BIOL 201 Exam 2

Competition

for competition to take place, two or more species must be using the same limited resources in the same time and space

scramble or exploitive competition- competition occurs indirectly. little interaction between individuals of the two species

ex. bears live on island and eat berries. deer are introduced and they also eat the berries; the two are competing for the same resource. deer deplete berries so bears die

interference competition- one or both species directly attempt to exclude the other from resources (food and space) when resources are not in short supply.

ex. sage bush and grasses growing in the west. sage bush produces chemicals that kill off the grass competition.

Lotka-Volterra Model- Interspecific competition (2+ species)

red wing and yellow headed black bird

dNR/dt = rRNR((KR-NR)/KR) intraspecific

$\frac{dN_{R}}{dt}=r_{R}N_{R}\left(\frac{K_{R}-N_{R}-\alpha N_{y}}{K_{R}}\right)$ where alpha is a conversion factor

stable equilibrium- the point on the vector field diagram that the two populations drift toward

if the lines cross and the stable equilibrium point is in the middle where they cross, then the two species will coexist

unstable equilibrium point- if the population gets bumped off a little, they will drift toward carrying capacity of one or another and one species will be excluded. competition can go either way. If population is bigger for one species then that species will likely have the advantage.

competitive exclusion principle- Gouse’s principle that states two species exploiting the same resource cannot coexist in the same space (based on his experiments with protists).

niche- its ecological role in the environment, how a species ‘fits in’ to an ecosystem, especially in terms of energy flow. the biotic and abiotic conditions that a species is found in

Fundamental v Realized Niche

fundamental niche- all the abiotic conditions that a species can possibly exist in in the absence of other species

realized niche- niche that adds other species into the factors (like prey, predators, parasites, etc). niche space shrinks when other species are there

paradox of competition- according to the competitive exclusion principle, species should not be able to coexist but they do in nature all the time.

predators can influence competition between species

resource partitioning- allows two species that are competing for the same resources to ‘specialize’