PRACTICE EXAM 1 ANSWERS (Questions handed out in class on Tuesday 14 February)
EXAM - Thursday 23 February in class

The exam has several sections:

1.      Definitions – choose 6 of 7 terms to define.  For full credit you must both define the term and explain why it is important in marine ecology.  This section is worth 18 of 100 points (<20%).

2.      Short answer – fill in the blanks, circle the correct answer, multiple choice.  Some of these questions will involve interpretation of graphs.  This section is worth ~40 points (~40%).

3.      Short essays – these questions can be answered with short essays or bulleted lists.  Some of these questions will involve graph interpretation and applying knowledge to case studies.  This section is worth ~40 points (~40%).


A few sample questions of each type are below.  There will be several graphs on the exam, so be sure that you are comfortable with graph interpretation.  I've attempted to make the exam itself well-balanced in course content, although that may not be reflected in this practice test, which is just meant to give you a flavor of the kinds of questions that I tend to put on exams.  Good luck and be sure to email or stop by office hours if you have any questions.  Answers (along with all lecture notes and power point files) are on the website


PART 1 -- Definitions
Please define the following terms and explain briefly why each term has significance in marine ecology (2 points each)

Be sure to include two parts in your answers -- (1) the definition; (2) why it is important.

1. Lecithotrophic larvae

2. DOC
3. Echolocation
PART 2. Short answer
Please fill in the blanks or circle the correct answer(s) (1 point for each correct response)

1.  In the above figure, the zone pointed at by the arrow is known as the:   oxygen minimum zone .
2.  Three factors that contribute to this pattern of oxygen distribution are:
    a.     high rates of respiration (use up oxygen)
    b.     lack of photosynthesis (due to low light; so no/little oxygen is produced) 
    c.     lack of exchange of oxygen with the atmosphere (because of the stratified water column)

3. Diatoms have a higher requirement for nitrogen / phosphorus / silica than do many other algae.  As diatoms reproduce asexually during the growing season, the average size of individuals in the population will increase / stay the same / decrease.

PART 3. Multiple choice
Please circle the correct answer
1. A
2. D
3. E

PART 4. Essays.  Please provide concise but complete answers to the following questions.

1. Some scientists are concerned that the frequency and severity of El Nino events is increasing.  Describe what happens during and El Nino/Southern Oscillation event, and what effects might result if the scientists are correct.

Normally trade winds blow from East to West across the Pacific, and there is upwelling of cold, nutrient rich water off the West coast of South America.  When El Nino occurs, the trade winds slow and the upwelling is stopped.  Warm water occurs off the Pacific coast of South America.  When you have an El Nino event, there are many effects on the ocean and the earth.  If ENSO events increased, we might expect that the primary production of the ocean off of South America would decrease (due to the lack of upwelling and nutrients), fish production would decrease, and fish and bird populations would either starve or move to more productive regions.  Further, we would expect changes in weather over the continents, as well.  In particular, the weather would be rainer over Peru and there would be drought conditions in Australia and Indonesia.  Human deaths and economic costs from mudslides, floods and drought-induced fires would also be predicted.  We might also expect more snowfall in the W. US and milder winters in the Northern US and Europe.

2. Describe 3 mechanisms by which pelagic organisms avoid sinking into the abyssal.

Possible answers include:

Organisms can reduce sinking rates by either decreasing their density or changing their resistance (as described by Stoke's Law).  Some specific adaptations are:

(1) Reduce density by exchaning heavy ions for lighter ones (this is done by some squids that replace SO42- with Cl-)
(2) Reduce density by having pockets of gas (for example, gas vacuoles in Cyanophyta, floats in Portuguese Man-O'-War (Physalia), and swim bladders of fish).
(3) Reduce density by accumulting fats and oils, which are more buoyant/lighter than water (for example, the blubber of whales)
(4) Change resistance (increase drag), by increasing surface area to volume -- either being small, being flat, or having spines and body projections.
(5) Also many phytoplankton, zooplankton and, of course nekton, can actively move back up in the water column if they sink.

3. Explain the relationship between the fisheries science concept of maximum sustainable yield (MSY) and the population biology concepts of logistic growth (population growth rate and carrying capacity).  It may be helpful for you to draw a graph and to define the relevant terms.

The maximum sustainable yield of a fishery is maximum harvest that can be taken without impairing the prospects of exploiting the fishery in the future.  Harvesting a population such that populations size is maintained around half the carrying capacity (as predicted by logistic growth) will maximize the population growth rate and therefore productivity.   If the population is harvested to extremely low numbers, the population may crash completely, or take a very long time to come back to harvestable levels, as predicted by the logistic growth equation.  See the lecture ppt. file or your text for a figure of logistic growth and MSY.

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