Tracy Petznick, a sophomore majoring in international relations, might work for an environmental organization after she graduates, so she wants to take an ecology class offered by the Biological Sciences department. But first she has to overcome a psychological barrier.

“Prerequisites are scary,” she explained, referring to the required classes she must take in order to qualify for the courses that pique her interest.

Petznick is not alone. Humanities and social science majors who want to learn about cell biology or about the structure of the genome have found that their opportunities for serious study of the hard sciences can be limited at Stanford. In contrast, students in the hard sciences say they feel encouraged to take elective classes on subjects ranging from International Security to Jane Austen.

“It’s a significant problem,” says Prof. Robert Simoni, who is chair of the Biological Sciences department. “Most people say if you’re a student in the natural sciences you get pretty good access to the humanities, but if you’re a humanist or social scientist, the exposure to the natural sciences is not great.”

Prerequisites and core sequences are part, but not all, of the problem. Sometimes departments simply lack the resources, in terms of money and manpower, to teach non-science majors. The Biological Sciences department is not the only department that humanities and social sciences students have difficulty accessing, although it can be viewed as representative of the problem.

Some of the most popular science courses are the ones that are open to humanities and social science students. For example, Biology Prof. Robert Sapolsky’s enormously popular “Human Behavioral Biology” class, which has no prerequisites, drew over 600 students last year, many of them non-science majors, according to Sapolsky.

Aside from Sapolsky’s class and one or two others, “bio-curious fuzzies” are limited to one of the department’s 12 freshman and sophomore introductory seminars.

During her freshman year, Petznick took an introductory seminar called “Plants and Civilizations” through the Biological Sciences department. She loved the course but said “it was basically a history of imperialism” that described how plants moved across the world but not how environmental systems worked.

What Petznick really wants to take is “Plant Biology, Evolution, and Ecology,” the third course in the biology core sequence. However, in the Stanford Bulletin the course has a heavy list of prerequisite classes that she has not taken, including the entire chemistry core.

The chemistry core has a reputation for difficulty and competitiveness that can frighten even the most intense of biology majors.

Junior Danica Lomeli came to Stanford thinking she would go to medical school after graduation. But during her freshman year, she said she was so “overwhelmed and intimidated” by the chemistry core that she dropped the whole idea of becoming a doctor.

“I think it’s a horrible idea that people are immediately put in an environment that is highly stressful and competitive,” Lomeli said of the chemistry core, which is designed to be taken during freshman year. “It makes a lot of smart kids feel stupid.”

Eventually, Lomeli came back to the chemistry core in her sophomore year, when she had “more perspective.” She is now majoring in biology.

Lomeli said that even the Bio core classes can be intimidating. She guessed that about 100 students dropped her core class between the first day and the first midterm.

Biology Prof. Martha Cyert, who teaches cell biology in the core sequence, said she “emphatically” disagreed with the commonly held notion that biology core classes are intended to “weed out” students. But she said that the chemistry prerequisite was a “reality of the biology core.”

However, Simoni said that while courses in the biology core are not designed for non-science majors, they can be “quite accessible” to these students, even if they have not taken the chemistry core, provided they are willing to put in some extra work.

While maintaining that the core is not for everyone, Simoni suggested that it might benefit very willing and motivated non-science majors to know that they could take one or more of the core classes without an advanced knowledge of chemistry.

“I don’t think we’ve tried to advertise it, but maybe we ought to,” Simoni said.

Another option is for “techie” departments to design courses specifically for non-science majors, but this raises another nest of problems dealing with faculty and budgetary resources.

Some biology professors, for example, believe that their department already offers too few upper division courses for the number of majors they have.

“To mount the effort for a really first-class non-majors course, we would have to have additional people to do it or to shift some of the responsibilities of existing faculty,” said Biological Science Prof. H. Craig Heller.

Heller’s comment highlights the difficulty of making science available to those who want to learn it at a university where individual departments often must compete for resources.

“We can and ought to do a better job of teaching science to non-science majors,” Prof. Simoni said. “Science is an increasingly important part of our lives, and if people leave here without at least a conversant knowledge in it, they’re not going to be able to participate in that part of their lives.”