Lotka-Volterra Model Quiz
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Questions and Answers

What does the Lotka-Volterra Model primarily describe?

  • Competition between multiple predator species
  • Effects of environmental changes on species
  • Interactions between a predator species and its prey (correct)
  • Population growth of a single species

Which of the following assumptions is NOT part of the Lotka-Volterra Model?

  • Rabbits reproduce without limits
  • Foxes die only through natural causes
  • Only two species exist: predator and prey
  • Both species have interspecific competition (correct)

What is the relationship between the populations of foxes and rabbits according to the Lotka-Volterra Model?

  • Foxes only die through predation
  • Increased rabbit numbers lead to a rise in fox population (correct)
  • Fox population is unaffected by rabbit numbers
  • Rabbits thrive when foxes are abundant

In what situation does competitive exclusion occur according to the Lotka-Volterra Model?

<p>When one species consistently survives over the other (A)</p> Signup and view all the answers

Which condition must be satisfied for both species to coexist in the Lotka-Volterra dynamics?

<p>α12/K1 must be greater than 1/K2 and α21/K2 must be greater than 1/K1 (A)</p> Signup and view all the answers

What do the first-order, nonlinear, differential equations of the Lotka-Volterra model describe?

<p>The interaction dynamics between the populations of two species (A)</p> Signup and view all the answers

What type of ecological systems is the Lotka-Volterra Model most frequently applied to?

<p>Predator-prey dynamics between two species (D)</p> Signup and view all the answers

According to the Lotka-Volterra Model, which type of competition is more significant for species to coexist?

<p>Intraspecific competition must dominate interspecific competition (C)</p> Signup and view all the answers

What is the primary effect of weak interactions in predator-prey relationships?

<p>They can help reduce inherent instabilities in strong interactions. (C)</p> Signup and view all the answers

In mobile generalist predators, what can lead to transient spikes of high predation risk for prey species?

<p>Concentration in habitat remnants. (C)</p> Signup and view all the answers

Which of the following statements reflects the impact of saturating functional responses on apparent competition?

<p>They diminish apparent competition in unstable systems. (B)</p> Signup and view all the answers

What role does selective predation by specialist predators play in species coexistence?

<p>It helps offset competitive exclusion. (A)</p> Signup and view all the answers

What has Peter Chesson and Jennifer Kuang suggested regarding the explanations of coexistence in communities?

<p>Predation and competition are of comparable importance. (B)</p> Signup and view all the answers

In the Lotka–Volterra model, what is the expected outcome of herbivore and predator populations over time?

<p>There is a cyclical dynamic for both consumers and consumed. (B)</p> Signup and view all the answers

What is a potential consequence of a highly mobile predator feeding across multiple habitats?

<p>Severe overexploitation of prey in specific habitats. (A)</p> Signup and view all the answers

What aspect of predation is highlighted in terms of its effects on biodiversity?

<p>The effects of predation on biodiversity are not uniform. (C)</p> Signup and view all the answers

How does apparent competition differ in unstable systems compared to stable systems?

<p>It is reduced due to saturating functional responses. (B)</p> Signup and view all the answers

Why is further investigation into complex theoretical studies of trophic interactions needed?

<p>To explore effects like trophic cascades in multilevel webs. (B)</p> Signup and view all the answers

What can influence the per predator prey consumption rate when multiple predators are present?

<p>Predator interference (B)</p> Signup and view all the answers

Which model specifically incorporates resource competition among species?

<p>Tilman's resource-based model (D)</p> Signup and view all the answers

What is considered a resource according to Tilman's definition?

<p>Any substance or factor consumed that promotes growth (D)</p> Signup and view all the answers

In Tilman's model, which component describes how availability of resources decreases as they are consumed?

<p>Resource consumption (B)</p> Signup and view all the answers

What does the zero-growth isocline represent in Tilman's resource-based model?

<p>Combination of resources with stable population (C)</p> Signup and view all the answers

Which statement accurately describes the isoclines in Tilman's model?

<p>They can indicate competitive superiority based on resource needs (D)</p> Signup and view all the answers

What occurs when the resource levels drop below A1* or B1* in Tilman's model?

<p>Species predicted to become locally extinct (B)</p> Signup and view all the answers

In the context of competition dynamics, what do the consumption curves illustrate?

<p>The impact of species on resource levels (C)</p> Signup and view all the answers

What hypothesis is suggested when isoclines intersect in Tilman's model?

<p>Species may coexist depending on resource allocation (B)</p> Signup and view all the answers

If species 2 is competitively superior, what can be inferred about its resource requirements?

<p>It can survive on lesser amounts of both resources (C)</p> Signup and view all the answers

Which component of Tilman's model encompasses the idea that resources are replenished over time?

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

What does the parameter 'z' in the Beddington–DeAngelis model signify?

<p>Level of predator interference (B)</p> Signup and view all the answers

What is a key difference between the Lotka–Volterra model and Tilman's resource-based model?

<p>Tilman's model includes resource consumption vectors (C)</p> Signup and view all the answers

In Tilman's resource-based model, which graph component indicates points of competitive exclusion?

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

What does a gently sloping curve indicate regarding resource consumption?

<p>Resource B is consumed more rapidly. (D)</p> Signup and view all the answers

What condition allows for the coexistence of two species in a competitive scenario?

<p>Intraspecific competition being greater than interspecific competition. (C)</p> Signup and view all the answers

When does competitive exclusion occur according to the outlined model?

<p>Under specific resource concentrations and supply rates. (A)</p> Signup and view all the answers

Which factor is crucial in determining the outcomes of competition in species?

<p>The position of the resource supply point. (D)</p> Signup and view all the answers

What role do generalist predators play in predator-prey dynamics?

<p>They can lead to both stabilization and destabilization of prey dynamics. (A)</p> Signup and view all the answers

In the context of resource competition, what does the term 'zero-growth isocline' refer to?

<p>The populations where neither species grows or declines. (D)</p> Signup and view all the answers

What outcome is possible if the resource supply point is situated between the axes and the closest isocline?

<p>Both species will go locally extinct. (B)</p> Signup and view all the answers

What phenomenon occurs when generalist predators switch their focus to patches with high prey abundance?

<p>Increased stability of prey population dynamics. (B)</p> Signup and view all the answers

Which interaction has been shown to have a mixed effect on species biodiversity?

<p>Generalist predator interactions across multiple trophic levels. (A)</p> Signup and view all the answers

In Tilman's experiments, what was concluded about the coexistence of diatom species?

<p>Coexistence is contingent upon resource supply rates being between consumption curves. (A)</p> Signup and view all the answers

What is a potential outcome of weak predator-prey interactions in unstable systems?

<p>Weak interactions may reduce instabilities in strong interactions. (B)</p> Signup and view all the answers

What leads to chaotic dynamics in a predator-prey Lotka-Volterra model?

<p>Numerical responses of a mobile predator to multiple prey species. (C)</p> Signup and view all the answers

What is necessary for the model predictions regarding resource competition to hold true?

<p>Specific concentrations and supply rates of resources. (B)</p> Signup and view all the answers

Which aspect of predator behavior can disrupt prey dynamics in certain environments?

<p>High mobility and swift responses to prey abundance. (D)</p> Signup and view all the answers

What does the Lotka-Volterra model primarily assume about prey consumption rates?

<p>It is directly proportional to prey abundance. (C)</p> Signup and view all the answers

Which functional response resembles the Lotka-Volterra linear functional response?

<p>Holling type I functional response (A)</p> Signup and view all the answers

What limitation does the Holling type II functional response account for?

<p>Limited prey handling time. (C)</p> Signup and view all the answers

How do numerical responses relate to predator feeding according to M.E. Solomon?

<p>They represent the impact of prey consumption on predator recruitment. (A)</p> Signup and view all the answers

In the context of predator dynamics, what does 'Rcrit' represent in a functional response?

<p>The critical prey density below which the response stabilizes. (B)</p> Signup and view all the answers

Which of the following best describes the Holling type III functional response?

<p>It features a sigmoid shape due to prey density dependence. (D)</p> Signup and view all the answers

What factor did G.F. Gause identify as necessitating a revision of the Lotka-Volterra model?

<p>Nonlinear functional dependencies in prey-predator interactions. (D)</p> Signup and view all the answers

What happens to the predator consumption rate as prey abundance increases in a Holling type II functional response?

<p>It approaches an upper limit determined by handling time. (D)</p> Signup and view all the answers

How does an increase in prey density affect the predator search rate in a Holling type III model?

<p>It leads to a nonlinear increase in search rate. (A)</p> Signup and view all the answers

What are the implications of competitive exclusion observed in natural settings like the Bismarck birds?

<p>Certain species may dominate and replace others. (B)</p> Signup and view all the answers

What does the efficiency constant 'e' signify in predator-prey models?

<p>The efficiency of converting prey into newborn predators. (D)</p> Signup and view all the answers

Which statement correctly identifies the relationship between functional and numerical responses?

<p>Functional responses affect numerical responses through prey consumption. (D)</p> Signup and view all the answers

Which ecological phenomenon can lead to sufficient resource partitioning for coexistence among competing species?

<p>Minor environmental heterogeneity. (C)</p> Signup and view all the answers

Which type of predators typically exhibit a type I functional response?

<p>Predators like web-building spiders and filter feeders. (A)</p> Signup and view all the answers

Flashcards

Lotka-Volterra Model

A mathematical model describing the relationship between a predator and its prey population.

Positive Effect of Prey on Predator

The positive impact of prey population size on predator population growth.

Negative Effect of Predator on Prey

The negative impact of predator population size on prey population growth.

Interspecific Competition

Two species competing for the same resources (food or space) within a habitat.

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Intraspecific Competition

Competition between individuals of the same species.

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Carrying Capacity

The maximum population size a species can reach in a given environment.

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Competitive Exclusion

The outcome of competition where only one species survives and the other goes extinct.

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Coexistence

The outcome of competition where both species coexist.

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Lotka-Volterra Model Assumption

The rate at which a predator consumes prey is directly proportional to prey abundance, meaning that predator feeding is limited only by the amount of prey available.

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Type II Functional Response

This type of functional response occurs when predators are limited by their total available time, which is split between searching for prey and handling prey.

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Type I Functional Response

This type of functional response occurs when predators have a ceiling on their prey consumption rate, meaning they can only eat so much even if there's an abundance of prey.

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Type III Functional Response

This type of functional response occurs when the predator's search rate increases with increasing prey density, resulting in a sigmoid shape.

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Functional Response

The rate at which a single predator consumes prey as a function of prey abundance.

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Numerical Response

The effect of prey consumption on the predator's population growth, taking into account factors like reproduction and survival.

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Conversion Efficiency (e)

The efficiency with which prey is converted into new predators.

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Critical Prey Density (Rcrit)

This is the point at which the functional response starts being stabilizing, meaning it helps control the population.

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Stability Condition

The ratio of consumed prey to total prey abundance needs to be an increasing function of prey abundance for the system to be stable.

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Apparent Competition

A type of interaction where two species indirectly compete for resources through a shared predator. The predator's impact on both prey species is more pronounced when the prey are abundant, making the competition fiercer.

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Passive Predators

These are predators that do not actively hunt, but passively capture prey, such as web-building spiders or filter feeders.

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Holling Type II Assumption

This mathematical model assumes that the predator search rate (λ) is independent of prey density, meaning the predator will always hunt at the same rate.

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Hill Function

This is a mathematical function that describes the cooperative binding of multiple substrate molecules with an enzyme.

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Trophic Cascade

A phenomenon in ecosystems where the removal of a top predator indirectly affects lower trophic levels, causing cascading effects that can alter the structure and function of the entire ecosystem.

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Search Time (Ts)

This is the time a predator spends searching for prey.

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Predator Concentration

The tendency for generalist predators to concentrate in areas with high prey density, leading to a temporary increase in predation pressure and heightened extinction risk for prey species in those areas.

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Handling Time (Th)

This is the time a predator spends handling prey after capturing it.

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Holling Type II Model

A mathematical model that describes how predator feeding is limited by both prey availability and the predator's time to eat.

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Predator Mobility

The ability of a predator to feed in multiple habitats, potentially leading to overexploitation of prey in some areas due to the predator's ability to move and consume prey from different locations.

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Multi-Prey System

Interactions in ecosystems involving a predator and multiple prey species, where the predator has a mixture of strong and weak interactions with different prey species.

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Predator-Mediated Coexistence

The process of a prey species benefiting from the presence of a predator, as the predator reduces the population of a stronger competitor, allowing the weaker prey to persist.

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Selective Predation

A type of predator specialization where the predator focuses on consuming a specific prey species, potentially influencing the competitive outcome between prey species.

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Multitrophic Perspective

The idea that predation and competition are equally important in explaining the diversity of natural communities, emphasizing the need for a multitrophic perspective to understand ecosystem dynamics.

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Consumption Vector

The rate at which a resource is consumed by a species. A steeper slope indicates faster consumption.

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Resource Supply Point

The point on a resource graph representing the availability of resources if no species were consuming them.

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Zero-Growth Isoclines

The point on the resource graph where a species' population growth rate is zero. Species can only persist in areas where the resource supply is above their isocline.

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Tilman's Resource-Based Model

A model that predicts the outcome of competition between two species based on their resource requirements and consumption rates.

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Similar Consumptive Requirements

Species with similar resource requirements and consumption rates are more likely to compete for resources, potentially leading to competitive exclusion.

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Dissimilar Consumptive Requirements

Species with different resource requirements or consumption rates are less likely to compete directly and may be able to coexist.

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Predator Switching

When a generalist predator preferentially consumes the more abundant prey species, favoring the less abundant species and potentially leading to coexistence.

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Indirect Interactions

Interactions between species that are indirect and mediated through a third species, such as a shared predator or a common resource.

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Beddington–DeAngelis Functional Response

A functional response where the per-predator prey consumption rate is influenced by predator interference.

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Lotka–Volterra Competition Model

A model that explores how competition influences the abundance of two species.

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Resource (Tilman's definition)

Any factor or substance that is consumed by an organism, leading to increased growth rates as its availability increases.

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Resource Requirements

The resources required by a species for growth and reproduction.

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Resource Consumption

The process by which organisms consume resources, reducing their availability to others.

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Resource Supply

The replenishment of resources as they are being consumed.

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Resource Minimum (A* or B*)

The minimum level of a resource needed for a species to survive.

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Resource-Dependent Isocline

A line representing the combination of two resources that allow a species to maintain a stable population.

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Equilibrium Point

The point on a resource-dependent isocline where the species' resource consumption is balanced by resource supply.

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Resource-Based Competition Model

A graphical representation of the competitive relationship between two species, based on their resource requirements.

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Competitive Superiority

The species that can survive on less of both resources is competitively superior.

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Resource Consumption Vector (C1, C2)

A vector showing the rate at which a species consumes each resource.

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Intersecting Isoclines

The situation where two species' isoclines intersect, meaning each species requires less of one resource, but more of the other.

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Coexistence (in Tilman's model)

Two species can coexist when the supply point for both resources lies between their consumption curves.

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Exclusion (in Tilman's model)

Two species cannot coexist if their isoclines 'cross over,' indicating one species consumes resources faster.

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Study Notes

Lotka-Volterra Model

  • Describes predator-prey interactions in ecological systems
  • Assumes two species (e.g., fox and rabbit)
  • Explains how changes in predator population affect prey, and vice versa
  • Simplified model: only two species, prey birth/death (predation/natural), fox birth (affected by predation), and fox natural death
  • Predator and prey populations change in relation to each other
  • Size of predator negatively impacts prey, prey positively impacts predator

Model Predictions and Outcomes

  • Can theoretically predict outcomes of interspecific competition
  • Outcomes depend on initial population sizes, carrying capacity, and competition coefficients.
  • Possible outcomes: one species survives, both coexist, or competitive exclusion
  • Coexistence assured when intraspecific > interspecific competition
  • Predictions are "local," within a specific habitat patch

Model Limitations and Extensions

  • Lotka-Volterra assumes linear prey consumption (predator feeding only limited by prey abundance)
  • This is unrealistic at high prey densities (factors like time, digestive capacity limit predator)
  • G. F. Gause's work showed the need for non-linear functions to explain real-world observations
  • Functional and numerical responses introduced to understand prey-predator dynamics
    • Functional response describes prey consumption rate vs. prey abundance
    • Numerical response describes effect of prey consumption on predator recruitment
  • Most simple models assume new predators are directly proportional to food consumption
  • Holling introduced three types of functional response, differing in how predators consume prey.
    • Type I: linear, flattens out. Observed in passive predators (e.g., spider, filter feeder).
    • Type II: concave, approaches a maximum. Time constraints are considered. (Michaelis-Menten relationship)
    • Type III: sigmoid (s-shaped). Predators struggle to find prey, learning, or switching plays a factor.

Beddington-DeAngelis response

  • An additional function used when multiple predators present.
  • Considers predator interference to calculate per predator prey consumption.
  • Z is a positive parameter that models predator interference; the equation is dependent on both predator and prey densities

Tilman's Resource-Based Model

  • Focuses on competition over resources (e.g., food, space)
  • Resource defined as any factor needed for survival and reproduction
  • Model has three components: resource requirements, resource consumption, and resource supply
  • Isocline shows the combination of resources where population is stable
  • Isoclines can intersect to predict coexistence or competitive exclusion
  • Position of resource supply point is critical in determining outcomes

Predator Effects on Stability and Diversity

  • Generalist predators can have many effects on community stability (stable cycles, chaotic dynamics)
  • Their effects often depend on prey availability in relation to switching and time lags
  • Switching behavior may stabilize prey dynamics in patchy environments
  • Interactions can also be affected by strong/weak interactions affecting stability
  • Generalist predation can be stabilizing, reducing apparent competition
  • Selective predation can mitigate competitive exclusion

Classic Lotka-Volterra cycles

  • Standard model shows cyclical population dynamics of predator and prey
  • Specialized predator manages herbivore density (rise/fall)
  • Lag between prey and predator density growth can be a factor in natural variations
  • Parasites/other trophic interactions also important

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Test your understanding of the Lotka-Volterra model, which describes the intricate dynamics of predator-prey interactions. Explore how population sizes, carrying capacities, and competition coefficients influence ecological outcomes. Challenge yourself with the model's predictions, limitations, and possible extensions.

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