Problem 3
How could you determine if an ecological community was an equilibrium or a nonequilibrium system, if you were placed on a new continent to study a community for which you had no background data? Discuss your research plan and the time scale needed to answer this question.
Problem 4
Compare and contrast the following statements of an evolutionist and an ecologist about species diversity and the stability of biological communities: a. \(\operatorname{simpson}(1969, \mathrm{p}, 175)\) states: "If indeed the earth's ecosystems are tending toward long-range stabilization or static equilibrium, three billion years has been too short a time to reach that condition." b. Recher \((1969, \mathrm{p}, 79)\) states: "The avifaunas of forest and scrub habitats in the temperate zone of Australia and North America have reached equilibrium and are probably saturated."
Problem 5
How is it possible for stable isotope ratios to change between trophic levels? List several possible physiological mechanisms that might cause such changes. Are there any population mechanisms for achieving these changes? Would you expect differences in isotope ratios if you measured different parts of an animal or plant? Kelly (2000) discusses the use of stable isotopes and their limitations for studying diets.
Problem 8
Keystone species can be discovered by species removal experiments. Is there any other way to identify potential keystone species in a community, or must we always proceed by trial and error? Libralato et al. (2006) discuss this question.
