Allele: Each variation of a gene or DNA sequence in a specific locus (see below).

Bergmann’s rule: Principle that states that species of larger size are found in colder environments and species of smaller size are found in warmer regions .

Breeding system: the structure of a group regarding sexual behavior.

Ectotherms and endotherms: Ectotherms (“cold-blooded”) use external sources to regulate their body temperature, while endotherms (“warm-blooded”) create heat via metabolism.

Evolution: Broad concept that describes successive changes across generations of biological populations. It refers to changes in heritable characteristics.

Fitness: A species’ ability to survive and reproduce.

Locus: The specific location of a gene on the chromosome.

Natural selection: Key concept of evolution in which biological traits gradually become either more or less common in a population depending on the reproductive advantage these traits give to individuals.

Phenotypic traits: Distinctive observable characteristics of an organism. They may be inherited or environmentally determined.

Price equation: Theorem that helps understand the effect of gene transmission and natural selection in the proportion of genes of each new generation.

Primary production: the production of organic compounds from atmospheric or aquatic carbon dioxide.

Thermoregulation: The ability of an organism to keep its body temperature level at a specific range.