Darwinism

Artificial selection demonstrates the power of selective breeding to dramatically modify organisms, suggesting that a similar process (natural selection) operates in nature over longer periods.

The selective pressure (predation) favors one extreme of the phenotypic spectrum (dark fur), causing a directional shift in the population's average fur color over time.

Differential reproductive success is the core of natural selection; it means that individuals with traits better suited to the environment leave more offspring behind than less-suited individuals.

Evolution is the broader phenomenon (descent with modification), whereas natural selection is one of the primary mechanisms (alongside drift, gene flow, mutation) that drive it.

Wallace independently co-discovered the theory of natural selection, prompting Darwin to quickly publish his own extensive findings in "On the Origin of Species" in 1859.

The Modern Synthesis integrated Darwinian natural selection with Mendelian genetics, mathematical population genetics, and chromosome theory to explain evolution at the molecular and population levels.

Because both extreme phenotypes (white and dark brown) are favored in their respective micro-habitats, while intermediate colors are less fit in both, disruptive selection is at play.

Without pre-existing genetic variation, natural selection has no raw material to work with. If the environmental change is lethal to all identical individuals, the population will go extinct.

Darwin's 1859 book went beyond speculating about evolution; it presented a vast array of evidence and proposed natural selection as the functional mechanism of evolutionary change.

The selective pressure (predation) favors the faster extreme of swimming speeds, causing a directional shift in the average speed of the prey population over time.

Special Creation is a non-evolutionary concept proposing that species are fixed, unchanging entities created in their current forms, whereas Darwinism emphasizes descent with modification.

Stabilizing selection favors the intermediate phenotype (medium-sized wings) and selects against both extreme phenotypes (very short and very long wings).

Meiotic processes (independent assortment, crossing over, and random fertilization) shuffle alleles to create unique genetic combinations, producing the heritable variation key to selection.

As a population grows toward its carrying capacity, resources (food, shelter, water) become limiting, which intensifies competition and the struggle for survival.

Mutation and variation generation are random events, but natural selection is a non-random sorting process that systematically favors traits that confer a reproductive advantage.

Evolutionary fitness is defined solely by reproductive success; it is a measure of how many copies of its genes an individual passes on to subsequent, reproducing generations.

The HMS Beagle voyage (1831–1836) exposed Darwin to diverse ecosystems and fossil beds, particularly in South America and the Galapagos, which inspired his thinking on evolution.

Speciation occurs gradually as populations diverge genetically and phenotypically in response to different selective pressures, eventually leading to reproductive isolation.

Directional selection shifts the phenotypic distribution toward one extreme (larger beaks), typically in response to a directional change in environmental conditions.