At the present time, some geneticists are using the term ‘population dynamics’ for differences in the survival rates of different genotypes in the wild (population genetics), while some ecologists are using it for the balance between birth-rates and death-rates in a whole population (population ecology). Hence further clarification and definition seem desirable if confusion is to be avoided. My own studies are ecological. The reproductive rate of birds seems, in general, to he the highest possible, each species breeding when conditions normally permit it to raise young, and laying a clutch corresponding to the largest number of young that it can successfully nourish (Lack 1954). Since in the same population some individuals consistently lay rather larger clutches than others, there is probably some hereditary variability in clutch size. This may be a balanced polymorphism due to the fact that, through differences in feeding conditions, the most effective size of family differs somewhat in different years. My later research has been concerned with a different problem, namely, the variations in the clutch size of the same individual under different conditions. As such variations directly affect the number of offspring, the tendency to vary in such ways is presumably adaptive and subject to strong selection.
Population Genetics and Population Ecology
