Food-webs and predator- prey dynamics

food webs are…

complex

what are the trophic levels of a food web?

producers→primary consumers→secondary consumers→tertiary consumers

what are producers?

green plants

what are primary consumers?

herbivores

what are secondary consumers?

carnivores, insect parasites

what are tertiary consumers?

higher carnivores

what is exploitative competition

when individuals interact indirectly as they compete for common resources, like territory, prey or food

what is apparent competition?

two individuals that don’t directly compete for resources affect each other indirectly by being prey for the same predator

what would happen to size of prey if predator population was removed?

the prey population would grow or crash, depends on other interactions

what is the sea otter ecosystem like when they are present?

urchin population is in control and kelp is intact

what happens without sea otters?

no kelp, sea floor covered with urchins

what happens with more starfish?

more diverse rocky shore

what happens without starfish?

mussels dominate the shore

more bass->????

less fish->more zooalgae->less phytoplankton->water is more clear

how do humans impact food webs?

eliminate top predator

what are the types of predation?

herbivores, carnivores, parasides, parasitoids, cannibalism

what predates the snowshoe hare?

lynx

what is the Lotka-Volterra Predation Model?

equation that describes predator/prey relationship

what are the two parts of the Lotka-Volterra Predation Model??

n: # of prey, P: # of predator

what is the predator equation?

dP/dt=faPN-qP

what happens with no prey?

predators die of starvation

what is the prey equation?

dN/dt=rN-aPN

what happens in the absence of predators?

prey population increases exponentially

what are zero isoclines?

population size doesn’t change

what is the lynx/hare cycle

hare pop high, lynx low, causes hares to decrease cause predation, then lynx to decrease, then hare increases, restarts cycle

population of prey is…

dependent on population of predators but there is a time lag

what is the dynamic-stability hypothesis?

long food chains are less stable than short chains

what does the energetic hypothesis state?

length of a food chain is limited by the inefficiency of energy transfer along the chain

why are long food chains are less stable than short chains?

Population fluctuations at lower trophic levels are magnified at higher levels, making top predators vulnerable to extinction.

how much is transferred between trophic levels?

10%

what are trophic cascades?

predators limit the density and/or behavior of their prey and thereby enhance survival of the next lower trophic level.