evolution 2 exam

Neutral theory and Kimura

advantageous mutations are exceedingly rare and most alleles of most genes are selectively neutral; predicts that for most genes in most populations, the rate of evolution will be equal to the neutral mutation rate

Linkage

the tendency for alleles at different loci on a chromosome to be inherited together (genetic linkage)

linkage disequilibrium

non-random association between the genotype at one locus and the genotype at another locus

Linkage equilibrium

genotypes at one locus are randomly distributed with respect to genotypes at another locus

Admixture

occurs when individuals from two or more previously separated populations begin interbreeding; results in the introduction of new genetic lineages into a population

Outcrossing

the mating of unrelated individuals

recombination

creation of new combinations of alleles during sexual reproduction

Red Queen Hypothesis

the notation that sex is adaptive during perpetual arms races between biological antagonists; proposes that organisms must constantly adapt, evolve, and proliferate not merely to gain reproductive advantage, but also simply to survive while pitted against ever-evolving opposing organisms in an ever-changing environment

Two-fold cost of sex

asexual female produce twice as many granddaughters as sexual females; ultimately, asexuals should take over

Maynard-Smith null model

1) female’s reproductive mode does not effect # of offspring 2) female’s reproductive mode does not affect offspring survival

evolutionary ‘arms race’

a pattern of coevolution where two or more species reciprocally affect each other’s evolution through continuous, antagonistic adaptations and counter-adaptations

quantitative traits

measurable phenotypes that vary continuously across a population; many loci, selection on single locus weak

broad-sense heritability

(H2) measures the proportion of total phenotypic variance (VP) in a population caused by all genetic factors (VG), including additive, dominance, and epistatic variance (H2 = VG/VP), ranging from 0 to 1, and indicates how much of a trait’s variation is genetic versus environmental

narrow-sense heritability

(h2) is the proportion of phenotypic variance (VP) due to the additive genetic variation (VA), making it crucial for predicting selection response in breeding (h2 = VA/VP), ranging from 0 to 1 with higher values indicating greater resemblance between parents and offspring

parent-offspring regression

statistical method used to estimate narrow-sense heritability of quantitative traits by analyzing the similarity between parents and their offspring (study graphs)

phenotypic variation (VP)

the total variation in a trait

Directional selection

fitness consistently increases or decreases with the value of a trait (changes the trait average, reduces the variation)

Stabilizing selection

individuals with intermediate values of a trait have highest fitness (no change in trait average; reduces the variation)

Disruptive selection

individuals with extreme values of a trait have the highest fitness (no change in trait average; increases the variation)

Selection gradient

slope of the line fit to the association between a trait and fitness (survival or reproduction); selection gradient = selection differential/variance of trait

Selection differential

the difference between the mean phenotype of individuals selected to be parents and the mean phenotype of the entire population

R = h2S (Response = heritability*selection differential)

(breeder equation) predicting how a trait changes across generations

sexual dimorphism

the systematic difference in form, color, size, or structure between males and females of the same species, beyond their reproductive organs

selection on multiple traits

the simultaneous improvement of several characteristics in breeding or evolutionary contexts, utilizing genetic correlations to enhance overall merit

phylogenetically independent contrasts

a method for analyzing comparative data across species by transforming non-independent trait values (due to shared ancestry) into statistically independent data points (look at graph)

sexual selection

a mode of natural selection in which some individuals out-reproduce others of a population because they are better at securing mates

asymmetric parental investment

unequal contribution of time, energy, and resources by male and female parents toward their offspring

intrasexual selection

within a given sex, by intimidating, deterring or defeating same-sex rivals

intersexual selection

between the sexes, by making themselves attractive to the opposite sex

convergent evolution

the process where distantly related organisms independently evolve similar traits to adapt to similar environmental pressures or niches, rather than inheriting them from a common ancestor

Migration

refers to the movement of individuals or genetic material between populations, introducing new genetic variants and altering allele frequencies

genetic drift

fundamental mechanism of evolution where allele frequencies within a population change randomly over time due to change events, rather than natural selection

Hitchhiking

an evolutionary process where a neutral or deleterious gene increase in frequency because it is physically linked to a nearby beneficial gene undergoing strong positive selection; occurs when a strong positive selection acts on a particular amino acid change

founder effects

type of genetic drift occurring when a new, isolated population is established by a very small number of individuals from a larger, original population

Muller’s ratchet

an evolutionary process in which asexual populations irreversibly accumulate deleterious mutations over time, leading to decreased fitness

evolutionary constraint

restrictions, biases, or limitations on the variability of phenotypes that a biological system can produce, preventing or slowing down potential adaptations

parental investment

any parental expenditure (time, energy, resources) that benefits offspring, increasing their survival and reproductive success at the expense of the parent’s ability to invest in other offspring

Infanticide

adaptive strategy, primarily in males, to increase reproductive opportunities by eliminating rivals’ offspring, reducing female lactation periods, and forcing faster re-breeding

Siblicide

evolutionarily adapted behavior where an animal kills its sibling to monopolize resources, typically driven by food scarcity, competition for parental care, or asynchronous hatching

Adaptation

process by which natural selection increases the frequency of beneficial, heritable traits within a population, enhancing survival and reproduction in specific environment

evolutionary trade-offs

occur when improving one trait (increasing fitness) necessitates a decline in another, as organisms face constraints in energy, time, or genetic resources

Cooperation

process where organisms, from microbes to humans, work together for mutual benefit, increasing reproductive success despite natural selection often favoring competition

parent – offspring conflict

parents and offspring are often in conflict over the amount of parental investment; offspring are selected to demand more resources than parents are selected to provide, because the offspring is 100% related to itself but only 50% to its siblings and parent

Reciprocity

mechanism where individuals help non-relatives, anticipating future returns, which allows cooperation to evolve despite the temptation to defect

multilevel selection

theory that posits that natural selection operates simultaneously across nested biological levels (genes, cells, organisms, and groups) rather than solely on individuals; it explains the evolution of cooperation and complex life by balancing lower-level self-interest against higher-level group benefits

Altruism

a behavior where an organism reduces its down fitness to increase the fitness of another

Spite

behaviors that reduces an actor’s own fitness to harm others

Mutualism

evolves as a cooperative, often symbiotic relationship between different species that enhances their shared or individual fitness, transforming ecosystems and driving biodiversity

Selfishness

strategy that maximizes an individual’s reproductive fitness and gene transmission, often at the expense of others

Hamilton’s rule Br – C > 0

states that social behavior (specifically altruism) evolves when the genetic relatedness (r) multiplied by the benefit to the recipient (b) exceeds the cost to the donor (c)

kin selection

an evolutionary strategy where organisms favor the survival and reproduction of relatives, even at the cost of their own, because those relatives share a portion of their genes

male-male competition

sexual selection pressures males to compete for mates, driving the development of specialized “armaments” (horns, antlers) and behaviors

female choice

powerful evolutionary mechanism where females act as reproductive gatekeeper, selecting mates with specific traits (like strength, elaborate ornaments, or high-status indicators) which often signal superior genes and improved offspring survival

life history evolution

an individual’s pattern of allocation, throughout life, of time and energy to various fundamental activities, such as growth, repair of cell and tissue damage, and reproduction

mutation accumulation hypothesis

proposes that aging evolves because the force of natural selection weakens at older ages, allowing slightly deleterious mutations that act late in life to accumulate in the genome

rate of living theory of aging

an organism’s lifespan is inversely proportional to its metabolic rate

evolutionary theory of aging

posits that senescence arises because of the strength of natural selection declines with age, as most organisms die from extrinsic causes before reaching old age

antagonistic pleiotropy hypothesis

proposes that gene enhancing fitness, survival, or reproduction early in life are favored by natural selection, even if they cause detrimental, aging-related effects later in life

grandmother hypothesis

human menopause and long post-reproductive lifespans evolved because ancestral grandmothers enhanced their inclusive fitness by helping raise grandchildren, enabling their daughters to have more children

inclusive fitness (definition, data supporting)

genetic success that can be achieved through both direct reproduction (offspring) and indirect means (aiding relatives who share genes)

evolution and cancer (p53)

a transcription factor triggered when telomeres get too short that initiates the expression of proteins that cause permanent non-dividing stage and/or programmed cell death; research suggests a trade-off between cancer risk and aging

Monophyly

group or clade is a grouping of organisms that includes a single common ancestor and all of its descendants, living and extinct

Paraphyly

taxonomic classification where a group includes a common ancestor and some, but not all, of its descendants, often grouping organisms based on shared ancestral traits rather than exclusive evolutionary history

Polyphyly

set of organisms grouped together that do not share a recent common ancestor often united by homoplasy (similar traits evolved independently) rather than true homology; convergent evolution, where different lineages develop similar characteristics

Synapomorphy

shared, derived trait (apomorphy) inherited from a common ancestor, distinguishing a monophyletic group from others

Parsimony

a phylogenetic method used to reconstruct evolutionary trees by minimizing the total number of character changes (mutations or trait shifts) required to explain the observed data

Phylogenetics

the study of the evolutionary history, relationships, and lines of descent among organisms, visualizing them as branching trees based on genetic or physical similarities

sister species

the closest relatives in an evolutionary tree, arising simultaneously from a single immediate common ancestor