To get a more specific idea of what students are asked on the PA Biology Keystone Exam, please refer to the two documents linked below.
This document from the Pennsylvania Department of Education describes the "anchors" and "eligible content" on the exam.
This document also describes the eligible content but also provides sample questions for each exam anchor.
Also know that those of us who teach courses that conclude with a Keystone Exam may not read or look over the exam when students complete them.