Biology 221 Practice Midterm Exam 
(answer key included)

This practice test is intended to provide you with a sense of how this semester's exams will be organized and presented. It is obviously much shorter than an actual exam, and the questions provided here are not meant to suggest or imply a particular orientation towards subject material (Remember, you are essentially responsible for all materials covered in lectures and discussions, as well as the assigned readings).

The exam will consist of three basic types of questions.

A) Those requiring very short answers (less than one sentence)
B) That requiring short answers (one to three sentences)
C) Those requiring short essay responses (several short paragraphs) that may include calculations or graphs.

The relative contribution of each section to the total exam score will be 20, 40, and 40 % for A, B, and C, respectively.

A) Very short answer: (20% of exam grade)

1) In which direction do Coriolis effects cause drifting particles to deflect in the Southern Hemisphere?

To the left or counter clockwise

2) In seawater, Reynolds numbers are primarily determined by what two factors?

Size and relative speed

3) What is the most common kind of crustacean zooplankton in the oceans?

Copepods

4) Describe the general relationship between body mass and rate of oxygen consumption?

Negative... although there is a positive relationship between absolute consumption and body size

5) What circulatory pattern helps reduce heat loss in the extremities of marine mammals?

Countercurrent or heat exchanger circulation

6) Skin friction is an important component of what type of fluid force?

Drag

 

B) Short answer: (one to three sentences, worth 40% of grade)

1) Explain why seawater typically shows little exchange between depths.

Example answer: Water warmed by the sun "floats" above the denser, colder waters below. Without some active process of water motion such as currents or upwelling, warmer water will simply remain at the surface and colder water will stay below it, with little or no exchange between depths.

 

2) Explain why living in seawater represents an osmotic challenge to marine fishes and describe two things that marine fishes do to overcome this challenge.

Example answer: The body fluids of fish are significantly less saline than seawater (about 1/3 less). Because water flows across semi-permeable membranes from lower concentrations to higher, fish must compensate for the consistent loss of water from their gills (and also through urination) by drinking seawater.... However, this increases the concentrations of salts within their bodies, so they must also actively secrete salts via their gills and urine.

3) Contrast two sets of topographic features that cause differences in how wave energy is released on shorelines? Briefly justify your answers.

Example answer:

a) Gently sloping shorelines will cause waves to break more slowly than will steep beaches because of the relationship between when a wave breaks and the water depth.

b) Headlands concentrate wave energy while bays diffuse wave energy because waves slow down in shallower water and thus "wrap" onto headlands and bay mouths

 

Short Essay Answers (one to two paragraphs: worth 40% of grade) 

You're sitting on the lawn in front of the Manor House, engrossed with your Marine Biology text, when you hear a seductive voice from behind you say "Wow, are you studying marine biology? I think it's the greatest subject in the world…. I just wish I knew more about it..... Say, do you know anything about this el Niño thing"? You look up into a dazzlingly warm smile and realize (gulp!) that the quality of your answer just might change your life forever.

With this in mind, you launch into a brilliant discussion of what el Niño is all about. Below, describe your brief and succinct answer that ties it all together. Be sure to consider the following questions as you respond: A) What are the primary atmospheric and oceanographic processes associated with el Niño? B) How do these processes alter different (at least three) aspects of the physical and chemical environment in specific parts of the ocean? C) How these environmental effects influence different types of sea life (give at least three examples).

There are obviously many possible answers here. The key to a good answer is the ability to demonstrate that you clearly understand the successive links between environmental changes associated with el Niño and the ultimate effects upon specific marine organisms. The key is to logically tie these links together. As with all questions of this nature, several careful readings may help you recognize just what the instructor is looking for. A quick outline to help organize your thoughts is often helpful. Don't just jot down the first things that come to mind…. Identify the specific questions you need to consider, then write your answers to match those specific questions. A "shotgun" approach that simply puts down a list of ideas or terms without obvious cohesion will not receive much credit.

In this case, a good answer should include: a discussion of how reversal of high and low pressure on either side of the Pacific (the Southern Oscillation) causes a shift in wind patterns and a periodic reduction or reversal of water flow at the equator. This effectively shuts down upwelling along the west coasts of the Americas (particularly South America) because winds stop blowing along the coast… (together, these sentences answer part "A"). During large scale el Niño events, much warmer-than-normal water temperatures occur throughout the region, changing weather patterns on land and sea. Resulting changes in the rates of evaporation and runoff in coastal areas can change local salinity levels. Changes in the location and intensity of storms can influence how waves influence animals along the shoreline. Nutrient levels and the availability of oxygen in surface waters will fall as upwelling ceases… (these all help answer part "B"). El Niño most obviously influences primary productivity in areas where the loss of nutrients reduce the abundance of phytoplankton. This reduces food and oxygen for zooplankton and their predators and many may die or not reproduce. Sessile organisms or species tied to a specific region may also show lower rates of growth and reproduction… some even die, as bleached corals in Panama and sea lions in New Zealand did during the last el Niño. Motile animals such as fish, squid, and whales often follow thermal gradients and shift their ranges north or south in search of prey or to escape sub-optimal temperatures... ( all these statements help answer part "C").