BIOM 182Bang, Michel(Christofer)2013 SpringWeek 13Lecture 14February 18Sexual Selection- Influences reproductive success: fitness- Favors traits that increase reproductive success at potential cost to survivalSexual Selection vs. Natural Selection- Counteracting forces- A male with more conspicuous coloration or behavior is more vulnerable to predation- If the trait cause males to die earlier, the trait is still beneficial as long as the malesproduce more offspring than males lacking the traitRandom Genetic Drif1. Random changes in allele frequencies from one generation to next may over timeresult in large changes in frequencies2. Bottleneck Effect: Population is dramatically reduced in size due to an external cause,and it is random which alleles survive3. Founder Effect: Sample of the population colonize a new region, and it is randomwhich alleles followed the colonizersConstraints on Evolution1. Lack of genetic variation can prevent evolution of potentially favorable traits2. Evolution must work within the boundaries of universal constraints such as:- Cell size, Protein folding, and Laws of thermodynamic that constrain energytransfers3. Developemental processes also constrain evolutionThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.4. Adaptations involve both fitness costs and benefits- Benefit must outweigh the cost if adaptation is to evolve; the trade-offs must beworthwhileDramatic differences between sexes are known as sexual dimorphism*How is Genetic Variation maintained?*1. Sexual Reproduction- Results in new combinations of genes through crossing over andindependent assortment, and the combination of gametes2. Frequency dependent selection- Polymorphism can be maintained when fitness depends onits frequency in the population 3. Environmental variation- helps to preserve genetic variation4. Sub-populations- In different geographic regions maintain genetic variation5. Mutations- (Changes in DNA) can result new allele
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