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SAT Biology E or M? Which Test Should You Take?

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If you’re a high school student with an interest in the sciences, you might be considering taking one or more of the SAT’s subject tests in that field. These tests, formerly known as SAT IIs, allow you to show off your knowledge on topics more specific than those covered by the regular SAT.


The SAT subject test in biology has two variations, E and M; E stands for ecological biology, while M stands for molecular biology. In this post, we’ll go over the distinction between the two variation, what topics each variation covers, and how to decide which test would be better for you personally to take.


SAT Biology E and M: What’s The Difference?


First of all, it’s important to note that there’s not a huge difference between the two versions of the SAT Biology test. No matter which specific focus area you choose, you’ll sign up for the same SAT subject test, listed as Biology E/M. You don’t have to make a final decision on which variation to take until test day.


The SAT Biology E/M test gives you one hour to answer 80 multiple-choice questions. 60 of these questions will be the same regardless of whether you choose E or M. The remaining 20 questions will be specialized toward either ecological or molecular topics.


For both tests, you’ll be required to know and use some simple math skills, and you won’t be permitted to use a calculator. The test questions will use metric units of measurement, such as meters, grams, and degrees Celsius, so you should be familiar with these units.


As we’ve mentioned, you don’t have to specify whether you’re taking Biology E or M until the day of the test. At the test sitting, you’ll indicate your choice and answer the questions for the section you’ve chosen. You can’t answer both the E and the M questions at the same test session, but you can sign up for the SAT Biology E/M again at another test sitting and choose the other set of questions on that occasion.


Remember, 60 out of the 80 total questions on the SAT Biology test are the same, so there’s considerable overlap in content between the E and M versions of the SAT Biology test. It’s not a matter of a strict distinction between the two, and you’ll still need to study topics that come from both areas.


However, each version of the test is weighted more heavily toward a different set of topics. Below, we’ll go over which topics receive more attention on which test.


SAT Biology E


In the SAT Biology E test, E stands for ecological. This version of the test focuses on questions about how living things have developed through evolution and natural selection, and how they interact with one another in their communities, populations, and ecosystems.


Biology E questions typically cover the processes and relationships that occur between organisms, including predation and the flow of energy through the food web. You may also be asked about topics like biodiversity, conservation, and human impact on other living things.


Here’s a sample Biology E question from the College Board:

Which of the following individuals is most fit in evolutionary terms?


(A) A child who does not become infected with any of the usual childhood diseases, such as measles or chicken pox

(B) A woman of 40 with seven adult offspring

(C) A woman of 80 who has one adult offspring

(D) A 100-year old man with no offspring

(E) A childless man who can run a mile in less than five minutes

The correct answer is choice B. This is how the College Board explains that answer:


In evolutionary terms, fitness refers to an organism’s ability to leave offspring in the next

generation that survive to pass on genetic traits. The woman of 40 with seven adult offspring has left the most surviving offspring and is the most fit evolutionarily.

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SAT Biology M


The M in Biology M stands for molecular. In contrast to Biology E, Biology M is more heavily weighted toward understanding how life works on a microscopic level. You’ll be asked to answer more questions about what happens inside organisms rather than how these organisms interact with each other.


Biology M questions tend to focus on topics like biochemistry, genetics, and cellular structure and function. You might be asked about biological processes like respiration, photosynthesis, or mitosis.


Here’s a sample Biology M question from the College Board:

Which of the following most accurately reveals common ancestry among many different species of organisms?


(A) The amino acid sequence of their cytochrome C

(B) Their ability to synthesize hemoglobin

(C) The percentage of their body weight that is fat

(D) The percentage of their body surface that is used in gas exchange

(E) The mechanism of their mode of locomotion

The correct answer is choice A. This is how the College Board explains that answer:


To assess common ancestry or evolutionary relationships among organisms, differences

or similarities in homologous structures are studied. Differences in homologous structures reflect the accumulation of mutations over time. The only choice listed that represents a comparison of a homologous structure is choice (A): Cytochrome C is a protein that can be studied, and its amino acid sequences compared. The fewer differences in the amino acid sequence, the closer the relationship.


So Which Test Should I Take?


It’s worth repeating that the E and M versions of the SAT Biology test aren’t all that different. No matter which you choose, you’ll have to answer 60 of the same questions, and those 60 questions may cover topics from both areas. To score well on the test, you’ll have to have a strong, broad-based understanding of biology, and study a full range of topics.


You may be tempted to choose between E and M based upon your current career aspirations or planned college major. However, you don’t need to worry too much about matching up your test choice and your future plans; nothing is set in stone yet, and many people change their minds about majors or careers. The good news is that most careers in the biological sciences will make use of the information you’ve learned about both sets of topics.


The bottom line is that you should take whichever version of the test, E or M, you feel most comfortable with. Taking a few practice tests can help you decide which area you’re stronger in. Go with your strengths, and choose the test version that will allow you to get the highest score—ultimately, that will likely matter more than which test you took.


Getting Ready for Your Test


Since the E and M versions of the SAT Biology test overlap so heavily, your prep strategy won’t need to change a great deal depending on which test you choose, and you’ll still need to study the full range of topics either way. In fact, preparing for both topic areas will help you to decide which area you’re stronger in, and thus which version of the test to take.


As with most SAT subject tests, it’s best to take the Biology E/M test shortly after you’ve finished a high school course in the same subject. If your biology class in school doesn’t quite cover all the topics mentioned on the test, you may have to do some additional studying, but you’ll still benefit from what you’ve learned and from having that experience fresh in your mind.


When looking for SAT Biology test prep resources, start with those who established the test in the first place: the College Board. To learn more about the test, get access to resources, and register for your test, visit the College Board website for this specific test.


More broadly, many test-prep tactics can be useful to you regardless of which standardized test you’re taking. Here are a few of our favorites.


  • Make a prep plan and stick to it consistently. Keeping up a long-term study habit is much more effective than cramming at the last moment.
  • Try various study methods and resources, from books to apps to study groups, and use what works best for you.
  • Take practice tests to get comfortable with the format and timing of the test, not just its content.
  • If you’re struggling to understand the material, ask for help! Teachers, friends, or tutors might be able to get you back on the right track.


SAT Subject Tests aren’t required for every college, but it’s wise to look into how they may enhance your application. For everything you need to know about these tests, from choosing which tests to take to understanding your scores, visit the SAT II Subject Tests section on the CollegeVine blog.


Preparing for the SAT? Download our free guide with our top 8 tips for mastering the SAT.


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Monikah Schuschu
Senior Blogger

Short Bio
Monikah Schuschu is an alumna of Brown University and Harvard University. As a graduate student, she took a job at the Harvard College Office of Financial Aid and Admissions, and discovered the satisfaction of helping students and parents with the often-baffling college admissions process. She also enjoys fiber art, murder mysteries, and amateur entomology.