Bio Ch 15 - Predation and herbivory

Introduced species

a species introduced into a part of the world it has not been historically found in

also called exotic species or non-native species

Invasive species

an introduced species that spreads rapidly and has negative effects on other species, human recreation or human economies

Biological control

the introduction of one species to help control the abundance of another species

often leads to invasive species

Mesopredators

relatively small carnivores that consume herbivores

Top predators

predators that typically consume both herbivores and mesopredators

an reduction in top predators can cause a rise in the abundance of mesopredators

Predator-prey cycles

the synchrony of population cycles between predator and prey populations is a direct result of their interactions

i.e. as prey populations increase, so will predator populations- as prey populations decrease, so will predator populations

Predator prey cycles in the lab

stable predator-prey population cycles can be achieved when the environment is complex so that predators cannot easily find prey

Direct interactions

occurs when one species immediately affects another species, usually through physical contact or direct action

Indirect interactions

occurs when one species affects another through a third species or through changes in the environment

involves an intermediate species typically, is a ‘chain-like’ event

Resources

any substance or factor that is consumed by an organism and supports increased population growth rates as its availability increases

reduced availability reduces population growth

Limiting resource

a resource who’s available quantity cannot meet a population’s requirement for it

Population cycling

previous models predicted cycles for 1 species; upcoming model adds a second species into the model as a resource

Lotka-Volterra predator-prey model

a model of predator-prey interactions that incorporates oscillations in predator and prey populations and shows predator numbers lagging behind those of their prey

Growth of prey populations

growth of prey populations is dependent on the growth rate of a prey population (rN) and the rate of individuals killed by predators (cNP)

dN/dt = rN - cNP

Growth of predator populations

growth of predator populations depends on growth rate of predator populations (acNP) minus the rate of predator death (mP)

dP/dt = acNP -mP

Modelling prey

a prey population is stable when its rate of change of zero

dN/dt = 0 = rN -cNP ———> rN = cNP —> r/c = P

a prey population is stable when the addition of prey is balanced by the consumption of prey

prey population increase

the prey population will increase when the addition of prey exceeds the consumption of prey

rN > cNP ——> P < r/c

prey population decrease

the prey population will decrease whenever the consumption of prey exceeds the addition of new prey

rN < cNP ——> P > r/c