Of 1,000 Colorado beetle eggs, 700 are killed by predatory bugs. Of the resultant 300 larvae, 200 are eaten by birds. Of the resultant 100 pupae, 60 are killed by shrews, leaving 40 adults. What is the percent indispensable mortality at the larval stage?

Question

Quizplus · Accepted Answer

Indispensable mortality at the larval stage is calculated by the formula: [(initial number - final number) / initial number] * 100. Here, the initial number of larvae is 300, and the final number after birds eat 200 of them is 100. So, the calculation is [(300 - 100) / 300] * 100 = 66.6%. However, this calculation represents the total mortality at the larval stage, not the indispensable mortality. Indispensable mortality refers to the mortality that must occur to reduce the population to the number that can be supported by the environment (the number that reaches adulthood in this context, which is 40). Since 200 larvae are eaten by birds, reducing the number from 300 to 100, and only 40 are needed to reach the adult stage, the indispensable mortality at the larval stage is calculated based on the excess larvae that needed to be removed to achieve the final adult population. This means that the indispensable mortality is actually related to how the reduction at the larval stage contributes to achieving the final adult population size, not just the simple percentage reduction at that stage. The question seems to be asking for a specific value related to the larval stage's contribution to overall mortality necessary to reach the final adult population, but the provided calculation and choices do not directly correspond to the concept of indispensable mortality as typically defined. Therefore, the correct interpretation of indispensable mortality in this context is not straightforward from the provided options, suggesting a possible misunderstanding in the question's formulation or in the interpretation of the term "indispensable mortality."

Of 1,000 Colorado Beetle Eggs, 700 Are Killed by Predatory