Exam 16: Population Regulation

What are the main pupal predators of the oak winter moth?

If logN_t=2.0 and logN_t+1=1.8 then the killing power or k factor of the mortality is

Charles Krebs and colleagues applied three different treatments to populations to snowshoe hares: control (1), add fertilizer to increase growth of food plants (3), keep out mammalian predators by electric fences (2), and keep out predators together with added fertilizer (11). The numbers in parentheses represent the resultant numbers of hares relative to control numbers. What can you conclude?

What system provides evidence to support the idea of bottom-up control?

If there are four sources of mortality in a population and k₁ = 0.2, k₂ = 0.1, k₃ = 0.8, and k₄ = 0.4, what is K?

Adding fertilizer to plants often increases the densities of insect herbivores. This supports the top-down view of population control/

According to the environmental stress hypothesis the effects of natural enemies on herbivores would be greater towards the top of mountains, where the climate is more stressful.

In the Serengeti grasslands, star grass density controls the numbers of Thompson's gazelle, which in turn affects lion density. If lions are removed, what happens to the density of Thompson's gazelles?

Which of the following exert bottom-up control?

Key factors are often

Plants have an indirect effect on herbivores and a direct effect on plants.

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?

The key factor in the life cycle of the oak winter moth is

Competition would likely limit the number of secondary carnivores in a four trophic level system.

A farmer finds that a plague of cat fleas, which decimates cat numbers in his barn, has no effect on rat numbers and grain abundance. This supports the idea of top-down control.

A trophic cascade implies the presence of

Weather often acts as an additive mortality.

Predators have a direct effect on herbivores and an indirect effect on plants.

According to the ecosystem exploitation hypothesis, in a system with plants and herbivores, what factor limits the number of herbivores?

The part of the generational mortality that would not occur if the mortality factor in question was removed is known as