Download Final Short answer Questions

Here are some terms that you may see on the final multiple choice section.
Chap 11
Carrying capacity, density dependent factor, density independent factor, exponential population growth and its equation,
geometric population growth, logistic population and equation, sigmoidal population growth curve, limits to population growth
Chap 17
Dominant species, food web, keystone species, trong interactions, mutualistic, exotic predators, Lake Victoria, nile perch, nile
minnows, roach fry, cladophora, barnacles, Pisaster, Blue tit, Giraurdiella inclusa, zooplankton, phytoplankton
Chap 19
Nutrient cycling, phosphorus cycle, nitrogen cycle, carbon cycle, mineralization, decomposition, lignin, influence of lignin and
nitrogen content on decomposition (fig. 19.7), decomposition rates in tropical vs. temperate forest,
Chap 20
Succession, pioneer community, primary succession, secondary succession, climax community, changes in woody plant
species richness during secondary succession, chronosequence, facilitation model, tolerance model, inhibition model fig.
20.20 and 20.23, stability, resistance, resilience,
Chap 23
Atmosphere, troposphere, stratosphere, Greenhouse effect, greenhouse gases, ozone, El nino, southern oscillation, effects of
El nino fig. 23.6, El nino effects on sea lions in the Galapagos, red kangaroos in Australia, Depletion of ozone layer, CFC’s,
1987 Montreal Protocol
Final Short answer Questions Choose one question from each chapter.
Chap 11
A) For what types of organisms is the geometric model of population growth appropriate? Give examples. For what
types of organisms is the exponential model of population growth appropriate? Give examples. In what
circumstances would a population grow exponentially? Give an example. In what circumstances would a population
not grow exponentially? Give an example.
B) Population biologists may refer to abiotic factors, such as temperature and moisture, as density-independent
because such factors can affect population processes independently of local population density. At the same time,
biotic factors, such as disease and competition, are called density-dependent factors because their effects may be
related to local population density. Explain how abiotic factors can influence populations in a way that is independent
of local population density. Explain why the influence of a biotic factor is often affected by local population density.
Now, explain how the impact of an abiotic factor may also be affected by the local population density, that is, may
behave at least partly as a density dependent factor.
C) What factors will determine the earth’s carrying capacity for Homo sapiens? Explain why the earth’s long-term
(thousands of years) carrying capacity for the human population may be much lower than the projected population
size for the year 2050. Now argue the other side. Explain how the numbers projected for 2050 might be sustained
over the long term.
Chap 17
D) What is a keystone species? Paine (1966, 1969) experimented with two sea stars that act as keystone species in
their intertidal communities along the west coast of North America and in New Zealand. Describe how the intertidal
communities in these two areas are similar. Describe the differences between these two communities and the
differences in the design of Paine’s experiments in these two areas.
E) Using Tscharntke’s food web (1992) shown in figure 17.5, predict which species would be most affected if you
excluded the bird at the top of the web, Parus caeruleus. What species
F) would be affected less? Assume that P. caeruleus is a keystone species in this community.
Chap 19
G) Of all the naturally occurring elements in the biosphere, why have the cycles of carbon, nitrogen, and phosphorus
been so intensively studied by ecologists? Give details.
H) Explain in detail, how decomposition rate is influenced by temperature, moisture and chemical compostion of litter
and the environment. Give examples.
I) Explain how plants and animals can modify the distribution and cycling of nutrients in ecosystems. Also describe
how disturbance increases nutrient loss from ecosystems.
Chap 20
J) The rapid succession shown by the Sycamore Creek ecosystem is impressive. How might natural selection influence
the life cycles of the organisms living in Sycamore Creek? Imagine a creek that floods about twice per century. How
quickly would you expect the community and ecosystem to recover following one of these rare floods? Explain your
answer in terms of natural selection by flooding on the life cycles of organisms.
K) Species have come and gone in response to changing global climates during the history of the earth. Some of the
mass extinctions of the past have resulted in the deaths of over 90% of existing species. What do these biological
changes suggest about the long-term stability of the species composition of climax communities?
L) Succession seems to lead to predictable changes in community and ecosystem structure. Predict the characteristics
of a frequently disturbed community/ecosystem versus a largely undisturbed community/ecosystem. What do your
predictions suggest about a future biosphere increasingly disturbed by a growing human population?
Chap 23
M) Ecologists are now challenged to study global ecology. The apparent role played by humans in changing the global
environment makes it imperative that we understand the workings of the earth as a global system. However, this
study requires approaches that are significantly different from those that can be applied to traditional areas of
ecological study. Historically, much of ecology focused on small areas and short-term studies. What are some of the
main differences between global ecology and, for instance, the study of interspecific competition (see chapter 13) or
forest succession (see chapter 20)? How will these differences affect the design of studies at the global scale?
N) In chapter 23, we briefly discussed how humans have more than doubled the quantity of fixed nitrogen cycling
through the biosphere. In chapter 15 we reviewed studies by Nancy Johnson (1993) on the effects of fertilization on
the mutualistic relationship between mycorrhizal fungi and grasses. The increases in fixed nitrogen cycling through
the biosphere, particularly that portion deposited by rain, are analogous to a global-scale fertilization experiment.
Reasoning from the results of Johnson’s study, how should increased fixed nitrogen supplies affect the relationship
between mycorrhizal fungi and their plant partners? How would you test your ideas?
O) Ecologists predict that global diversity is threatened by land use change and by the reductions in habitat area and
the fragmentation that accompany land use change. Vitousek (1994) suggested that land use change may be the
greatest current threat to biological diversity (see fig. 23.3). What role do studies of diversity on islands and species
area relationships on continents play in these predictions?