With the concept of population, it is easy to apply indicators of demographic processes (birth rate, mortality, emigration, immigration) that give a population its dynamics. Because these processes depend on both individual and environmental properties, we speak of the population–environment system. The concept of species diversity is based on the fact that an individual organism’s variable features are recorded in its genetic heritage. The set of characteristics and behaviours of living things, known as the phenotype, studied by naturalists when they are working in the field depends first on their genetic structure, or genotype. Therefore, it is the set of genes and the genetic modifications that take place on the genes and chromosomes during DNA replication that determines species diversity (Collins and Qualset, 1998; Jarvis et al., 2007).