Keystone Species, Trophic Cascades and Communities as Ecological Networks

Explain Paine's experiment

- removed the sea star from an intertidal area - a mussel was able to take over the area and exclude algae / other invertebrates from that zone - evident that the sea star limited the number of mussels that could reproduce - with sea stars present, 15-20 different species of algae and invertebrates were present - without sea star, diversity declined = keystone species

keystone species

A species that influences the survival of many other species in an ecosystem

a trophic cascade is when an _______ ___________ controls the distribution of resources, leading to _________ of __________ effects

apex predator, cascades, indirect

when you remove a keystone species, what happens to the system?

it simplifies itself. ie, many species may disappear

indirect effect vs direct effect examples

lion eats impala which leads to increased plant biomass--(positive) INDIRECT EFFECT of lion on plant lion eats impala--(negative) DIRECT EFFECT

not all herbivores are ___________ limited

predator

green world hypothesis

predators reduce the abundance of herbivores, allowing plants to flourish

indirect and direct effects involve the interactions between 2+ _________

species