Deck 37: Communities and Ecosystems

Question 1

A hypothetical community on a barren mid-Atlantic island consists of two fish-eating seabirds (the booby and the noddy), the fungi and microorganisms that live on the birds' dung, a tick that feeds on these two birds, a cactus, a moth that feeds on cast-off feathers, a beetle that lives on dung organisms, and spiders that eat the other arthropods. There are no other plants and no lichens. Which pair of organism and trophic structure is incorrect?

A) fungi-detritivores
B) booby-primary consumer
C) moth-detritivore
D) cactus-producer

Answer 1

B

Question 2

The prokaryotes that cause tooth decay have a ________ relationship with humans.

A) parasitic
B) predatory
C) mutualistic
D) competitive

Answer 2

A

Question 3

In an ecosystem, you would expect to find interspecific competition between

A) males and females of a species in which both sexes occupy the same niche.
B) populations of two species that occupy the same niche.
C) a prey species and its predator.
D) two wasp species that mimic each other's appearance.

Answer 3

B

Question 4

Some herbivore-plant interactions evolved through a series of reciprocal evolutionary adaptations in both species. This process is called

A) herbivory.
B) coevolution.
C) selection.
D) competition.

Question 5

Camouflage typically evolves as a result of

A) predation.
B) interspecific competition.
C) mutualism.
D) herbivory.

Question 6

Dinoflagellates are important to coral and coral-dwelling animals because they

A) provide energy in the form of organic molecules that is used by coral animals.
B) provide shelter for the fast-growing seaweeds associated with coral.
C) produce carbon dioxide (CO2) and nitrogen for coral.
D) are toxic to species that prey on reef-dwelling fish.

Question 7

Within an ecosystem, a tree is a

A) secondary consumer.
B) detritivore.
C) primary consumer.
D) producer.

Question 8

A community is composed of

A) potentially interacting populations of different kinds of organisms.
B) one species of organism living in a specific environment on Earth.
C) living organisms and their nonliving environment.
D) the factors that constitute an organism's niche.

Question 9

The sum total of a population's use of the biotic and abiotic resources of its habitat constitutes its

A) environment.
B) evolution.
C) range.
D) niche.

Question 10

When two different populations in a community benefit from their relationship with each other, the result is called

A) herbivory.
B) mutualism.
C) parasitism.
D) competition.

Question 11

If an owl and a hawk both eat mice, what is the relationship between a hawk and an owl?

A) predation
B) competition
C) mutualism
D) parasitism

Question 12

If an overlap develops between the ranges of two closely related species, and if the species occupy the same niche in the zone of overlap, what will probably happen in the zone of overlap?

A) A new species will arise by hybridization.
B) Both species will coexist, provided the environment in the zone of overlap is different from that in either individual range.
C) Both species will coexist, provided the environment in the zone of overlap is similar to that of one of the individual ranges.
D) One species will take over most or all of the zone of overlap.

Question 13

In addition to abiotic factors, community composition of plants can be severely compromised by

A) parasites and pathogens.
B) mutualistic birds.
C) rapid coevolution.

Question 14

Most plants have a variety of chemicals, spines, and thorns because the plants

A) cannot run away from herbivores.
B) feed on the organisms that try to eat them.
C) are camouflaged into their surroundings.
D) must rely on photosynthesis for food.

Question 15

One predator avoidance mechanism that has evolved in prey is

A) chemical defenses and bright coloration.
B) secretion of digestive enzymes that hydrolyze glucose.
C) secretion of enzymes that break down toxic plant compounds.
D) development of a short gestation period.

Question 16

The freshwater leech is an organism that feeds off of the blood of other organisms such as frogs and turtles. Which interaction describes the relationship between freshwater leeches and frogs or turtles?

A) herbivory
B) predation
C) mutualism
D) parasitism

Question 17

In a hypothetical food chain consisting of grass, grasshoppers, sparrows, and hawks, the grasshoppers are

A) primary consumers.
B) primary producers.
C) secondary consumers.
D) tertiary consumers.

Question 18

What is an example of predation?

A) the camouflage of a lizard in rocky habitats
B) a hawk swooping down quickly to capture, kill, and eat a prairie king snake
C) a goldfinch feeding on the seeds of a thistle plant
D) the vivid colors of the poison-arrow frog in Costa Rica

Question 19

When a crocodile eats a fish, the interspecific interaction between the two could be expressed as ________ for the crocodile and ________ for the fish.

A) − ; −
B) + ; +
C) + ; −
D) − ; +

Question 20

One reason it is important to understand community ecology is to

A) understand the life cycle of fish, such as cichlids.
B) identify stomach microbes.
C) aid in conservation of endangered species.

Question 21

About how much of the energy in the producers of an ecosystem will be available to secondary consumers in this ecosystem?

A) 100%
B) about 50%
C) about 10%
D) about 1%

Question 22

A biology student takes fish, algae, pond plants, invertebrates, and bottom sediment from a local pond and establishes them in an aquarium. When the system is stable, the student seals it into a large, airtight glass box and leaves the box in a sunny location. After 3 months, the organisms in the aquarium appear alive and healthy. Which statement about the experiment is true?

A) No energy has entered or left the glass box during the 3 months.
B) Some of the energy in the system has moved from one organism to another during the 3 months.
C) The air in the glass box contains no carbon dioxide.
D) During the 3 months, the biomass of animal life was greater than the biomass of plant life.

Question 23

Given that CO2 is produced by cellular respiration, why does the amount of CO2 in the atmosphere remain relatively constant? (When answering this question, exclude the impact of human activities on atmospheric CO2.)

A) CO2 is converted to carbohydrates in photosynthesis.
B) CO2 is split apart during photosynthesis.
C) CO2 mostly forms carbonate rocks.
D) CO2 is trapped in dead organisms' bodies.

Question 24

Which statement regarding food webs is true?

A) A consumer eats only one type of producer.
B) Detritivores consume dead organic matter from a specific trophic level.
C) Several species of primary consumers may feed on the same species of producer.
D) Energy transfer moves from producer to consumer and back.

Question 25

Non-native species that are introduced to new environments, spread far beyond the original point of introduction, and cause damage are called

A) predators.
B) pathogens.
C) invasive species.
D) herbivores.

Question 26

In an average ecosystem, about how much energy is present in the organisms at a given trophic level compared to the organisms at the next higher trophic level?

A) a tenth as much
B) half as much
C) twice as much
D) ten times as much

Question 27

In a certain ecosystem, field mice are preyed on by snakes and hawks. The entry of wild dogs into the system adds a third mouse predator. The most likely short-term result of this addition is

A) an increase in the snake population.
B) a tendency for hawks to prey on the dogs.
C) a reduction in numbers of mice.
D) migration of the hawks to another ecosystem.

Question 28

In a food chain consisting of phytoplankton → zooplankton → fish → humans, the humans are

A) secondary consumers.
B) tertiary consumers.
C) quaternary consumers.
D) primary producers.

Question 29

The flow of ________ into ecosystems occurs in one direction only, while ________ are recycled within the ecosystem itself.

A) minerals; energy compounds
B) genetic information; genotypes
C) organic compounds; minerals
D) energy; chemicals

Question 30

The number of species in a community is called species

A) diversity.
B) richness.
C) composition.

Question 31

During ecological succession, the species composition of a plant community generally

A) changes from a diverse community in which many plants are common to one in which a few species are numerically dominant.
B) remains stable as long as climate and human interference remain constant.
C) changes gradually because each species responds differently to the changing environment.
D) changes until forest is established and a single species of plant remains.

Question 32

Which process does not occur in ecosystems?

A) Energy flows through the system.
B) Carbon is cycled between biotic and abiotic forms.
C) Producers convert light energy to chemical energy.
D) Consumers directly use the energy source that powers the system.

Question 33

One simple thing that you can do to help safeguard the environment is to eat a diet consisting only of

A) producers.
B) primary consumers.
C) secondary consumers.
D) a mix of producers and consumers.

Question 34

Which statement about the phosphorus cycle is false?

A) The main abiotic reservoir for phosphorus is in the water.
B) Plants release dissolved phosphate ions into the soil.
C) Phosphates that drain from soils into the sea become part of new rock and will cycle back into living organisms.
D) Guano can be used by farmers to add phosphorus to the soil.

Question 35

When a New England farm is abandoned, its formerly plowed fields first become weedy meadows, then shrubby areas, and finally forest. This sequence of plant communities is an example of

A) evolution.
B) a food chain.
C) secondary succession.
D) primary succession.

Question 36

Organisms that digest decaying organic material are

A) primary consumers.
B) decomposers.
C) primary producers.
D) detritivores.

Question 37

A keystone species that is a predator will

A) maintain the species diversity in a community.
B) harvest prey species to extinction.
C) help many of its prey reproduce.
D) reduce the diversity of the community.

Question 38

For a given area and time period, the amount of solar energy converted to chemical energy in organic compounds is called

A) primary succession.
B) secondary succession.
C) primary production.
D) secondary production.

Question 39

Carbon mainly cycles between the biotic and abiotic worlds through the processes of

A) cellular respiration and transpiration.
B) transpiration and photosynthesis.
C) evaporation and photosynthesis.
D) cellular respiration and photosynthesis.

Question 40

Which substance is cycled between organic matter and abiotic reservoirs?

A) fat
B) carbon
C) protein
D) nucleic acid

Question 41

After reading the paragraph below, answer the questions that follow.
Japanese stiltgrass is an invasive plant that was accidentally introduced to the United States in the early 1900s. It can be found on roadsides and in forests, and it has many impacts on native plants and animals. Biologists Jayna DeVore and John Maerz studied the effect of Japanese stiltgrass on American toads in their natural habitat. They enclosed American toads in cages with lycosid spiders and/or Japanese stiltgrass. The four treatments were (A) lycosid spiders and Japanese stiltgrass, (B) lycosid spiders without Japanese stiltgrass, (C) lycosid spiders and Japanese stiltgrass, and (D) no lycosid spiders and no Japanese stiltgrass. They compared the survival of American toads across the treatments (left graph). They also measured the density of lycosid spiders in different areas where Japanese stiltgrass was absent vs. present (right graph).
Source: DeVore, J. L., & Maerz, J. C. (2014). Grass invasion increases top‐down pressure on an amphibian via structurally mediated effects on an intraguild predator. Ecology, 95(7), 1724-1730.
What do their results demonstrate about the interactions between the species that they studied?

A) Lycosid spiders are predators of American toads.
B) American toads are herbivores of Japanese stiltgrass.
C) American toads are predators of lycosid spiders.
D) Japanese stiltgrass is a pathogen of lycosid spiders.

Question 42

In your backyard you overturn a large rock. In the damp soil underneath the rock, you see various insects scurrying for cover: two black beetles, five black ants, two brown beetles, and three pillbugs. In this community of organisms, relative abundance favors

A) pillbugs.
B) ants.
C) beetles.
D) pillbugs and beetles equally.

Question 43

Which arrow shows nitrogen fixation?

A) arrow A
B) arrow B
C) arrow C
D) arrow D

Question 44

Which arrow shows CO2 released as a product of cellular respiration?

A) arrow A
B) arrow B
C) arrow C
D) arrow D

Question 45

To stabilize the environment in the habitat and enable it to become self-sufficient again, it would be helpful to add

A) nitrates and phosphates to the terrestrial and aquatic ecosystems.
B) producers to absorb excess carbon dioxide and produce oxygen.
C) consumers to absorb carbon dioxide and produce oxygen.
D) decomposers to recycle nutrients in the soil and water.

Question 46

Which ecological problem might result from fertilizing a golf course with phosphorus-rich fertilizer?

A) poisoning of the grass caused by excess phosphorus
B) heavy growth of algae and cyanobacteria in lakes and rivers caused by phosphorus runoff
C) accumulation of toxic levels of phosphorus in animals in the vicinity, especially those higher on the food chain
D) a slowdown in the weathering of rock that releases phosphates into the soil under natural conditions

Question 47

Which process represents a step in the nitrogen cycle?

A) Nitrogen-fixing bacteria convert atmospheric nitrogen to nitrates.
B) Nitrites bind to soil particles.
C) Nitrogen-fixing bacteria convert atmospheric nitrogen to ammonia.
D) Denitrifiers convert ammonium to atmospheric nitrogen.

Question 48

Which statement about the nitrogen cycle is true?

A) The nitrogen cycle requires different types of bacteria.
B) Nitrogen gas is converted to nitrates in plant leaves.
C) Nitrogen cannot be cycled through living organisms.
D) When plants and animals die, nitrogen is removed from the nitrogen cycle.

Question 49

Eutrophication of a lake could occur if

A) phosphate-rich detergents were dumped into the lake.
B) fertilizers were applied in an insoluble form.
C) runoff from overfertilized lawns was prevented from reaching the lake.
D) fish were removed.

Question 50

After reading the paragraphs below, answer the questions that follow.
Biosphere II is a huge, dome-covered, self-contained structure located outside Tucson, Arizona. It was built to try to duplicate Earth's biosphere and ecosystems in miniature and to use the information gained from this experiment to help design similar habitats on the Moon and Mars. Biosphere II contained small versions of many of Earth's ecosystems, including an ocean with a coral reef, mangrove wetlands, a grassland, a desert, an agricultural system, and a house for humans. Eight men and women were sealed inside the habitat for a proposed 2-year stay. The air, water, and food for these "biospherians" all came from inside the sealed habitat, and their only contact with the outside world was through computers and telephones.
Before the 2 years were up, however, the experiment failed. Supplemental oxygen was pumped into the facility, and food supplies were provided through the airlocks. What caused the failure of the experiment? It was traced to nutrient pollution. The soil in some of the biosphere ecosystems was unusually rich in nutrients. These excess nutrients caused a huge population explosion in decomposer bacteria, which led to oxygen depletion.
How could a population explosion of bacteria lead to oxygen depletion?

A) The excess consumers used the oxygen for cellular respiration.
B) The excess producers used the oxygen to complete photosynthesis.
C) The excess decomposers removed all the nutrients from the habitat.
D) The excess decomposers prevented plants from performing photosynthesis.

Question 51

After reading the paragraph below, answer the questions that follow.
Consider the following marine community: Sea otters prey on sea urchins and therefore help maintain a healthy sea urchin population. Sea urchins prey on kelp. By helping to maintain viable sea urchin populations, the sea otters are also allowing enough kelp to grow and act as a habitat for other organisms.
In this marine community, the sea otter is a

A) primary consumer.
B) producer.
C) keystone species.
D) scavenger.

Question 52

What are the consequences if decomposers are removed from the carbon cycle?

A) Fewer carbon compounds are broken down.
B) CO2 levels in the atmosphere increase.
C) Primary consumers are not able to consume as many producers.
D) The burning of wood and fossil fuels increases.

Question 53

In your backyard you overturn a large rock. In the damp soil underneath the rock, you see various insects scurrying for cover: one black spider, five black ants, two brown beetles, and three gray pillbugs. In this community of organisms, species richness is represented by

A) the ants, since there are more of them than any other organism.
B) eleven total organisms.
C) four different species of organisms.
D) the ants and the spider equally, since they have the greatest number of organisms of the same color.

Question 54

Which list accurately orders a food chain in the grasslands of Africa from low to high trophic levels?

A) grass, giraffes, lions, vultures, fungi
B) grass, fungi, giraffes, vultures, lions
C) grass, lions, giraffes, fungi, vultures
D) grass, fungi, lions, vultures, giraffes

Question 55

Kudzu is a fast-growing vine that was introduced to the United States in 1876 as a fragrant, ornamental plant and was later used as a source of erosion control. Kudzu grows especially well in the warm, humid climate of the Southeastern United States. In fact, it grows so well that it can outgrow and kill off less successful native plants; it can also kill off areas of forest because it prevents forest trees from receiving sunlight. Kudzu can best be described as

A) a keystone species.
B) an invasive species.
C) a source of primary production.
D) an abiotic reservoir.

Question 56

Denitrifying bacteria convert ________ to ________.

A) ammonium; nitrates
B) nitrates; nitrogen gas
C) nitrogen gas; nitrates
D) nitrogen gas; nitrites

Question 57

The most worrisome results of the large-scale clearing and cultivation of land include

A) erosion and soil degradation.
B) the inability to supply fresh water.
C) the inability to supply enough food for growing populations.
D) hurricanes.

Question 58

Which trophic level in this food chain represents the secondary consumer?

A) trophic level A
B) trophic level B
C) trophic level C
D) trophic level D

Question 59

After reading the paragraph below, answer the questions that follow.
Consider the following marine community: Sea otters prey on sea urchins and therefore help maintain a healthy sea urchin population. Sea urchins prey on kelp. By helping to maintain viable sea urchin populations, the sea otters are also allowing enough kelp to grow and act as a habitat for other organisms.
Suppose that a bacterial infection swept across a sea otter population and killed most sea otters before they could reproduce. How would the marine community be affected?

A) For a period of time, there would be overpopulations of sea urchins and therefore a decline in kelp populations.
B) For a period of time, there would be an overpopulation of kelp and therefore a decline in sea urchins.
C) Sea otters would continue to decline until they reached extinction.
D) Kelp would become a primary predator of sea urchins.

Question 60

After reading the paragraph below, answer the question that follows.
A stonefly is an aquatic insect that has an incomplete life cycle. It spends its growing period (nymph life stage) on the bottom of streams, camouflaged by the rocky bottom. When it has finished growing, it crawls to the edges of streambeds to molt and emerges as a winged adult. Fish often eat the juvenile nymphs as they make their way to the edge of the streambeds.
Suppose that scientists who study predator-prey relationships notice that over a 50-year span, new color patterns evolve in the stonefly nymphs. What would be a logical and reasonable question that the scientists could investigate in relation to their observations and their knowledge of predator-prey relationships?

A) As the color pattern changes in nymphs developed, was there also a change in the color of the sand of the streambeds on which the nymphs molted?
B) As the color pattern changes in nymphs developed, was there an increase in the fish population size?
C) As the color pattern changes in nymphs developed, was there a decrease in the phosphorus concentration in the stream water?
D) As the color pattern changes in nymphs developed, did the fish eat a greater number of nymphs?

Question 61

After reading the paragraph below, answer the questions that follow.
Japanese stiltgrass is an invasive plant that was accidentally introduced to the United States in the early 1900s. It can be found on roadsides and in forests, and it has many impacts on native plants and animals. Biologists Jayna DeVore and John Maerz studied the effect of Japanese stiltgrass on American toads in their natural habitat. They enclosed American toads in cages with lycosid spiders and/or Japanese stiltgrass. The four treatments were (A) lycosid spiders and Japanese stiltgrass, (B) lycosid spiders without Japanese stiltgrass, (C) lycosid spiders and Japanese stiltgrass, and (D) no lycosid spiders and no Japanese stiltgrass. They compared the survival of American toads across the treatments (left graph). They also measured the density of lycosid spiders in different areas where Japanese stiltgrass was absent vs. present (right graph).
Source: DeVore, J. L., & Maerz, J. C. (2014). Grass invasion increases top‐down pressure on an amphibian via structurally mediated effects on an intraguild predator. Ecology, 95(7), 1724-1730.
What hypothesis is best supported by these results?

A) Japanese stiltgrass decreases the number of American toads by increasing the amount of habitat available to a predator (lycosid spiders) of American toads.
B) Japanese stiltgrass decreases the number of American toads by reducing the food supply (insects) of the toads.
C) Japanese stiltgrass increases the number of American toads by converting more solar energy to chemical energy than native plants do.
D) Japanese stiltgrass increases the number of American toads by decreasing species diversity of native plants.

Question 62

After reading the paragraph below, answer the questions that follow.
Japanese stiltgrass is an invasive plant that was accidentally introduced to the United States in the early 1900s. It can be found on roadsides and in forests, and it has many impacts on native plants and animals. Biologists Jayna DeVore and John Maerz studied the effect of Japanese stiltgrass on American toads in their natural habitat. They enclosed American toads in cages with lycosid spiders and/or Japanese stiltgrass. The four treatments were (A) lycosid spiders and Japanese stiltgrass, (B) lycosid spiders without Japanese stiltgrass, (C) lycosid spiders and Japanese stiltgrass, and (D) no lycosid spiders and no Japanese stiltgrass. They compared the survival of American toads across the treatments (left graph). They also measured the density of lycosid spiders in different areas where Japanese stiltgrass was absent vs. present (right graph).
Source: DeVore, J. L., & Maerz, J. C. (2014). Grass invasion increases top‐down pressure on an amphibian via structurally mediated effects on an intraguild predator. Ecology, 95(7), 1724-1730.
American toads consume insects. An American toad that is consuming herbivorous insects is considered a

A) secondary consumer.
B) primary consumer.
C) primary producer.
D) tertiary consumer.