Ecology: Chapter 15: Competition

Landscapers interested in sustainable agricultural practices often use plants such as fragrant sumac and creeping thyme to suppress growth of unwanted weeds. These plants release chemicals into the ground, making the soil uninhabitable for competitors. How is this an example of interference competition? -It demonstrates mutualism between species, whereas exploitative competition involves parasitism. -It illustrates physical interference preventing competitors from using shared resources. -Fragrant sumac and creeping thyme use shared resources to the extent that competitors cannot persist. -It involves the use of chemicals to prevent competitors from accesing resources. -Fragrant sumac and creeping thyme contain chemicals making them less susceptible to disease than others.

- It involves the use of chemicals to prevent competitors from accesing resources.

Desert rodents and ants both depend on seeds from scrub plants as a food resource. What conditions would favor the existence of both species within the biological community? -Rodents and ants inhabit different areas of the habitat based on temperature and rainfall patterns in the environment. -Foraging rodents are more efficient at gathering food resources in the desert habitat than the foraging ants. -Rodents prefer larger seeds as a food choice, while ants tend to consume smaller seed types. -An increase in rodent predators in the biological community causes a dramatic increase in the size of the ant population.

-Rodents and ants inhabit different areas of the habitat based on temperature and rainfall patterns in the environment. -Rodents prefer larger seeds as a food choice, while ants tend to consume smaller seed types.

When two competing species are each at equilibrium, why are their population growth rates zero? -The combined population size of the two competing species is at the carrying capacity of the environment. -The negative population growth rate of one species cancels out the positive population growth rate of the other. -One species has a positive population growth rate, and the other species is no longer in the shared range. -The increase in population size of one species equals the decrease in size by the same number of individuals.

-The combined population size of the two competing species is at the carrying capacity of the environment.

The common crow (Corvus brachyrhynchos) and a turkey vulture (Cathartes aura) both vying for the same dead animal carcass on the road by chasing each other away would be an example of -allelopathic competition. -exploitative competition. -interference competition. -apparent competition.

- interference competition

In the Lotka-Volterra competition model, when N is less than K, which of the following will be true? a. The population will decrease to zero and go extinct. b. The population will continue to grow. c. The population will decrease in size. d. The population will stabilize at this size.

b. The population will continue to grow.

In the logistic growth equation, when N is equal to K, which of the following will be true? a. The population's growth rate will be slightly negative. b. The population's growth rate will be minimal. c. The population's growth rate will be zero. d. The population's growth rate will be maximum.

c. The population's growth rate will be zero.

Which renewable resource responds to the rate of resource consumption? a. precipitation b. oxygen c. prey species d. sunlight

c. prey species

The study conducted by Joseph Connell examining barnacle distribution along the coast of Scotland best illustrates which of the following principles? a. Closely related species that are fierce competitors distribute themselves in such a way that they reduce competition with one another. b. When two organisms compete for a limiting factor, the organism that can utilize that limiting factor at the lowest levels will prevail. c. No two organisms can coexist indefinitely when they are in competition for the same resources. d. Tolerance for extreme abiotic conditions may determine the outcome of competition.

d. Tolerance for extreme abiotic conditions may determine the outcome of competition.

When two species have a negative effect on each other through an enemy, it is referred to as. a. an aggressive interaction b. exploitative competition c. interference competition d. apparent competition

d. apparent competition

When two species have a negative effect on each other through an enemy, it is referred to as. a. an aggressive interaction b. exploitative competition c. interference competition d. apparent competition

d. apparent competition

If a pond can support more turtles than ducks, what will be true about the relationship between the competition coefficients when α represents the number of turtles equivalent to one duck and β represents the number of ducks equivalent to one turtle? a. α − β = 0 b. α = β c. α < β d. α > β

d. α > β

When two species compete for limited resources, ecologists can model the outcome using two variables. The outcome of competition depends on the carrying capacities, 𝐾1 and 𝐾2, and the competition coefficients, 𝛼 and 𝛽, of the two species. The graph shows the zero population growth isoclines for two species with known carrying capacities and competition coefficients. species 1: 𝐾1=100, 𝛼=4 species 2: 𝐾2=50, 𝛽=3 Suppose that predation limits the size of the species 2 population. If the species 2 population could never rise above 10individuals, how would this change the outcome of competition with species 1? - Species 2 could never win in competition. Species 1 would have the possibility of excluding species 2. -Species 2 would always win in competition. Species 2 would have the possibility of excluding species 1. -Limiting the population of species 2 to 10 individuals would not affect the outcome of competition. -Species 1 and species 2 would coexist at a stable equilibrium point. Neither species would exclude the other.

- Species 2 could never win in competition. Species 1 would have the possibility of excluding species 2.

In the Lotka‐Volterra Competition model, what is true about the competition coefficient of species-2 relative to the number of species-1 when carrying capacity is reached for species-1? -The competition coefficient of species-2 has no bearing on the population size of species-1. -The lower the competition coefficient of species-2, the lower the population size of species 1 is when carrying capacity is reached. -The higher the competition coefficient of species-2, the lower the population size of species 1 is when carrying capacity is reached. -The higher the competition coefficient of species-2, the higher the population size of species 1 is when carrying capacity is reached.

- The higher the competition coefficient of species-2, the lower the population size of species 1 is when carrying capacity is reached.

Why are competition coefficients included in the Lotka-Volterra competition equations? -They convert between the number of individuals in one species and the number of individuals in the other species. -They account for the independent effects of two limiting resources on the population growth of a species. -They establish a numerical relationship between the fluctuating populations of competing predators and prey. -They are used to address the competition for renewable resources between two populations of the same species.

- They convert between the number of individuals in one species and the number of individuals in the other species.

The brain worm parasite is commonly found in white-tailed deer with little impact, but can be transmitted via intermediary hosts to moose with often fatal consequences. This is an example of -apparent competition. -interference competition. -allelopathic competition. -exploitative competition.

- apparent competition.

David Tilman's study of two diatom species, each with differing abilities to utilize different levels of multiple resources, showed that -coexistence is not possible. -coexistence is only possible when both resource levels are low. -coexistence is possible if each species is more efficient at using a different resource than the other species. -coexistence is only possible when both resource levels are high.

- coexistence is possible if each species is more efficient at using a different resource than the other species.

Two sifaka lemur species of genus Propithecus are allopatric and rely on the same parts of the same plant species for food. If human activity displaces one species into sympatry with the other species, then competition between the two species would most likely -increase -decrease - stay the same

- increase

The competition coefficient value for a species would be higher if that species -did not compete for the resource in question. -were less of a competitor for the resource in question. -were a better competitor for the resource in question. -were one of many competitors and not one of a pair of competitors.

- were a better competitor for the resource in question.

When two species compete for limited resources, ecologists can model the outcome using two variables. The outcome of competition depends on the carrying capacities, 𝐾1 and 𝐾2, and the competition coefficients, 𝛼 and 𝛽, of the two species. The graph shows the zero population growth isoclines for two species with known carrying capacities and competition coefficients. species 1: 𝐾1=100, 𝛼=4 species 2: 𝐾2=50, 𝛽=3 Based on the graph, what is the predicted outcome of competition between these two species? - Species 2 will win regardless of the initial number of each species. -Species 1 will win regardless of the initial number of each species. -Either species can win depending on the initial number of each species. -Neither species can win regardless of the initial number of species.

--Either species can win depending on the initial number of each species.

Identify scenarios in which two distantly related species would compete with one another. -Frogs and fish prefer different insects for food, but their diets overlap when resources are lacking. -Lemurs consume fruits and spiders consume small insects on one species of tree. -Birds build nests and spiders build webs on terminal tree branches at particular heights. -Snakes hunt mice, and mice defend themselves against predation by snakes. -Bacteria infect human hosts, and human hosts elicit an immune response.

--Frogs and fish prefer different insects for food, but their diets overlap when resources are lacking. -Birds build nests and spiders build webs on terminal tree branches at particular heights.

Identify statements as describing exploitative competition, interference competition, or apparent competition. Interference competition. -Green and blue aphids eat the same plant species. The green aphid population crashes after ladybugs increase feeding on them -Young male deer challenge the dominant Male of the group for mating for mating privileges -A hummingbird population patrols and defends wildflower patches from other bird populations -Ducks and bullfrogs eat snails with a parasite that does not affect ducks and is fatal to bullfrogs

-A hummingbird population patrols and defends wildflower patches from other bird populations - Young male deer challenge the dominant Male of the group for mating for mating privileges

Asterionella formosa and Synedra ulna are species of diatoms that rely on silicate (SiO2) . At carrying capacity, A. formosadrives the abundance of silicate down to 1 µM, whereas S. ulna drives the abundance of silicate down to 0.4 µM. Predict what will happen if Asterionella formosa and Synedra ulna attempt to inhabit the same space. -Asterionella formosa will not persist because there is insufficient silicate left in the environment by Synedra ulna. -Synedra ulna and Asterionella formosa will persist in sympatry, with A. formosa below carrying capacity. -Asterionella formosa and Synedra ulna will persist in sympatry, with both species at carrying capacity. -Synedra ulna and Asterionella formosa will persist in sympatry, with S. ulna below carrying capacity. -Synedra ulna will not persist because there is insufficient silicate left in the environment by Asterionella formosa.

-Asterionella formosa will not persist because there is insufficient silicate left in the environment by Synedra ulna.

Why are population growth rates at zero when two species are at equilibrium? -Two species can only coexist if neither population is growing. -When one species reaches carrying capacity, competition will prevent the other from growing. -Disturbances prevent further population growth. -At equilibrium, both species have reached carrying capacity for the particular resource.

-At equilibrium, both species have reached carrying capacity for the particular resource.

In a forest, there is a population of gray squirrels and a population of chipmunks. The population of gray squirrels is 150 and the population of chipmunks is 100. Based on your understanding of the Lotka‐Volterra competition model, if the carrying capacity of the forest for gray squirrels is 300, what will the population of gray squirrels be when carrying capacity is reached? - 250 -Cannot be determined without knowing the competition coefficients -300 -200

-Cannot be determined without knowing the competition coefficients

In the Lotka‐Volterra Competition model what is true about carrying capacity for species-1? -Carrying capacity for species-1 is reached when the reproductive rate of species-2 is zero (r2=0). -Carrying capacity for species-1 is determined by the number of individuals of species-1 and the number of individuals of species-2 (the competitor). -Carrying capacity for species-1 is determined by the number of individuals of species-1. -Carrying capacity for species-1 is reached when the reproductive rate of species-1 is zero (r1=0)

-Carrying capacity for species-1 is determined by the number of individuals of species-1 and the number of individuals of species-2 (the competitor).

Why do closely related species often experience more intense competition than distantly related species? -Closely related species are more likely to rely on the same limiting resource. -Distantly related species are more likely to have a significant competitive advantage. -Closely related species are more likely to live in the same place. -Closely related species are able to evolve traits to interfere with their competitor more effectively

-Closely related species are more likely to rely on the same limiting resource.

Identify statements as describing exploitative competition, interference competition, or apparent competition. apparent competition. -Green and blue aphids eat the same plant species. The green aphid population crashes after ladybugs increase feeding on them -Young male deer challenge the dominant Male of the group for mating for mating privileges -A hummingbird population patrols and defends wildflower patches from other bird populations -Ducks and bullfrogs eat snails with a parasite that does not affect ducks and is fatal to bullfrogs

-Green and blue aphids eat the same plant species. The green aphid population crashes after ladybugs increase feeding on them -Ducks and bullfrogs eat snails with a parasite that does not affect ducks and is fatal to bullfrogs

Why is allelopathy considered a form of interference competition? -It allows a species to prevent its competitors from competing effectively. -It gives one species an advantage over another by enabling it to substitute resources. -It attracts predators or herbivores to prey on the competing species. -It prevents competitive species from gathering resources in an area.

-It allows a species to prevent its competitors from competing effectively.

In a stream ecosystem, two species of aquatic plants rely on available nitrogen and phosphorus as nutrients. Under what conditions would these two species, in competition for two nutrient resources, be prevented from coexisting? -When one species is better able to persist at lower levels of nitrogen and phosphorus, while the other species requires high levels of both. -When one species is better able to survive at low levels of nitrogen, while the other species is able to survive with low levels of phosphorus. -When both species are able to persist at equivalent levels of nitrogen and phosphorus. -When both species are able to survive at lower levels of nitrogen but require higher levels of phosphorus.

-When one species is better able to persist at lower levels of nitrogen and phosphorus, while the other species requires high levels of both. -When both species are able to persist at equivalent levels of nitrogen and phosphorus. -When both species are able to survive at lower levels of nitrogen but require higher levels of phosphorus.

Exploitative competition -occurs when one species defends a resource from another. -causes the abundance of a resource to fall lower than other species can use. -is often due to aggressive interactions between species. -occurs when one species uses resources gathered by another species.

-causes the abundance of a resource to fall lower than other species can use.

Two bamboo lemur species of genus Prolemur are sympatric and rely on the same parts of the same plant species for food. If one species adapts to utilize different parts of the plant species for its food, then competition between the two species would most likely _____. -increase -decrease - stay the same.

-decrease

Classify resources as nonrenewable or renewable. Non-renewable resources. -sunlight -soilnitrates -space -rainfall -seeds -nesting sites

-nesting sites -space

Apparent competition -is the result of disturbances or abiotic conditions that favor one species. -occurs between two species with multiple limiting resources. -occurs when two species compete without the same limiting resource. -occurs when two species have a negative effect on each other through an enemy.

-occurs when two species have a negative effect on each other through an enemy.

The Lotka‐Volterra competition equations have four possible outcomes. Three of four possibilities have definite outcomes, while one outcome is contingent on -the initial population sizes of the two populations. -the initial carrying capacities of the two populations. -the reproductive rates of the two populations. -the competition coefficients of the two populations.

-the initial population sizes of the two populations.

The logistic growth equation that forms the basis for the Lotka‐Volterra Competition equations can be calculated using all variables EXCEPT -the mortality rate of the population in question. -the carrying capacity of the population in question. -the reproductive rate of the population in question. the starting population size of the population in question.

-the mortality rate of the population in question.

Under what conditions can two species competing for two resources coexist? -when the ecosystem does not experience any disturbances -when each species can persist at a lower level of one of the two different resources -when the competition is indirect -when the two resources are unrelated

-when each species can persist at a lower level of one of the two different resources

The studies concerning the bare patches found around shrubs on the coast of California eventually determined that which of the following factors were responsible for the bare patches? a. Mice that consumed other vegetation found shelter around the shrubs. b. All sunlight was captured by the shrubs' leaves, leaving none available for competitors. c. Oil found in the leaves of the shrubs promoted fires. d. Allelopathic compounds produced by the shrubs caused the bare patches.

a. Mice that consumed other vegetation found shelter around the shrubs.

With the following Lotka-Volterra competition models, what is used to indicate the outcome of competition between two species for a single resource? a. open circles b. green line c. closed circles d. purple line

a. open circles

Propithecus verreauxi and Lemur catta are sympatric and compete for the same food resources. Both species exhibit preference for fruits that are rare in their range. If fruit abundance suddenly increased, then competition between the two species would would most likely -increase -decrease -stay the same

stay the same