Natural Selection and Evolutionary Mechanisms

Vocabulary flashcards covering core terms and mechanisms of natural selection, types of selection, sexual selection, genetic drift, and the Hardy-Weinberg principle.

Natural Selection

The way in which nature favours the reproductive success of some individuals within a population over others.

Adaptation

A process where the frequency of a trait that helps individuals survive or produce more offspring increases in a population over time.

Biological Evolution

Descent with modification, defined by modern biologists as the change in the genetic makeup (or gene pool) of a population over time.

Selective Pressure

External or environmental factor that makes it more or less likely for organisms with certain traits to survive and reproduce

Directional Selection

Selection that favours an increase or decrease in the value of a trait away from the current population average, favouring individuals with a more extreme variation.

Stabilizing Selection

Selection against individuals exhibiting traits that deviate from the current population average, favouring the average phenotype within a population.

Disruptive Selection

Selection that favours two or more variations of a trait that differ from the current population average, favouring opposite extremes over intermediate variations.

Sexual Selection

Traits or behaviors developed that help them get more mates and reproduce, even if those traits do not help them survive

Sexual Dimorphism

Differences in appearance or physical form between males and females of the same species.

Reproductive Fitness

A measure of an organism's success in passing on genes to the next generation; individuals that survive but fail to mate have a fitness of zero.

Genetic Drift

A mechanism of evolution where allele frequencies change over generations due to random chance, typically occurring in small populations and resulting in reduced genetic diversity.

Genetic Bottleneck

A dramatic, often temporary reduction in population size that usually results in significant genetic drift and the loss of rare alleles.

Founder Effect

Genetic drift that results when a small number of individuals separate from their original population and establish a new population with different allele frequencies.

Hardy-Weinberg Principle

The principle stating that in large populations where only random chance is at work, allele frequencies are expected to remain constant from generation to generation.

Horizontal Gene Transfer

The process of gaining new alleles directly from an individual of a different species, leading to evolutionary change.