A personal statement for a PhD application in biology should demonstrate an applicant's commitment to the field, as well as their passion to pursue advanced study in this field. The statement should include a brief overview of the applicant's past academic and professional experiences, including any research they have conducted as well as any relevant internships or jobs they have held. It should also focus on their future aspirations and how the PhD program will help them reach these goals.

The statement should include a discussion of the applicant's current understanding of biology, any areas of interest they have already explored in depth, and any research questions they would like to pursue in the future. It should mention any research that the applicant has already conducted in the field and any awards or honors they have received. It should also discuss their background in mathematics and other scientific disciplines and any additional skills they possess that could contribute to their success in the program.

The statement should conclude with a summary of the applicant's overall motivation for pursuing a PhD in biology and how their unique perspective and skillset will help them make meaningful contributions to the field. It should be well-written, engaging, and demonstrate how the applicant is prepared for advanced study. With a compelling personal statement, a PhD application in biology can stand out from the competition.