Zoology101: Animal Biology Last Lecture Outline Lecture 35 1. MicroevolutionCurrent Lecture 1. Conservation2. Sexual selection Conservation• Why are we concerned about small populations ◦ Population sizes of other organisms may be small◦ Small populations experience greater effects of drift ◦ In small populations, drift can actually become more important than selection▪ habitat destruction, modification, degradation, exotic species, over harvest▪ Bottleneck can introduce drift, then small size= maintenance high drift ▪ Loss of genetic variation, accumulation of deleterious mutations= positive feedback → smaller population, increased drift, etc.• Case study: impact of genetic drift on Greater Prairie Chickens ◦ Prairie chickens habitat destroyed in much of Illinois, leads to greatly reduced population size◦ Use DNA from museum specimens to quantify genetic variation◦ Use data from field studies to compare reproduction • Fitness consequences Sexual Selection• Natural selection is related to mating • Survival isn't enough- genes must get into the next generation • Darwin distinguished 2 types ◦ Intrasexual selection▪ acts on traits that affect success in competition with members of your sex for mates▪ Males competing against males ◦ Intersexual Selection ▪ Acts on traits that affect success in being chosen for mating by opposite sex • Sexual dimorphism: differences in size, color, shape and behavior between the sexes◦ assess risk of cheating when in need for food • Why might natural selection not produce perfectly adapted organisms?◦ Natural selection works upon available variation ▪ selection constrained by past ▪ selection doesn't have a plan; not aware of the future ◦ Natural selection can vary in time and space◦ Selection can be opposed by another microevolutionary source (e.g. drift, migration, mutation)◦ There are no tradeoffs◦ Not all variation is subject to natural selection (Neurtal traits)▪ human finger prints ◦ Evolution by natural selection takes time ▪ rapid changes in environment may outpace the rate at which adaption can
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