Interactions - Competition Theory Flashcards
Intraspecific Competition
This is competition for resources between members of the same species
How is intra comp ecologically important?
In population regulation and evolutionary change
How does intra comp regulate populations?
Density-dependence limits resource availability, competition induces stronger survivorship.
Interspecific Competiton
This is competition between members of seperate species.
How is inter comp important?
Population regulation of bothj species, determines ecological structure
What does inter comp lead to?
Equilibrium of species-resource abundance of extinction of one species.
Interference Competition
The direct inhbition of a species ability to consume a resource
Exploitative Competition
Where one species reduces resources for the other, without species interaction
Diffuse Competition
Competition across an array of resources like plants with sunlight and water.
Why is competition theory hard to measure?
It happens slow enough for measurmenets to be difficult.
Ecological Succession
The change of species mix and habitat in an area changes over time
Competitive Exclusion Principle
Says two species cannot coexist if they occupy the same niche, if there is scarce demand for it.
Optimal Foraging Theory
Establishes effects of habitat quality and diet choice of organisms spatial distribution.
What does CEP result in?
Loss or extinction of the lesser competitive species
Example of CEP…
1947 Hawaiii Agriculture Department released 32 parasitoids to control parasites, where after compeittion, only one species remained.
Carrying Capaciyu
Measures amount of resources in an ecosystem that can support a population
Rate of growth is dependent on density equation…
dN/dt = rN(1-N/k)
If N > K
Intraspecific competition removes individuals with high resource demand.
Logistic Equation
Can be used to relate population change to current population given growth rate R and carrying capacity K
When is a population at stable equilibrium?
When N = K
What is important to consider when calculating inter/intraspecific equations?
The type of interactions may have, like measuring effect of j removal of resource ultimately on i
How can species behaviour be introduced into Logistic equations?
Coefficient of Competition
Coefficient of Competition
This measures interspecific competiton relative to intraspecif compeititon
Multiplying population size of j by coefficient…
Converts j into units of the species i of which j has an effect
When is growth rate negative in logistic equation?
If dN/dt is over 1
How to conceptulaise intra/inter comp graphically?
Both species of equal sized, which if full N=K; if j regulated to coefficient of 0.5, taking up half square(consuming half resources?
Why is coefficient of competition divided by Ni?
Describes how many individuals of i use resoruces of species j, determining effect of i on j dN/dt
How can logistic equation be used to predict how coexistence can occur?
By manipulating the equation so rate of growth are set in a stable population
What does Nt = Ki - aijNj describe?
Equilibrium state of i is at carrying capacity,
Apply Nt = Ki - aijNj…
50 species of i, with K of 150, dN/dt of 0.2 and a of 0.5 and J of 50, equilibrium potnetial is 125, can coexist
What should Comp coefficient bet for co-existnece?
Less than 1
What do Ni and Nj depend on?
Carrying capacity and competition coefficients, not size.
Lotka Volterra Equation
Describes growth rate of i in presence of Nj of a competing species j
When is coexistence possible?
When each species excel in using a resoruce that limits the other
Example of CEP not applying?
Paradox of the Phytoplankton
Plants
Lake Victoria Nile perch
Apparent Competition
Indirect interactions between population when two species are prey for the same predator.
Describe apparent competition…
If predator favours species a, there will be more predators around to consume species b
How might apparent competition result in population cycles?
If species A is preferred by predator due to abundance, species B is relieved of predation, growing to populations where predator consumes it over species A
What is optimal foraging theory based on?
Organisms maximising net energy gain whilst minimizing energy expenditure through adaptations.
What should OFT take into account?
Availability/Distribution of food and Risks/Benefits in Foraging strategies.
What is an example of OFT?
Darwin finches.
What can OFT models be used for?
Predictions of how beak morphology changes with changing seed resource for example.
How may OFT be used in predator-prey interactions?
Predators maximise nutritional value of prey in tandem with expenditure in ease of catching them.
Where can OFT be applied?
Conservation efforts like predicting limiting factors for wildlife populations.
What is assumed in OFT predictions?
Distribution/abundance of prey, metabolic cost associated with foraging and predators ability to detect/capture prey.
Logistic Equation
This is used to describe growth rate of a population over time taking into account intrinsic growth rate of the population and the environments carrying capacity.
What is the formula for the logistic equation?
dN/dt=rN(1-N/k)
What does dN/dt describe?
Rate of change of population over time (growth or decline_
What is r in the logistic equation?
Intrinsic growth rate of the population, measuring population growth if there were no limiting factors.
What does rN(1-N/k) represent?
Factors influencing rate of change.
What does 1-N/K represent?
Fraction of carrying capacity availabie to population at a given time.
This is population net growth multiplying intrinsice growth rate to environmental factors.
What if the logistic equation is close to 1?
qPopulation is growing rapidly, becoming smaller as population approaches carrying capacity
Why is the ‘1’ included in the logistic equation?
To ensure the term (1-N/k) is positve, as negative not biologically possible.
Coefficient of Competition
This is used to relate interactions between species and how their competition among shared resoruces such as food, water or space.
What is the value range of COC?
0-1(0 being no competition and 1 being maximum)
How is COC introduced into the logistic equation?
Introducing it as a multiplicative factor against K
Multiplicative Factor
This is a number/symbol multiplied with a variable or an unknown quantitiy in an algebraic term.
What is the equation of Logistic Growth with COC?
dN/dt=rN(1-N/(aK))
What does dN/dt=rN(1-N/(aK)) measure?
Effects of competition against carrying capacity.
When does carrying capacity reduce?
When a<1
Give example of multiplying COC and K together?
a=0.2 and K=0.8 = 0.16
How can the logistic equation with COC be used in conservation?
Relate potential of invasive species to outcompete natives, like estimating degree of plant compeietion.
Lotka-Volterra Equations
These describe interactions between species competing for the same resource in an environment.
Derive Nt = Ki - aijNj
Nt represents population size of i at time t
Ki is carrying capacity of species i
Nj is population size of species j at time t
Aij is COC measuring degree of which species j reduces growth rate of species i due to shared resource comp
What does Nt = Ki - aijNj describe?
N of i is a function of its carrying capacity and the effect of competition from species j.
