Analysis of a nonlinear delay-differential equation for an age-structured population

We give a brief description of a single-species growth model with time delay. The model considered in a recent publication is extended to include a nonlinear death rate. Positivity, boundedness, and stability of solutions have been considered. We have also considered the case when the delay is state-dependent, giving rise to a stage-structured model with state-dependent delay. Positivity, boundedness, and stability analysis for this model have also been analyzed. We give a predator-prey model, predator and prey both having stage-structure individually.