Table 1.

Classification of types of individual differences. (Numbers refer to citations in text.)

extrinsic source of variation	onset	definition	outcome (type)	potential carry-over effect?	reversible?
genetic	conception	breeding value for total fitness [1]	inherent individual quality	no	no
parental	prenatal and juvenile	the influence of parental genotype or phenotype on development [2]	parental effects on development	yes	context dependent
environmental	prenatal and juvenile	the influence of environmental conditions on development [3]	environmental effects on development	yes	context dependent
environmental	juvenile	the adaptive narrowing of variation in the annual routine [4]	development of annual routine	yes	plasticity varies among species
environmental	adulthood	reversible changes resulting from life-history trade-offs during adulthood	reversible state effects	yes	yes
environmental	adulthood	a decrease in physiological function with age [7]	senescence	yes	no