Problem 2
Does any increase in primary production lead to an increase in herbivore grazing pressure, thus maintaining a low standing crop of plants? Discuss what ecological processes might prevent this from happening. Van de Koppel et al. (1996) discuss this question and provide data from a salt marsh grazed by hares, rabbits, and geese.
Problem 3
In discussing the reality of trophic levels, Murdoch \((1966 a, p .219)\) states: Unlike populations, trophic levels are ill-defined and have no distinguishable lateral limits; in addition, tens of thousands of insect species, for example, live in more than one trophic level either simultaneously or at different stages of their life histories. Thus trophic levels exist only as abstractions, and unlike populations they have no empirically measurable properties or parameters. Discuss.
Problem 5
How would it be possible to have an inverted Eltonian pyramid of numbers in which, for example, the standing crop of large animals is larger than the standing crop of smaller animals? In what types of communities could this occur? Do Eltonian pyramids apply to both animals and plants? Del Giorgio et al. (1999) discuss these issues.
Problem 7
Would you expect that the relationship of metabolic rates to body size would also apply to bacteria and other prokaryotes? Would this imply a universal constant of metabolism for all living things? Makarieva et al. (2005) attempt to answer this question.
Problem 9
How would you expect trophic level biomass to change as the primary productivity of the community increases? Use your knowledge about hypotheses of community organization and discuss the assumptions underlying your predictions. Compare your expectations with those of Power (1992).
Problem 11
Could herbivores remove a high fraction of the net primary production in an ecosystem without depressing the standing crop of plants? How might this happen?
Problem 12
Population density (no. of individuals per \(\mathrm{m}^{2}\) ) of all organisms in all ecosystems falls with increasing body size, so that larger animals are less common. But for species of equal body size, aquatic organisms are \(10-20\) times more abundant in lakes than terrestrial organisms on land. Suggest two reasons why this might be. Cyr et al. (1997) discuss this issue.
