Where can I find my grade?

The total score for each exam is at (or near) the bottom of the last page.

How were the exams graded?

All exams were graded anonymously, by covering the names at the top of each sheet.

Each essay received one overall score.

An excellent essay was informative (contained lots of information) and clear (organized this information in an easily understandable way). The question I kept in mind was, "Could somebody who has not taken BIOL 277 understand the issues and evidence by reading this essay?"

An excellent essay included both principles and examples as well as definitions of important terms.   Really excellent essays also included correct information about some of the difficult material (not just the easy material).   All good essays included lots of correctly explained information.

More credit was earned by clear, complete, correct, convincing explanations than by less adequate explanations.

How do total scores correspond with letter grades?

No final decisions have yet been made. At the end of the semester I will total each student's points for the four exams (total points possible from four exams = 20x4=80), for reports on suggested readings, and for attendance.

Because I will give some credit for steady improvement or marked improvement after the first exam, there is no way to assign final letter grades to any one exam.

To follow the pattern for previous years, a semester total of 64 points (an average of 16 points per exam) would be a straight B (this goal might be adjusted some at the end of the semester).

A semester total of 32 points (an average of 8 points per exam) will be a straight C (guaranteed!).

See the Distribution of Grades for this exam.

What should I do if there has been an error in grading my exam?

• Wait at least one day after your exam is returned.

• Review the information below.

• On a separate sheet, write a brief (one paragraph) explanation.

• Return your exam and paragraph to me before 5:00 P.M., Thursday, October 7.

What can I do to improve my grade (regardless of my total score)?

• Read the comments on how essays were graded (below).

• Review your notes and the lecture notes.

• Then come talk to me about your exam.   Every essay was different, so it is difficult for me to give specific suggestions for how to improve your essays except by talking with you.   Good times are immediately after lectures -- please not before lectures -- or stop by my office any afternoon -- or see me after lecture to make an appointment.

What information did essays include?

... and how were points earned by essays?

Keep in mind that essays earned the most credit for clear, accurate, complete information.
Often essays earned partial credit.

Question 6. Why do populations of the same species often differ?

Nearly all essays focused on explanations for geographic variation, in other words, differences among populations of the same species.   This was the last topic disucssed in class before the exam.

Some essays earned credit for a clear definition of a population ... and for explaining that a difference between two populations is a difference between averages or frequencies of values for individuals in the two populations (2 points).   Many essays then earned credit for listing the four processes that change allele frequencies in populations (4 points).

Essays then earned credit for explaining each of the four processes and how they affect allele frequencies in populations.   Mutation and natural selection were less thoroughly discussed in class (3 and 5 points possible, respectively, for the material covered so far in class -- we will return to natural selection in more detail later!).

Genetic drift was discussed in detail in class and the lecture notes, and essays earned credit for clearly explaining its properties (10 points possible).   Some essays did a great job explaining that genetic drift in allele frequencies is random, occurs in all populations, but has its biggest effect in very small populations.   In addition, genetic drift affects all genetic loci equally.   Three situations that can lead to strong genetic drift are founder effects, bottlenecks, and reproductive skew.   Many essays earned at least partial credit for describing the first two, and some essays clearly explained how all three can lead to strong genetic drift.

Gene migration was also discussed in some detail in class and the lecture notes, and essays earned credit for explaining its properties (9 points possible).   Many essays made the point that gene migration, gene flow, and natal dispersal are all the same thing (and many explained natal dispersal correctly).   Most essays explained that gene migration increases similarities between populations (although it can -- but does not necessarily -- increase genetic differences within populations).   Some essays described how gene migration resembles diffusion of alleles (much like diffusion of molecules in gases or liquids).   Barriers to natal dispersal result in decreased gene migration between populations separated by these barriers.   A number of essays described examples of barriers to dispersal and their consequences for differences in populations of birds.

Most essays mentioned at least one example of differences between populations of one species, most often the Hairy Woodpecker as discussed in class, and many provided some details about this example (most essays earned 1-3 points for this information).

Finally, about half of the essays described how the amount of difference between two populations of the same species depends on a balance between the processes that increase differences (mutation, local natural selection, and genetic drift) and those that decrease differences (uniform natural selection and especially gene migration) (2 or more points).

Important things to consider

Note that the total number of possible points was at least 35.   No one had enough time to cover all of these points, so the maximal score was set at 25.   No essay received a score higher than 20.   Excellent essays often emphasized different aspects of the topic.

Essays that received the highest scores always included some of the difficult concepts and some detailed information about the examples.   A few essays were really outstanding.   It is not easy to master the difficult subjects, nor is it easy to pull all the information together into a clear essay.   Keep up the great work!

Regardless of your score, I would be glad to meet with you to find a way to improve!