Top-down and Bottom-up control

Within a food chain, interactions between members of different species in a community can operate in two directions:

Top-down control: acts from a higher trophic level to a lower one

--> an increase in predator number will decrease the population size of prey

Bottom-up control: acts from a lower trophic level to a higher one

--> a population of producers may be limited by the numbers of nutrients in the soil or water