All essays were graded anonymously (by covering the name at the top of the sheet).

Each question was graded separately.

Scores are on the back of each sheet.

The maximal score for each question was 10 points. To receive 10 points an essay did not have to include all the information we discussed on the topic, but it did have to include enough clear and accurate information that someone reading the essay would understand most of the important points we covered.

Most essays received partial credit as a result of including incomplete or inaccurate information.

To determine your total points for this exam, add up the three scores for the three questions. The maximal number of points for this exam is thus a total of 30.   (Check the distribution of grades for this exam.)

To receive a straight B for the semester, you should earn a total of 90 points (an average of 18 points on each of 5 exams).   To receive a straight C, you should earn a total of 60 points (an average of 12 points on each of 5 exams).   At the end of the semester I also examine everybody's scores and award some extra credit for consistent improvement on exams (especially after the first exam).   The target for a B is subject to adjustment by me at the end of the semester.   The target for a C is engraved in stone!

If you would like me to regrade your exam, return your exam (all three questions) to me with a separate note about what you feel needs correcting before the next exam.

Most important ... I will be glad to talk to each of you about any exam. Good times are immediately after class or later in the afternoon (see me after lecture to arrange a time).


1. (10 minutes) Describe free-running activity rhythms.

Many essays correctly definited activity rhythms (including diurnal and nocturnal) and free-running activity rhythms (in constant conditions).   Most also mentioned the drift of free-running activity rhythms because their period is normally slightly greater than 24 hours.   Several essays included a diagram of free-running periods, although nearly all of these diagrams were placed in the margin and consequently were so small that they were not labeled or explained so that a reader could understand them (scientific essays use large, correctly labeled figures and plots, in the middle of the page).   Most essays also mentioned entrainment, some defined this term, and many described an example (although often incompletely) and mentioned the analogy with human "jet leg".

2. (10 minutes) Describe the yearly cycle of gonadal hormones.

Most essays described the chain of hormones from the hypothalamus to the gonads (although sometimes incompletely) and desribed the negative feedback of gonadal hormones on the hypothalamus.   Most essays also described the annual cycle of these hormones and the gonads (which regress to inactivity during the winter in temperate regions).   Most also mentioned that this annual cycle is controlled by daylength.   Descriptions of experiments showing the effects of daylenth were sometimes not clear, but some essays did a good job of describing how gonadal activity is stimulated by shifts (at any time of year) from short days to long days, how the hypothalamic-gonadal axis becomes refractory to stimulation by long days, and how a period of short days is necessary to terminate the refractory period.

3. (10 minutes) Describe use of the sun for orientation by birds.

Most essays described some basics of orientation using the sun.   Many described the experiment with starlings exposed to either the sun or an artificial light.   Many essays failed to include all features of this study (sun, fixed light, moving light) or to draw a conclusion from the results (to describe an experiment correctly requires brief descriptions of the question, the method, the result, and the conclusion).   The experiments with homing pigeons had the same problems.   In addition, in this case some essays had results for magnetic and solar orientation confused.   A few essays did a good job of describing the hierarchy of mechanisms for orientation by birds, but this topic was a difficult one and some essays had the complex interactions of these mechanisms confused.