6- competition

Flashcards about species interactions, competition, niches, and the Lotka-Volterra equations.

Competition

A species interaction where both species are negatively affected.

INTRAspecific competition

Competition between individuals of the same species.

INTERspecific competition

Competition between individuals of different species.

Niche

The range of environmental conditions under which a species can survive and reproduce.

• Niches are multi-dimensional

What happens when two or more species use the exact same niche, potentially leading to one species being eliminated?

Competitive Exclusion Principle

Competitive Exclusion Principle

two or more species using the exact same niche should not be able to coexist

Define Competitive exclusion

one species eliminates the other

Define niche partitioning

When species share resources to avoid direct competition.

Fundamental niche

The complete range of conditions under which an organism could theoretically exist.

Realized niche

The part of the fundamental niche actually occupied by the species after accounting for species interactions.

In Joseph Connell’s famous barnacle experiment, what occured when Chthamalus was removed?

Balanus did not invade (limited by dessication)

In Joseph Connell’s famous barnacle experiment, what occured when Balanus was removed?

Chthamalus invades lower tidal zone (limited by competition)

What types of species interactions does the Lotka-Volterra equations describe:

• Competition

• Predator-Prey

• Host/parasite

• Mutualism/Symbiosis

In population growth, the Exponential model represents what?

Exponential growth

• Density independent per capita rates

In population growth, the logistic model represents what?

Logistic models add a ‘brake’ based on carrying capacity

• density dependent per capita rates & INTRASPECIFIC competition

Define competition coefficient

describe how much one species negatively affects the other

What does α (alpha) represent?

effect of species 2 on species 1

What does 𝛽 (beta) represent?

Effect of species 1 on species 2

If α = 0

Individuals of species 2 have no effect on population growth of species 1

If α = 1

Individuals of species 2 have the same effect on species 1 equivalent to another individual from species 1

If  0 < α <1

Individuals of species 2 reduce the growth of species 1, but less than species 1 would inhibit itself (Intraspecific competition is greater)

If α > 1

Individuals of species 2 reduce the growth of species 1 to a greater extent than species 1 would inhibit itself (Interspecific competition is greater)

Define Zero Growth Isocline

A set of values for N1 and N2 at which the population growth rate for the given species is zero.

what are the Zero Growth Isocline for species 1 and 2?

• Species 1: K1 = α N2 + N1

• Species 2: K2 = 𝛽 N1 + N2

When will growth stop?

(dN/dt) = 0

when looking at species 1, what is the value of N2 and N1 when they equal 0?

• N2 = 0 —> K1 = N1

• N1 = 0 —> K1 / α = N2

when looking at species 2, what is the value of N1 and N2 when they equal 0?

• N1 = 0 —> N2 = K2

• N2 = 0 —> N1 = K2 / 𝛽

what is the outcome?

species 1 wins

what is the outcome?

species 2 wins

what is the outcome?

either specie can win, but depends on the initial numbers of Species 1 and 2 (unstable equilibrium)

what is the outcome?

stable coexistence