The SAT used to have a subject test for Biology, but it was discontinued in 2020. It was not divided into E and M, so this distinction does not exist.

It's possible you might be thinking of the AP Biology exam, which does have two main components:

* AP Biology Exam - E (Ecology): This section of the exam focuses on ecological principles and concepts. It covers topics such as population dynamics, community interactions, ecosystems, and human impacts on the environment.

* AP Biology Exam - M (Molecular Biology): This section of the exam focuses on the molecular basis of life. It covers topics such as cell structure and function, DNA replication, protein synthesis, and cellular respiration.

If you have any questions about the AP Biology exam, please let me know!