IB Biology Topic D4.1: Natural Selection Key Definitions

A non-living component of the environment, such as temperature, light, or water availability, that influences the survival and reproduction of organisms.

Adaptations are traits that increase an organism’s fitness in response to environmental factors.

Allele frequency refers to how common a particular allele is within a population. It is expressed as a proportion or percentage of all alleles for a specific gene.

A biotic factor is a living organism that shapes its environment.

Favors one extreme phenotype, shifting the population in that direction.

Favors extreme phenotypes at both ends, increasing variation.

Fitness refers to how well an organism is adapted to its environment, influencing its ability to survive and reproduce.

The total collection of all alleles present in a population.

The genome is the complete set of genetic instructions that determines the structure, function, and traits of an organism.

Genotype refers to the genetic makeup of an organism, specifically the combination of alleles it inherits for a particular trait.

Heritability refers to the ability of a trait to be passed from parents to offspring through genetic information.

Natural selection is the process where individuals with traits better suited to their environment have higher reproductive success, passing these traits to the next generation.

A fundamental change in understanding.

Favors intermediate phenotypes, reducing variation.

The Hardy–Weinberg principle is a mathematical model that predicts how allele and genotype frequencies remain constant in a population—unless evolutionary forces act upon it.

Variation refers to differences in traits among individuals within a population, encompassing physical characteristics, behaviors, and genetic sequences.