evolution of health & disease midterm #1

what is a hypothesis

a tentative statement about the natural world leading to deductions that can be tested

what is a theory

a well established explanation of the natural world that is based on tested hypotheses; answer to a “why” question

what is a law

statements based on repeated experiments & observations that describe or predict a range of natural phenomena (answers “what” or “how” question)

what is error

the difference between observed/measured values and the true information on nature

what is a bias

any factor that might influence data collection/interpretation; conferring disproportional weight to 1 of many potential interpretations

what is an observation

physical, palpable manifestations of things; anything that can be seen, smelled, tasted, etc.

what is an inference

educated guesses taken after considering all info and data available

what is evolution

• change in the gene pool of a population from generation to generation by processes such as mutation, natural selection, and genetic drift

• change in gene pool composition/frequency over time

• process of adaptation through mutation, allowing more desirable traits to pass onto next generation

• any change to genetic composition of a population

population

all members of a species living in the same area

population genetics

• area of biology investigating change of genetic composition within populations

• study of how selective forces change allele frequencies in a population over time

evolution has ___ direction, ____ purpose, and ____ goal to reach

NO

darwin-wallace theory of evolution by natural selection

1.) resources in nature are scarce, forcing individuals to compete for them (ex: water, food, shelter, mates). some individuals have better qualities enabling them to be better at securing those resources (survival of the fittest)

2.) these individuals will have more reproductive success & pass these advantageous qualities to their offspring. these descendants will eventually make up the whole population

what is mendell’s law of inheritance

1.) law of segregation; gametes only carry 1 of the alleles for each gene

2.) law of independent assortment; genes for different traits are independently passed

3.) law of dominance; some alleles have a stronger signal than others (dominant) & will mask the presence of the weaker one (recessive)

individuals don’t evolve, _____ evolve

species

for evolution to occur, _____ must be passed down from 1 generation to the next

genetic information

what is the finest level of evolution

population genetics

what is a gene pool

• the sum of all genetic material from all individuals in a population

• all alleles that individuals in a population carry

what are frequencies in terms of evolution

genetic variation in gene pool described as relative frequencies (genotype, phenotype, allele)

what does p represent in evolution

the frequency of the dominant allele

what does q represent in evolution

the frequency of the recessive allele

what is the equation for the frequency of genotypes

homozygous dominant + heterozygous + homozygous recessive

p² + 2pq + q² = 1

what is the sum of all frequencies added together (p +q)

1; p + q = 1

what is hardy weinberg equilibrium

under certain ideal conditions, allele frequencies will remain constant from generation to generation in sexually reproducing populations

what are the ideal conditions under hardy-weinberg equilibrium

• no genetic mutation

• no migration of individuals in/out of population

• very large population size

• no natural selection; equal survival & reproduction

• mating combines genotypes at random (no preference)

under the hardy-weinberg principle, if there is no evolution happening, the allele frequencies are the _____

same

what are the applications of the hardy-weinberg principle

1.) determine allele frequencies if assumptions are met

2.) test whether a population is evolving or not

• if the population doesn’t meet the hardy-weinberg expectations, at least one of the conditions if affecting it (selection, mutation, migration, drifting, random mating)

what is a process

mechanisms'; set of events/steps leading to an outcome

what is a pattern

derives from a process; set of accidents that are interconnected

there is ____ single mechanism for evolution

NO

what are the 5 processes of evolution

1.) natural selection

2.) mutation

3.) non-random mating

4.) gene flow

5.) gene drift

what is EES (extended evolutionary synthesis)

• incorporates epigenetics, developmental bias, plasticity, and niche construction to develop a more comprehensive evolution theory

• considers that organisms can pass on acquired traits to offspring through epigenetic changes

• challenges belief that only genetic mutations can be inherited

what is phenotypic plasticity

• the ability of organisms to change phenotypes in response to environmental conditions

• allows rapid adaptation without genetic changes

• phenotypes can be altered to respond to environmental pressures without genetic basis

what is modern synthesis

merges genetic inheritance with natural selection as factors of adaptation/evolution

what is an adaptation

• a heritable trait/behavior that aids survival and reproduction

• attributes that have evolved through natural selection & increase an organism’s reproductive success/fitness directly or indirectly

• result of natural selection, aids reproductive fitness

what is allopatric speciation

speciation via geographic separation

what is behavioral isolation

reproductive isolation when behavior/lack of behavior prevents reproduction

what is convergent evolution

• when groups of organisms independently evolve to similar forms

• 2 unrelated populations deal with similar environmental pressures & find the same optimal solution to them

what is divergent evolution

when groups of organisms evolve in diverse directions from a common point

what is a genetic barrier

a prezygotic barrier where closely related individuals of different species mate, but differences in gamete cells (eggs/sperm) prevent fertilization

what is the gradual speciation model

shows how species gradually diverge over time in small steps

what is habitat isolation

reproductive isolation when species’ populations move to a new habitat and don’t overlap with the same species’ other populations

what are homologous structures

parallel structures in diverse organisms with a common ancestor

what is a hybrid

an offspring of 2 closely related individuals of different species

what is a hybrid zone

area where 2 closely related species interact and reproduce

what is natural selection

• reproduction of individuals with favorable genetic traits that survive environmental change because of those traits; leads to evolutionary change

• selects alleles that selects for beneficial traits/behaviors and selects against deleterious qualities

what is a postzygotic barrier

reproductive isolation occurring after zygote formation

what is reproductive isolation

when a species is reproductively independent from other species (behavior, isolation, location, reproductive barriers, etc)

what is speciation

the formation of new species

what are species

groups of organisms that interbreed and produce fertile offspring

what is sympatric speciation

• speciation occurring in the same geographic space

• errors in meiosis form gametes with extra chromosomes (polyploidy)

what is temporal isolation

differences in breeding schedules; acts as a prezygotic barrier and can lead to reproductive isolation

what is genetic variation

differences in individuals’ form & function allowing some to survive certain conditions better than others

what is a vestigial structure

a physical structure present in an organism with no apparent function; may be from a functional structure in a distant ancestor

_____ must be present for organisms to adapt and change to environmental pressures

genetic variation

what are some examples of evidence of evolution

DNA code, fossil record, homologous & vestigial structures

what must be introduced in order for new species to develop

reproductive barriers

what is the gradual speciation model

species slowly change over time

what is the punctuated equilibrium model of speciation

change quickly occurs from parent generation to new species

what is adaptive evolution

increased frequency of beneficial alleles & decrease in harmful alleles due to selection

what is allele frequency

the rate of a specific allele appearing in a population

what is assortative mating

when individuals mate with those phenotypically similar to themselves

what is the bottleneck effect

• magnification of genetic drift resulting from natural events

• large population passing through occasional periods when only a small number of individuals randomly survive

what is directional selection

selection favoring phenotypes at one end of the spectrum of existing variation

what is evolutionary fitness

an individual’s ability to survive and reproduce

what is frequency-dependent selection

selection favoring phenotypes that are:

• common (positive frequency-dependent selection) or

• rare (negative frequency-dependent selection)

what is genetic drift

• effect of chance on a population’s gene pool

• stems from chance occurrence that some individuals in gene line have more offspring than others

• change in allele frequency due to chance (random/unpredictable events)

what is genetic structure

distribution of different possible genotypes in a population

what is genetic variability

diversity of alleles and genotypes in a population

what is geographical variation

differences in phenotypic variation between geographically separated populations

what is inbreeding

• mating of closely related individuals

• extreme of assortative mating

• mating with close genetic relatives

what is inbreeding depression

• increase in abnormalities & disease in inbreeding populations

• increases frequency of homozygotes

• deleterious recessive phenotypes are more likely to reappear

• population survivability reduces

what is macroevolution

broader evolutionary changes scientists see over paleontological time

what is mircoevolution

changes in a population’s genetic structure

what is nonrandom mating

changes in a population’s gene pool due to forces causing individuals to mate with certain phenotypes more than others

what is population variation

distribution of phenotypes in a population

what is relative fitness

individual’s ability to survive and reproduce relative to the rest of the population

what is selective pressure

environmental factor causing 1 phenotype to be better than another

allele frequencies change as a result of _____ when individuals leave or join the population

gene flow

natural selection acts at the ______ level

individual; selects for those with higher overall fitness compared to rest of population

what is diversifying selection

increased genetic variability by selecting 2 or more distinct phenotypes

what is sexual selection

1 sex has more variability in reproductive success than the other

members of a population vary mostly because of _____

genetic variation

what are the conditions for natural selection to occur

• variation in a trait

• variation in reproductive success

• correlation between reproductive success & the trait

• trait is heritable

what is a mutation

• any alteration on an organism’s genetic structure

• changes in sequence of DNA bases or in chromosome structure

what are the 2 most important characteristics of mutations

• spontaneous; happen at any given time

• random; location, intensity, and effect are unpredictable

what kinds of factors can alter the likelihood & rate of mutations

mutagenic properties; radiation, chemicals, infectious agents, etc.

what is the ultimate goal of all species

to leave copies of their genes to the next generation

what is dissasortative/negative assortative mating

mating with individuals of different phenotypes; increases genetic variance

what is assortative/positive assortative mating

mating with individuals of similar phenotypes; decreases genetic variance

what is selfing

self-fertilization; found in many parasites and plants (ex: malaria, peas)

what is gene flow/migration

movement of existing genes from 1 population to another; alters genotype and allele frequency

what factors affect gene flow

• mobility; physically where/how much organisms can move

• territoriality; tendency of species/population to remain in circumscribed area

• nature of environment; environment can create barriers to gene flow or corridors allowing large gene flow

what are the good effects of gene flow

• can introduce new mutations and rare alleles

• adds variety to gene pool

• can increase survivability of population by increasing spread of good alleles

what are the bad effects of gene flow

• can bring harmful alleles into population

• if migration flux is recurrent, it’s harder to eliminate bad genes

what is the random walk process

movements of object/changes in variable follow no clear discernible pattern or trend

genetic drift occurs in populations of ____ sizes

ALL

• chance effects averaged out in larger populations

• smaller population = more pronounced effects

what is the founder effect

• few individuals become isolated from original larger population

• settle in area without previous members of species

• allele frequencies in founder population can be very different from parent population

what is the biological evolution theory

changes in populations over time through generations of individuals by series of processes resulting in discernible patterns

what are the patterns resulting from biological evolution theory

adaptations, biodiversity, organismal relations

what do direct adaptations do

help organisms get more mates, increase fertility, etc.; directly help mating process