• Selection can alter organisms .
  • Selection occurs at the levels of individuals, populations and species,

• Selection can affect only the alleles currently present in the population.
  • The alleles present reflect historical contingency and evolutionary history.
  • Selection alone cannot produce new alleles.

• Selection may act on all characteristics of an organism such as development, behavior, life history.

• Selection acts directly on phenotypes and indirectly on genotypes and gene pools.
  • Over time, selection alters the frequency of alleles in a population.
  • Selection acts most strongly on features that directly affect growth and reproduction.

• Mutation is random, Selection is not.
  • New types are generated randomly.
  • Selection may be stabilizing, directional, or disruptive, but it is not random.

• Evolution is nonrandom.
  • The net result of mutation and selection is to produce nonrandom changes in populations through time.