BILD 3 Lecture 8: BILD 3 Lecture 8
13 Jun 2018
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BILD 3 Lecture 8
4/18/2018
• Gene flow
o HW assuptio: o igratio etwee populatios is’t et
o Gene flow is the transfer of alleles into or out of a population as a result of the
movement of fertile individuals or their gametes (e.g. pollen)
o Can alter the frequency of a particular allele in a population
o Can reduce existing genetic differences between populations
o Can counteract loss of genetic variation caused by genetic drift
o Can oppose natural selection and adaptation
o Ex: copper tolerance is an advantage in polluted mine soil, but decreases growth
rate in absence of copper, but wind disperses both types of copper tolerant and
intolerant grasses prevents the grass types from fully adapting to their
environmental conditions
o Ex: in a mussel that has planktonic larvae that readily disperse. The salinity
tolerance varies of the mussels. Gene flow alters the frequency of the tolerance,
regardless of how saline their environment is. The gene flow prevents fixation of
one type of allele
• Founder effect causes genetic drift
• Sexual selection
o “tates the atig is ot rado of HW
o Is a type of natural selection in which certain traits cause individuals to be more
likely to obtain mates
o Can result in sexual dimorphism
o Secondary sexual characteristics: the traits the differ between the sexes and are
not directly associated with survival and reproduction→what is selected for in
sexual selection
o Intersexual selection
▪ Individuals of one sex are choosy in selecting their mates
▪ Competition for the attention of the opposite sex
▪ Most common in females
▪ Traits females use to select potential males can involve characteristics
with no apparent survival advantage and may even carry some survival
risk
• i.e. more visible to predators, or makes escape harder
• e.g. coloration, ritualized behaviors, vocalizations
o intrasexual selection
▪ individuals of one sex compete for mates
▪ usually males
▪ e.g. defense of territory, physical combat, or ritualized aggression
o how do female preferences for specific traits evolve in the first place?
▪ good gees hypothesis
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