Trophic Interactions In Communitues

Question 1

What is a keystone species

Answer 1

Am organism that helps to define an entire ecosystem.
Activity keystone species determines community structure.
Affect much greater than would be predicted from their overall abundance.

Question 2

What happens if keystone species is removed

Answer 2

The community organization changed dramatically.
Influence of keystone species may be too down (when ks is predator) or may be bottom up (when la is producer)

Question 3

Example of keystone species

Answer 3

Enhydra lutris is an example.
Important predators for Strongylocentrotus polycanthus that are capable of deforesting established kelp forests.
(Harold + Pearse, 1987)

Other consumers of sea stars not capable of limiting populations.
Islands w/ high sea otter density:
Low sea star biomass and high algal cover.

Question 4

What are dominant species

Answer 4

Unlike keystone species dominant species in a community are numerically dominant.
Tend to be good competitors - do better than most at trophic levels.
More tolerant to extreme environments.
Human removal of dominant species can cause huge changes to community structure.

Question 5

Scientific name for sea star

Answer 5

Strongylocentrotus polycanthus.

Question 6

Scientific name for sea otter

Answer 6

Enhydra lutris

Question 7

How can removal of species through hunting/ fishing impact trophic interactions

Answer 7

Killer whale switching to sea otter prey due to declines in fish species.
Draw keep forest food chain and killer whale food chain.
Trophic cascade in Baltic ecosystem
Draw piscivorous fish..phytoplankton food chain
Overfishing top predators (cod) resulted in global shift from long lived predatory fish to short lived plankton feeding fish.