MCQs

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.

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.

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.

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.

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.

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.

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.

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

Neo-Darwinism combines Darwinian selection with Mendelian genetics, defining evolution as a change in allele frequencies within a population's gene pool over generations.

Selective pressure (e.g., predators, climate, disease) is the environmental force that drives natural selection by favoring certain phenotypes over others.

The rapid development of resistance in bacteria and pests is a documented, direct observation of natural selection occurring in contemporary times under strong selective pressures.

The drought alters the environment, making the brown phenotype more advantageous. Brown insects will survive predation better, reproduce more, and increase the frequency of the brown allele.

Darwin argued that complex structures evolve via the gradual accumulation of many slight, heritable modifications, with each step improving the organism's fitness compared to the previous state.

Individuals do not adapt by mutating their own genomes in response to environmental demands. Mutations are random; natural selection simply filters pre-existing genetic variations.

Natural selection requires a choice of variants to "select" from. If all individuals are genetically identical, any differential survival is due to chance, and no evolutionary adaptation can occur.

Because both phenotypic extremes (very long and very short tails) are selected against, stabilizing selection acts to maintain intermediate tail lengths.

The inheritance of acquired characters is a postulate of Lamarckism, which Darwinism does not rely on (although Darwin did occasionally speculate on soft inheritance, it is not a core tenet of natural selection).

Natural selection only acts on traits that influence differential reproductive success. If a trait is completely neutral with respect to fitness, natural selection does not influence it directly.

Darwin emphasized that natural selection relies on the pre-existing, heritable variations that naturally occur among individuals within any wild population.