Features that are developed during the lifetime of an individual, e.g. the enlarged arm muscles of a tennis player. Such characteristics do not involve any alteration in the base sequence of genes and hence cannot be passed on to the next generation. However, exposure to certain environmental factors, such as malnutrition or toxic chemicals, can cause epigenetic changes that are transmitted to subsequent generations. Although these can be regarded as acquired characteristics, they are not stably inherited and after a variable number of generations are liable to revert to the original state. See also baldwin effect; lamarckism; neo-lamarckism.