Argue that for many species, a minimum population level is required for survival. Give several examples. Call this minimum survival level N_s. Suggest a simple cubic growth submodel meeting these requirements, as depicted in Figure 13.22. Answer the questions posed in Problem 1 using your graphical submodel.

Figure 13.22

Data from problem 1

Assume that the environmental carrying capacity N_u is determined principally by the availability of food. Argue that under such an assumption, as N approaches Nu the physical condition of the average fish deteriorates as competition for the food supply becomes more severe. What does this suggest about the survival of the species when natural disasters such as storms, severe winters, and similar circumstances further restrict the food supply? Where should conservationists attempt to maintain the population level?

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8(N) Growth rate N N Whale population Figure 13.22 N Whale population N Time Nu Cengage Learning