Study guide for Exam 4 General Ecology Jesse Brunner General guidance: This class is focused much more heavily on concepts than on memorized facts. Yes, you need to know some terminology in order to understand the questions (or provide concise answers) and I am asking you to remember certain relationships (e.g., PET≈2 x °C), but the overall emphasis is on using relationships, rules of thumb, and ecological principles to explain and predict. Along those lines, then, I strongly recommend you: ∴ Make sure you understand the rules of thumb we’ve talked about. These are quick and dirty short cuts in thinking through a problem. ∴ Think of connections between the concepts we’ve learned. (E.g., how do physiological tolerances relate to population growth rates?) ∴ Think of examples you could use to illustrate these ideas/connections. (E.g., what is a good example of geometric growth? Of exponential growth?) ∴ Think about when a process or concept applies, and when it does not. (E.g., when would the theory of Island Biogeography work well? In what cases would it not work?) ∴ Work on interpreting and drawing graphs. You will notice that a lot of the arguments and support for them have provided in graph form. That is no accident. So, what do they tell you? Can you put them into words? Can you draw curves on graphs illustrating the different ideas/concepts/processes? (E.g., what does the logistic model look like? Where does the line start? Where does it end?) ∴ Get comfortable with the equations. This doesn’t mean you should be able to derive them, but you should understand what the parameters are (the terms that control the rate or shape of the relationship), what they represent, and what happens if they take on certain values. (E.g., what happens in the logistic model if r is really large? Really small?) Similarly, what do these models assume? When it comes to test time, my advice is very simple: 1) Carefully read the question. 2) If you are uncertain about it, re-­‐read it, think about it, or ask a question. 3) Think about your answer for a bit. Does it answer the question that was asked? Does it answer more than I was asking? 4) Make sure that your answer highlights the logical connections between ideas and that it connects all of the dots. (This is the most common problem I’ve seen-­‐-­‐-­‐logical connections implied, but not written out. Please make our jobs easy and say exactly what you mean.) 5) Clearly write down your answer. There is no need to re-­‐write the question. There is no need to fill space. Just be simple and clear. 6) Re-­‐read your answer. Is it clear? Are there extra or missing words? Can someone else read your writing? Page 1 of 4 Potentially useful equations €
(a) N t = N 0 λt (b) λ = N t+1 N t = exp(r ) (c) dN
= rN dt
€
€
(d) # N&
dN
= rN%1 − ( $ K'
dt
(e) dP
= cP(1 − P) − eP
dt
€
€ (f) (g) (n) € (o) €
€ (h) R0
€
R0 = SβL €
R0 = ∑ lx mx x
dN prey
= rN prey − aN prey N predators,
(k) dt
dN predators
= abN prey N predators − mN predators
dt
(m) lx = n x /n 0
mx = bx /n x
∑ xl m
T=
⎛ N + α12 N 2 ⎞
dN1
= rN1⎜1 − 1
⎟,
K1
(j) dt
⎝
⎠ ⎛ N + α 21N1 ⎞
dN 2
= rN 2 ⎜1 − 2
⎟
dt
K2
⎝
⎠
€ x
€
€
(r) pc > 1 −1/R0 NPP = GPP − Ra ; NEP = GPP − Re CE = I Pn −1
AE = A I
PE = Pn A
(i) r = ln(R0 ) /T €
€ €
€
€ Nutrient Cycling: What’s a flux? A store? What is the primary difference between energy and nutrient flows? What do we track or follow in a nutrient cycle? What types of nutrients do we care most about? Why? How does Nitrogen cycle and move through an ecosystem? What controls the rate of N cycling? The size of the pools? How does the N cycle relate to the cycling of other nutrients? How does N-­‐cycling work throughout succession? How does P cycling differ from N cycling? From C cycling? Is P or N more important to ecosystem productivity? How does nutrient cycling link different ecosystems? What does it mean for a nutrient cycle to be “tightly coupled” and what does that mean for nutrient retention in an ecosystem? How does decomposition work into nutrient cycling? Page 2 of 4 What is the role of microbes in nutrient cycling? How about mutualistic symbioses? What are the consequences of excess P and N on ecosystems? What about pumping SO2 and NOx into the atmosphere? How does acid rain affect terrestrial and aquatic ecosystems? Why is limestone important? How does stoicheometry relate to nutrient availability and productivity? To community composition? Ecosystem Ecology What is production? How does primary production differ from secondary production? How are GPP, NPP, Ra, and Re related? How do we measure each? (Think flux towers, light-­‐dark bottles, etc.) What are reasonable units of these measurements? Can NPP or NEP be negative? How does this relate to autotrophy/heterotrophy? How does production relate to standing biomass? What controls GPP in terrestrial and aquatic ecosystems? How do GPP and NPP vary in space and time? (Think cycles and general patterns of high vs. low.) What is the ultimate source of the energy in top predators? In detritivores/decomposers? How do we define an ecosystem? How are the inputs into an ecosystem related to the outputs? What controls secondary production? How does this differ in different types of ecosystems? How does this relate to the various aspects of trophic efficiency (CE, AE, PE)? What are average TE’s? How does this relate to food chain length? What determines how much NPP ends up in the grazer versus detrital food chain? What is residence time and how does it vary between ecosystems (e.g., forests, grasslands, and aquatic ecosystems)? Be able to draw Sankey diagrams showing energy transfer from one trophic level to another. Also be able to draw Eltonian pyramids for biomass, energy, and numbers of individuals Bigger picture/connections How does nutrient cycling influence primary and secondary production, or trophic transfer efficiency? Why do we see specialized metabolic functions in grazers and decomposers much more than in carnivores? Why are there so few large, top predators? How do communities and ecosystem processes (e.g., nutrient or energy cycling) change after different sorts of perturbations? Are the effects different at different time scales? Page 3 of 4 Try to connect nutrient cycling to community dynamics (e.g., succession, stability) and to competition. Think about how mutualisms affect ecosystems. Think about nutrient cycling and food chain length. How do functional responses relate to “dead zones” in places like fresh water lakes or the Gulf of Mexico? Page 4 of 4