Questions and Answers
What type of interaction involves one species benefitting while the other is harmed?
In which interaction do both species benefit from their relationship?
Which ecological interaction is characterized by limited resources affecting the survival of both species?
What term describes an interaction that has no significant effect on either species involved?
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How is competition within the same species distinguished?
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Which relationship typically harms one species while aiding another?
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Which of the following interactions can involve changes in effects over time?
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What is an example of exploitation in ecological interactions?
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What is the primary conclusion derived from G.F. Gause's experiments with Paramecium species?
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Which factor is part of an organism’s ecological niche?
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What does the term 'resource partitioning' refer to in ecology?
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What distinguishes a species' realized niche from its fundamental niche?
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In Joseph Connell's barnacle study, what was the result of removing Balanus from its habitat?
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How does natural selection influence niche differentiation between competing species?
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What is typically the consequence of two species having identical niches?
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What role do abiotic factors play in establishing an organism's niche?
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What does competitive exclusion imply regarding resource competition in ecosystems?
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What is a primary reason that species like Anolis lizards can coexist despite competing for resources?
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What happens to the realized niche of a species when a competitor is removed?
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How does the temporal division of niches occur between Acomys cahirinus and Acomys russatus?
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In ecological terms, what characterizes the 'fundamental niche' of a species?
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What is implied by a high percent reduction in snake swimming speed due to the presence of cane toads?
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Which of the following adaptations might allow a predatory animal to successfully capture prey?
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How might natural selection influence the development of mimicry in prey species?
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What type of graph is most suitable for demonstrating the relationship of two continuous variables in the study?
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What would likely happen if a novel enzyme evolved in snakes that deactivates cane toad toxin?
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Why might a scatter plot be more informative than a bar graph in some studies?
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Which of the following statements best describes Batesian mimicry?
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In the context of the experiments, which variable is considered dependent?
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What advantage does aposematic coloration provide to certain prey species?
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What role does selective pressure play in the evolution of mimicry?
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What might be a consequence of a high concentration of unpalatable species existing in an environment?
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What feature of the natural environment might affect the hunting efficiency of ambush predators?
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If researchers find that the introduction of cane toads has led to decreased snake populations, what conclusion might they draw?
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What is a necessary condition for an interaction to be classified as mutualism?
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In the example of mycorrhizae, what might lead a plant to stop supplying carbohydrates to its fungal partner?
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What type of interaction is most accurately described as one species gaining a benefit while the other is unaffected?
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How does the black rush (Juncus gerardii) influence other plant species in its habitat?
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In the interaction between cattle egrets and herbivores, what is a potential mutual benefit that may arise?
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What can happen to the relationship between species over time, as illustrated in the text?
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Which of the following statements about commensalism is true?
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What advantage does Juncus provide to the surrounding plant species in salt marshes?
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What might occur if a mutualistic interaction becomes too one-sided?
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What behavior change occurs in A.russatus when A.cahirinus individuals are removed from their habitat?
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What does character displacement primarily demonstrate in sympatric populations?
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In the study of Geospiza fuliginosa and Geospiza fortis, what was observed in their beak morphology in allopatric populations?
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What type of interaction is defined as predation?
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How did the introduction of cane toads affect native black snakes in Australia?
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What adaptation was observed in the sympatric populations of Galápagos finches?
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What is the main reason for the character displacement in sympatric populations?
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What is the primary role of exploitative interactions in ecosystems?
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What happened to the predation behavior of black snakes in the area with cane toads after 40 to 60 years?
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What is a consequence of species competing for resources in overlapping habitats?
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In the experiment involving cane toads, what was measured to assess the physiological effect on black snakes?
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Why do adaptations in both predators and prey tend to become refined through natural selection?
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What signifies adaptations in species that exhibit character displacement?
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What is herbivory characterized by?
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Which of the following animals is an example of a herbivorous marine mammal?
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How do most herbivorous insects distinguish between plants?
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What type of parasitism involves an organism that lays eggs in a living host?
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Which of the following is NOT a mechanism plants use to defend themselves against herbivores?
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What is one way that parasites can affect their host populations?
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What type of interaction is mutualism?
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Which plant compound is an example of a chemical defense against herbivores?
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What is a characteristic of ectoparasites?
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What do acacia trees gain from their mutualistic relationship with certain ants?
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Which term best describes the relationship where one organism benefits and the other is harmed?
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What is NOT a factor in the adaptations of herbivores?
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In the context of positive interactions, what is commensalism?
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Which of the following statements about plant defenses is accurate?
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What is a significant environmental consequence of overgrazing and agricultural disturbance in Africa?
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How does ocean trawling compare in scale to forest clear-cutting?
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What is a major ecological effect of human-caused disturbances in marine environments?
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In terms of ecological disturbance, how does the impact of trawling affect the marine environment?
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What kind of impact does ocean trawling have on the diversity of life in marine ecosystems?
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What concept challenges the idea that communities always exist at a stable equilibrium?
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What is a key factor that ecologists believe disrupts the stability of biological communities?
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How did proponents of the equilibrium model view the relationship between species in a community?
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What can be inferred about the climax community according to traditional ecological views?
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What alternative explanation do some ecologists propose regarding the composition of species in a community?
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How do disturbances impact the concept of community stability?
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In what way do ecological disturbances challenge the traditional views on community stability?
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What might be a significant consequence of embracing the nonequilibrium model in understanding community dynamics?
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What does the intermediate disturbance hypothesis suggest about species diversity in affected communities?
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Which factor primarily contributes to the dominance of competitively superior species in low disturbance environments?
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How do small-scale disturbances influence the overall community structure?
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What effect did the severe drought have on the lodgepole pine forests of Yellowstone in 1988?
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In the context of ecological succession, what is primary succession primarily characterized by?
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Which of the following best defines 'nonequilibrium communities' in ecological terms?
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What is a consequence of frequent high-intensity disturbances on species diversity?
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What role do lodgepole pine cones play in the ecosystem following a fire?
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During ecological succession, what species typically colonizes first in primary succession?
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What phenomenon occurs when high-frequency flooding affects invertebrate species richness in streams?
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How do frequent but low-intensity fires compare with high-intensity fires in forest ecosystems?
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What is a typical outcome of climatic conditions causing natural disturbances in an ecosystem?
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In ecological studies, what does 'taxa' refer to?
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Why is the concept of ecological succession important in understanding community changes?
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What is the primary factor that allows early colonizers like lichens and mosses to thrive in barren environments after glacial retreat?
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How do pioneering species like Dryas influence the establishment of later plant species during primary succession?
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What role does sphagnum moss play in the spruce-hemlock forest ecosystem after primary succession?
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What distinguishes primary succession from secondary succession in ecological terms?
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What happens to soil nitrogen content as succession progresses from the Alder stage to the Spruce stage?
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How can human activities disrupt natural ecological succession?
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What physical changes occur to an area as it transitions through the various stages of primary succession after glacial retreat?
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What is a consequence of the nitrogen-fixing ability of certain pioneer species like Dryas and alder?
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What characterizes the primary succession process visible at Glacier Bay?
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What role do herbaceous species play in the process of secondary succession?
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What is a significant outcome of the interactions between different plant species during primary succession?
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What ecological phenomenon illustrates the long timescales required for primary succession?
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What is the ecological significance of studying primary succession at locations like Glacier Bay?
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What ecological role does the phenomenon of 'facilitation' play during primary succession?
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Study Notes
Interspecific Interactions
- Organisms engage in various interspecific interactions, including competition, predation, herbivory, parasitism, mutualism, and commensalism.
- Interactions can have positive, negative, or neutral effects on the survival and reproduction of the species involved.
Competition
- Competition occurs when individuals of different species utilize the same limited resources, impacting both their survival and reproduction.
- Intraspecific competition refers specifically to competition between members of the same species.
- Examples include weeds competing with garden plants for nutrients and lynx competing with foxes for prey.
Competitive Exclusion
- G.F. Gause's experiments demonstrated that two species competing for the same resources cannot coexist indefinitely; one will outcompete the other, leading to competitive exclusion.
- A species with a reproductive advantage will eliminate the inferior competitor over time.
Ecological Niches
- An organism's ecological niche encompasses the biotic and abiotic resources it uses, including habitat, activity periods, and food sources.
- Two species cannot permanently coexist if their niches are identical; however, resource partitioning allows similar species to coexist by utilizing different resources or times.
- The realized niche is the portion of the fundamental niche occupied by a species in a community.
Resource Partitioning and Character Displacement
- Species can partition their niches in both spatial and temporal dimensions.
- Example: Anolis lizards in the Dominican Republic differentiate their perching locations to reduce competition.
- Character displacement occurs when sympatric populations of similar species show morphological differences, as seen in Galápagos finches with varying beak depths.
Exploitation Interactions
- Exploitation refers to interactions where one species benefits at the expense of another, including predation, herbivory, and parasitism.
- Predation involves a predator killing and consuming prey, shaping adaptations in both predators and prey through natural selection.
Predator-Prey Adaptations
- Predators have acute senses, physical adaptations like fangs or claws, and behaviors that enhance hunting success.
- Prey species develop defenses such as fleeing, camouflage, or warning coloration to evade predators.
Mimicry
- Batesian mimicry occurs when a harmless species resembles a harmful one, increasing its survival rate by deceiving predators.
- Müllerian mimicry involves multiple unpalatable species resembling one another, aiding predators' learning to avoid them.
- The mimic octopus showcases advanced mimicry abilities, imitating various marine animals to evade threats and capture prey.
Cane Toad Experiment
- Researchers studied the effects of cane toads on native red-bellied black snakes in Australia, observing adaptations and changes in predation behavior after prolonged exposure to the toads.
- The experiment revealed a selective effect of cane toads on snake behavior.
Defensive Adaptations
- Various defensive adaptations, including mechanical (porcupine quills) and chemical defenses (skunk spray), evolve in species to deter predators.
- Bright coloration (aposematism) signals toxicity, while cryptic coloration helps prey blend into their environment.
These notes encapsulate the essential concepts and examples related to interspecific interactions and their ecological implications.### Herbivory
- Herbivory involves organisms (herbivores) consuming parts of plants or algae, causing harm but typically not death.
- Invertebrates, such as grasshoppers and caterpillars, represent a larger portion of herbivores compared to large mammals like cattle and buffalo.
- Marine herbivores include species like sea urchins and some tropical fish, exemplifying herbivory in ocean ecosystems.
- Many herbivores have evolved specialized adaptations, including chemical sensors to assess plant toxicity and nutritional value.
- Mammalian herbivores often utilize scent to discriminate among plant types and can prefer specific plant parts.
- Plants defend themselves against herbivores with chemical toxins (e.g., strychnine, nicotine) and physical structures like thorns and spines.
Parasitism
- Parasitism is an exploitative interaction where a parasite derives nourishment from a host, causing harm.
- Internal parasites are termed endoparasites (e.g., tapeworms) while external ones are called ectoparasites (e.g., ticks).
- Approximately one-third of Earth's species are estimated to be parasites, highlighting their prevalence.
- Some parasites exhibit complex life cycles requiring multiple hosts (e.g., the blood fluke uses humans and freshwater snails).
- Certain parasites can alter their host's behavior to facilitate transmission to the next host, enhancing their lifecycle success.
- Parasites significantly influence host survival, reproduction, and population density, such as ticks affecting moose health and predation risk.
Positive Interactions
- Positive interactions between species can involve mutualism and commensalism, benefiting at least one species without harming others.
- Mutualism is defined as a reciprocal relationship where both species benefit (e.g., ants and acacia trees).
- Mutualisms can include nutrient exchange (fungi and plant roots) and collaborative survival strategies (e.g., animal pollination).
- Costs are also associated with mutualisms; each partner gives up some resources for mutual benefit.
- Commensalism occurs when one species benefits while the other is unaffected, such as wildflowers thriving in forest shade without impacting tree health.
- Ecological interactions can shift over time, with commensal relationships transforming into mutualistic ones under changing conditions.
Community Impacts
- Positive interactions can dramatically shape ecological communities; for example, black rush (Juncus gerardii) creates favorable soil conditions in salt marshes.
- Juncus reduces soil salt concentration and increases oxygen levels, thereby enhancing biodiversity by supporting more plant species.
- The removal of beneficial species like Juncus can lead to decreased plant community diversity.
Equilibrium vs. Nonequilibrium Perspectives
- Traditional ecological views held that biological communities are stable and at equilibrium, primarily influenced by competition among species.
- Stability signifies a community’s ability to maintain a constant species composition, with the climax community seen as shaped by climate alone.
- Some ecologists questioned this, arguing that various factors (soils, topography) result in multiple stable community configurations, not just one climax community.
- Communities can be perceived as random species assemblies based on similar abiotic needs rather than functioning as cohesive units.
Disturbance and Community Dynamics
- Disturbance alters community structure by removing organisms or changing resource availability, with examples including storms, fires, floods, and human activities.
- High disturbance intensity or frequency usually decreases species diversity, while low disturbance allows dominant species to exclude others.
- The intermediate disturbance hypothesis posits that moderate disturbance levels promote greater species diversity than extreme low or high disturbance levels.
Evidence Supporting the Intermediate Disturbance Hypothesis
- Studies in New Zealand showed that invertebrate species richness was highest in streams with moderate flooding intensity, validating the hypothesis.
- Small-scale disturbances create diverse habitats, whereas large disturbances, such as significant fires, can rejuvenate ecosystems adapted to such events.
Case Study: Yellowstone National Park
- Lodgepole pine forests in Yellowstone rely on periodic fires; cones only release seeds when exposed to intense heat, fostering regrowth after fires.
- Post-1988 fires, areas within Yellowstone rapidly regrew, showcasing community adaptation to large-scale disturbances, supporting nonequilibrium community models.
Ecological Succession Overview
- Ecological succession describes species turnover in communities following disturbances, with primary succession starting in lifeless areas (e.g., after glacial retreats).
- Primary succession involves initial colonization by simple organisms like prokaryotes and protists, followed by lichens, mosses, and then vascular plants as soil develops.
- Facilitation, inhibition, or independence describes interactions between early-arriving and later species during succession.
Primary Succession Research: Glacier Bay
- Glacier Bay studies reveal a sequence of colonization post-glacial retreat, starting with pioneering species leading to a dense forest over centuries.
- Nitrogen-fixing species like Dryas play a crucial role in enhancing soil quality, gradually promoting biodiversity during succession.
Secondary Succession and Human Impact
- Secondary succession occurs after major disturbances that leave some organisms intact, leading to recolonization akin to the original community structure.
- Human activities significantly disrupt ecosystems, leading to habitat loss such as in prairies and tropical rain forests, impacting biodiversity.
- Ocean trawling poses severe threats to marine ecosystems, comparable to land deforestation, further reducing species diversity globally.
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Description
Test your knowledge on different types of ecological interactions. This quiz covers relationships such as commensalism, competition, mutualism, and more. See if you can identify how these interactions impact species in an ecosystem.