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Ecology Review: An Introduction to Ecology and the Biosphere
1. Contrast the terms ecology and environmentalism. How does ecology relate to environmentalism?
2. How can an event that occurs on the ecological time scale affect events that occur on an evolutionary time scale?
3. A wheat farmer tests four fungicides on small plots finds that the wheat yield is slightly higher when all four fungicides are
used together than when any one fungicide is used alone. From an evolutionary perspective, what would be the likely long
term consequence of applying all four fungicides together?
4. Give examples of human actions that could expand a species’ distribution by changing its dispersal or biotic interactions.
5. Explain how the sun’s unequal heating of Earth’s surface influences global climate patterns.
6. You suspect that deer are restricting the distribution of a tree species by preferentially eating the seedlings of the tree. How
might you test that hypothesis?
7. Many organisms living in estuaries experience freshwater and salt water conditions each day with the rising and falling of
tides. What challenge does this pose for the physiology of the organisms (use the figure)?
8. Why are phytoplankton, and not benthic algae or rooted aquatic plants, the dominant photosynthetic organisms of the
oceanic pelagic zone (use the figure)?
9. Water leaving a reservoir behind a dam is often taken from deep layers of the reservoir. Would you expect fish found in a
river below a dam in summer to be species that prefer colder or warmer water than fish found in an undammed river?
Explain.
10. Based on the climograph below, what mainly differentiates dry tundra and deserts?
11. Identify the natural biome in which you live and summarize its abiotic and biotic characteristics. Do these reflect you
actual surroundings? Explain.
12. If global warming increases average temperatures on Earth by 4°C in this century, predict which biome is most likely to
replace tundra in some locations as a result. Explain your answer.
Ecology Review: Population Ecology
1. One species of forest bird is highly territorial, while a second lives in flocks. Predict each species’ likely pattern of
dispersion, and explain.
2. Each female of a particular fish species produces millions of eggs per year. Draw and label the most likely survivorship
curve for this species, and explain your choice.
3. An important assumption of the mark-recapture method is that marked individuals have the same probability of being
recaptured as unmarked individuals. Describe a situation where this assumption might not be valid, and explain how the
estimate of population size would be affected.
4. Consider two rivers: one is spring fed and has a constant water volume and temperature year round; the other drains a
desert landscape and floods and dries out at unpredictable intervals. Which river would you predict is more likely to
support many species of iteroparous animals? Why?
5. In the fish called the peacock wrasse, females disperse some of the eggs widely and lay other eggs in a nest. Only the latter
receive parental care. Explain the trade offs in reproduction that this behavior illustrates.
6. Mice that cannot find enough food or that experience other forms of stress will sometimes abandon their young. Explain
how this behavior might have evolved in the context of reproductive trade offs and life history.
7. Explain why a constant rate of increase (rmax) for a population produces a growth graph that is J-shaped rather than a
straight line.
8. Where is exponential growth by a plant population more likely – on a newly formed volcanic island or in a mature,
undisturbed rain forest? Why?
9.
In 2006, the United States had a population of about 300 million people. If there were 14 births and 8 deaths per 1000
people, what was the country’s net population growth that year (ignoring immigration and emigration, which are
substantial)? Do you think the United States is currently experiencing exponential population growth? Explain.
10. Explain why a population that fits the logistic growth model increases more rapidly at intermediate size than at relatively
small or large sizes.
11. When a farmer abandons a field, it is quickly colonized by fast growing weeds. Are these species more likely to be Kselected or r-selected species? Explain.
12. Add rows to the table for three cases where N>K:N = 1600, 1750, and 2000. What is the population growth rate in each
case? In which portion of the figure is the Daphnia population changing in a way that corresponds to the values you
calculated?
13. Identify three density dependent factors that limit population size, and explain how each exerts negative feedback.
14. Describe three attributes of habitat patches that could affect population density and rates of immigration and emigration.
15. If you were studying an endangered species that, like the snowshoe hare, has a 10 year population cycle, how long would
you need to study the species to determine if its population size is declining? Explain.
16. How does a human population’s age structure affect its growth rate?
17. How has the growth of Earth’s human population changed in recent decades? Give your answer in terms of growth rate
and the number of people added each year.
18. What choices can you make that influence you own ecological footprint?
Ecology Review: Community Ecology
1. Explain how interspecific competition, predation, and mutualism differ in their effects on the interacting populations of two
species.
2. According to the principle of competitive exclusion, what outcome is expected when two species with identical niches
compete for a resource? Why?
3. Suppose you live in an agricultural area. What examples of the four types of community interactions (competition,
predation, herbivory, and symbiosis) might you see in the growing or use of food?
4. What two components contribute to species diversity? Explain how two communities that contain the same number of
species can differ in species diversity.
5. Describe two hypotheses that explain why food chains are usually short, and state a key prediction of each hypothesis.
6. Consider a grassland with five trophic levels: plants, grasshoppers, snakes, raccoons, and bobcats. If you released
additional bobcats into the grassland, how would plant biomass change if the bottom-up model applied? If the top-down
model applied?
7. How do high and low levels of disturbance promote species diversity? What does an intermediate level of disturbance
promote species diversity?
8. During succession, how might the early species facilitate the arrival of other species?
9. Most prairies experience regular fires, typically every few years. How would the species diversity of a prairie likely be
affected is no burning occurred for 100 years? Explain your answer.
10. Describe two hypotheses that explain why species diversity is greater in tropical regions than in temperate and polar
regions.
11. Describe how an island’s size and distance from the mainland affect the island’s species richness.
12. Based on MacArthur and Wilson’s model of island biogeography, how would you expect the richness of birds on islands to
compare with the richness of snakes or mammals? Explain.
13. What are pathogens?
14. Some parasites require contact with at least two host species to complete their life cycle. Why might this characteristic be
important for the spread of certain zoonotic diseases/
15. Suppose a new zoonotic disease emerges from a tropical rain forest. Doctors have no way yet to treat the disease, so
preventing infections is particularly important. As a community ecologist, how might you help prevent the spread of the
disease?
Ecology Review: Ecosystems
1. What is the transfer of energy in an ecosystem referred to as energy flow, not energy cycling?
2. How does the second law of thermodynamics explain why an ecosystem’s energy supply must be continually replenished?
3. You are studying nitrogen cycling on the Serengeti Plain in Africa. During your experiment, a herd of migrating
wildebeests grazes through your study plot. What would you need to know to measure their effect on nitrogen balance in
the plot?
4. Why is only a small portion of the solar energy that strikes Earth’s atmosphere stored by primary producers?
5. How can ecologists experimentally determine the factor that limits primary production in an ecosystem?
6. As part of a science project, a student is trying to estimate total primary production of plants in a prairie ecosystem for a
year. Once each quarter, the student cuts a plot of grass with a lawnmower and then collects and weighs the cuttings to
estimate plant production. What components of plant primary production is the student missing with this approach?
7. If an insect that eats plant seeds containing 100 J of energy uses 30 J of that energy for respiration and excretes 50 J in its
feces, what is the insect’s net secondary production? What is its production efficiency?
8. Tobacco leaves contain nicotine, a poisonous compound that is energetically expensive for the plant to make. What
advantage might the plant gain by using some if its resources to produce nicotine?
9. As part of a new reality show on television, a group of overweight people are tying to safely lose in one month as much
weight as possible. In addition to eating less, what could they do to decrease their production efficiency for the food they
eat?
10. For each of the four biogeochemical cycles, draw a simple diagram that shows one possible path for an atom or molecule
of that chemical from abiotic to biotic reservoirs and back.
11. Why does deforestation of a watershed increase the concentration of nitrates in streams draining the watershed?
12. Why is nutrient availability in a tropical rain forest particularly vulnerable to logging?
13. How can the addition of excess nutrients to a lake threaten its fish population?
14. In the face of biological magnification of toxins, is it healthier to feed at a lower or higher trophic level. Explain.
15. There are vast stores of organic matter in the soils of northern coniferous forests and tundra around the world. Based on
what you learned about decomposition, suggest an explanation for why scientists who stud global warming are closely
monitoring these stores.
Ecology Review: Conservation Biology and Restoration Ecology
1. Explain why it is too narrow to define the biodiversity crisis as simply a loss of species.
2. Identify the three main threats to biodiversity and explain how each damages diversity.
3. Imagine two populations of a fish species, on e in the Mediterranean Sea and one in the Caribbean Sea. Now imagine two
scenarios: (1) The populations breed separately, and (2) adults of both populations migrate to the North Atlantic to
interbreed. Which scenario would result in a greater loss of genetic diversity if the Mediterranean population were
harvested to extinction? Explain your answer.
4. Why does the reduced genetic diversity of small populations make them more vulnerable to extinction?
5. Consider a hypothetical population of 100 greater prairie chickens, a species in which females choose a mate from a group
of displaying males. What is the effective population size if 35 females and 10 males of the species breed?
6. In 2005, at least ten grizzly bears in the greater Yellowstone ecosystem were killer through contact with people. Three
things caused most of these deaths: collisions with automobiles, hunters (not of grizzly bears) shooting when charged by a
female with cubs nearby, and conservation managers killing bears that attacked livestock repeatedly. If you were a
conservation manager, what steps might you take to minimize such encounters in Yellowstone?
7. What is a biodiversity hot spot?
8. How do zoned reserves provide economic incentives for long term conservation of protected areas?
9. Suppose a developer proposes to clear cut a forest that serves as a corridor between two parks. To compensate, the
developer also proposes to add the same area of forest to one of the parks. As a professional ecologist, how might you
argue for retaining the corridor?
10. Identify the main goal of restoration ecology.
11. How do bioremediation and biological augmentation differ?
12. n/a
13. What is meant by the term sustainable development?
14. How might biophilia influence us to conserve species and restore ecosystem?
15. Suppose a new fishery is discovered, and you are put in charge of developing it sustainable. What ecological data might
you want on the fish population? What criteria would you apply for the fisher’s development?