BIO 321: Ecology, Review 1 KEY, Dr. Chris Paradise, Fall 2004
Instructions: This review is worth 100 points (10% of course grade) and will be due on Wednesday, 9/22/04 in class. Late reviews will not be accepted. You may not consult any references or any other person while working on this review. Your signature at the bottom of the last page signifies that the work is yours alone, was completed in three hours or less, and is pledged under the Honor Code. When you begin you will have a maximum of three hours to complete the review.
Confine your answers to the space below each question. Print legibly! Alternatively, the review may be done on the computer. You may type your answers to each question, and attach the printout to the review. For each question or part to a question, limit your answers to one concise paragraph, unless otherwise specified. Lengthy answers will be penalized the same as handwritten answers that spill out over the space given.
1. FILL IN THE BLANK (2 pts each = 16 pts)
a. The prevailing winds within the temperate zone, south of the equator, are from the west or northwest.
b. Upwelling is caused by movement of ocean currents away from shore, and brings cold, nutrient-rich water from ocean depths.
c. The prevailing winds in the Northern tropical zone circulate clockwise (accepted southwest).
d. On the sides of large mountains opposite the direction of prevailing winds (the leeward side), we often find arid or dry (desert is not completely correct) biomes. This is caused by the rainshadow effect (adiabatic cooling accepted) effect – as air moves up over the mountains on the windward side it cools.
e. In the Whitaker biome distribution scheme, the two variables that best determine what biome occurs where are annual average temperature and annual average precipitation.
2. Answer the following questions on the themes of this course, using a specific example of fire ecology from one of the papers we read on that subject (10 pts).
a. What is the ecosystem you chose?
Yellowstone National Park – mostly coniferous forest
California Shrubland
Everglades
b. Describe briefly the fire regime (frequency and intensity) in that ecosystem and how fire relates to two themes of the course.
This should be straightforward and directly related to the article you read and used to answer this question.
YNP – mostly coniferous forest subject to stand-replacing fires. Historically, YNP has not been controlled as much as surrounding areas by humans, in terms of fire suppression, but over the last few decades, fire has been used as a management tool. Natural fires appear to be driven more by climatic conditions than fuel age.
California Shrubland – stand-replacing fires that are not related to fuel age or fire suppression. Fires seem to be driven more by climatic conditions.
Everglades – Fires tend to be low intensity and occur on an annual basis (at least in some parts of the Everglades) predictable based on season and hydrologic cycle.
Fire is a DISTURBANCE and causes spatial VARIATION in ecosystems, both of which lead to DYNAMIC ecosystems. Organisms ADAPT to fire regimes, HUMANS alter fire regimes.
c. Describe briefly how humans have altered the fire regime in your chosen ecosystem.
YNP – in the park itself, fires have not been suppressed historically.
California Shrubland – control has not affected fire regime
Everglades – control of hydrology in eastern part of Everglades, near development has increased risk of fire by drying out the land.
d. Which would be a more accurate perception to apply to this ecosystem – balance of nature or dynamic equilibrium? Why?
Dynamic equilibrium is a more accurate perception. Fire is a disturbance, and you must recognize that it throws ecosystems out of balance, such that there is no balance. Nature is dynamic and parts of ecosystems or entire ecosystems are constantly being disturbed by small or large disturbances. As such, many habitats are always “recovering” from the last disturbance.
3. Describe briefly how the pattern of solar radiation and solar energy on Earth relates to
a. atmospheric air circulation patterns (4 pts).
The areas that get the most sunlight per unit area vary on an annual basis, although areas closer to the equator generally get more sunlight than high latitude areas. At the solar equator air is warmed by the solar radiation and evapotranspiration is high. Therefore, warm, wet air masses are formed, which rise. As they rise and expand, they cool via adiabatic cooling, releasing the moisture as rain over the solar equator. Cool, dry air masses eventually sink at or around 30oN and S. This air circulation pattern is a Hadley cell. The winds and pressure systems set up by Hadley cells and solar heating shift on an annual basis with the solar equator. Hadley cells are connected, in that air descending at 30oN is deflected both northeast and southwest. The northeast-moving air gradually warms and rises at 60oN, creating a temperate Hadley cell.
b. the pattern of biome distribution (4 pts).
Distribution of biomes is related to atmospheric air circulation patterns. Highly productive biomes are found at the equator, less productive ones where cool, dry air is descending. Latitudinal variation across the globe is also caused by the angle of incidence of sunlight and the tilt of the Earth. Higher latitudes receive less sunlight annually, and that sunlight hits the Earth’s surface at a less direct angle, spreading the energy over a larger surface area. The tilt also causes temporal, annual variation as the solar equator is found between 23.5oN and 23.5oS, depending on the time of year. This causes seasonality to occur in many temperate biomes.
c. ocean currents (4 pts).
Winds generated from atmospheric air circulation patterns are primarily what drives ocean surface currents, although differential heating of ocean water can also affect currents that move water up and down the water column.
4. You’re an ecologist interested in how food webs may be disrupted by global climate change. You have decided to simulate ponds using cattle tanks. The treatments are normal and high CO2 (additional CO2 bubbled into the water), fully crossed with average and 2oC warmer water (achieved by using submersible heating elements), for a total of 4 (four) treatment combinations. You have just received a sizeable grant from the National Science Foundation, so you have unlimited funds to perform the experiment (money is no object). OUTLINE how you would set up this experiment. Include all experimental design parameters and constraints (e.g., numbers of replicates, assignment of tanks, etc.) (10 pts).
You must indicate the number of replicates you would use, where and how tanks would be placed, and what considerations you would make in placing them. For instance, what abiotic factors, such as shading, might you consider when placing the tanks? How would that constrain your design? It might constrain your design by forcing you to use a stratified random placement of the tanks. Indicate how you would set up the tanks, and how you would control for the experimental manipulations (shams to control for the effects of the immersible heater and the bubbling of CO2). I was looking for a thoughtful, logical approach to setting up this experiment, not a replication of what is in the laboratory manual on the steps of setting up our tank experiment. Simply repeating things like “add phytoplankton after one week, add zooplankton after two weeks” does not allow me to assess your ability to actually DESIGN an experiment.
5. Is there a scientific consensus on the role tropical forests play in climate regulation in the face of global climate change? Why or why not? (8 pts)
No, there is no consensus at this time. The basic problem is that we have yet to accurately account for the carbon budget in tropical forests. There are many reasons for this, including the inaccessibility of many areas, the lack of studies on biomass accrual and long-term dynamics, the difficulties of harvesting even a single acre of tropical forests, the dynamic nature of forest growth and regrowth, and variation inherent in estimates of acreage of forests, areas affected by fire, and areas in early stages of succession, as well as rates of carbon dioxide flux in those different areas.
6. Examine the Walter climate diagrams below. For each biome, predict whether you would expect to see a preponderance of C3, C4, or CAM plants. The name of the biome is not important (6 pts).
C4, C3, and CAM, in that order from left to right
7. Dromedary camels can exist in the desert for a considerable period of time, with neither food nor water. OUTLINE how natural selection works to produce the suite of adaptations that camels possess for desert survival. Include major selective forces and constraints to adaptations (e.g., why do camels need to drink water at all?). (8 pts).
Natural selection in the face of lack of water and high temperatures has led to a suite of adaptations to help deal with the stresses associated with these two major selective forces. Camels have nasal countercurrent heat exchange, using evaporative cooling in the nasal passages to cool and dehumidify exhaled air. They possess hygroscopic turbinates. They excrete extremely concentrated urine and dry feces. They have thick fur dorsally, and thin fur ventrally. Their large size allows them to heat up more slowly during the day, they can consume a lot of vegetation with a high water content and can drink a lot of water in a short time period. There are several constraints to these adaptations, including the fact that their large size precludes finding shelter from the sun, drinking lots of water precludes a smaller size, thick fur is needed to heat up slowly during the day, but if it were all over their body they’d cool down slower at night, too. If they used their fat stores to generate water, they’d heat up more due to generation of metabolic heat. They can drink a lot, but they can’t drink 200 L in 10 minutes.
8. Answer the following questions on abiotic factors and adaptations (9 pts).
a. LIST two factors that affect the LOCAL distribution of plants and animals?
Almost any two abiotic factors could have been listed. Soil nutrients, elevation, water availability are just a few.
b. What is one way in which spatial variation in abiotic factors might relate to the field experiment on Eupatorium and wild carrot?
If there is spatial variation in an abiotic factor, such as the distribution of nutrients in the soil, thickness of the soil, soil moisture, light levels, or any other abiotic factor, that variation could help account for the clumped distribution of the two species we studied in the old field.
c. Why have most organisms adapted to a saltwater existence been eliminated from the Aral Sea in the past 10-20 years?
The Aral Sea has shrunk greatly over the last couple of decades due to diversion of water from its two major in-flowing rivers for the purpose of irrigation. The water levels have dropped, but the salt content has remained the same, increasing the concentration of salt beyond levels that most saltwater organisms can tolerate.
9. Consider the article by Schindler et al. (2003) on Pacific salmon. Draw an energy flow schematic of a Pacific coastal freshwater ecosystem that includes salmon in two different life stages. In the schematic, point out two connections that have been affected by habitat alteration or overfishing (10 pts).
The drawing could include any two or more salmon life stages, and ENERGY connections between them and other components of the stream ecosystem. You must include multiple ENERGY connections, depicting aquatic, freshwater organisms, or terrestrial connections, and all involving energy flow. Many energy flow connections have been altered by anthropogenic factors. The ones you chose should have something to do with disruption of energy flow in the system, and should also point out the ramifications of such disruption.
10. Outline of an essay (10 points). Select ONE of the two questions below, a or b. Use the back side of this page to answer. Do not write an essay; simply make an outline of how you would organize an essay on this topic, using specific examples. This will form the basis of your first writing assignment.
a. Several physical and biological laws, concepts, or principles determine or affect the number of trophic levels found in any ecosystem. OUTLINE these laws, concepts, and principles in terms of 1) productivity and energy flow, 2) abiotic factors that constrain productivity or energy flow, & 3) adaptations to overcome those constraints.
Part one should include some or all of the following: the Second Law of Thermodynamics, Lindeman’s concept of the trophic dynamic aspect of ecosystems, the steady state and dynamic aspect of ecosystems, and how they all relate to energy flow. They must be defined in an ecological context and related to ecosystem productivity and energy flow. You should also discuss efficiencies, including ecological efficiency, as they are affected by the above principles and relate those ideas to the number of trophic levels in ecosystems, the production of heat, and energy or biomass pyramids. Many abiotic factors constrain productivity, at both the individual or ecosystem levels. These constraints include climate (related to latitude), altitude, topography, soils, biotic interactions, etc. Adaptations vary, but the point is to present one to several specific examples of adaptations exhibited by species in various ecosystems to overcome the constraints you presented earlier. Then, relate those adaptations back to productivity and energy flow in ecosystems.
b. Consider the factors that set up an ENSO event and the resulting impacts of this phenomenon. Prepare an OUTLINE of this phenomenon. Include conditions used to predict such an event and some of the local and global impacts of an ENSO. Also consider impacts to weather patterns, food webs, and human economies.
Include the normal conditions in the Pacific Ocean,
such as Trade winds blowing east to west, the piling up of warm water in the
western pacific, the tongue of cold water off the coast of Peru, the high
pressure centered over Tahiti, and the low pressure over Darwin, Australia.
The weakening of the Trade winds and the pressure switch cause winds to weaken
or reverse, and the ocean currents begin to reverse, lowering sea levels in
the west and bringing warm water eastward. A weakening of the west-flowing
winds around the equator helps sets up the ENSO event. A switch in pressure
systems centered over Tahiti and
