Practice question

Small mammals such as mice generally have a much higher intrinsic rate of increase than large, slow-lived vertebrates. They mature early, have short generation times, reproduce frequently, and produce several offspring per litter. These traits place reproductive contribution early in the life table, which strongly elevates r because offspring produced sooner can themselves reproduce sooner. Elephants and humans mature late, have long gestation, small litters, and long intervals between births; their populations therefore increase slowly even when adult survival is high. Many snakes have intermediate life histories, with reproductive schedules slower than those of mice. Intrinsic rate of increase is not simply lifetime fecundity: its value emerges from the timing of reproduction and survival across ages, often estimated from the Euler–Lotka equation. High juvenile mortality can lower realized growth, but rmax denotes potential increase under favorable conditions. The comparison illustrates the life-history continuum from fast species with rapid turnover to slow species that invest heavily in fewer offspring and depend more on adult survival.