In the first spring since the cancellation of the beloved science lecture commonly known as “Porn in the Morn,” non-science majors are flooding courses that promise the chance to look at fossils and contemplate black holes in exchange for a science credit.

Take, for example, “History of Life,” a science class capped at 120 that had 58 students last year and 27 in 2008. Suddenly, this year, some 300 students registered to shop the class, and more than 200 showed up to the first two lectures.

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“The level of interest this year is totally unprecedented, and I apologize for the inconvenience this has caused,” the professor, Derek Briggs, said in a Jan. 15 e-mail to shoppers.

But the disappearance of “Porn” (formally titled “Biology of Gender and Sexuality”) may not necessarily be to blame for crowding, professors said. While some science professors are enforcing strict enrollment caps on science courses for non-science majors, others are using the opportunity to encourage students to explore lesser-known options and more difficult science courses.

Meanwhile, the standards of rigor in science classes for non-majors are a topic of debate among administrators — and so is the decision to offer these classes at all, said William Segraves, associate dean for science education and the vice chair of the Science Council. Segraves — who participated in the Science Council’s review of “Biology of Gender and Sexuality,” which stripped the course of its science credit last spring — said Yale and its peer institutions struggle with the decision to offer courses for non-majors in any discipline.

“Not everyone agrees that it makes sense to offer such courses – and in many cases, I think a non-major would get a great deal out of taking the same introductory science course that majors would take,” Segraves said. “But I also think there are sound pedagogical reasons for creating some topically oriented courses that might be different from what we would envision as an introduction for majors.”

Ronald Breaker, the head professor for “An Issues Approach to Biology” this spring and next year’s chair of the Department of Molecular, Cellular and Developmental Biology, said the size of the classroom and number of teaching fellows available to staff a course motivate the decision to cap enrollment. Breaker does not cap his course, which introduces students to contemporary debates in biochemistry and is designed for those with no science background. But on the first day of class this year, Breaker found that his new students were not the novices he was expecting to teach.

“I actually asked on the first day of class how many students had Advanced Placement biology in high school,” Breaker said. “And half the hands went up.”

Though Breaker still allows more experienced students to take the course, other professors are less willing to satisfy students’ appetites for easy science courses — so-called “guts.” Richard Prum, who teaches “Ornithology” this semester, said students’ AP science credentials prove they are capable of taking harder science courses — but harder grading can discourage students from doing so, he said.

“At some point, students are going to have to buck up,” Prum said. “I recommend to students: Go out and get a C! Go do something different.”

But before Breaker offered courses like “An Issues Approach to Biology,” students shared class space with more serious science students to introductory courses like “Principles of Molecular, Cellular and Developmental Biology,” the prerequisite for the MCDB major. Breaker said the class was comprised of seniors trying to fulfill the science requirement, pre-med students and prospective MCDB majors.

“Making sure that our future MDs and PhDs in life sciences had the right basis for the next upper level courses and balancing that with the students who had far less experience or maybe far less desire to have that solid foundation was a big challenge,” Breaker said. “That’s one of the reasons why we created [‘An Issues Approach to Biology’].”

Tom Sanchez ’12, a theater studies and political science double major, was not in search of a solid foundation in science this semester. Thursday afternoon found Sanchez still awaiting word of his acceptance into “History of Life, ” which he said he wanted to take so he could look at fossils. Sanchez said he likes to think he would take science courses were he not required to, but he doubts that he would really follow through. He also doubted the existence of the perfect gut science course.

“A gut class is one that has no work, no reading, no section,” Sanchez said. “Unfortunately, I don’t think that class exists at Yale.”