Community Ecology and Ecosystems

Question 1

An event that changes resource availability and removes individuals from a community is a

a) disease
b) predator effect
c) competitor effect
d) disaster
e) disturbance

Answer 1

e) distrubance

Question 2

Primary succession differs from secondary succession in what way?

a) Primary succession occurs in areas with little precipitation.
b) Primary succession occurs in areas devoid of all living organisms.
c) Primary succession occurs after an intermediate disturbance.
d) Primary succession occurs in areas with no soil.
e) They differ in the length of time that succession takes.

Answer 2

d) Primary succession occurs in areas with no soil

Question 3

Species richness increases

a) as we travel southward from the North Pole
b) as we increase in altitude in equatorial mountains
c) as depth increases in aquatic communities
d) on islands as distance from the mainland increases
e) as community size decreases

Answer 3

a) as we travel southward from the North Pole

Question 4

Dwarf mistletoes are flowering plants that grow on certain forest trees. They obtain nutrients and water from the vascular tissues of the trees. The trees derive no known benefits from the dwarf mistletoes. Which of the following best describes the interactions between dwarf mistletoes and trees?

a) commensalism
b) mutualism
c) facilitation
d) competition
e) parasitism

Answer 4

e) parasitism

Question 5

The symbols +, -, and o are to be used to show the results of interactions between individuals and groups of individuals in the examples that follow. The symbol + denotes a positive interaction, - denotes a negative interaction, and o denotes where individuals are not affected by interacting. The first symbol refers to the first organism mentioned.

What interactions exist between a bee and a flower?

a) +/+
b) +/o
c) +/-
d) o/o
e) -/-

Answer 5

a) +/+

Question 6

Gross primary production

a) is the total energy from light converted to chemical energy of organic molecules per unit time
b) is not as important as net primary production
c) is equal to NPP - respiration of autotrophs
d) is the total biomass of all photosynthetic autotrophs
e) is about half of NPP

Answer 6

a) is the total energy from light converted to chemical energy of organic molecules per unit time

Question 7

A 3-hectare lake in the American Midwest suddenly has succumbed to an algal bloom. What is the likely cause of eutrophication in freshwater ecosystems, such as this one?

a) iron dust blowing into the lake
b) increased solar radiation
c) introduction of non-native tertiary consumer fish
d) accidental introduction of prolific culture of algae
e) nutrient runoff

Answer 7

e) nutrient runoff

Question 8

The major role of detrivores in ecosystems is to

a) prevent the buildup of the organic remains of organisms, feces, and so on.
b) recycle chemical nutrients to a form capable of being used by autotrophs.
c) return energy lost to the ecosystem by other organisms.
d) provide a nutritional resource for heterotrophs.

Answer 8

b) recycle chemical nutrients to a form capable of being used by autotrophs

Question 9

Which of the following pairs is incorrectly matched?

a) secondary production — the amount of chemical energy in a consumers’ food that is converted to their new biomass in a given time period
b) trophic efficiency — percentage of production transferred from one trophic level to the next
c) tertiary production — the number of top predators in the food web
d) production efficiency — energy in assimilated food that is not used for respiration
e) eutrophication — excess nutrients resulting in high cyanobacteria concentrations and algae blooms

Answer 9

c) tertiary production - the number of top predators in the food web

Question 10

Which of the following is primarily responsible for limiting the number of trophic levels in most ecosystems?

a) Nutrient cycles involve both abiotic and biotic components of ecosystems
b) Energy transfer between tropic levels is in almost all cases less than 20% efficient
c) Decomposers compete with higher-order consumers for nutrients and energy
d) Many primary and higher-order consumers are opportunistic feeders
e) Nutrient cycling rates tend to be limited by decomposition

Answer 10

b) Energy transfer between tropic levels is in almost all cases less than 20% efficient

Question 11

Which marine zone would have the lowest rates of primary productivity (photosynthesis)?

a) intertidal
b) neritic
c) continental shelf
d) pelagic
e) abyssal

Answer 11

e) abyssal

Question 12

Generalized global air circulation and precipitation patterns are caused by

a) polar, cool, moist high-pressure air masses from the poles that move along the surface, releasing precipitation along the way to the equator where they are heated and dried.
b) rising, warm, moist air masses that cool and release precipitation as they rise and then, at high altitude, cool and sink back to the surface as dry air masses after moving north or south of the tropics.
c) mountain ranges that deflect air masses containing variable amounts of moisture.
d) the revolution of Earth around the sun.
e) air masses that are dried and heated over continental areas that rise, cool aloft, and descend over oceanic areas followed by a return flow of moist air from ocean to land, delivering high amounts of precipitation to coastal areas.

Answer 12

b) rising, warm, moist air masses that cool and release precipitation as they rise and then, at high altitude, cool and sink back to the surface as dry air masses after moving north or south of the tropics.

Question 13

Which of the following examples would most accurately measure the density of the population being studied?

a) counting the number of times a 1 kilometre transect is intersected by tracks of red squirrels after a snowfall
b) counting the number of zebras from airplane census observations
c) counting the number of prairie dog burrows per hectare
d) multiplying the number of moss plants counted in 10 quadrats of 1m2 each by 100 to determine the density per kilometre2
e) counting the number of coyote droppings per hectare

Answer 13

b) counting the number of zebras from airplane census observations

Question 14

Which of the following is the most important assumption for the capture-recapture method to estimate the size of wildlife populations?

a) All females in the population have the same litter size
b) There is a 50:50 ratio of males to females in the population before and after trapping and recapture.
c) Marked individuals have the same probability of being recaptured as unmarked individuals during the recapture phase.
d) Over 50% of the marked individuals need to be trapped during the recapture phase.
e) More individuals emigrate from, as opposed to immigrate into, a population.

Answer 14

c) Marked individuals have the same probability of being recaptured as unmarked individuals during the recapture phase.

Question 15

In a positive-feedback system in which hormone A alters the amount of protein X

a) an increase in X always produces a decrease in A.
b) a decrease in A always produces an increase in X.
c) an increase in A always produces an increase in X.
d) it is impossible to predict how A and X affect each other.
e) a decrease in X always causes a decrease in A.

Answer 15

c) an increase in A always produces an increase in X.

Question 16

After eating a carbohydrate-rich meal, the mammalian pancreas increases its secretion of

a) thyroxine
b) insulin
c) glucagon
d) oxytocin
e) ecdysteroid

Answer 16

b) insulin

Question 17

The yolk of the frog egg

a) is concentrated at the animal pole.
b) supports the higher rate of cleavage at the animal pole compared to the vegetal pole.
c) prevents gastrulation.
d) impedes the formation of a primitive streak.
e) is homogeneously arranged in the egg.

Answer 17

b) supports the higher rate of cleavage at the animal pole compared to the vegetal pole.

Question 18

The formation of the fertilization membrane requires an increase in the availability of

a) potassium ions.
b) bicarbonate ions.
c) sodium ions.
d) calcium ions.
e) hydrogen ions.

Answer 18

d) calcium ions

Question 19

Phagocytosis of microbes by macrophages is enhanced by

a) the binding of antibodies to the surface of microbes and antibody-mediated agglutination of microbes only.
b) antibody-mediated agglutination of microbes.
c) the release of cytokines by activated B cells.
d) the binding of antibodies to the surface of microbes, antibody-mediated agglutination of microbes, and the release of cytokines by activated B cells.
e) the binding of antibodies to the surface of microbes.

Answer 19

a) the binding of antibodies to the surface of microbes and antibody-mediated agglutination of microbes only.

Question 20

The osmoregulatory process called secretion refers to the

a) formation of filtrate at an excretory structure
b) reabsorption of nutrients from a filtrate
c) formation of an osmotic gradient along an excretory structure
d) expulsion of urine from the body
e) selective elimination of excess ions and toxins from bodily fluids

Answer 20

e) selective elimination of excess ions and toxins from bodily fluids

Question 21

Which of the following best describes resource partitioning?

a)a climax community that is reached when no new niches are available
b) competitive exclusion that results in the success of the superior species
c) differential resource utilization that results in a decrease in community species diversity
d) slight variations in niche that allow similar species to coexist
e) two species that can coevolve to share identical niches

Answer 21

d) slight variations in niche that allow similar species to coexist

Question 22

Why are food chains relatively short?

a) Food chain length is ultimately determined by the photosynthetic efficiency of producers.
b) Longer chains are less stable and energy transfer between levels is inefficient.
c) Top-level feeders tend to be small but are capable of conserving more energy.
d) Top-level feeders tend to be more numerous than lower-trophic-level species.
e) There are only so many organisms that are adapted to feed on other types of organisms.

Answer 22

b) longer chains are less stable and energy transfer between levels in inefficient

Question 23

According to bottom-up and top-down control models of community organization, which of the following expressions would imply that an increase in the size of a carnivore (C) population would negatively impact on its prey (P) population, but not vice versa?
a) C ↔ P
b) P → C
c) C ← P →
d) P ← C
e) P ← C → P

Answer 23

P ← C

Question 24

Evidence shows that some grasses benefit from being grazed. Which of the following terms would best describe this plant-herbivore interaction?

a) commensalism
b) mutualism
c) predation
d) competition
e) parasitism

Answer 24

Mutualism

Question 25

According to the competitive exclusion principle, two species cannot continue to occupy the same

a) habitat
b) territory
c) range
d) niche
e) biome

Answer 25

niche

Question 26

What are two key factors controlling primary productivity in lakes and oceans?

a) light and temperature
b) light and phytoplankton
c) light and nutrients
d) nutrients and temperature
e) nutrients and wind

Answer 26

light and nutrients

Question 27

Which of the following is an example of an ecosystem?

a) a pond and all of the plant and animal species that live in it
b) interactions between all of the organisms and their physical environment in a tropical rain forest
c) the intricate interactions of the various plant and animal species on a savanna during a drought
d) all of the brook trout in a 500 hectare2 river drainage system
e) the plants, animals, and decomposers that inhabit an alpine meadow

Answer 27

b) interactions between all of the organisms and their physical environment in a tropical rain forest

Question 28

In ecosystems, why is the term cycling used to describe material transfer, whereas the term flow is used for energy exchange?

a) Materials are cycled into ecosystems from other ecosystems, but energy constantly flows within the ecosystem.
b) Both material and energy are recycled and are then transferred to other ecosystems as in a flow.
c) Materials are repeatedly used, but energy flows through and out of ecosystems.
d) Both material and energy flow in a never-ending stream within an ecosystem.
e) None of the choices is correct.

Answer 28

c) Material are repeatedly used, but energy flows through and out of ecosystems

Question 29

Which of the following terms encompasses all of the others?

a) primary consumers
b) herbivores
c) carnivores
d) secondary consumers
e) heterotrophs

Answer 29

e) heterotrophs

Question 30

Generally speaking, deserts are located in places where air masses are usually

a) tropical
b) expanding
c) rising
d) descending
e) humid

Answer 30

d) descending

Question 31

Species introduced by humans to new geographic locations

a) increase the diversity and therefore the stability of the ecosystem.
b) can outcompete and displace native species for biotic and abiotic resources.
c) are always considered pests by ecologists.
d) always spread because they encounter none of their natural predators.
e) are usually successful in colonizing the area.

Answer 31

b) can outcompete and displace native species for biotic and abiotic resources

Question 32

Which of the following causes populations to shift most quickly from an exponential to a logistic population growth?

a) removal of predators
b) increased birth rate
c) competition for resources
d) favourable climatic conditions
e) decreased death rate

Answer 32

c) competition for resources

Question 33

The human population

a) is no longer growing exponentially but still increasing rapidly
b) and its carrying capacity can be estimated using age structure pyramids
c) worldwide has reached its demographic transition
d) is still growing exponentially, but its increasing slowly
e) can keep increasing because technology will enable continuous growth

Answer 33

a) is no longer growing exponentially but still increasing rapidly

Question 34

Why do tropical communities tend to have greater species diversity than temperate or polar communities?

There are fewer parasites to negatively affect the health of tropical communities.
Tropical communities are generally older than temperate and polar communities.
Tropical communities are low in altitude, whereas temperate and polar communities are high in altitude.
More competitive dominant species have evolved in temperate and polar communities.
They are less likely to be affected by human disturbance.

Answer 34

Tropical communities are generally older than temperate and polar communities.

Question 35

Resource partitioning would be most likely to occur between

sympatric populations of species with similar ecological niches.
sympatric populations of a predator and its prey.
sympatric populations of a flowering plant and its specialized insect pollinator
allopatric populations of species with similar ecological niches.
allopatric populations of the same animal species

Answer 35

sympatric populations of species with similar ecological niches.

Question 36

Use the following diagram to answer the next few questions.

Which of the following statements is a valid conclusion of this experiment?

a) These two species of barnacle do not show competitive exclusion.
b) When Balanus is removed, it can be observed that the realized niche of Chthamalus is smaller than its fundamental niche.
c) Balanus is inferior to Chthamalus in competing for space on intertidal zone rocks.
d) If Chthamalus were removed, Balanus’s fundamental niche would become larger.
e) Balanus can only survive in the lower intertidal zone, because it is unable to resist desiccation (drying out).

Answer 36

b) When Balanus is removed, it can be observed that the realized niche of Chthamalus is smaller than its fundamental niche.

Question 37

Which of the following studies would a community ecologist undertake to learn about competitive interactions?

a) selectivity of nest sites among cavity-nesting songbirds, the grass species preferred by grazing pronghorn antelope and bison, nitrate and phosphate uptake by various hardwood forest tree species, and stomach analysis of brown trout and brook trout in streams where they coexist
b) selectivity of nest sites among cavity-nesting songbirds
c) stomach analysis of brown trout and brook trout in streams where they coexist
d) nitrate and phosphate uptake by various hardwood forest tree species
e) the grass species preferred by grazing pronghorn antelope and bison

Answer 37

a) selectivity of nest sites among cavity-nesting songbirds, the grass species preferred by grazing pronghorn antelope and bison, nitrate and phosphate uptake by various hardwood forest tree species, and stomach analysis of brown trout and brook trout in streams where they coexist

Question 38

Why do logged tropical rain forest soils typically have nutrient-poor soils?

Most of the nutrients in the ecosystem are removed in the harvested timber.
Logging results in soil temperatures that are lethal to nitrogen-fixing bacteria.
The cation exchange capacity of the soil is reversed as a result of logging.
Nutrients evaporate easily into the atmosphere in the post-logged forest.
Tropical bedrock contains little phosphorous.

Answer 38

Most of the nutrients in the ecosystem are removed in the harvested timber.

Question 39

Which of the following locations is the reservoir for nitrogen in the nitrogen cycle?

fossilized plant and animal remains (coal, oil, and natural gas)
soil
sedimentary bedrock
atmosphere
plant and animal biomass

Answer 39

atmosphere

Question 40

Why does a vegetarian leave a smaller ecological footprint than an omnivore?

Answer 40

Eating meat is an inefficient way of acquiring photosynthetic productivity

Question 41

Which trophic level is most vulnerable to extinction?

Answer 41

Tertiary consumer level (carnivores, predators)

Question 42

Decomposers obtain energy from

other heterotrophs
fungi
detritus
bacteria
live organic material

Answer 42

detritus

Question 43

“How do seed-eating animals affect the distribution and abundance of the trees?” This question

would be difficult to answer because a long-term experiment would be required.
is one that a present-day ecologist would be likely to ask.
would be difficult to answer because a large experimental area would be required.
would require an elaborate experimental design to answer.
All options are correct.

Answer 43

all options are correct

Question 44

Which of the following life history traits is incorrectly matched?

Answer 44

r selection - density dependent selection

Question 45

Which of the following statements about the evolution of life histories is correct?

K-selected populations are most often found in environments where density-independent factors are important regulators of population size.

The reproductive efforts of r-selected populations are directed at producing just a few offspring with good competitive abilities.

Stable environments with limited resources favour r-selected populations.

Most populations have both r- and K-selected characteristics that vary under different environmental conditions.

K-selected populations rarely approach carrying capacity.

Answer 45

Most populations have both r- and K-selected characteristics that vary under different environmental conditions.

Question 46

Feeding behaviour with a high energy intake-to-expenditure ratio is called

optimal foraging.
heterotrophy.
search scavenging.
autotrophy.
herbivory.

Answer 46

optimal foraging

Question 47

Which statement best describes the evolutionary significance of mutualism?

Interaction increases the survival and reproductive rates of mutualistic species.
Mutualistic relationships allow organisms to synthesize and use energy more efficiently.
Mutualism offers more biodiversity to a community.
Mutualistic interaction lessens competition in communities where it is present.
Individuals partaking in a mutualistic relationship are more resistant to parasites.

Answer 47

interaction increases the survival and reproductive rates of mutualistic species

Question 48

Which statement best describes what ultimately happens to the chemical energy that is not converted to new biomass in the process of energy transfer between trophic levels in an ecosystem?

It is used by organisms to maintain their life processes through the reactions of cellular respiration.
Heat produced by cellular respiration is used by heterotrophs to thermoregulate.
It is undigested and winds up in the feces and is not passed on to higher trophic levels.
It is eliminated as feces or is dissipated into space as heat in accordance with the second law of thermodynamics.
It is recycled by decomposers to a form that is once again usable by primary producers.

Answer 48

it is eliminated as feces or is dissipated into space as heat in accordance with the second law of thermodynamics

Question 49

Which of these ecosystems accounts for the largest amount of Earth’s net primary productivity?

tundra
salt marsh
tropical rain forest
open ocean
savanna

Answer 49

open ocean

Question 50

In mountainous areas of western North America, north-facing slopes would be expected to

a) be warmer and drier than comparable southern exposed slopes.
b) support biological communities similar to those found at higher elevations on similar south-facing slopes.
c) receive more sunlight than similar southern exposures.
d) consistently be steeper than southern exposures.
e) support biological communities similar to those found at lower elevations on similar south-facing slopes.

Answer 50

b) support biological communities similar to those found at higher elevations on similar south-facing slopes.

Question 51

Which variables define the ecological life history of a species?

timing breeding sessions with optimal environmental conditions and the number of offspring produced during each breeding session

the amount of parental care given after birth, the number of reproductive episodes per year, and the number of years females are capable of producing viable offspring

the age at which reproduction begins, frequency of reproduction, and the number of offspring for each reproductive episode

the number of offspring produced over a lifetime by a breeding pair and the survivability of the offspring

the ratio of females to males, the length of the breeding season, and the number of offspring for each reproductive episode

Answer 51

the age at which reproduction begins, frequency of reproduction, and the number of offspring for each reproductive episode

Question 52

Uniform spacing patterns in plants such as the creosote bush are most often associated with

Answer 52

competitive interaction between individuals of the same population