IB 150 Unit 3 UIUC

Gene pool

the total collection of all alleles present in a population at a given time

Population genetics

a branch of biology that studies how genes and alleles are distributed and change in population over time

What does population genetics look at?

the gene pool, frequencies of traits (p & q), and patterns across generationssuch as natural selection and genetic drift

What are the 2 parts of the Hardy-Weinberg equation?

the frequency of alleles and the frequency of genotypes

Non-random mating

individuals don’t choose their mates randomly

Natural selection

when some traits help organisms survive and reproduce more so than others

Small population effects (Genetic Drift)

random changes in allele frequencies due to chance, especially in small populationsWh

What are the two types of Genetic drift?

Bottleneck and Founder effectB

Bottleneck effect

the population is drastically reduced (due to disaster, disease, etc.)

survivor’s alleles dominate the future population

Founder effect

a small group starts a new population

their alleles may not represent the original population

Which event occurs because of migration?

a founder event

What event occurs because of a disaster or a random event?

a bottleneck event

Gene flow

the movement of alleles between populations when individuals (or gametes) migrate and reproduce

Metapopulation

a group of separate populations (subpopulations) of the same species that live in different areas/patches but are connected by gene flow

Imagine there’s 2 groups of birds living on nearby islands, some bird fly between islands and breed. What do the islands represent?

subpopulations

Imagine there’s 2 groups of birds living on nearby islands, some bird fly between islands and breed. What do the birds represent?

gene flow

Imagine there’s 2 groups of birds living on nearby islands, some bird fly between islands and breed. What do the birds and islands represent?

a metapopulation

What pattern can you expect to see in allele frequencies in two distinct populations over time due to gene flow?

they become more similar, alleles from pop. A enters pop. B and vice versa, this causes the differences between the pops. to decrease

T/F: Each subpopulation is initially in Hardy-Weinberg equilibrium b/c allele frequencies are stable and genotype proportions follow p², 2pq, and q²

true

What is a key assumption of the Hardy-Weinberg equilbrium?

that there’s no gene flow (so no migration in/out of the population)

Why does gene flow violate Hardy-Weinberg equilibrium?

it introduces or removes alleles and changes allele frequenciesDo

Does gene flow always mean a population is not in HWE?

Yes

Can a metapopulation still be in HWE even if there’s gene flow between subpopulations?

Yes, if it’s only happening within the metapopulation and not from the outside

Why doesn’t gene flow violate HWE at the metapopulation (sometimes)?

because alleles are not entering or leaving the total population but rather mixing internally

Does more gene flow mean closer or further from HWE?

closer

Non-random (assortative) mating

instead of individuals mating randomly, they choose mates based on traits

Positive assortative mating

like mates with like

AA mates with AA

aa mates with aa

Negative assortative mating

AA mates with aa

Non-random mating changes ______ frequencies but not ______ frequencies

genotype ; allele

What are the 3 prerequisites for a trait to evolve via natural selection?

pre-existing phenotypic variation, heritability, differential fitness in a given environment

What does “pre-existing phenotypic variation” mean?

individuals differ in a trait (such as color, size, or behavior)Wha

What does “heritability (genetic basis)” mean?

those differences are at least partly dye to genetic variation, so parents pass them to offspring

What does “differential fitness in a given environment” mean?

based off the environment, some variants lead to higher reproductive success than others (non-random)F

Fitness

number of surviving offspring

What role does the environment play in natural selection?

it determines which traits lead to a higher fitness (reproductive success)

Relative fitness

how successful a genotype or phenotype is at reproducing compared to others in the same population

Absolute fitness

total number of offpsring an individual produces

______ fitness drives evolution

relativeW

What are the 3 components of fitness?

survival, mating success, fecundity

What does “survival (viability)” mean?

the ability to stay alive long enough to reproduce

• avoid predators, resist disease, tolerate environment

What does “mating success (sexual selection)” mean?

the ability to reproduce

• uses this with displays, colors, behaviors

• involves competition with others

What does “fecundity (reproductive success)” mean?

the ability to reproduce

• number of offspring and the quality/viability of offspring