BIO201 UNIT 3 LEC1-4

Variation

Differences among individuals within a population or species

Common perspective on variation

Personal observation represents the true range, while outliers are ignored

Biological perspective on variation

Observed variation is a tiny fraction, and outliers represent important new variation

Three processes that create genetic variation

Mutation, genetic recombination, and independent assortment

Association study

A study that tests for a relationship between variables without manipulation

Pattern vs. process in evolution

Pattern is what is observed, whereas process is what causes the pattern

Individual

A single member of a population

Population

A group of individuals of the same species living in the same area

Species

A group of potentially or actually interbreeding organisms that can produce fertile offspring

Temporal variation

Change over time within a single population

Spatial variation

Differences across locations between populations

Range of variation

The spread of variation from minimum to maximum values

Frequency of variation

How common each variant is within a population

Trend

Consistent, directional change in data over time

Association in data

A relationship where one variable changes similarly to another

Significant feature in data

An aspect of data relevant to explaining a pattern

Random process

A process characterized by a lack of order, predictability, or pattern, driven by chance

Non-random process

A process characterized by order, predictability, and pattern, driven by selection

Biological fitness

Reproductive success, measured by passing alleles into future generations

Measurement of biological fitness

The number of surviving offspring produced in an individual's lifetime

Individual fitness

The reproductive success of one individual organism

Genotypic fitness

The average number of surviving offspring among all members of a specific genotype

Calculation of genotypic fitness

Averaging individual fitness across all members of that genotype

Influence of random processes on genotype fitness

Random processes (chance) do not influence genotype fitness

Influence of non-random processes on genotype fitness

Non-random processes (selection) influence individual fitness, which averages into genotype fitness

Cause of genotypic fitness changes across environments

Changes in which phenotypes match the environment, resulting in different fitness levels for genotypes

Genetic drift

Random change in allele frequencies due to chance

Population bottleneck

An event where population size drops sharply

Outcome of a population bottleneck

Genetic drift, or the change in allele frequencies caused by the bottleneck event

Founder event

An event where a small group breaks off from a main population to establish a new, smaller population

Effect size rule

Smaller sample sizes result in larger effects of genetic drift

Populations most affected by genetic drift

Small populations

Neutral traits

Traits that do not affect survival or reproduction

Reason to use neutral traits to detect drift

Frequency changes reflect chance events rather than selection

Anomaly in data

A data point that seems out of place and does not follow nearby patterns

Conceptual model sequence for non-random processes

Individual fitness $\rightarrow$ Genotype fitness $\rightarrow$ Allele/phenotype frequencies

Conceptual model sequence for random processes

Directly influences allele/phenotype frequencies (does not influence genotype fitness)

Population size effect on genetic drift

Large population = small effect of drift; small population = large effect of drift