Deck 16: Population Regulation

Question 1

Which of the following exert bottom-up control?

A) Parasites
B) Predators
C) Pathogens
D) Roots
E) None of the answers is correct

Answer 1

None of the answers is correct

Question 2

A trophic cascade implies the presence of

A) Bottom up control
B) Top down control
C) Strong competition
D) Nutrient limitation
E) No natural enemies

Answer 2

Top down control

Question 3

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

A) The control of cottony cushion scale by Vedalia beetles
B) The increase of tree growth following habitat colonization by wolves
C) Fertilizer increasing water hyacinth nutrient levels and beetle abundance
D) Overfishing in the cod industry
E) The increase in skates and rays following shark removal

Answer 3

Fertilizer increasing water hyacinth nutrient levels and beetle abundance

Question 4

The idea that predators control herbivore numbers, which in turn permits increased plant growth, is known as

A) The nitrogen-limitation hypothesis
B) The green earth hypothesis
C) The environmental stress hypothesis
D) Bottom-up control
E) Compensatory mortality

Question 5

Cod feed on small fish and crabs, which in turn feed on large bodied zooplankton. Zooplankton in turn feed on phytoplankton which themselves use up nitrates in the water. If cod were overfished which organisms should decrease?

A) Large bodied zooplankton
B) Small fish and crabs
C) Phytoplankton
D) a and b
E) b and c

Question 6

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?

A) Top-down control is most important
B) Bottom-up control is most important
C) Food limitation is important, but only after predator removal
D) Predation by hawks and owls is important

Question 7

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?

A) Increases
B) Decreases
C) Remains unchanged

Question 8

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

A) Herbivory
B) Competition
C) Predation
D) Nutrient limitation

Question 9

The environmental stress hypothesis suggests predation causes the highest levels of mortality under __________ environmental stress.

A) Low
B) Medium
C) High
D) Variable

Question 10

Key factors are often

A) Density dependent
B) Density independent
C) Inversely density dependent
D) Unaffected by density

Question 11

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

A) 0.2
B) 3.6
C) 3.8
D) 0.9
E) 1.0

Question 12

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

A) Overwintering loss
B) Parasitism by Cyzenis
C) Parasitism by Cratichneumon
D) Pupal predation
E) Disease

Question 13

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?

A) 0.1
B) 0.5
C) 1.0
D) 1.5
E) 1.7

Question 14

In a population of moths, if predation and parasitism are both density dependent, overwintering loss is density independent and disease is inversely density dependent, what is likely the key factor?

A) Predation
B) Parasitism
C) a and b
D) Disease
E) Can't tell from the information given.

Question 15

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

A) Earthworms
B) Birds
C) Newts and toads
D) Beetles and shrews
E) Badgers

Question 16

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

A) The density dependent factor
B) Compensatory mortality
C) Percent mortality in stage
D) Indispensable mortality
E) The key factor

Question 17

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?

A) 4
B) 8
C) 60
D) 66.6
E) 88

Question 18

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

Question 19

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

Question 20

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

Question 21

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

Question 22

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.

Question 23

The key factor for most insects seems to be predation.

Question 24

Weather often acts as an additive mortality.

Question 25

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.