D4.1 Gene Pools (HL)

Vocabulary flashcards summarising major terms from the lecture on biodiversity, gene pools, allele frequencies, selection types, artificial selection and Hardy–Weinberg principles.

Biodiversity

The variety of life within a given area, measured by the number of species and the size of their gene pools

Gene Pool

The sum total of all alleles for all genes present in a population

Allele Frequency

The relative proportion of a specific allele within a gene pool

Cumulative Change

Gradual alteration in allele frequencies over time that drives evolution

Heritable Characteristic

A trait that can be passed from parents to offspring via genes

Neo-Darwinism

Modern evolutionary theory combining natural selection with genetics

Natural Selection

Evolutionary process in which environmental pressures favor certain alleles, altering their frequencies

Selection Pressure

An environmental factor that affects an organism’s chances of survival and reproduction

Beneficial Allele

A gene variant that increases an organism’s fitness under specific conditions

Detrimental Allele

A gene variant that decreases an organism’s fitness under specific conditions

Directional Selection

Natural selection favoring one phenotypic extreme, shifting the population distribution

Stabilising Selection

Natural selection favoring intermediate phenotypes, reducing extremes

Disruptive Selection

Natural selection favoring both phenotypic extremes, producing a bimodal distribution

Continuous Variation

Range of phenotypes forming a normal distribution within a population

Bimodal Distribution

Phenotypic spread with two distinct peaks, typical of disruptive selection

Genetic Drift

Random changes in allele frequencies, especially in small populations

Gene Flow

Movement of alleles between populations through migration or breeding

Artificial Selection

Human-directed breeding to enhance desired traits in future generations

Selective Breeding

The deliberate mating of individuals with preferred traits to influence offspring characteristics

Biological Fitness

An organism’s ability to survive and reproduce in its environment

Hardy-Weinberg Equation

p + q = 1 and p² + 2pq + q² = 1; predicts allele and genotype frequencies

Hardy-Weinberg Equilibrium

State in which allele and genotype frequencies remain constant generation to generation

Genetic Equilibrium Conditions

No mutation, random mating, no gene flow, large population, no natural selection

Dominant Allele (p)

Allele that masks the effect of a recessive allele in heterozygous individuals

Recessive Allele (q)

Allele whose effect is masked by a dominant allele in heterozygotes

Homozygous

Having two identical alleles for a given gene (AA or aa)

Heterozygous

Having two different alleles for a given gene (Aa)

Diploid

State of having two copies of each chromosome and therefore two alleles per gene

Antibiotic Resistance

Example of directional selection where resistant bacterial alleles increase after drug exposure

Peppered Moth Pigmentation

Example of disruptive selection where different colored moths thrive on matching tree bark

Wild Mustard Derivatives

Broccoli, cabbage, kale and others produced via artificial selection of Brassica oleracea

Dog Breeds

Pugs, corgis, beagles, etc., created through selective breeding for specific traits

Extinction Risk

Higher probability of species loss associated with small gene pools

Normal Distribution

Bell-shaped curve representing phenotypic variation in many traits

Phenotypic Extreme

Trait value at one end of a variation range, often targeted in selection types