The biggest difference is that unlike the SAT, which tests general knowledge and critical reasoning, SAT Subject Tests are designed to measure knowledge in specific areas, such as biology, history, French, or math.

The books used mostly are The Kaplan book , The Barron's book.

Hello,

The main and the biggest difference is that General SAT tests for the general Knowledge and critical reasoning while SAT subject test your knowledge in specific areas say: biology, math etc.

Also, General SAT is around 3 hours paper whereas, SAT subject is a 1 hour paper. General SAT is offered for around 7 times a year and SAT Subject is offered for like 6 times a year that too, depending on the subject (date wise).

There are two test for SAT Biology- Biology (E) and Biology (M), you cannot take both of them on the same date. (E) stands for Ecological and (M) for Molecular. The syllabus topics are as follows:

1. Cellular and Molecular Biology- 15%(E) and 27%(M)

2. Ecology - 23%(E) and 13%(M)

3. Genetics - 15%(E) and 20%(M)

4. Organismal Biology- 25%(E) and 25%(M)

5.  Evolution and Diversity - 22%(E) 15%(M )

*Consider these figures to be approximate and cross check before finalizing.