Chapter 15 (Pg )

 To an evolutionary biologist—having more fertile offspring than other individuals  Being adapted to a particular environment increases those chances  BUT, there’s also sexual selection  Not based strictly on environment, but on displays and rituals  Male and female choice

 Small, measureable changes in a population from one generation to the next  Variation itself cannot bring about evolution  Those variations must impart some sort of survival and/or reproductive advantage

 Population genetics: described in terms of the gene pool  Characterized by allele frequencies How common is any given allele in that population Are 99% of the alleles recessive, or is it a combination of multiple alleles?  In this case, you just look at the frequency of individual alleles, not how they are paired  Assumes random mating  Predicts allele frequency in next generation

p = frequency of the dominant allele q = frequency of the recessive allele p 2 + 2pq + q 2 = 1 p 2 = DD 2pq = Dd q 2 = dd

1. No mutations (source of variation) 2. No gene flow in or out of the population (migration can increase variation in a population) 3. Random mating 1. Assortative—mating with similar individuals, divides population into two subgroups 2. Sexual selection—attracting a mate 4. No genetic drift (need a large population) 1. Bottleneck and founder effect 5. No selection

Umm…yeah. These conditions are hardly ever met. So—microevolution happens. These conditions tell us what drive evolution. Can measure the deviation from the equilibrium to measure degree of evolution.

 Individuals show differential survival and reproduction rates based on factors in nature  Predators, competition for food and resources  Non-living factors (temperature, salinity, pH…)

 Directional—when population is pushed toward one extreme or another  Stabilizing—average is selected for, extremes of the trait narrow in range  Disruptive—extremes are favored and middle value decreases in frequency

 Evolution and natural selection have to “work with” what is available  It would be great for birds if they had lightweight, titanium bones, but bird’s ancestors had Ca based bones  Blind spot in vertebrate eyes  Wisdom teeth that cause us problems  Human lower back problems  Sometimes, the benefit is worth the cost

 Hidden benefits to “bad” alleles—malaria and sickle cell trait  Gene flow into a population  New mutations  Changing environments  New gene combinations due to sexual reproduction  Heterozygotes “hide” recessive alleles— natural selection works on traits, not individual alleles