The motivational beliefs of students, who were mainly bioscience majors interested in careers in health professions, in mandatory large introductory level algebra-based physics courses were surveyed. Although female students outnumbered male students in these courses, they had lower physics motivational beliefs including self-efficacy and identity at the beginning of the physics course, and this gender gap increased by the end of the course. Moreover, the present study used a slightly modified version of the physics identity framework by Hazari et al. (2010) to investigate whether the relation between gender and physics identity was mediated by other motivational beliefs, including perceived recognition by others, self-efficacy, and interest. The model shows that perceived recognition by others, self-efficacy, and interest mediated students' physics identity and there was no direct path from gender to identity. The increased gender gap in these beliefs measured at the end of the physics courses may signify inequity and the non-inclusive nature of the physics learning environment. These findings related to the gender gap in physics motivational beliefs are valuable because they may signify that classroom representation alone will not change the pernicious effects of systemic gender inequities in physics perpetuated by society and bolstered further by the physics learning environments.