IB Biology Quiz: Apply Ecological Niches
18 questions · exam conditions
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Apply Ecological NichesQuestion 1 of 18

Several species of Anolis lizards that live on the same island feed on similar insects but hunt on different parts of the vegetation: some on tree trunks, some on twigs, and others in the canopy. Which ecological concept does this pattern of behaviour best exemplify?

Competitive exclusion, where superior species force others into suboptimal habitats.
Niche construction, where each species modifies its environment to suit its needs.
Fundamental niche expansion, as each species occupies a new area of the vegetation.
Resource partitioning, where species divide a limiting resource to reduce interspecific competition.
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IB Biology Quiz

IB Biology Quiz: Apply Ecological Niches

Practice Apply Ecological Niches in IB Biology with focused quiz questions that help you check what you know, review explanations, and build confidence with test-style prompts.

What this quiz covers

This quiz focuses on Apply Ecological Niches, giving you a quick way to practice the rules, question types, and explanations that matter most for IB Biology.

How to use this quiz

Try each quiz question before looking at the correct answer. Use the explanations to review missed ideas, then come back to similar questions until the pattern feels familiar.

All questions

Question 1

Several species of Anolis lizards that live on the same island feed on similar insects but hunt on different parts of the vegetation: some on tree trunks, some on twigs, and others in the canopy. Which ecological concept does this pattern of behaviour best exemplify?

  1. Competitive exclusion, where superior species force others into suboptimal habitats.
  2. Niche construction, where each species modifies its environment to suit its needs.
  3. Fundamental niche expansion, as each species occupies a new area of the vegetation.
  4. Resource partitioning, where species divide a limiting resource to reduce interspecific competition. (correct answer)
Explanation: The correct answer is D. Resource partitioning is an evolutionary process where species with similar resource needs divide those resources to minimize direct competition. In this case, the 'resource' is the habitat space for hunting insects, and the lizards have specialized in different parts of the vegetation. A is incorrect because competitive exclusion would lead to the elimination of species, not their coexistence through specialization. B, niche construction, involves organisms actively changing their environment (e.g., beavers building dams), which is not what is described. C is incorrect; this is a narrowing or specialization of their niche, not an expansion of their fundamental niche.

Question 2

On a rocky seashore, two species of barnacles, Balanus and Chthamalus, occupy different zones. Chthamalus is found in the upper intertidal zone where it is exposed to air for long periods. Balanus is found in the lower intertidal zone where it is mostly submerged. In an experiment, all Balanus individuals were removed from a test area. Following this removal, the Chthamalus population expanded downwards into the lower zone.

Based on the experiment, which statement correctly interprets the ecological niches of these barnacles?

  1. The fundamental niche of Chthamalus is larger than its realized niche due to competition with Balanus. (correct answer)
  2. The realized niche of Balanus is smaller than its fundamental niche due to desiccation stress in the upper zone.
  3. Both species exhibit niche partitioning, allowing them to occupy their identical fundamental niches without competition.
  4. The experiment demonstrates that the fundamental niche of Balanus is restricted to the lower intertidal zone.
Explanation: The correct answer is A. The experiment shows that Chthamalus can live in the lower zone when its competitor, Balanus, is absent. This lower zone is part of its fundamental niche (the full range of conditions it can tolerate). However, in the presence of Balanus, it is restricted to the upper zone (its realized niche). Therefore, competition restricts its fundamental niche. B is incorrect because while Balanus may be limited by desiccation, the experiment doesn't provide the data to determine its fundamental niche; it only shows the effect of removing Balanus on Chthamalus. C is incorrect because their fundamental niches are not identical; Chthamalus can tolerate the upper zone while Balanus cannot, and this scenario shows competition, not its complete avoidance. D is incorrect because the experiment did not test the upper limits of Balanus's tolerance, so we cannot make a conclusion about its complete fundamental niche.

Question 3

In regions where the grey wolf was reintroduced, populations of elk, its primary prey, changed their grazing behaviour. They began to avoid open river valleys where they are more vulnerable to predation. This behavioural change has allowed willow and aspen trees to regrow in these valleys. How does this scenario illustrate the concept of an elk's ecological niche?

  1. The reintroduction of wolves expanded the fundamental niche of the elk by forcing them into new areas.
  2. The realized niche of the elk was contracted by the biotic factor of predation pressure from wolves. (correct answer)
  3. The elk's niche is defined solely by abiotic factors, which were altered by the presence of wolves.
  4. The wolves and elk now exhibit resource partitioning to reduce competition for the same habitat.
Explanation: The correct answer is B. The fundamental niche of the elk includes all areas they can physically inhabit and find food in, including the river valleys. The reintroduction of a predator (a biotic factor) forces them to avoid certain areas. This restriction of their range and behaviour due to an interacting species is a classic example of a realized niche being smaller, or contracted, compared to the fundamental niche. A is incorrect because the niche was contracted, not expanded. C is incorrect because predation is a biotic, not an abiotic, factor. D is incorrect as this describes a predator-prey interaction, not resource partitioning between competitors.

Question 4

Climate change is causing temperatures to rise, forcing a mountain-dwelling pika species to move to higher elevations. However, the soil and plant communities at these higher elevations are different and less suitable. This situation describes a potential mismatch between the pika's:

  1. Realized niche and its trophic level.
  2. Fundamental niche for temperature and its fundamental niche for food resources. (correct answer)
  3. Geographic range and its competitive ability.
  4. Fundamental niche and its realized niche due to a new predator.
Explanation: The correct answer is B. The pika's fundamental niche is defined by a set of conditions, including a specific temperature range and the availability of certain food resources. As temperatures rise, the pika follows its required temperature conditions uphill, but this new location lacks the other necessary components of its niche (food, soil). This creates a mismatch between different dimensions of its fundamental niche, threatening its survival. A is incorrect as trophic level is not the issue. C is too general; the core issue is the uncoupling of required niche components. D is incorrect as the primary driver described is an abiotic factor (temperature), not a new predator.

Question 5

A conservation plan aims to reintroduce a species of butterfly into a restored meadow habitat. The butterfly's larvae feed on only one species of host plant. Which action is most critical for ensuring the butterfly can establish a viable population, based on niche requirements?

  1. Introducing a variety of flowering plants to provide nectar for adult butterflies.
  2. Ensuring the restored meadow has the specific host plant required by the larvae. (correct answer)
  3. Removing all potential avian predators from the area before reintroduction.
  4. Planting trees around the meadow to provide shelter from wind and extreme temperatures.
Explanation: The correct answer is B. The butterfly is described as a specialist, with its larvae depending on a single host plant. This plant is a critical, non-negotiable component of its niche. Without the larval food source, the butterfly cannot complete its life cycle and the population cannot be established. While nectar for adults (A), protection from predators (C), and shelter (D) are all important components of its niche, the absolute requirement for the specific larval host plant is the most critical limiting factor described.

Question 6

In an ecosystem, the removal of a keystone species, such as a sea otter, leads to a trophic cascade and a drastic reduction in biodiversity. How can this be explained in terms of the niches of other species?

  1. The removal of the keystone species allows one competitively dominant species to expand its realized niche and exclude many others. (correct answer)
  2. The keystone species' fundamental niche was the largest in the ecosystem, and its removal leaves a vacuum that cannot be filled.
  3. All species in the ecosystem were engaged in resource partitioning with the keystone species, which collapses upon its removal.
  4. The removal causes the fundamental niches of all other species to contract, leading to population declines.
Explanation: The correct answer is A. Keystone species often control the population of a competitively dominant species. For example, sea otters prey on sea urchins. Without otters, the sea urchin population explodes. The urchins, as strong competitors for space and voracious herbivores, expand their realized niche (grazing everywhere), eliminating kelp forests and the many species that depend on them. This expansion by one species leads to the competitive exclusion of others, reducing overall biodiversity. B is incorrect because niche size is not the defining trait of a keystone species; its impact is disproportionate to its abundance. C is incorrect as the primary interaction is often predation, not resource partitioning. D is incorrect; the fundamental niches (the theoretical possibilities) remain unchanged, but the realized niches are drastically altered by the new competitive landscape.

Question 7

A species of flatworm lives in the digestive tract of a fish, absorbing nutrients from the host. The flatworm can only survive within a narrow temperature range maintained by the fish's body and requires specific nutrients only available from the fish's diet.

This description suggests that the flatworm has a:

  1. Broad fundamental niche but a narrow realized niche due to competition with the fish.
  2. Narrow fundamental niche due to high specialization on specific biotic and abiotic factors. (correct answer)
  3. Large geographic range because its host, the fish, is highly mobile.
  4. Realized niche that is significantly larger than its fundamental niche.
Explanation: The correct answer is B. The flatworm is a specialist parasite. Its requirements are very specific: a narrow temperature range and particular nutrients found only within its host. These requirements define its fundamental niche—the full range of conditions under which it can survive. Because these conditions are inherently very restrictive, its fundamental niche is narrow. A is incorrect because there is no indication that its fundamental niche is broad; it seems specialized from the start. C confuses the parasite's range with the host's range; the parasite's niche is still narrow regardless of where the host travels. D is impossible by definition; the realized niche can be equal to or smaller than the fundamental niche, but never larger.

Question 8

Two species of birds feed on the same type of seeds. When rainfall is high and seeds are abundant, the two species coexist with little conflict. However, during a drought, when seeds become scarce, the population of one species declines significantly more than the other. What does the drought reveal?

  1. The fundamental niches of the two species are identical.
  2. The high rainfall conditions represent the realized niche for both species.
  3. Niche overlap leads to intense competitive exclusion when resources are limiting. (correct answer)
  4. Resource partitioning is only effective when resources are abundant.
Explanation: The correct answer is C. The scenario shows that when resources (seeds) are not limiting, the niche overlap does not result in strong competition, allowing coexistence. However, when the resource becomes scarce during the drought, the competition intensifies. The superior competitor is able to acquire enough seeds to maintain its population, while the weaker competitor is outcompeted and its population declines. This is a classic example of competitive exclusion being most apparent under resource limitation. A is unlikely, as no two species have truly identical niches. B is an incorrect application of the term; the conditions are just one aspect of the niche. D is plausible, but C is a more direct and accurate description of the underlying principle being demonstrated.

Question 9

A strain of bacteria is discovered that can perform chemosynthesis using sulfur compounds in deep-sea hydrothermal vents. This environment is characterized by extreme temperature, high pressure, and total darkness. How does this discovery affect the understanding of ecological niches?

  1. It demonstrates that all niches ultimately depend on solar energy captured by producers.
  2. It confirms that competition is the primary factor defining the boundaries of any niche.
  3. It shows that an organism's niche is defined by its role, not by its physical environment.
  4. It expands the known range of abiotic conditions under which a producer niche can exist. (correct answer)
Explanation: The correct answer is D. A niche includes the range of abiotic conditions an organism can tolerate. The discovery of life in such an extreme environment (high temperature, pressure, no light) demonstrates that the set of possible conditions that can support life, specifically the producer niche, is much wider than previously thought. A is directly contradicted by this discovery, as chemosynthesis uses chemical energy, not solar energy. B is incorrect as this discovery is primarily about tolerance to abiotic factors, not competition. C is incorrect because a niche is defined by both the organism's role and its relationship to the physical environment.

Question 10

Two closely related species of finches live on different islands and have very similar beak depths. On a third island where both species coexist, their beak depths are significantly different, with one species having a much deeper beak and the other a much shallower beak than the allopatric populations. This is an example of:

  1. Convergent evolution, where unrelated species develop similar traits.
  2. Character displacement, driven by selection to reduce interspecific competition. (correct answer)
  3. A founder effect, where the coexisting populations have different traits by random chance.
  4. Stabilizing selection, which maintains the average beak depth in all populations.
Explanation: The correct answer is B. Character displacement is an evolutionary divergence of characteristics (like beak depth) observed when two competing species co-occur (sympatry), but not when they occur separately (allopatry). This divergence is driven by natural selection to lessen niche overlap and reduce competition for food resources. A is incorrect because the species are closely related, not unrelated. C is incorrect because the pattern is linked to the presence of the other species, not random chance from a founding event. D is incorrect because the coexisting populations show directional selection leading to divergence, not stabilizing selection maintaining an average.

Question 11

A species of beetle feeds exclusively on the leaves of a single plant species that grows only in acidic, waterlogged soil at high altitudes. A scientist is asked to define the beetle's ecological niche.

Which statement provides the most complete description of the beetle's niche based on the information provided?

  1. The beetle's niche is the high-altitude environment where its host plant is found.
  2. The beetle's niche is its role as a primary consumer in the high-altitude food web.
  3. The beetle's niche includes its diet, the soil chemistry, and the altitude required by its host plant. (correct answer)
  4. The beetle's niche is defined by its competitive interactions with other herbivorous insects.
Explanation: The correct answer is C. An ecological niche is a multidimensional concept that includes all the resources a species uses and all the environmental conditions it can tolerate. This includes its diet (leaves of a specific plant), abiotic factors (acidic, waterlogged soil), and physical location (high altitude). A describes the beetle's habitat, not its full niche. B describes its trophic level, which is only one component of its niche. D describes one potential biotic interaction, but the niche is much broader and the information given is primarily about its resource and abiotic requirements.

Question 12

Two species of protozoa, Paramecium aurelia and Paramecium caudatum, are grown in separate cultures with a fixed amount of bacterial food. Both populations thrive. When they are grown together in the same culture, the P. caudatum population eventually dies out. What is the most precise explanation for this observation?

  1. P. aurelia is a predator of P. caudatum, demonstrating a classic predator-prey relationship in the shared niche.
  2. The two species have completely different fundamental niches, and the culture conditions only support P. aurelia.
  3. Competitive exclusion occurs because the realized niches of the two species overlap too significantly for coexistence. (correct answer)
  4. P. caudatum experienced a genetic bottleneck leading to its extinction when placed in competition with P. aurelia.
Explanation: The correct answer is C. This scenario describes Gause's principle of competitive exclusion. Both species can survive alone, indicating their fundamental niches include the culture conditions. When grown together, one species outcompetes the other for the limited resources, leading to the elimination of the weaker competitor. This happens because their realized niches (the portion of the fundamental niche they actually occupy in the presence of competitors) overlap to a degree that is unsustainable. A is incorrect because the scenario describes competition for food, not predation. B is incorrect because the fact that both thrive in separate cultures shows their fundamental niches are similar, not different, with respect to these conditions. D is a possible but less direct and less certain explanation; competitive exclusion is the direct ecological principle demonstrated here.

Question 13

Black walnut trees produce a chemical called juglone, which is toxic to many other plant species and inhibits their growth nearby. Which ecological concept is most directly illustrated by this phenomenon?

  1. Resource partitioning, as the walnut tree secures resources by eliminating competitors.
  2. Allelopathy, a form of interference competition that alters the realized niche of neighboring plants. (correct answer)
  3. Commensalism, where the walnut tree benefits and other plants are unaffected.
  4. Niche construction, as the walnut tree is improving soil conditions for its own growth.
Explanation: The correct answer is B. Allelopathy is a biological phenomenon where an organism produces biochemicals that influence the germination, growth, survival, and reproduction of other organisms. This is a form of interference competition. By releasing juglone, the walnut tree actively harms its competitors, preventing them from occupying their fundamental niche near the tree and thus shrinking their realized niche. A is less precise; while it does secure resources, the specific mechanism is allelopathy. C is incorrect because other plants are negatively affected. D is incorrect because niche construction usually implies a modification of the physical environment (like a beaver dam), and in this case, the tree is harming other species rather than just modifying the environment for itself.

Question 14

A generalist species is best described as having a:

  1. Broad niche, allowing it to utilize a wide variety of resources and tolerate diverse conditions. (correct answer)
  2. Narrow niche, making it highly efficient at exploiting a specific, limited resource.
  3. Realized niche that is identical to its fundamental niche, indicating a lack of competitors.
  4. Fundamental niche determined primarily by predation rather than by abiotic factors.
Explanation: The correct answer is A. A generalist species, by definition, is adaptable and can thrive in a wide variety of environmental conditions and use many different types of resources. This corresponds to having a broad ecological niche. B describes a specialist species. C is a specific ecological situation that does not define a generalist; a generalist could still have competitors that restrict its niche. D is an oversimplification; a niche is always defined by a combination of biotic and abiotic factors, and this statement doesn't relate to the generalist/specialist distinction.

Question 15

If two species are to coexist in a stable community despite having a high degree of niche overlap, what is the most likely requirement?

  1. One species must be able to switch to a completely different food source when the other is present.
  2. The carrying capacity of the environment for both species must be very low.
  3. Intraspecific competition for each species must be stronger than interspecific competition. (correct answer)
  4. The fundamental niches of both species must be identical in all dimensions.
Explanation: The correct answer is C. For two competing species to coexist, the negative effect of an individual on members of its own species (intraspecific competition) must be greater than its negative effect on individuals of the other species (interspecific competition). This means each species limits its own population growth more than it limits the growth of its competitor, allowing the competitor to persist. A is a form of resource partitioning, but it's not the underlying theoretical requirement for coexistence. B is incorrect; a low carrying capacity would likely intensify competition. D is incorrect; if fundamental niches were identical, competitive exclusion would be the most probable outcome.

Question 16

What is the key distinction between an organism's habitat and its niche?

  1. Habitat describes the abiotic factors, while niche describes the biotic factors of the environment.
  2. Habitat is the physical location, while niche is the functional role and resource use of the organism. (correct answer)
  3. Habitat refers to the fundamental niche, while niche refers to the realized niche.
  4. Habitat is a broad geographical area, while a niche is a specific microenvironment within that area.
Explanation: The correct answer is B. A habitat is essentially the 'address' of an organism—the physical place where it lives. A niche is its 'profession' or role—what it does, what it eats, what eats it, and how it interacts with the abiotic and biotic components of its environment. A is incorrect because both habitat and niche involve abiotic and biotic factors. C is an incorrect analogy; fundamental and realized niches are both aspects of the niche concept, not synonyms for habitat and niche. D is a matter of scale and not the core conceptual difference.

Question 17

Which of the following scenarios is the best example of niche construction?

  1. A chameleon changing its skin colour to camouflage itself from predators.
  2. A beaver building a dam, which creates a wetland ecosystem that benefits the beaver and other species. (correct answer)
  3. Several species of finches evolving different beak shapes to feed on different seeds.
  4. A cuckoo laying its eggs in the nest of another bird species to be raised by the host.
Explanation: The correct answer is B. Niche construction is the process whereby an organism actively modifies its own (and other species') environment. A beaver dam is the classic example, as it fundamentally alters the physical and biotic environment, creating a new habitat that the beaver is adapted to exploit. A is an example of adaptation (phenotypic plasticity). C is an example of adaptive radiation and character displacement. D is an example of brood parasitism. None of these involve the organism actively engineering its external environment in the way the beaver does.

Question 18

The concept of the n-dimensional hypervolume, as proposed by G. Evelyn Hutchinson, is a way to model an organism's ecological niche. What does the 'n' represent in this model?

  1. The number of individuals in the population.
  2. The number of trophic levels in the ecosystem.
  3. The total number of species competing for the same resources.
  4. The number of environmental factors and resources that define the niche. (correct answer)
Explanation: The correct answer is D. In the n-dimensional hypervolume model, each environmental factor (e.g., temperature, pH, humidity) and each resource (e.g., prey size, nutrient concentration) is treated as a dimension. The niche is the multidimensional space that contains all the values for these 'n' dimensions within which the species can survive and reproduce. A, B, and C are incorrect as they represent population size, ecosystem structure, or community interactions, not the dimensions of the niche itself.