Question

Explain how the outcomes of bottom-up and top-down community regulation are similar and different

Answer 1

There are two types of controls on a population -

Top - down control refers to the situations where the structure of lower trophic levels depends directly or indirectly on trophic activities of higher trophic levels.

Bottom - up control is the limitation placed by resources allowing growth or refers to direct or indirect dependence of community structure on factors producing variation at lower trophic levels . An important exception to this pattern occurs in aquatic food webs where inverted biomass pyramids occurs.

As producer biomass changes over time, the effect trickles up to produce correlated changes in each of the higher trophic levels. And in top - down control a top predator controls the structure of the whole ecosystem. For example kelp forest ecosystem. Sea otters prey on urchins which in turn eat kelp.

From above we conclude that either the top trophic level or the bottom trophic level is controlling or regulating the whole ecosystem. So, this the great similarity and difference between these two controls.