Figure 5. Plots of the distribution of fertility for a hypothetical population of males, for a hypothetical species. The upper panel shows the overall distribution (solid line) when typical numbers of sperm are used for intrauterine insemination (IUI) or in vitro fertilization (IVF). A bimodal distribution is evident. The major part of the population has a tail toward lower values. Deconvolution of the profile shows (as dotted or dashed lines), however, that (a) the larger population includes subpopulations of subfertile males (for simplicity, only 2 are shown); (b) the distribution of normal males is symmetrical and reasonably narrow; and (c) the smaller population, on the extreme left, includes sterile males (stippled band) and others with severe subfertility. In the lower 2 panels, distributions of fertility for the normal males are shown when typical numbers of sperm per IUI or IVF are used (center panel) or when ca 50% of the typical number of sperm per IUI or IVF are used (dashed line, lower panel). With a reduced number of sperm per IUI or IVF, far more males had a relatively low fertility, and individuals otherwise perhaps giving similar fertility now are distinguishable. This facilitates detection of the effect of exposure of sperm from these same males to a profertility molecule or procedure (solid line in lower panel). Maximum fertility is not substantially changed, but it is evident that the fertility of many males is increased. This obvious change would have been lost had the treatment been imposed on sperm used as in the middle panel.