The Phi Sigma Biological Sciences Honor Society was founded in 1915 at Ohio State University. With 86 active chapters and a total membership of more than 90,000, it promotes academic scholarship in the Biological Sciences and recognizes students who demonstrate academic excellence and involvement in scholarly research. 

The Gamma Delta Chapter was established at UC Davis in 1984 by a group of students and faculty members who wanted to provide recognition to outstanding undergraduate students. Among the founders are Dr. Barbara Horwitz, past vice president, and Dr. John Horowitz, past treasurer.

The criteria for nomination to the Gamma Delta Chapter are greater than most chapters. At UC Davis, a minimum GPA of 3.5 is mandatory for undergraduates. This GPA requirement is significantly higher than the national requirement of 3.0 and is a reflection of the high caliber of students at UC Davis.