Sample Midterm Exam Questions
I prefer short answer questions that test your understanding of basic concepts. Following are examples of questions that could occur on the mid-term exam.
1. Write a phenomenological energy budget model (i.e., an equation) describing the energy balance of a leaf, identifying the processes (terms in the equation) of energy gain and loss. What does this budget suggest about the role of transpiration?
2. Write a phenomenological water budget model for a field over the entire growing season, identifying the processes of water input and output into the system. What does this budget suggest about improving seasonal water-use efficiency, expressed as yield over total inputs?
3. Yields in the tropics are consistently lower than those for the same crop (e.g., maize or rice) when grown in the temperate zone, even under conditions of good management. What are some of the climatic factors that account for this "yield gap"?
4. Most of the tropical zones have a dry season, and this dry season nearly always occurs around the time of the winter solstice. Describe the global circulation papers that cause winters to be dry in the tropics.
5. Discuss the three fundamental ways in which yields (productivity) of agroecosystems can be increased.
6. What are the major classes or types of clay minerals? What is the significance of clay mineralogy for soil fertility? Over time, how does weathering modify the types of clays found in soils?
7. What is meant by the term "externality"? What are the major externalities associated with nitrogen fertilizer use in agriculture?
8. Soils almost always decrease in soil organic matter after being converted from natural vegetation (forests or grasslands) to crop lands; describe the processes that account for this change.
9. Where are the subtropical high-pressure zones? Describe their climate, and the global circulation the processes that account for these climatic conditions.
10. What was the "Green Revolution"? When did it occur? What factors contributed to the crop yield increases during the Green Revolution?
11. What are the key processes that lead to acidification of agricultural soils?
12. The reduction of atmospheric dinitrogen gas requires large amounts of energy; what is the source of this energy for (a) industrial, (b) atmospheric, and (c) biological nitrogen fixation?
13. Contrast C3, C4, and CAM plants in terms of their temperature tolerances, instantaneous photosynthetic rates, radiation-use efficiency (photons per mole of CO2) fixed, and water-use efficiencies. Give an example of a crop plant having each photosynthetic pathway.
14. What soil properties of importance to agroecosystem function are influenced by soil organic matter?
15. What are the key features of crops and the environment that determine water-use efficiency: (1) at the leaf level over very short (physiological) time periods, and (2) at the whole crop level over the growing season?
16. Explain why precipitation is always associated with rising air masses. What are the mechanisms that lead to uplift of air masses?
17. What are the characteristics of mollisols, and where are these soils found on the earth?
18. Describe three types of biological nitrogen fixation of significance to agriculture: identify the (1) prokaryotic symbionts, (2) plant hosts, and (3) agroecosystems where each association is important.
19. Contrast mineralization and immobilization. Which process dominates when heterotrophic microbes (bacteria and fungi) decompose crop residues, and why? Which process dominates when grazers and predators in soil food webs consume their food sources, and why?
20. Be able to identify the processes that control changes that occur in residue, microbial, ammonium (NH4+), and nitrate (NO3-) nitrogen pools after adding a residue with a high C:N ratio.
21. Define leaf-area index and leaf-area duration; how are these related to light-interception by crop canopies?
22. Define vapor pressure, relative humidity, and dew point, and describe how these concepts are related to each other. Describe the relationship between saturation vapor pressure and air temperature.
23. In general, how does temperature affect crop phenology and development (for example, time from flower production to seed maturation)? Include the concept of degree-days in your answer. How are degree-days calculated for a particular crop?
24. In what forms and by what processes is nitrogen lost from agroecosystems?
25. What is a mycorrhiza? How does this association benefit plants? How might these associations alter the structure of below-ground ecosystems?
26. What is cation exchange capacity (CEC)? What constituents of soils contribute to its CEC? What does base saturation refer to? How does soil pH affect CEC and base saturation?
27. New lands are continually being cleared for crop production, yet, according to Food and Agricultural Organization (FAO) statistics, the total amount of arable land globally has remained more or less constant over the past several decades. Explain this apparent contradiction.
28. Contrast Liebig-type ("limiting"), multiplicative, and synergistic interactions between resources in determing crop yield. How would you determine how 2 resources interact?
29. Distinguish between conceptual, phenomenological, empirical, and simulation models.
30. Contrast calibration and validation steps in developing a simulation model.
31. Contrast the three soil orders commonly associated with broad-leaved forests: alfisols, ultisols, and oxisols.
32. What is a factorial experiment? What are the limitations to using such experiments to understand the complexity of agroecosystem function?
33. Assuming that recent analyses of global temperatures are correct and that the earth's surface temperature has increased during the past century, what are the presumed causes of this warming? How have researchers tried to determine the potential effects of global climatic change on agriculture? What are some of the strategies for ameliorating potential negative effects?
34. Contrast field capacity, permanent wilting point, and available water. What factors determine the amount of available water a soil can store?
35. Contrast the instantaneous and seasonal effects on crops associated with simultaneous CO2 and temperature increases.
URL: http://ag.arizona.edu/~spmcl/Sample508Midterm.htm
25 February 2003