Week 11 Monday

Question 1

what maintains populations and diversity?

Answer 1

• through competition and predation, species compositions and abundances can reach equilibria
• Stability is attained by opposing forces
  —isoclines of zero growth
  —niche overlap and partitioning
  —competitive hierarchies and competitive equivalences
  —increased food web diversity increase community stability

Question 2

what does the intermediate disturbance hypothesis propose?

Answer 2

that high diversity was a consequence of continually changing conditions
– increased diversity was a result of constantly changing conditions
– predicted that intermediate levels of disturbance is common

Question 3

give an example of intermediate disturbance hypothesis

Answer 3

• the effect of wave action on diversity of algae and invertebrates growing on boulders in the intertidal zone
  – boulders that experienced intermediate rates of disturbance supported more species

Question 4

what is stability?

Answer 4

the absence of change
–although generally lack of disturbance, it can be found in the presence of it as well

Question 5

what is resistance?

Answer 5

ability to maintain structure and/or function in face of potential disturbance

Question 6

what is resilience?

Answer 6

Ability to recover from disturbance

Question 7

what is Alternative State?

Answer 7

the disturbance fundamentally shifts the baseline so much that the new equilibrium that occurs afterwards is distinct from before

Question 8

what is the park grass experiment

Answer 8

-study of effect of fertilizer treatments on yield and structure of hay meadow community
-researchers investigated ecosystem stability measured by community composition variability
– proportion of major species groups appears very stable overtime
– but if we consider the community at the level of species,
– perception of stability depends on how we view the community

Question 9

what is the insurance hypothesis?

Answer 9

Diversity increases stability due to increased probability of there being some species able to cope with any particular disturbance

Question 10

what is a key expectation of the insurance hypothesis?

Answer 10

that the overall response of a community is not driven by the same species every year - different species become important under different conditions

Question 11

what is the redundancy hypothesis?

Answer 11

in diverse systems there are more likely to be species that can compensate for changes

Question 12

how does competition, predation, and disturbance fit together?

Answer 12

• Relative importance of the effect of disturbance, competition and predation on community regulation can vary predictably with trophic position, recruitment, and environmental conditions