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🧬 Free AP Biology Study Guide

AP Biology · All 8 Units

Master AP Biology from the chemistry of life through ecology. Flashcards, cheat sheets, essential terms, practice questions, and visual reviews for all 8 units — all completely free.

8 units covered
175+ practice questions
175+ flashcards
College Board aligned
100% free

Choose your unit

Each unit has 6 study resources — flashcards, cheat sheet, essential terms, practice questions, visual review, and FRQ practice.

💧
Unit 1
Molecules of Life
Chemistry of Life
Water's properties, the elements of life, and the four classes of biological macromolecules.
📊 8–11% of exam
Start Unit 1 →
🔬
Unit 2
From Cells to Systems
Cell Structure & Function
Organelles, the plasma membrane, osmosis and tonicity, and the endosymbiotic origins of mitochondria and chloroplasts.
📊 10–13% of exam
Start Unit 2 →
Unit 3
Powering the Cell
Cellular Energetics
Enzymes, ATP, and the two great metabolic pathways: photosynthesis and cellular respiration.
📊 12–16% of exam
Start Unit 3 →
🔄
Unit 4
Coordination & Division
Cell Communication & Cell Cycle
Cell signaling and signal transduction, feedback loops, and the cell cycle and its regulation.
📊 10–15% of exam
Start Unit 4 →
🧬
Unit 5
Inheritance
Heredity
Meiosis and genetic variation, Mendel's laws, and real-world inheritance patterns like incomplete dominance and sex linkage.
📊 8–11% of exam
Start Unit 5 →
🧬
Unit 6
Reading & Writing DNA
Gene Expression & Regulation
DNA replication, transcription, translation, the operon model, mutations, and biotechnology tools like PCR and CRISPR.
📊 12–16% of exam
Start Unit 6 →
🐦
Unit 7
Change Over Time
Natural Selection
Natural and artificial selection, Hardy-Weinberg equilibrium, evidence of evolution, phylogeny, and speciation — the largest unit on the exam.
📊 13–20% of exam
Start Unit 7 →
🌳
Unit 8
Populations to Ecosystems
Ecology
Population growth models, energy flow through food webs, community interactions, biodiversity, and ecosystem disruptions.
📊 10–15% of exam
Start Unit 8 →

About AP Biology

AP Biology is a college-level introductory biology course that explores life from the molecular level up through ecosystems. The course builds from the chemistry that makes life possible, through how cells work and divide, to how traits get passed from one generation to the next, how genes are expressed and regulated, how populations evolve, and how organisms interact within ecosystems.

This page covers all 8 units — Chemistry of Life, Cell Structure & Function, Cellular Energetics, Cell Communication & Cell Cycle, Heredity, Gene Expression & Regulation, Natural Selection, and Ecology.

Every page on this site is aligned to the College Board's official AP Biology Course and Exam Description and completely free. Use what works for your study style — flashcards for active recall, the cheat sheet for a one-page overview, or practice questions to test yourself before the exam.

What's included in each unit

Every unit has the same 6 study resources, designed for different learning styles.

🗂
Flashcards
Interactive cards per unit
🗺
Cheat Sheet
One-page visual summary
Essentials
Key terms and big ideas
🎨
Visual Review
Slide-by-slide walkthrough
📝
Practice MCQ
Exam-style questions
FRQ Practice
Free-response practice

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