Population ecology, also known as demecology, focuses on the study of population and metapopulation sizes, emphasizing their evolution and distribution. This data is crucial for understanding the evolution of an ecosystem and the interactions of the populations that inhabit it. Rozenn Perrigot points out that, according to population ecology theory, variations within organism populations are primarily explained by environmental selection, rather than simple adaptation of the organisms. Indeed, the key process in the evolution of organism populations relies on selection influenced by environmental constraints and competition. In accordance with this principle, organisms that align with environmental criteria are favored and manage to survive, while others are destined to disappear or evolve to better meet the demands of their environment.