Competition

What is competition?

It is the interaction between two organisms using the same limited resources

• There are two main types

  • Direct and indirect competition

When does competition not occur?

When resources are unlimited

When does competition occur?

When resources are limited

Why is competition common in nature?

Because resources are almost always limited over the long term

What is indirect (exploitation) competition?

A type of competition where individuals compete indirectly by consuming the same shared resources, reducing resource availability for others

• Ex: animals consuming the same food source

What is scramble competition?

A type of competition where individual(s) scramble to consume a limited resource and because every one is scrambling for the resource, they are negatively effecting each other

What is contest competition?

A type of competition where individuals fight for a resource with the winner securing all necessary resources, while the losers get nothing

What is apparent competition?

A type of competition where two individuals compete with each other for a certain type of location or nesting site to avoid predation

What is direct (interference) competition?

A type of competition where individuals compete directly for a resource through aggressive or defensive interactions

• Ex: fighting for mates or defending territory

What is an example of individuals competing directly for a shared resource?

• Fighting over mates/territory

• Allelopathy

• Preemption

What is allelopathy?

A phenomenon where plants release chemicals that inhibit the growth of nearby plants

What is preemption?

A type of competition where an individual gets to a resource first and gets the prime location/spot, preventing others from establishing themselves

What is intraspecific competition?

A type of specie competition where individuals of the same species compete with each other, producing a growth rate that is dependent on the relationship

What causes intraspecific competition?

It is caused by limited resources such as food, space, or nutrients

What type of growth model does intraspecific competition result in?

results in a logistic population growth model, meaning that as population density increases, growth rate decreases

What is ecological niche?

Environmental limits within which individuals of a species can survive, grow, and reproduce

• There are two ways that it can be conceptualized

  • Fundamental niche

  • Realized niche

What is fundamental niche?

A complete set of conditions under which species can theoretically survive

What is realized niche?

A set of conditions under which species are actually living in

Why is the fundamental niche the bigger niche?

Because competition and other biotic interactions affect the realized niche

What is competitive exclusion?

It is the idea where two species cannot coexist at the same time, at the same niche, using the same resources

When is dN1/dt and dN2/dt the fastest?

When N1 and N2 are very small respectively

What does the equilibrium population with interspecific competition depend on?

It depends on the carrying capacity and competition resource consumption

What is competition coefficient?

Its the effect that one specie has on the growth of another specie, or more specifically, the use of a resource by one specie relative to another

What does a12 represent?

It represents the effect that species 2 has on species 1

• Ex: if a12 is 0.25, it means species 2 is equivalent to ¼ of species 1

What if a12 is less than 1?

intraspecific competition has a stronger per capita impact on resource availability for that specie

What if a12 is greater than 1?

interspecific competition has a stronger per capita impact on resource availability for the specie

What if a12 = 1?

the inter and intraspecific competition has a similar per capita impact on resource availability for that species

What is the steady state point?

the equilibrium population size (dN/dt = 0) that occurs when both populations are unchanging (N1 = K1)

What is isocline?

When two populations converge and meet/intersect in a graph

What do isoclines help predict?

Competition outcomes by determining whether a species population will increase or decrease depending on the population size

What happens when species 1 is below or above its zero growth isocline?

The population decreases but when its above, the population increases

Why does species 1 increase below the isocline?

because the low population density and competition causes the growth rate to be positive

Why does species 1 increase above the isocline?

because the high competition causes the growth rate to be negative

What does the relative position of species isocline help determine?

It helps determine which specie wins in lots-volterra competition