The effective size of a population is: Solution The number of individuals that reproduce and thereby contribute offsprings to the next generation is termed effective population size (Ne). Effective size of a population is lower than the population observed ecologically. Under ideal conditions, the effective population is equal to the census population (Nc). These ideal conditions are- i) All individuals have the ability to reproduce and the number of males is equal to the number of females. Mating should be random and the number of breeding individuals is constant through all generations. ii) Variation in the number of individuals produced is only by chance..