ot(cid:455)pe f(cid:396)o(cid:373) a fit(cid:374)ess pe(cid:396)sp (cid:271)e(cid:272)o(cid:373)es the a(cid:448)g le(cid:448)el its stable overtime. Directional selection: a(cid:272)ts agai(cid:374)st o(cid:374)e e(cid:454)t(cid:396)e(cid:373)e of a phe(cid:374)ot(cid:455)pe shift to(cid:449)a(cid:396)d othe(cid:396)