Review for Final exam
Lecture 8: Different kinds of species interactions.
1) Be able to discuss what kind of species interactions can be classified as (+/+; both partners
benefit), and as +/- , + / 0, and - / -.
2) Discuss one example of how a predator or herbivore can have effects on the whole community.
Examples include foxes in Alaska eating birds and changing plant community, grazing of cows
changing grasses, and starfish eating a dominant competitor and thus promoting species diversity.
3) Why do predators lead to oscillations of populations? Understand two ways: 1) predators that live
longer than their prey, so that when there is a large population and their prey collapses they don’t
go immediately extinct, but decline after a time lag. 2) prey that can escape to predator-free areas
for a while and build their numbers up again, before the predators find them (the Huffaker
example).
4) Understand the equation DI/dt = βSI – mI (although if I ask a question about it on the exam, I will
give you the equation). I is the number of infected people and the change over time in I is
influenced by the number of people infected already (I) times the number of susceptible people
(S), time the transmission ability (β), minus the people who die (m – mortality – times I). Be able
to interpret the finding that: ST (number of susceptible people needed for disease to spread) must
be larger than m/ β. What does this tell us about how to control disease? In general, also
understand how parasites and diseases influence their hosts to help them be transfer between
hosts.
5) Think of the range of positive interactions between organisms from commensalism (one species
is not affected), to facultative mutualism (both species are able to live without partner) to
obligatory mutualism (the partners are unable to live without each other). Give one example each
for the underlined words here.
Lecture 9. Introduction to communities.
1) Define a community. What characteristics does a community have?
2) Be able to understand the idea of a species accumulation curve. Be able to use one to estimate
how many species there are: see slide 15.
3) Be able to calculate Shannon-Wiener index for simple examples like that given on slide 20. I will
give you the equation, but you need to know how to use it.
4) Be able to define and give an example of each of these “VIP” species: dominant species, keystone
species, ecological engineers.
5) Define succession, distinguish between primary and secondary succession. In general, understand
that succession is usually facilitative in the beginning, with the earliest pioneer plants helping
prepare the soil for those that come later. Usually there is also a climax community: an endpoint
towards which succession moves towards over time. But also understand recent work has shown
it’s not such a simple story (there is tolerance or even inhibition; there can be multiple potential
endpoints). Be able to define all the underlined words here.
Lecture 10: How and why species diversity varies.
1) Be able to understand why plate tectonics explains Wallace’s line.
2) Describe at least three reasons for why there is more species diversity in the tropics.
3) Island biogeography. I would like you to understand in detail this graphical theory. For the two
lines (immigration and extinction) understand where they are zero and why they are curves and
not straight lines. For each line, if I tell you that the island is farther away, or larger, be able to
adjust the curve up or down. Then do this for the two lines at once (like slides 31 and 32), and be
able to understand what happens to the equilibrium and the turnover values (understand these last
two underlined words).
4) Understand that island biogeography is applicable not just to real islands but also to any kind of
patches of habitat. Know about the Biological Dynamics of Forest Fragments Project (BDFFP) in
Brazil, one the world’s largest ecological experiments ever performed.
5) We then turned to theories that explain why some communities might have more species than
others. Understand both these theories.
a. Heterogeneous environment theory: Environments that are variable have room for more
niches, and hence more species. Example: rainforest has vegetation with a variety of
heights.
b. Intermediate disturbance theory: Environments that are not too stable (dominant
competitors outcompete all species) or too disturbed (harsh conditions don’t allow many
species to live) will have most diversity.
6) Lastly we looked at some evidence that if there are higher species the overall community is more
stable or resilient to a disturbance. Experimental plots with more species had higher biomass one
year after a drought.
Lecture 11. Introduction to ecosystems.
1) Define an ecosystem and know what characteristics it has.
2) Contrast Gross Primary Production to Net Primary Production (NPP). How is NPP estimated?
3) Know the major limiting factors for NPP in terrestrial and aquatic ecosystems.
4) Know what happens during the process of eutrophication.
5) Be able to explain why there are fewer species and individuals at the top of the food web than at
the bottom. When discussing the efficiency of energy transfer, think about the different processes
where energy is lost. For example, transferring energy from plants to insects (slides 32 and 33):
some plants are not eaten; of those that are some energy is excreted, more is metabolized, and
only a little bit is put into biomass and growth.
6) Understand why some toxins accumulate at the tops of food webs (they can’t be excreted or
metabolized), and know some examples of dangerous substances that do this.
Lecture 12. Nutrient cycling and environmental crises.
1) Define and understand the following words: nutrient, weathering, leaching.
2) Nutrients cycle between different pools (atmosphere, vegetation, soil, rocks, freshwater, marine
waters), with the amount of time they spend in any one pool measured by the “residence time”.
3) Know the cycles for C, N, and P (slides 16, 18, 20). Compare and contract: which nutrients have
large pools in the atmosphere? Which have large pools in sediments under the ocean? Which of
these nutrient cycles is most affected by human disturbance?
4) For the environmental problems we talked about:
a. For habitat loss, contrast loss with fragmentation and degradation (they are three aspects
of the same problem). This is a clear #1 in terms of problems. Understand how it is
caused both by human population, and rising consumption per person.
b. For species invasions, remember how earlier we talked about situations in which a
species was introduced to a new area without its predator and became very abundant
before the predator was introduced as a way of “bio-control”. This is one reason why
invasives can be dangerous.
c. For over-harvesting, global climate change, nitrogen deposition and toxins know the
basics of the problems. What side-effects of global climate change are there (melting ice,
rising sea levels, ocean acidification)?
d. Know the history of the ozone layer problem, as it’s a good example of a problem that
has been addressed, and shows that these kinds of problems can be fixable.
Lecture 13. I will give out this review after Tuesday’s class.
The readings:
Isack and Reyes 1989:

What data do they show to establish that both sides (humans, honeyguides) benefit?

What data do they show to establish that honeyguides communicate information about the hiveto
humans?
Terborgh et al. 2001
 Why would you call this a natural experiment? Describe what happened at the site where the
scientists worked before they started collecting data.
 What happened ecologically on islands without predators (big cats and ant-eating armadillos)?
Jackson et al. 2001
 What kind of scientists wrote this article? What do they study and what kind of data did they
collect.
 What kind of marine habitats do they review?
 What’s their conclusion as to what has been the most important human activity that has harmed
these ecosystems?
Myers et al. 2000
 How do the authors define a hotspot?
 Are there any in China and where?
 How do the authors want their hotspot list to be used?