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UNIVERSITY OF EAST ANGLIA School of Biological Sciences Main Series UG Examination 2012-2013 COMMUNITY, ECOSYSTEM AND MACRO-ECOLOGY BIO-2B26 Time allowed: 2 hours Answer ALL questions in Section A, ALL PARTS of the question in Section B and ONE question from Section C. Write answers to EACH SECTION in a SEPARATE booklet. The maximum number of marks available for your answers in SECTION A is 40 marks The maximum number of marks available for your answer in SECTION B is 30 marks The maximum number of marks available for your answer in SECTION C is 30 marks The TOTAL number of marks available for the paper is 100 Numbers in square brackets [ ] indicate the relevant mark applied to each part of the question. Notes are not permitted in this examination. Do not turn over until you are told to do so by the Invigilator. BIO-2B26 Copyright of the University of East Anglia Module Contact: Dr Richard Davies, BIO Version 1 2 SECTION A: MULTIPLE CHOICE AND SHORT ANSWER QUESTIONS Answer ALL questions. Unless stated otherwise all multiple choice questions have ONE answer. 1. The known ranges of tolerances to two environmental factors of two species (ABCD and WXYZ, respectively) are presented in the diagram below. In the field, however, species 1 is found only in the area ABEWFD. Which of the following statements is true? [2 marks] a) The two species have the same fundamental niche b) There is an interaction between the effects of temperature and humidity on species 1 c) Species 1 is a weaker competitor than species 2 d) The realized niche of species 2 is WECF e) Competition between the species is avoided 2. Many ideas have been proposed to explain the coexistence of multiple species with the same basic resource requirements. Identify the hypothesis that best describes our current understanding of co-existence in territorial coral reef fish: [2 marks] a) b) c) d) e) The regeneration niche hypothesis The resource ratio hypothesis The lottery hypothesis The random walk hypothesis Character displacement Section A continues/ . . . BIO-2B26 Version 1 3 .../Section A continued 3. According to Odum’s model of successional development of an ecosystem, which of the following propositions is true? [2 marks] a) b) c) d) e) Primary succession gives way to secondary succession Net primary production is maximal at the climax stage Community respiration increases with successional stage Species diversity declines with successional stage K-selected species give way to r-selected species 4. In which one of the following habitat types would you expect to find halophytes growing? [2 marks] a) b) c) d) e) 5. Biogeochemical cycling in an ecosystem is driven primarily by: a) b) c) d) e) 6. Acid heathland Salt marsh Shallow lake Deciduous woodland Tropical rain forest Pollution Precipitation Succession Catchment river flow Energy flow The pH of heathland soils is typically: a) b) c) d) e) [2 marks] [2 marks] <5 5-6 6-7 7-8 >8 Section A continues/ . . . TURN OVER BIO-2B26 Version 1 4 .../Section A continued 7. In a stream ecosystem, which of the following is not a source of allochthonous ecosystem productivity? a) b) c) d) e) 8. [2 marks] Fallen leaves from overhead branches Organic field run-off Aquatic plants Wind-blown dust and soil A submerged rabbit carcass Terrestrial as opposed to ocean pelagic communities have: [2 marks] a) b) c) d) e) A greater ratio of biomass to Net Primary Productivity A greater ratio of nutrients to biomass A lower level of size structuring of organisms across trophic levels Lower rates of biomass turnover Greater proportions of support tissue among their primary producers f) Relatively less energy passing through the herbivore as opposed to detritivore system Which one of the above options completes an incorrect statement? 9. If gross primary productivity = GPP, net primary productivity = NPP, net eocosystem productivity = NEP, autotrophic respiration = RA, and heterotrophic respiration = RH, then which of the following is true: [2 marks] a) b) c) d) e) NPP = GPP + RA NPP = GPP – RA – RH NEP = NPP + RA NEP = GPP – RA – RH NEP = GPP – NPP 10. Compared with unsaturated insect communities, saturated insect communities: [2 marks] a) Are likely to show community structure that is less influenced by competition b) Are closer to equilibrium c) Have a greater proportion of empty niches d) Have species richnesses that are more influenced by the richness of their regional species pools e) Are more common Section A continues/ . . . BIO-2B26 Version 1 5 .../Section A continued 11. Certain regions may be considered “museums” of biological diversity because they have: [2 marks] a) b) c) d) e) Low extinction rates Unstable climate High rates of DNA evolution High net primary productivity Many endemic species 12. A “collection of species that consume the same class of environmental resources in similar ways” defines: [2 marks] a) b) c) d) e) Taxocene Assemblage Cohort Guild Food web compartment 13. The combined effects of climate change and habitat loss on biodiversity are predicted to be synergistic. In this context, does “synergistic” mean: [2 marks] a) The effects of climate change and habitat will be additive b) The effects of climate change and habitat loss will result in evolutionary changes in species c) The effects of climate change and habitat loss will result in disaggregation of species associations d) The effects of climate change and habitat loss will result in nonrandom extinctions e) The effects of climate change and habitat loss will be greater than the sum of their individual effects 14. Which one of the following species’ traits is not typically associated with greater extinction risk? [2 marks] a) b) c) d) e) Large body size Wide niche breadth Narrow distributional range High trophic level Long generation time Section A continues/ . . . TURN OVER BIO-2B26 Version 1 6 .../Section A continued 15. Using a full factorial sampling design and assuming a minimum spatially independent level of replication of five sites sampled per combination of treatments, how many sites would you have to sample to tease apart the multiple effects of surface fires (two burn treatments: burnt and unburnt), soil types (two soil types: clay and sandy), fertilizer input (two treatments: low and high), and season (four seasons: early-dry, late-dry, early-wet and late-wet seasons) on the plant diversity of a grassland community? [2 marks] a) b) c) d) e) 16. 20 40 80 160 320 Resource partitioning would be most likely to occur between: [2 marks] a) Sympatric populations of a predator and its prey b) Sympatric populations of species with similar ecological niches c) Sympatric populations of a flowering plant and its specialized insect pollinator d) Allopatric populations of the same animal species e) Allopatric populations of species with similar ecological niches 17. Elephants are not the most common species in African grasslands. The grasslands contain scattered woody plants, but they are kept in check by the uprooting activities of the elephants. Take away the elephants, and the grasslands convert to forests or to shrublands. The newly growing forests support fewer species than the previous grasslands. Elephants can be defined as what type of species in this grassland community? [2 marks] a) b) c) d) e) Redundant Dominant Keystone Dominant and keystone None of the above Section A continues/ . . . BIO-2B26 Version 1 7 .../Section A continued 18. Two barnacle species, Balanus and Chthamalus , can both survive on the lower rocks just above the low-tide line on the Scottish coast, but only Balanus actually does so, with Chthamalus adopting a higher zone. Considering the fundamental and realized niches of these species, which of the following best accounts for this habitat separation? [2 marks] a) b) c) d) e) Competitive exclusion Predation of Chthamalus by Balanus Cooperative displacement Primary succession Mutualism 19. Consider the three alternatives 1 to 3 (below) to complete the statement “Introduced or exotic species…” [2 marks] 1) Often fail to colonize the new area 2) May become common enough to become pests 3) Can disrupt the balance of the natural species with which they become associated Which of the following is true? a) b) c) d) e) Only option 1 completes a correct statement Only option 2 completes a correct statement Only option 3 completes a correct statement Both options 2 and 3 complete correct statements 1, 2 and 3 all complete correct statements Section A continues/ . . . TURN OVER BIO-2B26 Version 1 8 .../Section A continued 20. On the basis of the figure below, which of the following sentences can be interpreted as correct for oceanic islands that are isolated from the mainland: [2 marks] a) The extinction rate is higher in islands because their island habitats are smaller than those in the mainland; b) The extinction rate is lower in the mainland because there are more species there to begin with; c) The extinction rate is higher in islands because there is little or no rescue effect from the mainland; d) The species richness is higher in the mainland because mainland species are intrinsically less prone to extinction; e) The species richness is lower in islands because mainland species require larger areas. END OF SECTION A Section B begins on next page BIO-2B26 Version 1 9 SECTION B: Answer ALL PARTS of this question 21. A macro-ecologist is investigating the environmental determinants of the distribution of species richness of amphibians across the Oriental region. S/he has sampled the presence/absence of each species to a 400-km x 400-km equal-area grid (i.e. where grid cells sample the same amount of area) and calculated species richness as the sum of all species presences within each grid cell. For each grid cell, there are data for each of five environmental predictors of interest including: Net primary productivity (NPP); mean annual temperature; number of habitat types; elevational range (maximum minus minimum elevation); and annual precipitation. The ecologist intends to use ordinary least squares (OLS) regression to carry out the analysis. (a) At the sampling resolution of this study (400-km x 400-km), does total amphibian species richness within a grid cell represent a measure of alpha-, beta- or gamma-diversity? Explain the reasons behind your answer. [5 marks] Figure 1. Histogram of (A) amphibian species richness, and (B) square-roottransformed amphibian species richness. Estimated normal curves are fitted by PASW (or SPSS). Results of Kolmogorov-Smirnov normality tests are presented within each histogram. (b) The ecologist looked at histograms of the amphibian richness data (A) and square-root-transformed amphibian richness (B), and performed a normality test of each (Kolmogorov-Smirnov test) before doing any linear regression analysis. Based on the results of these tests, explain whether the ecologist should perform the regression analysis on A (amphibian species richness) or B (square-roottransformed amphibian species richness) and why? [5 marks] Section B Q21 continues/ . . . TURN OVER BIO-2B26 Version 1 10 .../Section B Q21 continued (c) First the ecologist carried out simple linear regressions (single-predictor models) of each of the candidate predictors on its own (see Table 1A). Based on the single-predictor models (Table 1A), which is the most important predictor, and which is the least important, in explaining amphibian species richness, and why? [5 marks] A Predictor Number of habitat types NPP Temperature Elevation range Precipitation Single-predictor models B (slope) P-value Adjusted-R2 0.084 0.002 0.164 7.862 <0.0001 0.424 -0.152 0.034 0.123 3.041 <0.0001 0.328 5.223 <0.0001 0.358 B Predictor Number of habitat types NPP Temperature Elevation range Precipitation Multi-predictor full model B (slope) P-value Overall Adjusted-R2 0.079 0.001 6.111 0.002 0.531 0.075 0.265 1.753 0.105 <0.0001 0.941 C Multi-predictor MAM model Predictor B (slope) P-value Overall Adjusted-R2 Number of habitat types 0.065 0.001 NPP 6.331 <0.0001 0.534 Temperature removed Elevation range 1.753 <0.0001 Precipitation removed Table 1 B (slope) is the regression coefficient for each predictor, P-value is the significance of that slope, and Adjusted-R2 is the proportion of total variation explained. Section B Q21 continues/ . . . BIO-2B26 Version 1 11 .../Section B Q21 continued Next the ecologist wishes to construct a minimum adequate model (MAM), in other words to determine the minimum set of predictors needed to explain the maximum variation in amphibian species richness. The first step in achieving this is to carry out a multiple linear regression using all the candidate predictors together in a ‘full model’ (see Table 1B). (d) Looking at the full model results in Table 1B, you will notice that two of the predictors have become non-significant, in contrast to their single-predictor models (Table 1A). Give a statistical explanation for why this might be happening. Additionally, give a spatial ecological reason? [5 marks] In order to find the minimum adequate model (MAM), the ecologist performs a stepdown procedure in which predictors are removed in ascending order of their importance in the model until only significant predictors remain in the final MAM (see Table 1C). (e) Looking at the results in Table 1C, what is the percentage of variation in amphibian species richness that is explained by the MAM? Describe the main ecological relationships (including their directions of slope) explaining amphibian species richness that are highlighted by the MAM results. [5 marks] (f) Describe one plausible underlying mechanism to explain the influence of each of (i) NPP, and (ii) Elevation range, on the distribution of amphibian species richness. [5 marks] END OF SECTION B Section C begins on next page TURN OVER BIO-2B26 Version 1 12 SECTION C: ESSAY QUESTION Answer ONE question [30 marks] 22. How do biogeochemicals cycle in ecosystems? Using examples, discuss the significance of such cycles, locally and globally. 23. In the context of food web ecology, discuss the importance of indirect effects and their role in structuring ecological communities, giving examples of their relevance to conservation and natural resource management. 24. With examples from both terrestrial and marine systems, critically outline Joe Connell’s (1978) ‘Intermediate Disturbance Hypothesis’ ,including its theoretical basis, major predictions and assumptions, and how this hypothesis can help us understand the species diversity of ecological communities under more severe and/or more frequent natural or anthropogenic disturbance regimes. END OF PAPER BIO-2B26 Version 1 13 BIO-2B26 EXAMINATION MARKERS 2012-13 [Do not print this when printing to take to Examinations Office! This is for our information only.] Question No. Section A Section B Q21 Section C Q22 Section C Q23 Section C Q24 BIO-2B26 1st Marker Prof T Davy Dr R Davies Prof T Davy Dr R Davies Prof C Peres 2nd Marker Dr R Davies Prof T Davy Prof C Peres Prof T Davy Dr R Davies Version 1