OAT Biology Review: High-Yield Topics for the Natural Sciences Section

Biology opens the Survey of the Natural Sciences on the Optometry Admission Test (OAT) with questions 1 through 40, and it rewards breadth over depth. Cover each of the six official domains once, then let practice questions drive your depth. Train with active recall: cheat sheets, explain-aloud drills, partner quizzing, and flashcards for pure-memorization lists like taxonomy, hormones, and enzymes.

Forty of the 100 Survey of the Natural Sciences questions are biology, and they always come first. Biology questions are also the fastest in the section, which makes them your time bank: every second you save here pays for a general chemistry setup later. The trap is that biology feels endless, and students respond by drowning in minutiae. This guide shows you what the Optometry Admission Test actually draws from and how to review it without losing your mind. For the full exam picture, see our complete OAT exam guide.

How Biology Fits the Survey of the Natural Sciences

The SNS gives you 100 questions in 90 minutes, which works out to about 54 seconds per question on average. The internal order is fixed: questions 1 through 40 are biology, 41 through 70 are general chemistry, and 71 through 100 are organic chemistry.

Biology questions are the fastest of the three. A fact you know takes 15 to 20 seconds. That speed matters strategically: a strong biology pass can bank five or more minutes for the calculation-heavy chemistry that follows. Slow, hesitant biology burns that cushion before you ever see question 41.

The Six Official Domains

The biology specifications for the Optometry Admission Test organize the 40 questions into six domains. Here is each domain with the high-yield subtopics students and prep data point to:

• Cell and Molecular Biology: Membrane transport, photosynthesis and cellular respiration, enzymes and enzymology, mitosis vs. meiosis, cell structure and function, signal transduction, experimental design.
• Diversity of Life: Six-kingdom and three-domain classification: plantae, animalia, protista, fungi, eubacteria, archaea.
• Structure and Function of Systems: Integumentary, skeletal, muscular, circulatory, lymphatic and immune, digestive, respiratory, urinary, nervous and sensory, endocrine, reproductive, and how the systems integrate.
• Developmental Biology: Fertilization through early development, key stages and structures.
• Genetics: Inheritance patterns, molecular genetics, gene expression.
• Evolution, Ecology, and Behavior: Natural selection, speciation, population and community ecology, animal behavior.

Notice what the list rewards: coverage. Every domain appears, so skipping one is voluntarily donating points.

The April 2022 Spec Update Matters

The biology specifications were updated on April 13, 2022, and several topics were added that older materials never covered. The current blueprint includes items like the origin of life, cellular thermodynamics, signal transduction, experimental design, and the three-domain taxonomy system.

If your review book or hand-me-down notes predate 2022, they have invisible gaps. You cannot miss questions on topics you never knew existed. Whatever you study from, confirm it was built or updated for the post-2022 specifications, and always reference the specifications in effect on your test date.

Breadth Over Depth: The Rule That Saves You

The classic biology mistake is memorizing minutiae. Students spend a week on one chapter of a review book, emerge knowing obscure details, and then miss a basic ecology question because they never got there.

Top scorers do the opposite: cover each domain once at survey level, then let practice questions drive the depth. A wrong answer is a precision instrument. It tells you exactly which subtopic deserves another pass. A textbook never does that. Your error log, sorted by domain, becomes your real syllabus.

Active Recall Methods That Actually Work

Passive re-reading is the enemy of biology retention. The methods that show up again and again in high-score breakdowns:

• Cheat sheets plus explain aloud. Condense each domain onto a single sheet, then teach it out loud without looking. If you can explain the nephron, the light reactions, or the endocrine axes out loud, you own them. If you stumble, you just found tonight's work.
• Rapid-fire partner quizzing. Ten minutes of back-and-forth with a study partner beats an hour of silent re-reading. No partner? Quiz yourself against your cheat sheet.
• Flashcards for pure-memorization lists. Taxonomy, hormones, enzymes, and developmental stages are flashcard-native content. Space the reps across your whole study window instead of cramming them in the final week.

One caution from student breakdowns: start the flashcard habit early. More than one scorer wished they had begun bio flashcards in their learning phase instead of the final push.

Timing Strategy for Questions 1 to 40

Your biology game plan inside the SNS:

1. Answer the sure things first. Anything you know cold gets answered on sight. Do not second-guess a fact you own.
2. Mark everything uncertain. Use the marking feature aggressively and keep moving.
3. Use the marked-questions review. Return to your marks with the time biology speed bought you, and re-read each stem once before answering.
4. Never leave a blank. There is no penalty for guessing. Every question gets an answer.

Target under 50 seconds per biology question on average. Hit that, and you walk into general chemistry with real breathing room. The same pacing logic feeds your overall score, which our OAT scoring explained guide breaks down by section.

A Four-Week Biology Review Plan

Fold this into your broader OAT study plan alongside chemistry and physics:

• Week 1: Cell and Molecular Biology plus Diversity of Life. One cheat sheet per domain. Start taxonomy flashcards on day one.
• Week 2: Structure and Function of Systems. One body system per day, explained aloud. Hormone and enzyme flashcards join the rotation.
• Week 3: Developmental Biology plus Genetics. Punnett squares and molecular genetics drills. Mixed bio sets begin.
• Week 4: Evolution, Ecology, Behavior plus full review. Timed 40-question biology blocks. Review the error log by domain and patch the two weakest.

Biology then moves into maintenance: daily flashcards and mixed sets inside your full-length cadence. The OAT chemistry study guide picks up right where this plan ends, since questions 41 to 100 follow the same timing discipline.

Our Recommendation

Biology is won by coverage and recall speed, not by depth. Sweep all six domains, convert everything to active recall, and bank time for the chemistry that follows. A good prep platform with domain-specific quizzes and smart flashcards can automate the review cycle, but honestly, a handwritten cheat sheet and a study partner work just as well if you're disciplined. Do that, and the first 40 questions become the easiest points on your Optometry Admission Test.