evolution final 2023

human virulence is side effect of traits that are adaptive in the pathogen's normal habitat, for pathogens that do not usually have a human host

pathogens that live for many generations in single host aren't under selection for transmissibility

damage to host is acceptable if it increases the chances of transmission to new hosts

coat protein that helps virus bind to host cells, recognized by the host immune system

strains that are rapidly acquiring amino acid substitutions in sites under positive selection

parts of the protein of the virus that the immune system recognizes and remembers

Species is a group of populations whose members have the potential to produce fertile offspring.

defines a species as the smallest group of individuals that share a common ancestor

characterizes a species by body shape and other structural features

species concept using bacteria and lateral gene transfer

formation of species with physical isolation

formation of new species in the same range- due to other barrier

condition in which an organism has extra sets of chromosomes, can create rapid sympatric speciation

allopatric speciation that occurs when something in the environment separates organisms of the same species into separate groups

the movement of organisms from one place to another to create new species

must occur to split species after isolation. reasons- adaptation to different habitats, assortative mating, more mutations

hybrids have reduced fitness

where geographic ranges of 2 species overlap

morphological differences between taxa

number of taxa and relationships between taxa

ranges of trait values may be occupied or not, usually uneven- theoretical range is broader than observed range

Pattern of evolution in which long stable periods are interrupted by brief periods of more rapid change

Species evolve by the accumulation of many small changes over a long time period

rapid increase in disparity and diversity, driven by ecological opportunity or morphological innovation

most gene flow is from continent to island. every individual that comes from mainland significantly impacts allele frequencies in island gene pool, way less impactful for mainland gene pool

2 islands gene pools are more equally influence by each other

describes the effect of random chance on allele frequencies. random

= xbar - mu

actual mean

sample mean

example of genetic drift, allele frequencies of those who migrate may not represent frequencies of population

The formation of new species in populations that are geographically isolated from one another.

probability of an allele becoming fixed due to random chance is equal to its starting frequncy

happens on the way to fixation

heterozygosity in the next generation

= Hg (1- 1/2N)

fixation index, models loss of heterozygosity in isolated subpopulations

= (Ht-Hs)/Ht

expected heterozygosity if entire population is in HWE, 2pq

observed average heterozygosity across all subpopulations

loci that are not under selection give better idea of when and how fast drift acts, good for molecular clock

both sexual selection and inbreeding

mating with genetic relatives, exacerbated by small population sizes, does not change allele frequencies but increases proportion of homozygotes

result of increased homozygosity, deleterious recessive alleles are more likely to be expressed in this population

When a pair of alleles from two loci are inherited together in the same gamete more/less often than random chance would expect, increased by inbreeding

multilocus genotype of a chromosome or gamete

physically proximate, less likely to be separated by crossing over during meiosis

genotype of a chromosome at one locus is independent of its genotype at the other locus

coefficient of linkage disequilibrium

frequency of each haplotype in population

=gABgab - gAbgaB

recombination rate, probability of crossing over

reduces LD by crossing over during meiosis generating new haplotypes

the less closely linked it is to a certain haplotype

young and under positive selection

describes accumulation of deleterious mutations in an asexual population and loss of genetic diversity to drift

traits that show continuous variation ex. height, controlled by many different loci and environmental factors

marker locus, helps identify loci that contribute to quantitative trait. if M predicts average phenotype, marker is linked to quantitative trait locus

quantitative trait loci

variance

V genetic / V phenotypic

Vg + V environmental

= Vg/ Vg+Ve

narrow sense heritability, equal to slope of least-squares regression line on plot of midparent and midoffspring trait values

trait is more heritable, identical twins will have more similar trait values than dizygotic twins

mean trait value of population

mean trait value of individuals that reproduce

the difference between the mean of the group selected for reproduction and the mean of the entire population, s = tstar-tbar

plots relative fitness vs trait value, connects trait value to fitness

calculates response to selection

R = h2s

changes the average trait value, moves curve over

decreases variance of trait without changing the average trait value

trait or integrated suite of traits that increases the fitness of its possessor, process in which a lineage evolves a trait that confers higher fitness

how to test if trait is adaptive

higher investing parent

lower investing parent

reproductive success limited by resources and time

reproductive success limited by number of mates

sex with heavy investment in offspring is choosy about mating, one sex exacting selection on another

sex with light investment in offspring will compete to mate, same sex exacting selection on each other

adaptations for display or combat, sneaky behaviors

"sneak" in and mate with females when the dominant or territorial male is not looking, do not fight or display. can be equally fit as competitive strategies

competition between sperm of different males to fertilize eggs

individual killing the offspring of other males to increase own fitness

daughters preferred trait value often matches brothers measured trait value, increases likelihood of brothers mating success. "sexy sons hypothesis"

arbitrary, exploit sensory biases, increases resources available, signals that individual has good genes

benefits fitness of actor and recipient, ex. communal nesting

benefits actor at expense of recipient, ex. cane toad eggs eat each other

benefits recipient at expense of the actor, ex. ground squirrel alarm calls

harms both actor and recipient, ex. bacteria making toxins that kill other strains of their species

Individual's own reproductive success

reproductive success of relatives

direct fitness + indirect fitness

predicts when altruistic behavior will occur, B*r - C > 0

relatedness

cost of direct fitness actor gives up

benefit of direct fitness recipient gains

probability that shared allele is identical by descent

shared allele is shared because was present in an ancestor