Microevolution and macroevolution
Evolutionary processes that tend to occur at a population level are considered to be microevolutionary, while evolutionary processes (the formation and disappearance of the large branches of the phylogenetic tree, the formation of new body plans) that occur at the level of species can be considered to constitute macroevolution. Macroevolutionary processes are slow and prolonged and it is hardly possible for us to study them in our experiments. The element of chance plays a much greater role in them than in microevolutionary processes, see Chapter 4 in the book. The main source of evolutionary novelties in macroevolution consists in mutations arising in a local population, while the main source of novelties in microevolution is gene flow – the arrival of new alleles in the population through migrants.