In biology and demography , fecundity is the ability to reproduce of an organism or population , measured by the number of gametes ( eggs ) , seed set or asexual propagules . In demography , fecundity is the potential reproductive capacity of an individual or population . In biology the definition is more equivalent to fertility , or the actual reproductive rate of an organism or population , measured by the number of gametes ( eggs ) , seed set or asexual propagules .