This preview has intentionally blurred sections. Sign up to view the full version.View Full Document
Unformatted text preview: Lecture 12 - EEB 13 - 19 February 2008* Dr. Hespenheide two conflicting theories of evolution: Selectionist theory (Darwin) - most change is from natural selection Neutralist theory - most change is from genetic drift What is the relative importance of selection vs . genetic drift?- in fact, difficult to distinguish because both operate from differences in survival and reproduction- genetic drift - no relationship between genotype (allele) success and environment, success is random- selection - genotype (allele) success (fitness) is determined by environment conclusions : most loci probably drift - neutral changes in molecules produce high levels of variability, evolutionary clocks a few loci are under selection - produce visible changes in phenotypes (adaptations); genetic diseases show obvious differences in fitness Micro evolution - summary: recombination- produces new genotypes from existing alleles- depends on genetic system , which controls amount of recombination - by itself, recombination is not evolution mutation migration- change kinds and frequencies of alleles selection genetic drift these changes occur within local populations, demes- thus, if we look at a series of demes: migration mig mig deme 1 ↔ deme 2 ↔ deme 3 ↔ deme n ↑ ↑ ↑ ↑ (mutation) mu, sel, g-d mu, sel, g-d mu, sel, g-d selection genetic drift- mutation /selection /genetic drift make populations/demes more different- migration tends to make populations/demes more alike the “inexorability of [micro-]evolution”- change must happen because- sexual reproduction constantly produces new genotypes...
View Full Document
- Winter '08
- Evolution, E. Mayr