Practice Questions

Stabilizing selection favors intermediate variants by acting against extreme phenotypes, reducing variation and maintaining the status quo of a phenotypic trait.

Natural selection is a non-random, directional process that adapts populations to their environments, whereas genetic drift is random and non-adaptive.

Natural selection can only change the genetic makeup of a population over generations if the phenotypic variations being selected have an underlying heritable genetic basis.

The differing beak morphologies are adaptations developed over generations as ancestral finches colonized islands with distinct food resources (seeds, insects, nectar).

Under Darwinism, variation exists prior to environmental change. Penicillin acts as a selective agent, removing susceptible cells and allowing pre-existing resistant cells to populate.

Evolutionary fitness is defined by reproductive success; an organism must not only survive but also successfully pass its genetic material to fertile offspring.

Malthus's work on human populations made Darwin realize that in nature, overproduction of offspring coupled with limited food and space leads to a struggle for survival.

Natural selection is context-dependent; a trait that is highly beneficial in one environment (e.g., thick fur in the Arctic) may be detrimental in another (e.g., a hot desert).

Disruptive (or diversifying) selection occurs when environmental conditions favor individuals at both extremes of a phenotypic range over those with intermediate phenotypes.

Darwin noted that organisms have a massive reproductive potential (overproduction), yet environmental resources remain stable and limited. This discrepancy inevitably leads to competition or a struggle for existence.