Section One--Definitions

  1. gradient analysis- an approach to community analysis. One examines community composition on the basis of the niche requirements of each species. One one finds is that the species are located at positions along existing environmental gradients: soil pH, precipitation, temperature, etc.
  2. primary succession--the pattern of succession that occurs when an area devoid of any soil is colonized by primary producers. Examples would be fields of new cooled lava, glacial till, mud slides, etc. Differs from secondary succession where plants invade an environment that has an established soil layer (old field succession)
  3. standing crop--the amount of biomass present at any one moment in time. Not to be confused with density which is a measure of biomass or individuals per unit of area. For example, if I were to mow my lawn only once a year (at the end of the growing season) and weight the clippings, that would be the standing crop.
  4. LAI--the initials stand for leaf area index. The LAI is a measure of the total leaf area as compared to the "shadow area" of the tree on the ground. Typically, LAI values are two to three times the ground shadow.
  5. Euphotic zone--the depth to which photosynthesis takes place in an aquatic environment. Differs from compensation point which is the point at which photosynthesis equals respiration.
  6. NPP--the initials stand for Net Primary Production. NPP is the Gross Primary Production minus the energy lost to respiration (maintenance). In aquatic ecosystems, easily measured by dark-light bottle technique.
  7. Nutrient spiraling--situation in freshwater streams where as the stream goes from its headwaters to the ocean, nutrients are recycled both within the stream and within adjacent wetlands. Thus nutrients are lost from the stream in some areas, but regained when wetlands drain back into the stream.
  8. Keystone species--typically, but not always, a top level predator. When this organism is removed, membership in lower trophic levels is dramatically changed and the whole system may become more bottom up rather than top-down controlled.
  9. Resilience--when perturbed, resilience is a measure of how well an ecosystem can bounce back to previous conditions. Low resilient systems remain changed, high resilient systems return to previous establish values.
  10. Species disharmony--A situation with respect to island biogeography, where one expects a certain suite of species to be present at a location, but actually finds some, but not all of the species. This is partially related to dispersal abilities of species, where not all species have equal abilities.

Section Two-List and describe

  1. List and briefly describe three regions on the globe that have high biological productivity and the specific factors that are associated with those levels. (6 points)--
  1. coral reefs--energy subsidized systems. Receive nutrients from both environments (terrestrial and marine), recycle those nutrients intensively, and are spatial heterogenous.
  2. Areas of upwelling--high solar insolation, high levels of nutrients available (brought up with the cold nutrient rich water)
  3. Tropical rainforest--high solar insolation, high level of nutrient recycling, stable conditions over a long time.
  1. List and briefly describe three factors that might limit terrestrial primary productivity (3 points).
  1. amount of insolation available for photosynthesis
  2. amount of precipitation
  3. temperature regieme
  1. Relate the following to each other: consumption efficiency, assimilation efficiency, production efficiency and trophic level efficiency.(4 points)--
  1. ratio of amount of material to be consumed as actually consumed
  2. ratio of material ingested to actually absorbed in the digestive tract
  3. ratio of material assimilated to biomass added to the individual (a measure of how much it costs an organism to remain alive)
  4. a measure of how much energy is available to be passed along to the next trophic level. Usually associated with the 10% rule
  1. Briefly describe the species-area relationships as associated with islands. Why is the concept of islands not strictly associated with real "islands"? What are some other examples of biological islands? (3 points)--large islands and close islands usually have larger numbers of species than small islands or islands distant from the mainland. Also islands in general tend to have fewer species than continental areas of the same size. A geographic location where this a barrier to dispersal exists can be thought of as an island. Thus mountain tops, lakes in the southwestern US, or even leaves of a plant, can be thought of as islands.
  2. Describe how Simberloff's work in the Bay of Florida or Wilcox's work in the Gulf of California support some of the aspects of island biogeography.( 2 points)--Simberloff despeciated mangrove islands in the Bay of Florida and then recorded patterns of respeciation. Wilcox examined islands in the Gulf and knowing age of environments and distances and sizes related those concepts to species area curves. Both pieces of research explain why islands have fewer species than continental areas.
  3. Describe how ordination and classification might provide information as to how communities are organized in space.(2 points)--By plotting patterns of vegetation similarities/dissimilarities and then comparing those patterns to environmental variables, eg., soil pH, soil moisture, etc., the researcher can obtain a better understanding why certain communities are distributed the way they are.
  4. Describe the differences between top-down and bottom up control of food webs. How are the two related to the number of trophic levels in an ecosystem?(4 points)--top down are predator controlled systems, bottom-up are primary producer controlled systems (competition driven systems). Rule of thumb is that systems with odd numbers of trophic levels are bottom-up controlled and even numbered systems are top-down controlled.
  5. List and briefly describe the sections and contents of a paper that is published in a scientific journal (e.g., Ecology)( 8 points).
  1. title--very brief description of papers contents with indication of location or species used.
  2. Authors--names and address of authors that allows reader to get in contact with them
  3. Abstract--global statement of paper purpose, specific statement of what was undertaken, and brief statement of major findings.
  4. Introduction--relates research to other projects that have been done and indicates what the reader will find if they read the whole paper.
  5. Materials/methods--indication of the protocol followed by the authors in enough detail so that reader could carry out the same study to check results
  6. Results-findings of the research
  7. Discussion/conclusion--how the results fit into the global picture
  8. Literature cited--references used in the paper
  9. Key words
  10. Acknowledgements

Section Three--Concepts

  1. Briefly discuss how the concept of the climax has changed from Clements to Whitaker.(2 points)--Clements believe that the community was a superorganism. Thus the climax to him was a monoclimax and represented the most mature state or the superorganism. Whitaker favors a gradient explanation for communities and thus believes that there not one outcome for patterns of succession, but many outcomes
  2. What are some of the units of energy that an ecologist might use to describe the flow of energy through an ecosystem?(2 points)--joules or calories
  3. How does the flux of mater through an ecosystem differ from the flux of energy through the same system?(4 points)--matter can be recycled, but energy can only be degraded as every time a chemical reaction takes place, the entropy of the system increases.
  4. What did Hairston mean by his "world is green" proposition? What are some of the counter arguments to that proposition?(4 points)--Hairston implied that primary consumers can never keep up with primary production, and thus more plant matter is produced than consumed. Other counter arguments include that plants can and do protect themselves by harboring bad tasting chemicals and having spines and prickles, thus precluding consumption. Also with top down control, primary consumers may be restricted in numbers and not have a chance to consume the primary production.
  5. By means of a graph and words discuss MacArthur and Wilson's "equilibrium " theory. (4 points)

    6. I've just drawn two possible lines. The number of species for this island would be where the two curves intersect. Other lines for larger islands or islands closer or more distant would have different points for the equilibrium number of species.

  6. The number of trophic levels could vary widely, but most ecosystems commonly have four or fewer levels. What factors may limit ecosystems to such a small number of levels?(4 points)--There are a number of factors. Probably is the most basic is the loss of energy as energy is passed from the lower to the higher trophic levels. A second is the area needed to support higher level carnivores (the Why fierce carnivores are rare book). Another relates to how much energy is available at the lowest level.
  7. How does the ratio of predators to prey differ between ecotherms and endotherms? How have paleontologist made use of this difference to analyze past populations of dinosaurs? (4 points)--Since the metabolic rates of ecotherms are much lower than endotherms, their total intake is much lower per unit of time, and thus larger number of predacious ectotherms can be supported based on lower numbers of prey items. In contrast, endotherms require high levels of energy intake and need far more prey items to support them than do ectotherms. Paleonologists by examining ratios of predator to prey associations can get a feeling whether the predators were physiologically ecto- or endotherms
  8. What is the conventional wisdom concerning the relationship of community stability and food-web structure?(2 points)--Conventional wisdom is that the more complex communities are more stable. Recent work disputes this and is related to the question #9.
  9. How might a complex community be less stable when disturbed as compared to a simple community? Bring into your answer r vs. K strategies.(2 points)--complex communities may have more resilience, but less persistance. When severely perturbed, they may not be able to bounce back. This is due to the fact, that many of the members of K strategists, and thus can not produce large numbers of offspring in a short time. In contrasts, simple communities may be more persistant (that is, resist change more diligently) and also because they have mostly r strategists, can produce more offspring in a short period of time to compensate for individuals lost during the disturbance.
  10. Develop a model that describes the relationships amongst range of resources, number of species and degree of overlap amongst species that might explain why some regions have larger numbers of species than other regions.(4 points). The model is the one that appeared in the book. With a bar at the bottom representing resouces, and smaller bars representing species and species overlap. The idea here is that the greater the resouces, the more species that can be supported. The more finally the niches are divided the more species or conversely, the more overlap between species, the more species.

Section Four--Essays. Answer one or the other of the following questions completely. Provide specific examples for your general statements (10 points)

  1. Species richness can be related to a number of factors that directly or indirectly influence the composition of communities. Briefly discuss each of the following in this context:
  1. richness of resources and productivity
  2. spatial heterogeneity
  3. climatic variation
  4. environmental harshness
  5. environmental age: evolutionary time
  1. There are many gradients of richness. Briefly describe each of the following:
  1. latitude
  2. altitude
  3. depth
  4. succession