Both the population growth rates and number of days to gravidity varied greatly with the particle concentration. The higher concentration to which the animals were exposed, the fewer days they experienced to gravidity, and the higher population growth rate they obtained. This phenomenon was a result of the natural particles on which the organisms fed. The organisms exposed to NP suspensions experienced fewer days to gravidity and obtained a higher population growth rate, but lower growth rates (Fig. 3) compared to those exposed to NPn suspensions, indicating that the fecundity was much stronger in the NP treatment. This observation further indicates that the NP were of greater assistance for
the fecundity than the NPn, but less beneficial for the body growth of D. magna. Therefore, the organisms showed different selections
in allocating resources when the organisms were exposed to particles
of different size scales, which may be a result of the generation
of different assimilation and digestion patterns.