What's Tested on the OAT Survey of Natural Sciences?

The OAT consists of four timed sections: the Survey of Natural Sciences, Reading Comprehension, Physics, and Quantitative Reasoning.
The OAT Survey of Natural Sciences section contains the Biology, General Chemistry, and Organic Chemistry OAT subtests. The OAT Survey of Natural Sciences has a total of 100 questions that must be completed in 90 minutes. Questions 1–40 are always related to biology, questions 41–70 are always related to general chemistry, and questions 71–100 are always related to organic chemistry. The content in each subtest does overlap in some areas (such as chemical bonding, which is tested in both General Chemistry and Organic Chemistry), but the questions always remain in three discrete groups, and you will receive separate scores for each subtest in addition to your cumulative OAT Survey of Natural Sciences score. Therefore, when you first begin studying for the OAT Survey of Natural Sciences, it’s generally best to treat the section as three separate tests and master each content area separately, except for those topics that obviously overlap.
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The 40 biology questions cover the following topics: Cellular and Molecular Biology, Diversity of Life, Structure and Function of Systems (Anatomy and Physiology), Developmental Biology, Genetics, and Evolution, Ecology, and Behavior.
The 30 general chemistry questions cover the following topics: Stoichiometry and General Concepts, Gases, Liquids and Solids, Solutions, Acids and Bases, Chemical Equilibria, Thermodynamics and Thermochemistry, Chemical Kinetics, Oxidation-Reduction Reactions, Atomic and Molecular Structure, Periodic Properties, Nuclear Reactions, and Laboratory Techniques.
The 30 organic chemistry questions cover the following topics: Mechanisms, Chemical and Physical Properties of Molecules, Stereochemistry (structure evaluation), Nomenclature, Individual Reactions of the Major Functional Groups and Combinations of Reactions to Synthesize Compounds, Acid-Base Chemistry, and Aromatics and Bonding.

Survey of Natural Sciences Pacing

On Test Day you will be able to freely navigate among all 100 questions in the OAT Survey of Natural Sciences section. Time is shared for all three subtests, giving you an average of 54 seconds per problem. Because the Survey of Natural Sciences is one long section, some test takers find themselves overwhelmed by the need to keep track of time, since there are so many questions yet less than one minute per question. Therefore, you should not only study each subtest separately but also consider each separately when managing the entire section. Among the three subtests, you should complete Biology in the least amount of time since its questions are mostly fact based and require few calculations. Spend 30 seconds or less on each question to finish the Biology subtest within 20 minutes.
General Chemistry, which involves many more calculations and therefore more use of your scratch work, will take the most time. You should average 75 seconds for each General Chemistry question, which means the entire subtest will take you a total of 37.5 minutes. 
Finally, Organic Chemistry will be somewhere in the middle, with some questions that involve drawing out reactions or complex figures taking longer and other questions that require just naming or identifying molecules taking less time. With 60 seconds per question, you will be able to complete this section in 30 minutes.
The Kaplan timing guidelines for the OAT Survey of Natural Sciences are summarized below: 

Biology: 20 minutes (30 seconds per question) 

General Chemistry: 37.5 minutes (75 seconds per question) 

Organic Chemistry: 30 minutes (60 seconds per question) 

Review Marked Questions: 2.5 minutes 

Total: 90 minutes

Following these guidelines will allow you to break down the OAT Survey of Natural Sciences into more reasonable pieces and give you a more realistic sense of how you’re progressing through the section than if you were to use the overall average of 54 seconds per question. If you stick to the Kaplan guidelines closely, you’ll also have 2.5 minutes left at the end of the section to review any questions that you marked to return to later because they involved lengthy calculations or otherwise would take too long to answer during your first pass through the section.