Ecology: Interspecific Interactions and Competition
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Questions and Answers

Which of the following best describes the core principle of competitive exclusion?

  • Resource partitioning allows species to avoid competition by using different resources.
  • Two species competing for the exact same limited resources cannot stably coexist; one will eventually outcompete the other. (correct)
  • Competition is most intense between distantly related species that utilize similar resources.
  • Species can coexist indefinitely if their resource needs are exactly the same.

In the context of interspecific interactions, what does a '+/0' relationship signify?

  • Both species are harmed by the interaction.
  • One species benefits, while the other is neither helped nor harmed. (correct)
  • One species benefits, while the other is harmed.
  • Both species benefit equally from the interaction.

What is the primary difference between interspecific and intraspecific competition?

  • Interspecific competition occurs between different species, while intraspecific competition occurs within the same species. (correct)
  • Interspecific competition is always more intense than intraspecific competition.
  • Interspecific competition always leads to the extinction of one species, while intraspecific competition does not.
  • Interspecific competition involves direct physical confrontation, while intraspecific competition does not.

Which of the following scenarios best illustrates a mutualistic (+/+) interaction?

<p>A bee pollinating a flower while collecting nectar. (A)</p> Signup and view all the answers

If two species occupy the same niche and rely on the same limited resource, what is the likely outcome according to the principle of competitive exclusion?

<p>One species will eventually outcompete and eliminate the other. (A)</p> Signup and view all the answers

Which of the following interactions is characterized as exploitation (+/-)?

<p>Predation (A)</p> Signup and view all the answers

Why might oxygen not typically be a source of intense competition among terrestrial organisms?

<p>Oxygen is generally abundant in terrestrial environments. (B)</p> Signup and view all the answers

G.F. Gause's experiments with Paramecium aurelia and Paramecium caudatum demonstrated what ecological principle?

<p>The competitive exclusion principle. (C)</p> Signup and view all the answers

Which of the following is an example of an animal acquiring toxins passively for defense?

<p>An animal accumulating toxins from consuming toxic plants. (D)</p> Signup and view all the answers

A harmless fly that closely resembles a wasp is an example of:

<p>Batesian mimicry, where a harmless species mimics a harmful one. (C)</p> Signup and view all the answers

How does Müllerian mimicry benefit the involved species?

<p>By causing predators to quickly learn and avoid a common warning signal. (A)</p> Signup and view all the answers

The mimic octopus Thaumoctopus mimicus demonstrates an advanced survival strategy by:

<p>Imitating other marine animals to hunt or avoid predation. (D)</p> Signup and view all the answers

Which of the following is NOT a typical plant defense against herbivory?

<p>Having specialized teeth for grinding plant matter. (C)</p> Signup and view all the answers

Which of the following best describes the relationship between a parasite and its host?

<p>An interaction where one organism benefits and the other is harmed. (C)</p> Signup and view all the answers

What distinguishes endoparasites from ectoparasites?

<p>Endoparasites live inside the host's body, while ectoparasites live on the host's external surface. (A)</p> Signup and view all the answers

An insect that has chemical sensors on its feet is most likely:

<p>An herbivore that can distinguish plants based on toxicity. (B)</p> Signup and view all the answers

Which of the following is an example of a behavioral adaptation for defense in animals?

<p>Forming herds or schools. (D)</p> Signup and view all the answers

What is the purpose of aposematic coloration?

<p>To warn predators of the animal's toxicity or danger. (C)</p> Signup and view all the answers

How does cryptic coloration aid in survival?

<p>By making the organism difficult to see against its background (C)</p> Signup and view all the answers

A palatable species mimics an unpalatable species. This is an example of:

<p>Batesian mimicry (D)</p> Signup and view all the answers

Which of the following interactions is classified as herbivory?

<p>A caterpillar eating the leaves of a plant (C)</p> Signup and view all the answers

A plant with spines and thorns aims to:

<p>Defend against herbivores (C)</p> Signup and view all the answers

Which of the following is an example of active self-defense in animals?

<p>Vigorously defending young from predators (C)</p> Signup and view all the answers

Gause's experiments with Paramecium species led him to formulate the principle of competitive exclusion. Which of the following statements best describes this principle?

<p>Two species competing for the same limiting resources cannot coexist permanently in the same place; the species with a slight reproductive advantage will eliminate the other. (B)</p> Signup and view all the answers

An ecological niche is best defined as:

<p>The role a species plays in an ecosystem, including all biotic and abiotic resources it utilizes. (D)</p> Signup and view all the answers

Resource partitioning is an evolutionary process that allows similar species to coexist. Which of the following is an example of resource partitioning?

<p>Two fish species inhabiting the same lake, one feeding on insects during the day and the other feeding on them at night. (D)</p> Signup and view all the answers

A species' fundamental niche is often different from its realized niche. What is the key difference between these two concepts?

<p>The fundamental niche is the potential niche occupied in the absence of competitors, while the realized niche is the actual niche occupied in the presence of competitors. (B)</p> Signup and view all the answers

Connell's experiments with Chthamalus and Balanus barnacles demonstrated which ecological principle?

<p>That competition can limit the realized niche of a species. (D)</p> Signup and view all the answers

The study of spiny mice (Acomys cahirinus and A. russatus) in the Middle East revealed that:

<p><em>A. russatus</em> is naturally nocturnal but becomes diurnal in the presence of <em>A. cahirinus</em> due to competition. (C)</p> Signup and view all the answers

What is character displacement?

<p>The divergence of characteristics in sympatric populations of two species, compared to allopatric populations, due to competition. (B)</p> Signup and view all the answers

Which situation would most likely lead to resource partitioning?

<p>Two species of fish that consume similar insect larvae develop different mouthparts to specialize on different sizes of larvae. (C)</p> Signup and view all the answers

Imagine two species of insects that compete for the same food source in the same habitat. According to the principle of competitive exclusion, what is the most likely long-term outcome?

<p>One species will eventually outcompete the other, leading to the local extinction of the less competitive species. (A)</p> Signup and view all the answers

If a researcher removes a potential competitor species from a habitat and observes that the remaining species expands its range of resources used, what can the researcher conclude?

<p>The original species' realized niche was smaller than its fundamental niche due to competition. (D)</p> Signup and view all the answers

Two species of plants that require the same soil nutrients are grown in the same field. Over time, one species develops a more extensive root system that allows it to access nutrients more efficiently. What is the most likely outcome?

<p>The plant species with the more efficient root system will eventually outcompete the other species. (A)</p> Signup and view all the answers

Seven species of Anolis lizards coexist in the Dominican Republic, each with a different preferred perch. This is an example of:

<p>Resource partitioning (A)</p> Signup and view all the answers

Which of the following describes a species' realized niche?

<p>The specific set of environmental conditions and resources a species actually uses in the presence of competitors. (D)</p> Signup and view all the answers

Two species of finches on an island have beaks of similar size, allowing them to feed on similar seeds. After many generations, the average beak size of one species increases, while the average beak size of the other decreases. This is an example of:

<p>Character displacement (C)</p> Signup and view all the answers

In the context of ecological competition, what does 'limiting resources' refer to?

<p>Resources that are scarce and essential for the survival and reproduction of a species, thus influencing population growth. (B)</p> Signup and view all the answers

In the context of character displacement, what is the most likely long-term outcome if Geospiza fuliginosa became extinct on Floreana Island, where it previously coexisted with Geospiza fortis?

<p>The beak depth of <em>G. fortis</em> would likely increase to utilize a broader range of seed sizes, converging towards the morphology observed in allopatric populations. (B)</p> Signup and view all the answers

Which of the following scenarios best illustrates an exploitative interaction, as defined in the text?

<p>A lion preying on a zebra, where the lion benefits by gaining nutrition and the zebra is harmed. (A)</p> Signup and view all the answers

How does natural selection refine the adaptations of both predators and prey in a predator-prey relationship?

<p>Predators evolve adaptations that increase their efficiency in capturing prey, while prey evolve adaptations that help them avoid being eaten. (D)</p> Signup and view all the answers

In the experiment involving cane toads and red-bellied black snakes, what is the most likely explanation for the observed difference in the percentage of snakes eating cane toads between areas with and without cane toad presence?

<p>Snakes from areas with cane toads have learned to avoid them due to the toxin, while snakes from areas without cane toads are more likely to consume them out of naivete. (D)</p> Signup and view all the answers

Based on the cane toad and black snake experiment, what is the most plausible prediction if researchers repeated part 1 of the study with snakes possessing a novel enzyme to deactivate cane toad toxin?

<p>The percentage of snakes eating cane toads would be approximately equal in both areas, and significantly higher than the original study. (A)</p> Signup and view all the answers

What conclusion can be drawn from the Scientific Skills Exercise data regarding the selective effect of cane toad exposure on swimming speed?

<p>Exposure to cane toads can lead to increased toxin resistance, likely resulting in reduced impact on swimming speed over time. (B)</p> Signup and view all the answers

Why is a bar graph appropriate for presenting the data in part 1 of the cane toad experiment (percentage of snakes eating different prey types) while a scatter plot is more suitable for the data in part 2 (years of cane toad presence vs. swimming speed reduction)?

<p>Bar graphs are used to compare discrete categories, while scatter plots are used to show the relationship between two continuous variables. (C)</p> Signup and view all the answers

Which of the following is NOT an example of predation, as the term is defined in the text?

<p>A bear consuming berries from a bush. (B)</p> Signup and view all the answers

How do the heat-sensing organs of rattlesnakes and other pit vipers contribute to their success as predators?

<p>They allow the snakes to detect potential prey by sensing their body heat. (C)</p> Signup and view all the answers

What is the most probable evolutionary response of prey populations to increased hunting efficiency in their predators?

<p>The evolution of enhanced camouflage, speed, or defensive mechanisms. (C)</p> Signup and view all the answers

In the context of character displacement observed in Galápagos finches, what is the environmental factor driving the divergence of beak depths in sympatric populations?

<p>Competition for available seed resources. (A)</p> Signup and view all the answers

Considering the data from the experiment on cane toads and black snakes, what is the most likely explanation for the initial reduction in swimming speed of snakes injected with cane toad toxin?

<p>The toxin disrupts the snakes' nervous system, affecting muscle coordination and function. (C)</p> Signup and view all the answers

Which of the following scenarios is the LEAST likely outcome of a successful adaptation in a prey species that allows it to completely avoid predation by a specific predator?

<p>The predator species experiences an increase in population size due to the increased health of the prey species. (D)</p> Signup and view all the answers

How can the concept of 'exploitation' be applied to understand the relationship between humans and fish populations in the ocean?

<p>Overfishing exemplifies exploitation, where humans benefit by harvesting fish, but fish populations are depleted. (A)</p> Signup and view all the answers

Suppose a new invasive plant species is introduced to an ecosystem. This plant is highly palatable and nutritious but lacks any natural defenses against native herbivores. What is the most likely short-term ecological consequence?

<p>The native herbivores experience a population boom, potentially leading to overgrazing and decline in other plant species. (B)</p> Signup and view all the answers

Parasitoid insects are unique from other parasites because they:

<p>Lay eggs on or in a living host, with the larvae eventually killing the host as they feed. (B)</p> Signup and view all the answers

How might a parasite manipulate the behavior of its host to increase its own reproductive success?

<p>By altering the host's behavior to increase the chances of the host being consumed by the parasite's next required host. (B)</p> Signup and view all the answers

What potential indirect impact can ectoparasites like ticks have on a moose population?

<p>Weakening the moose, making them more vulnerable to cold stress or predation. (A)</p> Signup and view all the answers

What distinguishes a positive ecological interaction from an exploitative one?

<p>Positive interactions benefit at least one species without harming the other, while exploitative interactions benefit one species at the expense of another. (C)</p> Signup and view all the answers

In a mutualistic relationship, what condition must be met for the interaction to persist?

<p>The benefits to each species must outweigh the costs incurred from the interaction. (D)</p> Signup and view all the answers

How can environmental conditions influence the dynamics of a mutualistic relationship, such as mycorrhizae?

<p>Changes in soil nutrient availability can alter the balance of costs and benefits, potentially causing the relationship to break down. (D)</p> Signup and view all the answers

What is the primary distinction between commensalism and mutualism?

<p>Commensalism involves only one species benefiting, while mutualism involves both species benefiting. (D)</p> Signup and view all the answers

How does the commensal relationship between wildflowers and trees in a forest ecosystem function?

<p>Trees offer a shaded environment that benefits the wildflowers, without being affected themselves. (A)</p> Signup and view all the answers

Why might the relationship between cattle egrets and herbivores sometimes shift from commensalism to mutualism?

<p>If the egrets begin removing ectoparasites from the herbivores or warning them of predators, benefiting the herbivores. (D)</p> Signup and view all the answers

What is the role of black rush (Juncus gerardii) in New England salt marshes as a facilitator?

<p>It alters soil conditions by reducing salt concentration and increasing oxygen levels, benefiting other plant species. (A)</p> Signup and view all the answers

What does the removal of Juncus gerardii from New England salt marshes demonstrate about its ecological role?

<p>It reveals that Juncus is a keystone species whose presence significantly enhances plant diversity. (A)</p> Signup and view all the answers

Consider a scenario where a species of fish consumes the larvae of a parasitoid wasp. How would this predation affect the host insect population that the wasp larvae typically parasitize?

<p>The host insect population would likely increase as the fish reduces the number of parasitoid wasps. (B)</p> Signup and view all the answers

A plant provides food and shelter to ants, which in turn protect the plant from herbivores. If a disease drastically reduces the ant population, what is the most likely outcome for the plant?

<p>The plant population will likely decrease due to increased herbivore damage. (D)</p> Signup and view all the answers

In a forest, a fungal species forms mycorrhizal associations with tree roots, aiding in nutrient uptake. If a severe drought occurs, how might this mutualistic relationship be affected?

<p>The relationship would likely break down as the fungus becomes more of a burden on the tree due to limited resources. (D)</p> Signup and view all the answers

An ecosystem contains a plant species that provides habitat for a variety of insects. A non-native vine is introduced, which grows rapidly and covers the plants, reducing sunlight. What is the most likely long-term effect on the insect community?

<p>The insect community will likely shift towards species that can tolerate low-light conditions or feed on the vine. (B)</p> Signup and view all the answers

Flashcards

Interspecific interactions

Interactions between individuals of different species affecting survival and reproduction.

Competition

A −/− interaction where individuals of different species use a limited resource negatively affecting both.

Predation

A +/− interaction where predators benefit while prey are harmed.

Herbivory

A +/− interaction where herbivores consume plants, benefiting themselves while harming plants.

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Parasitism

A +/− interaction where parasites benefit at the expense of their hosts.

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Mutualism

A +/+ interaction where both species benefit from the relationship.

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Commensalism

A +/0 interaction where one species benefits while the other is neither helped nor harmed.

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Competitive Exclusion Principle

The theory that two species competing for the same limited resource cannot coexist indefinitely.

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Competitive Exclusion

The principle stating two species competing for the same resources cannot coexist permanently; one will eliminate the other.

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Carrying Capacity

The maximum population size an environment can sustain without degrading; where growth levels off.

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Ecological Niche

The specific set of resources an organism uses in its environment, including biotic and abiotic factors.

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Resource Partitioning

The differentiation of niches that enables similar species to coexist by using resources differently.

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Realized Niche

The portion of a species' fundamental niche that it actually occupies, influenced by competition.

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Fundamental Niche

The niche potentially occupied by a species in the absence of competitors or other limiting factors.

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Character Displacement

The tendency for characteristics to diverge more in sympatric populations than in allopatric populations due to competition.

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Chthamalus stellatus

A barnacle species studied to understand competition and its influence on niche distribution.

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Balanus balanoides

A barnacle species that competes with Chthamalus and influences its realized niche.

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Nocturnal

Active during the night; behavior seen in the common spiny mouse.

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Diurnal

Active during the day; behavior sometimes overridden by competition in the golden spiny mouse.

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Interspecific Competition

Competition between individuals of different species for the same resources in an ecosystem.

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Sympatric

Populations of species that exist in the same geographic area and potentially compete.

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Allopatric

Populations of species that are geographically separate and do not compete directly.

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Natural Selection

The process where organisms better adapted to their environment tend to survive and reproduce more than others.

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Allopatric Populations

Populations of species that are geographically isolated from each other.

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Sympatric Populations

Populations of species that live in the same geographic area and interact.

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Exploitation

Interaction where one species benefits from feeding on another, harming it.

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Adaptive Change

Changes in species traits that enhance survival in response to environmental pressures.

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Cane Toad Introduction

The introduction of cane toads in Australia in 1935 aimed to control pests, but caused ecological issues.

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Snake Predatory Behavior

The feeding patterns and preferences of snakes in different environments influenced by prey presence.

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Toxin Resistance

The ability of organisms to tolerate or neutralize harmful substances produced by other species.

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Red-Bellied Black Snakes

A species of snake studied for its response to cane toad toxin in Australia.

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Percent Reduction in Swimming Speed

The measure of how exposure to toxins affects the mobility of snake species.

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Bar Graph Usage

A visual representation appropriate for categorical data, showing comparisons across groups.

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Scatter Plot Usage

A graph that shows the relationship between two numeric variables, ideal for trend identification.

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Predator Adaptations

Traits that enhance a predator's ability to catch and subdue prey.

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Prey Adaptations

Traits that help potential prey avoid being captured by predators.

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Behavioral defenses

Actions animals take to avoid predation, like hiding or fleeing.

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Morphological defenses

Physical adaptations in animals that protect them from predators.

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Chemical defenses

Toxic substances that deter predators, found in some animals.

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Aposematic coloration

Bright warning colors used by toxic animals to deter predators.

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Cryptic coloration

Camouflage that enables prey to blend into their environment.

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Batesian mimicry

A harmless species mimics a harmful one to avoid predation.

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Müllerian mimicry

Two unpalatable species mimic each other, reinforcing their warning.

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Specialized adaptations in herbivores

Features that help herbivores select and process food effectively.

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Plant defenses

Defensive strategies plants use, such as toxins and thorns.

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Endoparasites

Parasites that live inside the body of the host.

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Ectoparasites

Parasites that feed on the external surface of the host.

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Natural selection and mimicry

The process by which mimicry evolves as predators learn to avoid harmful species.

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Defense mechanisms

Strategies used by animals and plants to protect themselves from threats.

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Mimic octopus

An octopus that can imitate various marine animals to deceive prey and predators.

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Parasitoid Insects

Insects that lay eggs on or in a living host, causing harm, typically leading to the host's death.

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Blood Fluke

A parasite that infects humans and freshwater snails, requiring both hosts in its lifecycle.

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Host Manipulation

Behavioral changes in hosts that help parasites reach their next host.

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Ectoparasite Effects

Parasites like ticks weaken hosts by feeding on blood, affecting their survival.

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Positive Interactions

Ecological interactions where at least one species benefits, and neither is harmed.

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Mutualism Definition

A +/+ interaction where both species benefit from their relationship.

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Mutualism Examples

Cases like fungi helping plants absorb nutrients while receiving carbohydrates.

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Commensalism Definition

A +/0 interaction where one species benefits without affecting the other.

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Commensalism Example

Wildflowers benefit from trees providing shade, without affecting the trees.

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Interaction Changes

Ecological interactions can shift from commensalism to mutualism over time.

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Black Rush

A plant that alters soil conditions to benefit other species in salt marshes.

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Juncus Benefits

Juncus reduces soil salt and increases oxygen, aiding diverse plant life.

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Impact of Positive Interactions

These interactions can increase species diversity in ecological communities.

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Mutualism Costs

In mutualism, both partners incur costs as well as benefits.

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Breaking Mutualism

If costs exceed benefits, mutualistic relationships may temporarily break down.

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Study Notes

Interspecific Interactions

  • Interspecific interactions (interactions between species) can positively (+), negatively (-), or neutrally (0) affect individuals involved.
  • Predation is a +/− interaction (positive for predator, negative for prey).
  • Mutualism is a +/+ interaction (positive for both species).
  • Competition is a −/− interaction.
  • Exploitation is a +/− interaction.

Competition

  • Competition occurs when individuals of different species use the same limited resource, negatively impacting both.
  • Competitive Exclusion: Two species competing for the same limiting resources cannot coexist indefinitely. One species will outcompete the other, leading to the elimination of the less efficient competitor.
  • Ecological Niches: A species' ecological niche is its specific set of biotic and abiotic resources. Two species cannot coexist if their niches are identical.
  • Resource Partitioning: Similar species can coexist by using different resources, at different times, or in different ways, reducing competition. This leads to niche differentiation.
  • Fundamental Niche: The full range of resources and conditions a species can potentially use.
  • Realized Niche: The portion of the fundamental niche that a species actually uses due to competition.
  • Character Displacement: Sympatric species tend to develop differences in traits that reduce competition, compared to allopatric (geographically separate) populations.

Exploitation

  • Exploitation interactions involve one species benefiting and the other being harmed (+/−).
    • Predation: A predator kills and eats a prey.
      • Predators have adaptations like acute senses, claws, fangs, or venom to capture prey.
      • Prey have adaptations like camouflage, hiding, fleeing, or forming herds to avoid being eaten.
      • Mimicry: Some prey species are protected by resembling harmful species (Batesian mimicry - harmless resembles harmful, Müllerian mimicry - both harmful resemble each other). The mimic octopus is a well-known predator mimic.
    • Herbivory: An herbivore eats parts of a plant or alga without killing it. Plants have defenses against herbivory (toxins, spines, thorns).
    • Parasitism: A parasite derives nourishment from a host, harming the host. Parasites can be internal (endoparasites) or external (ectoparasites).

Positive Interactions

  • Positive interactions involve at least one species benefiting, and neither species is harmed.
    • Mutualism: Individuals of both species benefit (+/+).
      • The benefits usually outweigh the costs. Examples include acacia trees and ants, mycorrhizae, and animals that pollinate flowers.
    • Commensalism: One species benefits (+/0), and the other is neither harmed nor helped. Example includes wildflowers benefiting from shade provided by trees.
      • Commensalism can potentially shift to mutualism over time (e.g., cattle egrets eating insects and ticks from herbivores).

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Explore ecological interactions like competition, mutualism, and exploitation. Understand competitive exclusion, niche differentiation, and mimicry. Review Gause's experiments and defense mechanisms like passive toxin acquisition.

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