How to teach Hardy-Weinberg equilibrium

Over on the Gene Expression blog there's a discussion about how to explain Hardy-Weinberg equilibrium. Commentors are claiming that it's best explained mathematically rather than verbally. I'm posting a comment arguing that the best explanation is pictorial. Because I don't think I can put the picture in the comment I'm putting it here.

And here's the text of the comment I posted:

The best way to describe (and teach) Hardy-Weinberg Equilibrium is neither mathematically nor verbally but graphically, using a drawing that's like a Punnett Square with allele frequencies replacing the alleles. I've posted an example on my teaching blog.

Viewed this way, HWE is so obvious and so intuitive that there's no need for ps and qs at all. (And there never was any need for the apparent complication of q, as it's just 1-p.) The sides of the square are simply labeled with the actual allele frequencies, and the areas they create are the genotype frequencies in the next generation.

Of course math will be needed to deal with the deviations from HWE produced by selection and other factors, but starting with this graphical explanation helps beginning students see how simple and inevitable HWE is. (My freshman class on this is titled "The incredible tedium of Hardy-Weinberg equilibrium".)

Why biology is harder than physics

Beginning university students in the sciences usually consider biology to be much easier than physics or chemistry. From their experience in high school, physics has math and formulae that must be understood to be applied correctly, but the study of biology relies mainly on memorization. But in reality biology is much more complex than the physical sciences, and understanding it requires more, not less, brain work.

Biological processes of course are consequences of physics and chemistry, which is why we require our biology students to study the physical sciences. But organisms are also historical entities, and that's where the complexities arise. The facts of physics and chemistry are constant across time and space. Any one carbon atom is the same as any other, and today's carbon atoms are the same as those of a billion years ago. But each organism is different. That's not just a statement that fruit flies are different from house flies. Rather, each fruit fly is different from every other fruit fly alive today, and from every other fruit fly that ever lived, and it's the differences that make biology both thrilling and hard.

The differences have several causes and consequences. One cause is that biology depends on past history, because descendants are not identical to their ancestors. This is true at all scales, and the fundamental reason is that the process of genetic inheritance is not perfect. The DNA sequences we inherit from our parents are never identical copies of their DNA - instead they contain copying errors. So every copy is slightly different, even between two siblings. We are all mutants. These differences also accumulate over the generations, like in the party game Americans call "telephone" and the British call "Chinese whispers".

The second cause is natural selection, which shapes the accumulation of differences, favouring those that improve survival and reproduction and making it harder for disadvantageous differences to persist over the generations. And because most natural selection arises from interactions with other evolving organisms rather than with the relatively stable physical environment, the changes are rapid.

The result is that all biological systems are diverse at all levels. Even high school students are used to the idea of 'biodiversity', meaning the dramatic differences between different species of plants and animals. But the diversity is much more ubiquitous. Within each multicellular species, every individual is genetically different; every fruit fly is genetically different from every other fruit fly. The invisible bacteria turn out to be much more diverse than anyone would have thought. Bacteria isolated from natural environments are so different that even the individuals we would have considered the same species turn out to have about 10% of their genes from unrelated sources. In lab cultures, bacterial mutation rates are high enough that a single ml of culture will contain millions of different genotypes.

Even genetically identical cells are not functionally identical. When a cell divides its molecules are randomly distributed between the two daughters; because 'randomly' does not mean 'evenly', these daughters will have inherited different sets of the proteins and RNAs that carry out their functions. And even if the two cells had identical contents, these contents would still have different interactions - repressors bump into cofactors at different times, DNA polymerase slips or doesn't slip at different points in its progress along a chromosome. Understanding the how and why of biological phenomena thus requires us to consider historical and ecological factors that are many orders of magnitude more complex than those of physical systems.

The critical word is probably 'population'. Biologists rarely try to define it, but they use the term everywhere to refer to similar but not identical organisms or cells (or even molecules) that interact in some way. 'Population thinking', the realization that species are populations, not pure types, is said to have been key to Darwin's insight that members of a species undergo natural selection. And population thinking is probably what makes biology so much more complex than the physical sciences.

Of course we can't consider all of the differences all of the time, so at different levels of study we biologists try to pull out the factors that we think will matter most. Molecular and cell biologists work with populations of molecules, but they keep everything else as identical as possible. Developmental biologists study how cells become different, but they use pure-breeding lines and clones to ensure that the genetic properties of their organisms are as identical as possible. Ecologists pay attention to the big differences between species, but under conditions where they can ignore the differences between the individuals of each species.

I don't think population thinking is addressed in high school biology. We can't really blame their teachers, because the issues probably were never made clear to them either. Instead high school teachers pass on the facts they remember from what they themselves learned at university. The result is that their students enter university expecting their biology education to consist mainly of memorizing lots of new facts.

We instructors want our new students to start focusing on understanding complex processes and interactions, between entities that are themselves populations of diverse and somewhat unpredictable entities. We're thus asking them to set aside all the learning strategies that worked well for them in high school biology, and to learn in a new way. To students this probably seems the height of foolishness, and they're understandably reluctant to take the chance. So one big challenge, for instructors and for our students, is to find ways to ease this transition. We need to give students confidence that deep understanding will bring better grades than will rote memorization, and that saying "What I don't understand is..." is not an admission of failure but the essential first step to this understanding.

Can we do a Genetics reading assignment?

The New York Times is publishing a series of very good articles (11 so far) under the heading The DNA Age, about the social and personal implications of DNA sequencing. I'd like to find a way to require all of my BIOL 121 students read and think about at least one of these articles.

How could this work? I'd tell them they need to choose one of the articles to read, and that they will be asked to write a paragraph about what they've read, in response to an article-specific question I'll post. They'll be encouraged to discuss their chosen article with other students, face to face or on the WebCT discussion board, but will need to compose their own paragraph answers. To discourage copying I can have them submit their paragraphs to Turnitin as well as in answer to a WebCT quiz question. I don't know yet what kind of questions I'd ask them.

Marking this would require some extra grader hours - I'd give them a strict word limit for their answers but even marking 400+ 50-word paragraphs will be a big chore. More generally, I'd like to shift at least 5% and maybe 10% of the course mark from the midterm and final to in-class and homework activities. I guess it's time I read up on ways to incorporate peer evaluation into such activities and assignments. I'm getting hold of a book by Eric Mazur called "Peer Evaluation"; I hope this will help me shift much of the marking burden onto the students (who will learn an enormous amount by doing it).

I think peer-marking is one of the things that our new WebCT-Vista system is supposed to facilitate. I hope it's not too hard to use.

The first day of class

I've been thinking about changing what I do on the first day of classes. In past years I've basically done a fast information-dump about the course and then dived right into content (shaking them up with the role of natural selection in the origin of life).

But this year I'm hoping to shift all of the classes in this course to less information-delivery by me and more thinking and doing by them. And it's important do actually do this on the first day. So I'm going to be asking them for input on what they hope to get from the course.

I also think that my default expectations have been shifted by spending the past 6 months developing learning objectives for the first-year biology courses. Learning objectives need to be stated as actions the students should demonstrate ("can do X, can explain Y, can interpret Z", not just states we want them to achieve ("understands X, knows Y"). I'm going to tell the students this, in the context of introducing the existence of learning objectives, and then I'm going to ask them to write down for me, not what they want to learn or understand or know by the end of the class, but what they want to become able to do.

I expect this will take some prompting, so I'll give them some examples: "I want to be able to explain to my parents why my sister has Down syndrome"; "I want to breed healthier Siamese cats"; "I want to help save polar bears from global warming"; "I want to help develop an AIDS vaccine". These goals are rather lame and/or unreasonable, but their only purpose is to stimulate the students to think of other ones.

I'm hoping this activity will accomplish several things. It will give me feedback that I can use in later classes. It will give them a chance to influence the course. It will require them to write. They will be encouraged to discuss their responses with other students (I'm not sure yet how best to do this). Most importantly, they'll experience (not just be told) that they are expected to do things in class, not just sit passively and watch me.

How to teach about dominance

Yesterday the team of people teaching BIOL 121 had our second meeting to discuss our new learning objectives. One issue that hadn't been included in the list of objectives is dominance. I added it to the list on our Instructors' Blog, stated as follows:

Students should be able to define dominance as a particular relationship between the effects of two alleles; dominance is said to exist when the phenotype of the heterozygote is the same as that of a homozygote for one of the alleles (the 'dominant' one). They should also be able to explain that dominance usually results when a single copy of the normal allele is sufficient to give the normal phenotype when combined with a defective allele, and to predict phenotypes when given such information.

Students find this very difficult, I think mainly because they are encouraged in high school to blindly accept "Mendel's Rules", and think of dominance as resulting from some mysterious gene inactivation process. At the meeting I put forward the way I have been trying to teach this concept. I was (slightly) mortified to discover how many assumptions my explanation relied on (assumptions fortunately not shared by my colleagues), so I've been trying to build a better explanatory framework, using ideas they raised.

Here are the figures I would use. The first three figures would be introduced at the end of the first class about how genotypes determine phenotypes (yes, I know that's an oversimplification that ignores the massive effect of environment in real organisms...).

Figure 1: Introduce lactase and lactose intolerance:

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Figure 2: Show a graph of how lactose digestion depends on the amount of lactase:

Students may need to be told that each tube contains the same amount of lactose.

(I don't know if students should be told that this is fake data.)
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Figure 3: Show the questions I'll ask about this information at the start of the next class.
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Here are the figures I would show at the start of the next class:

Figure 4: Show the first question again.

Students could be asked this question first, before being given the guidance suggested on the next figures.
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Figure 5: Remind them of the graphed data.

I've made the original graph pale, and superimposed on it the labels and numbers appropriate to thinking about the amounts of lactase in adults.
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Figure 6: Add bars showing how much lactose would be digested by each amount of lactase.

Students could be guided by asking them how high these bars should be.
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Figure 7:

Now we're back to the original question. After the guidance all students should be able to see that adults with 5µg/ml lactase digest lactose almost as well as adults with 10µg/ml lactase.
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Figure 8:

This question is intended to connect their understanding of genotypes to phenotypes. The answers should be: 0 = -/-, 5 = +/-, 10 = +/+.
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Figure 9:

The +/- heterozygotes have almost as much ability to digest lactose as the +/+ homozygotes. So they will be lactose-tolerant, and we will describe the + allele as being dominant to the - allele.

This is a lot of figures. Ideally the students would have the time to try to figure most of the steps out themselves; the figures are my ideas of the steps their thinking should take.

This lesson should also build the idea that dominance and recessiveness are not properties of alleles in isolation, but properties of relationships between pairs of alleles.

I usually tell students to ignore confusing terms like 'partial dominance' and 'incomplete dominance' and 'co-dominance', and to instead just describe any other interactions between alleles and phenotypes using more informative descriptions such as 'blending' (e.g. many pigments) or 'both phenotypes are present' (e.g. blood types A and B).

The numbers on the graphs are made-up data. Real human lactase assays are usually normalized to the ratio of sucrase to lactase, which is too confusing to present here. But here's a nice graph showing how lactase levels decline and sucrase levels rise in rats (from a page by R. Bowen at Colorado State).

What does 'memorize' mean?

Last night I had a conversation with some faculty friends about teaching. We reached the common point where some of us were saying that students shouldn't have to memorize lists of facts, and others were saying that students need to know the facts before they can begin to think about what they mean. One of us made the important point that the word 'memorize' may mean different things to different people, and different things in different contexts, which (slowly) got me thinking about how we can be more clear.

We all want our students to remember the facts we think important. When we complain that students are memorizing rather than learning (student readers of this blog should note that we are just as likely to be blaming the teachers as the students for this), we mean to distinguish 'rote memorization' from our more-or-less vague concept of 'real learning'. Maybe we could speak of 'remembering without understanding' and remembering with understanding'.

I'll use the cell-division process of meiosis as an example. Students are often expected to be able to define meiosis, name the stages of meiosis and reproduce the textbook illustrations of these stages. But students can accomplish this by rote memorization or as part of a richer remembering. A student who 'really understood' meiosis might be able to explain how the consequences of meiosis differ from those of mitosis and what role this difference plays in reproduction. They might be able to draw steps intermediate between the defined stages, or move paper chromosomes to simulate the entire process. They might be able to explain the physical forces and interactions that bring about the different stages, and how the genetics principles called 'Mendel's rules' are a consequence of what happens to chromosomes in meiosis.

I'll try another example, brought up by a botanist who teaches students about how the different parts of plants transport water and nutrients. Students could simply rote-memorize the names of the structures (phloem, xylem, cambium, stomata, root hairs...) and be able to reproduce textbook definitions and drawings of them, complete with labels of the substances transported and the directions of flow. Or they could also be able to explain why plants need root hairs, why some substances move up the phloem and others down the xylem (or vice versa?), which parts of this transport consume energy and why other parts don't.

Of course a student could have used rote memorization to remember all this information. And we often test students' learning in ways that can be satisfied by rote memorization, probably because this is much easier for us to assess than is deeper understanding. Our Physics colleagues have been discovering that tests that they thought were assessing understanding were in fact being passed by rote memorization. Students could 'plug and chug' - getting the answer to a question of a recognized type by inserting numbers into a memorized formula. When physicists began to assess students' understanding by putting the phenomena into new (simpler and more familiar) contexts where formulas weren't useful, they discovered that the students could no longer answer the questions. So now Physics faculty are leading the way in devising ways to measure genuine understanding, and using these measures to identify and change weaknesses in their teaching.

In Biology we of course do try to test understanding, not just memorization. We do this by asking such questions as "Would anything go wrong if a cell started meiosis with three copies of one of its chromosomes?" or "Would a plant growing in a greenhouse on Mars need the same number of root hairs as one growing under identical conditions (light, water, nutrients, atmosphere) on Earth?" One reason that I give only open-book exams is to discourage myself from asking questions whose answers can simply be looked up in the book.

One big question for Biology faculty is whether our students should be asked to rote-memorize some information before they develop their understanding of its importance, or whether the remembering should only be built up (and assessed) as part of the understanding. I favour the latter. I have been thinking that some of my colleagues disagree, but this may be only because we've meant different things by the word 'memorize'.

Skill-Development Objectives for First-year Biology Courses

These objectives were developed by the sub-committee we put together at the end of August. We did it in only 2 meetings!

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Understanding of the scientific process:
Given a suitable description of an experiment, students should be able to identify the hypothesis or question being addressed, the experiment’s design, the possible outcomes of the experiment, the observed results, and the conclusion.

• For first-year students, examples from the textbook or from everyday life are likely to be most appropriate.
• Students should also be able to identify situations where the experimental design and/or results mean that no conclusion can be made.

Communication skills:
Students should be able to construct a logical and clearly expressed argument supporting a statement.

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• A Short Guide to Writing about Biology (Jan. A. Pechenik) is an excellent resource for writing assignments. Instructors may choose to require their students to obtain it and use it as a framework for one or more assignments.
• Some instruction should be provided in class, possibly with examples of better and worse writing, but the actual writing can be done outside of class and assessed with WebCT, through the Help Centre or by peer review.
• Students should also be given experience in verbal communication and group work by having opportunities to explain a concept to another student or small group of students.

Study skills
Students should be able to make effective use of textbooks, including the table of contents, glossary, end-of-chapter summaries, figures and diagrams, and study questions.

• Students benefit from practice in constructing hierarchical summaries of information provided in textbooks and in lectures.
• Interpreting an unlabelled diagram is a good exercise.
• A textbook-based scavenger hunt for information is a good in-class exercise that could be done multiple times on different topics.

Societal context of science:
Students should be able to identify scientific issues relevant to societal problems, and societal issues arising out of scientific advances.

• Instructors may wish to choose one issue relevant to course material for in-depth consideration by the class, or have students consider a number of issues throughout the course.
• It is important that students gain experience in discovering the issues themselves, rather than simply learning about issues presented by the instructor.

Should undergraduates learn to read scientific papers?

Over at the biology blog Sandwalk, Larry Moran triggered a discussion of whether or not undergraduates should be encouraged to read and evaluate scientific papers. He thinks they're not ready for this challenge, but a number of the people commenting think differently. Here's my contribution:

Students in my first-year biology classes have an option of reading a scientific paper and writing a report on it; this replaces 15% of midterm+final exam marks. I provide a list of papers by local authors that aren't likely to be too technical, but they can select a different paper if they like. I don't vet their paper choices, and give them only a small amount of guidance.

Those who choose to do this find it very challenging, often telling me that "I had to read the paper six times before it started to make sense!". But they also find it very rewarding; they're proud to have accomplished this difficult task, and feel that the experience will give them an advantage over other students in future courses.

Our courses need 'process' objectives

Last spring a group of faculty (including me) put a lot of effort into developing detailed descriptions of the curricula of our first-year biology courses. Along with this we developed a list of about 30 learning objectives - abilities we wanted our students to acquire by taking these courses.

Recently we realized that, although we had done an excellent job on the scientific content of the courses, we had overlooked the need to explicitly describe the more general abilities we want our students to acquire. This category would include advanced reading and writing skills, the ability to interpret and design tests and experiments, and such learning skills as the ability to identify the gaps and confusions in their understanding (I think Dick Cheney called these "unknown unknowns").

So on Friday a sub-group of us are sitting down to begin developing these objectives for our first-year classes.

Preparing for Reading Week projects

I just had a meeting with the people looking after UBC's Learning Exchange, to discuss the arrangements that will let students in my classes participate in Reading Week projects. In these projects the students will spend their week off working as part of groups enhancing the experience of children in schools located in Vancouver's poorest communities (mainly the "downtown east side").

The biggest issue for me is to be sure the projects my students do include some biology, because I want to give academic credit for this work. The nature of the projects is driven mainly by the teachers' knowledge of their students' needs, and by the interests of the graduate students who coordinate the projects, but it should be possible to make sure our projects have a biology component.

Purple hair !?!

Lately I've gone back to tinting my hair interesting colours. We'll see what the students think when I start teaching again in January.

Preparing students to teach evolution

I just sent an email off to some faculty in the Faculty of Education, asking if they'd meet with me and a colleague to discuss how we are preparing (mostly failing to prepare) our students to teach evolutionary biology. These future teachers will be in the front ranks, defending evolutionary science against the 'war on biology' being waged by the Christian and Muslim fundamentalists. We can't complain about how they do this job if we haven't done our best to prepare them for it.

Rank, reward, filter...

I'm about to submit the final grades for my freshman biology course, which prompts some thinking about why we give grades (rather than e.g. pass/no credit).

A "pass/no credit" system accomplishes one of the functions of grading. It filters out the students who are not prepared to proceed to the next stage in their education program (or their like). When students complain (beg for special consideration), I often argue that "I've given you an 'F' for your own good", and I encourage them to think about other career plans than medical school (or Pharmacy, which is big here).

But when I fail students in their first year of university I'm also motivated by the benefits to other members of the university community. That's the filtering function - part of my responsibility is to prevent unprepared students from going on to more advanced courses. Such students are a tremendous drag on teaching; both the instructor and the other students pay a heavy price if the level of instruction has to be lowered to accommodate students who should never have been allowed to enroll.

The other functions of grading won't be satisfied by a "pass/no credit" system. One of these is ranking the students who have passed. Our university uses student grades to assign priority in registering for next year's courses. So students with good grades have first choice of the often-limited places in the courses they want, and students who have just scraped through have to put up with what's still available when are finally allowed to register.

Another function of grading is giving the best students the marks that get them scholarships and other benefits. It's not enough that a student is top of the class - if the top mark is only a B this student won't make the local equivalent of the Dean's List. With a class of 400 (well, two classes of 200), I want to give the top ten or so students A+s, even though my tough final might have left them with what would otherwise be an A-.

One final issue is consistency of grading in a big course with sections taught by different instructors. The different instructors may have to compromise our individual grading philosophies a bit to ensure that students in different sections are treated comparably. So I'm waiting for the course coordinator to give me the OK to click the "submit grades" button.

Not "hot"

My sense of responsibility to my students prevents me from reading what they're saying about me on RateMyProfessors.com until AFTER I've submitted their final grades.

Oral exams

One of my grad students is about to defend his PhD thesis, which got me thinking about oral exams. Most undergraduate students never experience an oral exam, but they're the best and I think fairest way to assess a student's understanding.

Usually the examining committee has several members, who each ask the candidate a series of questions. The goal is to find out the limits of the student's understanding, and the strength of oral exams is the flexibility of the questions. So when the student easily answers one question, the examiner responds with a harder question on the same general topic. If this is answered well, the next question will be even harder. Any question the candidate can't answer defines one boundary of their knowledge. The examiner responds by changing topics, again starting with an easy question and moving to harder questions if the student's answers are good, until another boundary is reached.

So taking an oral exam is a scary experience. No matter how well or how badly you are doing, you'll still spend a substantial fraction of the time dealing with questions you find very challenging, and you probably will be unable to answer some questions. But knowing that this is supposed to happen to even the best students can save you from panicking when it happens to you.

Gender bias in students' expectations

I'm still seething over a couple of postings an anonymous student made to the discussion board for my freshman biology course. I had asked a colleague (Dr. X) to give two lectures, in exchange for three I had done for him earlier in the term.

I've already responded on the discussion board to the implication that when I'm not lecturing I'm resting (see posts below), but here I want to point out the implicit gender bias in this student's expectations.

The student views Dr. X's research work as more important than his teaching responsibilities. (I had told my students he was doing botanical research, but in fact he was accompanying his wife on a trip combining her research with a vacation for them both.) The student assumes that of course I should make sacrifices to support this work.

On the other hand, although I run a much larger research program than Dr. X, I am seen as only a teacher. And in addition to teaching, I'm judged on how deeply I appear to care about my students.

These different expectations are one of the many reasons women faculty have a hard time. Students make excuses for male faculty (who they see as having more important things to do than teach), but expect women faculty to be substitute mothers, sacrificing any other goals to take care of their students. On Wednesday the students will do their teaching evaluations, and I expect as usual to be criticized for insufficient nurturing.

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Here are the discussion board posts:

From an anonymous student:

I felt really bad for him. He was just given a package of slides and then tried to teach from there. I thought a lot of people were really disrespectful. Like if you went the monday lecture and found him insanely boring, why did you come to the one on wednesday just so you could talk the whole time and then make a huge scene by leaving early?

My response:

Hi everyone,

Dr. X normally teaches another section of Biology 121. He taught
these two classes for me because I had taught three classes for him in
late February, while he was in Thailand.

He did not have any prepared material that he thought would be suitable
for my students, so I provided him with copies of the slides I used last
year, thinking that he could use them as a framework to develop two
classes on sustainability. I did not expect him to simply show my
slides, and I apologize for any problems with the classes he taught.

Dr. Redfield

From another anonymous student:

Its quite rediculous that she asked Mr. X to teach for her although she helped him
teach 3 classes. Mr. X was away for a reason, but dr. Redfield is just taking a
break and not being responsible for our class. Just so dissappointed.

(I deleted this post, and last night a new one appeared - same sentiment and same spelling error so probably the same student.)

I actually disagree on that. Some parts were interesting, but this teaching skill was not good. Dr. Redfield's teaching method was really better and have the skill to actually crab your attention! However, I am quite dissappointed that she wasn't able to teach our class. She taught Dr. Xs class because he was away to Thailand, but now he is taking over her class while she is resting. This really shows that she is very unresponsible for our class. She is a good, interesting and smart prof, but maybe she needs to care more.

And here's my response.

!!! RESTING???

Pardon the 'shouting', but I've been working night and day, holidays and
weekends, on this course; just check the dates and times of my
Discussion Board postings. Since my last lecture to you I've taken
exactly one day off (yes, it was a weekday, but I worked on all of the
weekend days).

If my lectures are interesting it's because of the work I put into them.
For example, I've spent part of the Easter weekend working on
Wednesday's final lecture. This is a lot of work because I've decided
to replace about half of what I had prepared with material from the new
IPCC Report on climate change. I'll be spending much of today on it too.

I also spent part of the Easter weekend compiling and posting the PRS
marks. This including tracking down the errors students had made in
entering their student numbers so they would get the marks their answers
have earned.

I spent part of it analyzing and posting the Reading Quiz marks. This
included going back over the original 'opt-out' quiz to find those
students who had never realized that if they weren't going to take the
quizzes they needed to actively opt out. (About 15 students had marks
of zero; I discovered that they had not opted out but never taken a
quiz, so I opted them out retroactively.)

I spent part of it reading and responding to Discussion Board postings.

I spent part of it working on the final exam.

I spent part of it reading reports of students' projects.

And I spent part of the weekend doing an experiment in my research
laboratory. Today (Easter Monday) I may even find time to analyze the data.

At the end of February I took valuable time away from preparing my grant
proposals to teach Dr. X's classes, so that he could spend an extra
week in Thailand. We agreed in advance that he would repay this favour
by lecturing to my classes, freeing me to catch up on other
responsibilities.

I realize that students don't have many opportunities to see the work
their professors do outside of class. But 'resting' is the last thing
we have time for.

Dr. Redfield

Last class: teaching evolution

I won't be teaching evolution in this class. Instead I want to address the problems raised by the sophisticated war being waged against evolution by Christian and Islamic fundamentalists. Nobody else I know covers this in their biology classes, but we can't just blame the high-school teachers for doing an inadequate job of teaching evolution, when we're the ones responsible for teaching the next generation of teachers.

Last year I taught this in the middle of the term, at the end of the Evolution section, but this year I've moved it to the last class. I'm also going to cut down on the mass of examples of fronts in this war, both to allow more time for introducing the resources available for biology teachers, and because we need to allow time for end-of-term teaching evaluations.

It's important to not put all the blame on the Christians. The richly funded Islamic fundamentalist group operating under the name Harun Yahya is not well known in the West, but they produce an enormous amount of very slick anti-evolution propaganda.

Playing fast and loose with the curriculum?

One of the weaknesses of the course I teach is also one of the reasons I like teaching it.

The curriculum revision committee I'm on has been discussing ways to maintain coherence between different sections of this multi-instructor course. Right now we have two courses to compare to. One of these, the one I'm presently teaching, has five or six different instructors, each teaching their interpretation of "Ecology, Genetics and Evolution". I kid you not, that's the full detailed curriculum.

I like teaching it because I can pick and choose freely among possible topics. So, for example, I've taught my students nothing about behaviour and almost nothing about DNA replication, but quite a lot about our local environment and about HIV in Canada and Africa. And in some ways this is good for the students, as I teach them the things I'm enthusiastic about. But, from the perspective of the goals of the Biology Program this is not a good situation, as different students learn very different things and sometimes learn nothing at all about some important topics. All sections do use the same excellent textbook.

The other first year course has the opposite problem. Instructors and students all use a common 200 page set of photocopied course 'notes' instead of a textbook. Coherence between different sections is thus not a problem (except if an instructor runs out of class hours before getting to the final topic). For inexperienced instructors this is a good thing, but there is little opportunity for experienced instructors to control what they teach. So it's hard to work up much enthusiasm.

So one goal of this committee is to come up with a curriculum document that's sufficiently specific to ensure that the important topics are covered, but sufficiently flexible to allow instructors to feel they control what they're teaching.

Are clickers worth the hassle?

I've spent most of the last 24 hrs wrestling with the software that goes with the Personal Response System (PRS) 'clickers' I have my students using in class. This is the third time I've assembled all the marks the students have earned for the answers they've given to the questions I've posed in class and posted the combined marks on WebCT. This time I think I've finally gotten it right. (Thank you, students, for your patience.)

The software isn't that bad, though it's a bit clumsy. Now I better understand how it works, it all seems quite straightforward. But getting myself to this point would have been easier if my university provided better support for instructors using PRS in their classes. The fuss I made about this last year produced some talk of a PRS Users Group, where we could help each other, but that seems to have been vaporware.

But I do think using clickers is worth the trouble. It enables me to push the students into doing 'active learning', rather than passively absorbing whatever I tell them. I really like to see the students talking with each other about what the answer should be.

'cumulative' exams

Students often ask me whether the final exam for my course will be 'cumulative', testing material covered both before and after the midterm. The alternative is that the final only tests material taught after the midterm.

I understand that some professors do give non-cumulative final exams, but I find it hard to think of a situation where this would be appropriate. In my courses, we build ideas onto other ideas. I select a particular order of topics (e.g. genetics then evolution then ecology) for precisely that reason. By first studying genetics, we develop the genetic underpinnings needed to understand evolution, and by understanding evolution we can better appreciate issues relevant to ecology. The exam questions I like best are the ones that ask students to pull together concepts taught in different parts of the course.

Telling students that material covered before the midterm won't be needed for the final is tantamount to telling them to forget that material - it's not even valuable enough to remember for another 6 weeks, much less beyond the final exam.

Researchers as teachers

I've been away from blogging for the past month, as I've been focused on getting two research grants submitted by a March 1 deadline. Yes, that's today, and they're both done.

I've been neglecting not only this blog, but also the students in my classes, as a consequence of caring more about my research than about my teaching. I originally wrote 'as much about my research', but that's not true - I do care more about research than teaching. But I'd like to think that caring about research makes for a good teacher, maybe better than someone who cares only about teaching.

Being taught by scholars (researchers in the science or humanities or whatever) is one of the supposed benefits of studying at a real university rather than at a college where the faculty have little or no time or facilities for scholarly work. The benefit is (should be) that the teachers are people who DO research. We care deeply about intellectual work, about scholarship, and we can communicate about the process from our ongoing experience. Active research also keeps us at the frontiers of knowledge, and gives us the perspective to make value judgments about what's in the textbooks.

The down side of this is that we're unlikely to be as dedicated to teaching as our non-researcher colleagues (at UBC, 'sessional lecturers' and 'instructors'). I, for example, have been skimping on my teaching responsibilities for the past couple of weeks, to get my grant proposals done.

But this isn't because we don't care about learning. I, and every researcher I know, care much more deeply about learning than the great majority of our students do. We LOVE learning - it's our favourite thing in the whole world. But we love learning as a concrete activity, experienced most rewardingly in the research we do, not as an abstraction. So it shouldn't be surprising that we value our own learning activities (our research) more than the learning activities of our students.

Too easy or too hard?

We spent yesterday's class working very slowly through one genetics problem, and now I can't decide whether what we did was way too easy or too hard.

I wanted the students to appreciate how best to approach genetics problems. Normally this would be done in tutorials, but the university administration has decided that this course doesn't need tutorials (1500 first-year biology students! (not all mine)), so I did it in class. Using clickers makes this possible, because students are participating, not just watching.

The problem was a complex one. To solve it students needed to combine information from three different crosses, so we worked through each cross in turn, considering possible hypotheses and testing them against the data. I wanted to emphasize that doing the analysis slowly made the logical steps easier to appreciate, but I fear we went too slowly through the first parts. Almost every student got the PRS questions right, which indicates that we probably should have been spending less time on these issues. And we didn't really get to the last part of the problem, which is both the most difficult and the most rewarding - not getting to the answer leaves the students hanging, and leaves them with the most difficult part.

And, based on comments from students after class, most students will find finishing the problem harder than it should be because they missed the significance of information I gave them about why the problem would interest a scientist. They don't understand how two genes can both affect one phenotype, in this case that the genes each code for an enzyme that produces a pigment (pink and blue respectively) and that the pigments mix to produce the purple wildtype flower colour.

So I'm going to have to spend part of the next class providing this explanation, which means less time to spend on pedigrees and sex chromosomes and aneuploidy.

Why posting the solutions isn't the solution

Students always ask me to post the answers to the questions I give them, but I'm reluctant to do so. This makes them unhappy, as they sincerely believe that seeing the right answers is a good way to learn. But I think that seeing the answers often just gives a false sense of confidence.

Say you first try to do the problem without looking at the answer. Because you know the answer is available, you don't spend a lot of time on it. Instead you try do the problem quickly.

If you're able to come reach an answer, you don't spend a lot of time trying to decide whether the answer you've come up with is right, you just check your answer against the posted one. If it agrees with yours, you pat yourself on the back and go on to the next problem. If it doesn't, you look at how your answer differs from the correct one, say "I see how it's done; I won't make that mistake again", and go on to the next problem.

If you can't reach your own answer, you look at the posted one, say "I see how it's done; I'll be able to do it right next time" and go on to the next problem.

Using my "going to university isn't like going to the tanning salon, it's like going to the gym" analogy helps explain why this doesn't really teach you how to solve the problem. Looking at the correct answer is like watching a trainer show you the right way to do squats. You know you need to practice doing them correctly, so you do lots more squats, matching your moves to those the trainer showed you. If you just say "OK, I see" and go on to do bench presses, your squats won't improve.

But you can't go back to the same genetics problem again and learn to do it right, when you already know the answer. Working back from the answer is very much easier than working forward through the forest of possible answers. You need to build the skills that let you evaluate the candidate answers you come up with, testing each one against all the information you have.

It's comforting to think that seeing how a problem is done gives you the skills to do it. But it doesn't. Instead it gives you a false sense of security that can hold you back.

(next time - why going slow teaches you to go fast.)

colour-coding

A student pointed out on the course discussion board that I'd not used colours consistently in drawing chromosomes. I apologized for the confusion and tried to clarify it in a response.

But then I raised the issue directly in class yesterday, pointing out that on Monday I'd coloured the two chromatids in a pair differently (dark ad light blue), but on Wednesday I'd coloured them the same shade of blue but coloured their homologs pink. And the transparent strips I used to demonstrate meiosis had the three different chromosomes from one parent green, whereas those from the other parent were blue.

And I then told them that I was about to use yet a different colour coding in yesterday's class, with the homologs the same colour (maternal distinguished from paternal by a wavy line drawn on them) and the different chromosomes (those with completely different genes) different colours.

The class had been given strips of coloured paper to use as their won chromosomes in solving our first genetics problems, and I told them to pay attention to the colours they used, with the goal of having the colours a guide to the relationships between the chromosomes they were representing rather than a source of confusion.

The most important thing isn't that they get the colours right, but that they learn to think about what colours will be least confusing, and more generally about how to represent the factors that matter in any given problem. It's this thinking that leads to the most learning.

Acting out

Yesterday in one of the two classes I teach, I had some volunteers come the front of the class and model the process I had just explained. Why is this worth doing, given that it's time-consuming and chaotic?

One reason is that it's just one more way of presenting information. Different ways work better for different people, and when a point is important I try to present it in as many ways as possible.

But there's a better reason for using students to model it. We're social animals. Almost from the day we're born, we find watching people to be more interesting than watching anything else. So, although many students will probably forget how I slid the model chromosomes around on the overhead projector, they'll remember the girls tied together at the front of the room, being tugged back and forth by boys with the yellow ropes and then released by the boy with the scissors. And maybe they'll remember that what happened to the girls is what happens to chromosomes.

What should biology students learn?

Our Biology Program has just been awarded a big 5-year grant (from the Carl Weiman Initiative) to improve how biology is taught. One issue that came up at our first meeting was "What should we be teaching our students?"

Students reading this may be horrified to realize that this is an open question. Surely professors decide what they should teach before they start to teach it! Well, we do try, but deciding what should be taught is a complicated problem and one we have no training for.

We university professors tend to teach a combination of what we learned as students and what we've learned since. This is bad for two reasons.

First, every time we learn something new and important we're tempted to add it to the curriculum, so the amount of information we're trying to teach keeps increasing. Most of us realize this, and keep trying to cut back on the information overload, but we never go as far as we probably should.

Second, the things we learned aren't necessarily the things our students should learn, because we were far from being typical students. Many of us were uber-geeks, and we were all the kind of students who go on to be university professors. But most of our students are nothing like we were. Their futures are likely to be much more diverse than ours, and many will have no direct connection to science at all.

There's another problem. We don't feel competent to teach many of the things we would like to teach, because we have no good ways to assess whether our students have learned them. We want to teach our students how to read critically, how to think creatively, how to write clearly. We want our students to really understand complex principles and processes, not just parrot back textbook explanations. But we don't know how to assess these abilities.

The Weiman Initiative grant will give us resources to develop the assessment tools we need. But that only addresses the second problem. First we need to decide what to teach. And these decisions need to be made in collaboration with our students.

We know what biology you need to learn if you're going to be a biology professor or a high school biology teacher, and some of the biology you'll need if you become a physician, dentist, or other medical professional. But many of you will go on to careers that have nothing to do with biology. So we'd like you to tell us how you might use your biology education when you're raising a family, or working in the family business, or selling real estate, or building furniture.

You can post comments to this blog entry, or if you're in my Biology 121 classes you can post them on the course's WebCT Discussion Board.

Finding the balance with clicker questions

Designing good clicker questions is tricky. I want them to be challenging enough that the students have to think quite a bit, but because correct answers count for marks, I want most students to get them right most of the time.

Usually I let the students discuss each question with each other before they answer. One way to improve both the benefits of the consultations, and the proportion of the answers that are correct, might be to first present the question not for marks, asking students to answer without consulting their neighbours. Then show them the range of answers (?) without indicating which is correct. Then ask them to consult their neighbours before answering again, this time for marks.

I have a couple of little books about using clickers in the classroom (gifts from the textbook rep). One is specifically about science teaching - I'll see what suggestions it has.

Ancestors

What we did:

1. Thought about how to infer properties of ancestors, when we know the properties of the descendants and the phylogenetic tree that connects them. This can be seen as learning to think as scientists, rather than as learning what scientists have found out.

2. Considered properties that might be shared by all cells. Not surprisingly, many students hadn't yet learned to include Bacteria and Archaea in their thinking about life. I wonder if the students who have taken Biology 112 were the ones who had?

3. Considered how the first cell could have evolved. It's difficult to be very specific, given how little scientists know about this, and difficult to be very thought-provoking, given the little exposure many of the students have had to molecular biology.

What we didn't do:

1. Use the clickers. The PRS software froze up when trying to create a PRS 'lesson' within PowerPoint even though it had worked fine on my computer this morning. To make matters worse, it also worked fine after class, when I tried to demonstrate the problem for the technician from Classroom Services. I suspect it was due to some changed setting on the podium PC that had returned to its default when I rebooted the computer. I'll come in on the weekend and check that Monday's questions are going to work.

2. Spend enough class time on student-thinking problems. I think this will be easy once we're into real genetics, but for next week I'll see if I can come up with a few thought-provoking ones.

big pictures

We tackled a number of very big issues in today's class. Probably too many, as none of them got the level of development they deserve.

The clicker questions didn't work. This was my own fault; I had assumed (hoped) that deleting the PRS logo from a slide would delete the associated clicker question, but instead it just created a mismatch between the questions and the slides that sent the PRS software into a tizzy. So we did the science questions by shows of hands, which was fine.

In both classes students raised a point I hadn't anticipated, that phylogenetic trees usually have the deepest branches on the left. I wonder if they learned that in high school. I'm pretty sure this isn't an explicitly-stated convention, but it is commonly done.

Learning about and with clickers

We didn't do anything with clickers in the first class, but I want to have some clicker questions in the next one, and to spend a bit of class time on the mechanics. So this requires two kinds of preparation.

First, I need to have a series of steps that get students started with clickers, because close to half said they hadn't used them before. 1. How to program your student number into your clicker. 2. How questioning works. 3. How answering works. For this I need to have a few very easy sample questions, and to allow time that would otherwise be spent on the science.

And there should be have at least one interesting thought-provoking clicker question about the science we're doing. This can come at the end of class, but I should allow at least a few minutes for it.

The pedagogical challenge is to move one or more concepts from lecture-style presentation, in which I tell the students the concept, to question-plus-thinking presentation, in which I raise the question, students evaluate possible answers, then I tell them the answer. The latter takes a lot more time, but gives much more real learning. So this is another pedagogical problem - because I need to spend less time lecturing on other concepts to create time for thinking about the most important ones.

Why have a 'teaching blog'?

Classes start on Monday, and I've put a link to this blog on the BIOL 121 WebCT homepage (only open to students), so curious students from my classes are likely to start visiting this blog. I doubt that any of their other profs have teaching blogs, so I'd better explain what I'm trying to accomplish here.

This is where I'll be reflecting a bit about my goals for the course. I'll discuss what I'm trying to accomplish in each class and the logic behind the different things I'll ask students to do. I'll probably also consider how to deal with problems (both practical and pedagogical), and now to improve approaches that are not working as well as I'd like.

I'm making it easy for students to read this blog because I'm a big believer in open information. People who study teaching often write about 'meta-learning' (learning about the process of learning) and argue quite convincingly that students who are encouraged to think about how they learn will learn better.

The comments are open (anonymous comments are allowed), and I'll always read them though I probably won't directly respond. Students who want responses should post their questions on the WebCT Discussions Board; I'll create a 'topic' there for posts about this blog, and allow anonymous posting.

And no, the blog material won't be on the exam.

Papers for students to report on

One of the Biology 121 project options is writing a report on a peer-reviewed scientific paper. Students are free to choose any paper that interests them, but I'm providing a list of suitable papers as well.

It's nice if the papers are by local researchers, so I've emailed my colleagues asking for suggestions of papers they've written that might be suitable. The paper shouldn't be overwhelmingly technical, which rules out a lot of molecular biology papers, but this course isn't about molecular biology so that's OK. And they shouldn't be too long. And they should be sufficiently well written that students can understand what the research question was and why it's interesting.

When I discussed their papers with last year's students, many said "I had to read my paper five times before I started to understand it!" But they weren't complaining - rather they were proud that they'd eventually mastered such difficult material, and felt that this new skill would be a big help in their future courses.