Zusammenfassung_Gemini_Flashcards

The process of organismal change and diversification through generational time from shared common ancestry. (Descent with modification)

Anagenetic: changes over time primarily through mutation and recombination. Cladogenetic: speciation occurs when a species or lineage branches and gives rise to two new species.

Complex forms, phenotype determined by genotype (central dogma), easiest visible in higher order taxa, not random, not progressing towards a goal. Evolution ≠ natural selection ≠ adaptation.

Hierarchical organization of life, homology, embryological similarities, vestigial characters, convergence, suboptimal design, geographic distributions, intermediate forms, fossils, molecular evidence.

Plato: metaphysical world. Aristotle: epigenesis (embryological differentiation) and pre-formation (preprogrammed unfolding).

Theory of inheritance of acquired characteristics (physiological changes acquired during an organism's life can be transmitted to offspring).

Δq = up - vq = u(1-q) - vq = u - q(u+v).

At equilibrium:

Δq = 0 → q = u / (u+v).

u/v = q/p.

q' = q + Δq = q + u - q(u+v).

qn = q̂ + (q0 - q̂)(1 - u - v)^n

Random change of allele frequencies in finite populations

Haploid population without sexes, finite size (2N individuals), random sampling, discrete generations. Null-model in population genetics.

K: number of A alleles.

p = K/2N.

P(K;2N;p) = (2N choose K) * p^K * (1-p)^(2N-K).

Effects of genetic drift are stronger in small populations.

u: mutation rate from A to a. v: mutation rate from a to A.

Δq = 0 → q = u / (u+v)

Represents the change in the frequency of allele 'a' in one generation.

Represents the frequency of allele 'a' after n generations.

Represents the initial frequency of allele 'a'.

Represents the binomial coefficient, calculating the number of ways to choose K items from a set of 2N items.

Represents the frequency of allele A.

Represents the frequency of allele a.

Represents the number of A alleles.

Represents the total number of individuals in the population. ## Flashcard 22

Formula for change in allele frequency due to mutation.

Represents the rate of mutation from A to a, considering the frequency of A (1-q).

Represents the rate of mutation from a to A, considering the frequency of a (q).

Formula for equilibrium frequency of allele 'a' when only mutation is occurring.

Ratio of forward and reverse mutation rates at equilibrium equals the ratio of allele frequencies.

Formula for calculating the frequency of allele 'a' in the next generation.

Formula for calculating the frequency of allele 'a' after n generations, considering mutation.

Random fluctuations in allele frequencies due to chance events, especially in small populations.

A null model in population genetics describing allele frequency changes due to random sampling in small, idealized populations.

A population where individuals have only one set of chromosomes.

Generations do not overlap; parents die before offspring reproduce.

Stronger effects; allele frequencies can change rapidly and randomly, potentially leading to fixation or loss of alleles.

When an allele reaches a frequency of 1 (100%) in the population.

Calculated using the binomial probability formula: P(K;2N;p) = (2N choose K) * p^K * (1-p)^(2N-K).

Variance measures the spread of allele frequencies across populations or generations. It quantifies how much the allele frequencies are likely to deviate from the mean.

Variance in allele frequencies increases over time due to random genetic drift. This means that allele frequencies become more spread out and unpredictable as generations progress.

The variance of allele frequency (p) is calculated as: Var[p] = (p * q) / (2N) where p is the frequency of allele A, q is the frequency of allele a, and N is the population size.

The formula shows that variance in allele frequency is inversely proportional to population size (N). This means that smaller populations have higher variance and experience more rapid and random changes in allele frequencies.

This formula is significant because it helps us understand the role of genetic drift in shaping allele frequencies in populations, especially in relation to population size.

Heterozygosity (H) is the probability of finding two different alleles at two homologous loci within a population or individual. It represents the genetic diversity or variability within a population.

Inbreeding reduces heterozygosity by increasing the likelihood of individuals inheriting identical alleles from their common ancestors. This leads to a decrease in genetic diversity.

Heterozygosity (H) can be calculated as: H = 1 - (homozygosity) where homozygosity is the probability of an individual having two identical alleles at a specific locus.

The change in heterozygosity (H') in one generation can be calculated as: H' = (1 - (1 / (2N))) * H where N is the population size and H is the initial heterozygosity.

The formula indicates that heterozygosity decreases over time due to genetic drift, and the rate of decrease is faster in smaller populations.

Heterozygosity (H_t) after t generations can be calculated as: H_t = (1 - (1 / (2N)))^t * H_0

where N is the population size, t is the number of generations, and H_0 is the initial heterozygosity.

Heterozygosity is a crucial measure of genetic diversity within a population. It helps us understand the potential for adaptation and evolution in response to environmental changes.

The mean census number (Nc) is the average number of individuals in a population over a certain period, while the effective population size (Ne) is the size of an idealized population that experiences genetic drift at the same rate as the actual population.

Factors such as sex ratio differences, fluctuations in population size, overlapping generations, and population structure can lead to a smaller effective population size compared to the mean census number.

The effective population size (Ne) can be calculated as: Ne = t / Σ(1 / Ni) where t is the number of generations and Ni is the population size at each generation.

The effective population size is a crucial parameter in understanding the rate of genetic drift and its impact on allele frequencies and genetic diversity within a population.

The Wright-Fisher model is a fundamental null model in population genetics that describes the random fluctuations of allele frequencies due to genetic drift in small, idealized populations.

The key assumptions include a finite, constant population size, random mating, non-overlapping generations, no selection, no mutation, and no migration.

The Wright-Fisher model explains that allele frequencies change randomly due to chance events in small populations, and the rate of change is inversely proportional to the population size.

The Wright-Fisher model provides a baseline for comparison when studying the effects of other evolutionary forces, such as natural selection, mutation, and migration, on allele frequencies in populations.

"Heterozygosity lost" refers to the reduction in heterozygosity (genetic diversity) in a population over time due to factors like genetic drift and inbreeding.

The rate of heterozygosity loss is inversely proportional to the effective population size (Ne). Smaller populations lose heterozygosity faster than larger populations.

The proportion of heterozygosity lost (Ht/H0) after t generations can be calculated as: Ht/H0 = (1 - (1 / (2Ne)))^t where Ht is the heterozygosity at time t, H0 is the initial heterozygosity, Ne is the effective population size, and t is the number of generations.

Understanding "heterozygosity lost" helps us assess the rate of genetic diversity loss in populations, which has implications for their adaptability and long-term survival.

The infinite sites model assumes that mutations occur at unique sites within a gene, while the infinite alleles model assumes that every new mutation creates a novel allele not previously present in the population.

These models are used to simplify the analysis of genetic variation and make predictions about the expected levels of diversity in populations.

"Mutation-drift balance" refers to the equilibrium state in which the rate of new mutations entering a population is balanced by the rate of loss of genetic diversity due to random genetic drift.

The equilibrium heterozygosity (Ĥ) can be calculated as: Ĥ = (θ) / (1 + θ) where θ = 4Neμ, Ne is the effective population size, and μ is the mutation rate.

The mutation-drift balance helps explain the observed levels of genetic diversity in natural populations and how they are influenced by mutation rates and population sizes.

The "neutral rate of substitution" refers to the rate at which neutral mutations (mutations with no effect on fitness) become fixed in a population due to random genetic drift.