Evolution: A relative change in allele frequency in a given population over time
1. Mechanisms of evolution
1.1. Selection (D)
1.1.1. Natural Selection (Environment is the agent of selection, directed rather than random)
1.1.1.1. Directional: -one extreme= favored over the other -both phenotypic and genotypic variation decreases -loss in variation because the population becomes specialized
1.1.1.2. De-stabilizing: -two extremes= favored -Phenotypic variation decreases and genotypic variation stays the same
1.1.1.3. Stabilizing: -Middle phenotype = favored -Phenotypic variation decreased, genotypic variation stays the same
1.1.2. Sexual Selection (Access to mates is the agent of selection) -Tends to occur more rapidly than sexual selection
1.1.2.1. Indirect: -Males fight for females and winner gets mate -Strength and weapons selected for
1.1.2.1.1. Intrasexual competition: Males competing among themselves to establish dominance and a hierarchy
1.1.2.2. Direct: -Direct female choice based on evaluation of males -Ornaments and displays selected for
1.1.2.2.1. Intersexual competition: Female assesses then chooses which of the males to reproduce with
1.1.2.3. Runaway Selection -When an offspring inherits both a mothers preference for and expression of a trait Requirements of runaway selection -The preference and the trait have to be genetic -Both sons and daughters get the genes for preference and appearance -Son expresses trait and daughter expresses preference of that trait -Trait must express male quality and enhance the quality of both offspring
1.2. Migration (R)
1.2.1. -Random -Variation can increase or stay the same -Movement of alleles into a population.
1.3. Mutation (R)
1.3.1. -Random -Increases variation -Random change in DNA sequence
1.4. Genetic Drift (R)
1.4.1. -Random -Decrease in variation -A sampling effect, which results in a loss of alleles from one generation to the next
2. Genes: Segment of DNA
2.1. Allele -Version of a gene
2.2. Genetic contribution: Evolution supports any strategy by females that increased her tendency to choose males whose genetic contribution enhances the quality of her offspring
2.3. Evolutionary Potential: amount of genetic variation in a population
2.4. Developmental Stability: -the ability of an organism to grow into itself (manifest itself physically) according to its genetic blueprint; bilateral symmetry - symmetry of sides reflects developmental stability
2.5. Reproductive Fitness: An individual’s lifetime reproductive success (based on the number of copies of their genes they pass on through their lifetime to their offspring, and whether or not their offspring pass on those genes)
2.5.1. Lifetime Reproductive Success The total number of offspring an organism has during its lifetime
2.6. Condition: -A reflection of an organism's probability of surviving and reproducing -Indicated by their physical fitness, health, and energy -Influences their ability to develop and display ornaments and other fitness indicators
2.6.1. Fitness Indicator: An indication of the condition (probability to survive and reproduce) of an individual Helps assess male quality
2.6.1.1. Honest Signal -When an ornament is an accurate representation of an organism’s condition/fitness
2.6.1.2. Fitness Matching Model
2.6.1.2.1. Fitness Pairing Assortative mating based on similar quality level: → Highest with the highest → Lowest with the lowest
2.6.1.2.2. Fitness Spreading occurs because the differential reproductive success between high and low quality males will increase over generations, leading to an increase in the rate of change in the population through assortative mating Because individuals with the same phenotypes are mating more often than would be expected with random mating, so those traits will be passed on more often and become more prevalent in the population faster
2.6.1.3. Fitness Marketing - Heavy investment in certain ornaments: - Creates artificial display of fitness level → enables mating with higher fitness mates.
2.6.1.4. Male Displays Advertisement of quality to other males/females. - Creates/maintains hierarchy - Attracts mates immediately/ for future - Females constantly conduct mate assessment even if they can’t reproduce (in the moment). Once free → select for individuals who advertise qualities.
2.6.2. 3 requirements Must be complex (reflects a wide range of genomes), costly to produce, and highly heritable
3. Mating Systems: The pattern of association amongst breeding individuals
3.1. Primate Distribution based on food
3.1.1. Herem: Food resources are patchy and in small clumps High Intrasexual competition amongst and indirect sexual selection amongst males: Because the bigger the group of females, the more males he has to fight off thus excluding other males Mating system: Polygny where one male mates with many females
3.1.1.1. Sexual Dimorphism Difference between two sexes of a species Degree of dimorphism is indicative of the level of competition for mates (difference in reproductive success)
3.1.2. Multi-Male, Multi-Female Food is highly concentrated in one area (large patches) Many females are attracted to the area creating too much competition for a single male to monopolize (because a single male cannot outcompete the other males to be the only one to reproduce)-----> leads to multi male-multi female groups Leads to weaker sexual selection and polygamy amongst both sexes
3.1.3. Uniformly Dispersed: Food resources spread out evenly, so females will spread out evenly Males can't monopolize resources or females Little to no sexual selection Mating system: monogamy or serial monogamy
4. Evolutionary Potential: Amount of genetic variation in a population
4.1. R Selectionists: -high evolutionary potential because they are generalists = easy to adapt to environmental change
4.2. K Selectionists: -low evolutionary potential because they are specialists = hard to adapt to environmental change
5. Rate of evolution: The rate at which the relative allele frequency changes in a population
6. Mate Assessment Evolution supports any strategy by females that increased her tendency to choose males whose genetic contribution enhances the quality of her offspring (genetic contribution)
6.1. Try A Dozen -Interview a dozen mates and remember the best one -After you've gone through them all, pick the next one you see that is better than the best of the 12 -quicker and more efficient than 37%
6.2. 37% rule -Estimate how many will apply -Find the best of the 37% -Pick the first one that is better than the best in the remaining 63%
6.3. Courtship Strategies
6.3.1. Courtship feeding: Males give females food during courtship to provide energy for offspring production. Direct parental investment.
6.3.2. Collective Courtship: Any effort you make that helps your relatives to find good mates helps your own genes to spread (inclusive fitness).
6.3.3. Copulatory Courtship: -copulation that provides mutual evidence of fitness through mutual pleasure. -Through this females mate with many males to test them as sexual partners, and then choose who they would allow to inseminate the
6.3.4. Parental Care As A Courtship Strategy: -explains why males who are dating a female who already has offspring would be kind to that female's offspring. Shows the female that the male is not of concern of committing infanticide. Also if males help females with their "chores"/activities that are costly and they need to do, this makes females more likely to have the desire/opportunity to mate with that male