Units of selection

Units of selection can be any replicator in an evolutionary system: genes, memes or other replicators which carry information. The units of selection persist across generations. They are often characterized by different scopes and levels, see Kin Selection, Group Selection and Multilevel Selection, if these levels are influenced by replicators. Natural selection acts on the genotype and selects always something which is replicated. This replicator can be a gene or meme.