Genetics and Evolution: Key Concepts for Biology Students

frequency

the proportion of a specific allele or genotype within a population's total gene pool

frequency vs percentage

converting between decimal form (like 0.35) and percent form (35%) to express allele or trait frequency

accuracy check

verifying that all frequencies or percentages add up to 100% (or 1.0) to ensure data consistency

phenotype → genotype

identifying the genetic makeup (alleles) responsible for an observable physical trait

genotype → phenotype

determining how genetic information (alleles) produces observable traits through gene expression

Hardy-Weinberg use

using p² + 2pq + q² = 1 to test if a population's allele frequencies are stable (no evolution)

Hardy-Weinberg meaning

a principle stating that allele and genotype frequencies remain constant if no evolutionary forces act

phylogenetic tree

a branching diagram that shows hypothesized evolutionary relationships among organisms based on shared traits

gene vs allele

a gene is a segment of DNA coding for a trait; alleles are different forms or variations of that gene

genotype-environment interaction

how environmental conditions influence how genes are expressed, affecting phenotype

evolution definition

a change in the genetic makeup (allele frequencies) of a population across generations

allele frequency calculation

measuring how common a particular allele is by dividing its count by the total number of alleles

gene pool vs genotype

a gene pool includes all alleles in a population; a genotype refers to one organism's pair of alleles for a trait

Hardy-Weinberg interpretation

comparing observed and expected genotype frequencies to determine if evolution is occurring

forces of evolution

processes that change allele frequencies: natural selection, mutation, gene flow, and genetic drift

natural selection

individuals with advantageous traits survive and reproduce more, passing those traits to offspring

sexual selection

traits that improve mating success become more common (e.g., bright feathers, mating calls)

artificial selection

humans select and breed organisms with preferred traits, directing evolution intentionally

stabilizing selection

selection that favors average traits, reducing variation in a population

directional selection

selection that favors one extreme trait, shifting the population's overall phenotype in that direction

disruptive selection

selection that favors both extremes of a trait, increasing variation and possibly leading to speciation

phylogeny meaning

the evolutionary lineage or history of species, showing common ancestry and divergence

human genotypes and ancestry

genetic variation among human groups caused by adaptations to ancestral environments

scientific racism

the false use of biology to justify racial hierarchies; disproven by genetics and evolutionary science

evolution and organization levels

evolution affects all biological levels — DNA, cells, organisms, populations, and ecosystems

testing evolution scientifically

forming hypotheses and collecting evidence (e.g., fossil, molecular data) to detect evolutionary change

fossil record

preserved remains or traces showing species' gradual changes and transitions over geological time

biogeography

study of species' geographic distribution that reveals patterns of common ancestry and adaptive radiation

homologies

similarities in structure, genes, or proteins that suggest common evolutionary origin

embryology evidence

similarities in early developmental stages that indicate shared ancestry among species

resistance examples

evolution seen today as bacteria, insects, or weeds develop resistance to antibiotics or chemicals

selective pressures

environmental challenges (predators, climate, disease) that favor survival of specific traits

allele frequency change

measurable shifts in genetic variation that reflect evolution across generations

evolutionary mechanisms

natural selection, sexual selection, drift, gene flow, and mutation that drive changes in populations

Hardy-Weinberg conditions

evolution does not occur if: population is large, mating is random, no migration, no mutation, no selection

Hardy-Weinberg equation purpose

used to calculate expected allele and genotype frequencies and check if a population is in equilibrium

human skin color variation

polygenic trait influenced by multiple genes and sunlight exposure, adapted for UV protection and vitamin D synthesis

race concept

a social construct without biological basis; humans share over 99.9% of their DNA

impacts of racial ideas

false biological assumptions about race leading to stereotypes, inequality, and discrimination

What is natural selection?

The mechanism through which evolution occurs, where organisms with traits that enhance survival and reproductive success are more likely to pass those traits to their offspring.

What are adaptations?

Traits or features that enhance an organism's ability to survive and reproduce in its environment.

What is genetic variation?

The raw material upon which natural selection acts, arising from mutations, recombinations, and genetic drift.

What does the fossil record demonstrate?

The progression of life, showing that simpler organisms are found in older layers.

How does biogeography relate to evolution?

Species' global distribution is shaped by both evolution and continental drift.

What are anatomical homologies?

Features inherited from common ancestors that suggest evolutionary relationships among species.

What are molecular homologies?

Similarities in protein sequences and DNA among different species that provide evidence for common ancestry.

What does comparative embryology reveal?

Shared early developmental stages among different organisms, suggesting common ancestry.

What is antibiotic resistance?

The survival of bacteria with resistance traits due to evolution, leading to challenges in treating infections.

What are selective pressures?

Environmental factors that influence the survival and reproductive success of individuals within a population.

What is genetic drift?

Random chance events that change allele frequencies in a population, often having a larger effect in small populations.

What is mutation in the context of evolution?

Random changes in DNA that create new alleles in a population.

What is artificial selection?

The process by which humans selectively breed organisms for desired traits.

What is the Hardy-Weinberg equilibrium?

A theoretical state where allele and genotype frequencies in a population remain constant over generations, indicating no evolution is occurring.

What is the significance of allele frequency?

It refers to the relative frequency of a specific allele variant in a population compared to the total number of alleles for that gene.

What is the genotype?

The genetic makeup of a specific trait, represented by alleles.

What is the phenotype?

The observable characteristics or traits of an organism, determined by its genotype.

What is stabilizing selection?

A type of natural selection that favors average traits in a population.

What is disruptive selection?

A type of natural selection that favors extreme traits at both ends of the spectrum.

What is directional selection?

A type of natural selection that favors one extreme trait over others.

What is gene flow?

The transfer of alleles or genes from one population to another, which can change allele frequencies.

What is the role of environmental factors in evolution?

They create selective pressures that influence which traits are advantageous for survival and reproduction.

What is the significance of mutations in evolution?

They introduce new genetic variations that can be acted upon by natural selection.

What is the relationship between evolution and allele frequency?

Evolution occurs when there are changes in allele frequencies within a population over time.