Marlbridge guide to AP® Biology

Unit roadmap

Units and topics exactly as numbered in the 2026–27 Course and Exam Description. Weightings are the official multiple-choice ranges. Marlbridge has written resources for 60 of 60 topics so far; the rest are planned and marked as such.

1. Unit 1: Chemistry of Life 8–11% of multiple choice · 7 topics

   • 1.1 Structure of Water and Hydrogen Bonding Study guideRevision notesPractice questionsTopic checklist
   • 1.2 Elements of Life Study guideRevision notesPractice questionsTopic checklist
   • 1.3 Introduction to Macromolecules Study guideRevision notesPractice questionsTopic checklist
   • 1.4 Carbohydrates Study guideRevision notesPractice questionsTopic checklist
   • 1.5 Lipids Study guideRevision notesPractice questionsTopic checklist
   • 1.6 Nucleic Acids Study guideRevision notesPractice questionsTopic checklist
   • 1.7 Proteins Study guideRevision notesPractice questionsTopic checklist
   • Chemistry of Life: Unit Diagnostic (Biology Unit 1)
   • Chemistry of Life: Mixed Unit Review (Biology Unit 1)
2. Unit 2: Cells 10–13% of multiple choice · 10 topics

   • 2.1 Cell Structure and Function Study guideRevision notesPractice questionsTopic checklist
   • 2.2 Cell Size Study guideRevision notesPractice questionsTopic checklist
   • 2.3 Plasma Membrane Study guideRevision notesPractice questionsTopic checklist
   • 2.4 Membrane Permeability Study guideRevision notesPractice questionsTopic checklist
   • 2.5 Membrane Transport Study guideRevision notesPractice questionsTopic checklist
   • 2.6 Facilitated Diffusion Study guideRevision notesPractice questionsTopic checklist
   • 2.7 Tonicity and Osmoregulation Study guideRevision notesPractice questionsTopic checklist
   • 2.8 Mechanisms of Transport Study guideRevision notesPractice questionsTopic checklist
   • 2.9 Cell Compartmentalization Study guideRevision notesPractice questionsTopic checklist
   • 2.10 Origins of Cell Compartmentalization Study guideRevision notesPractice questionsTopic checklist
   • Cells: Unit Diagnostic (Biology Unit 2)
   • Cells: Mixed Unit Review (Biology Unit 2)
3. Unit 3: Cellular Energetics 12–16% of multiple choice · 5 topics

   • 3.1 Enzymes Study guideRevision notesPractice questionsTopic checklist
   • 3.2 Environmental Impacts on Enzyme Function Study guideRevision notesPractice questionsTopic checklist
   • 3.3 Cellular Energy Study guideRevision notesPractice questionsTopic checklist
   • 3.4 Photosynthesis Study guideRevision notesPractice questionsTopic checklist
   • 3.5 Cellular Respiration Study guideRevision notesPractice questionsTopic checklist
   • Cellular Energetics: Unit Diagnostic (Biology Unit 3)
   • Cellular Energetics: Mixed Unit Review (Biology Unit 3)
4. Unit 4: Cell Communication and Cell Cycle 10–15% of multiple choice · 6 topics

   • 4.1 Cell Communication Study guideRevision notesPractice questionsTopic checklist
   • 4.2 Introduction to Signal Transduction Study guideRevision notesPractice questionsTopic checklist
   • 4.3 Signal Transduction Pathways Study guideRevision notesPractice questionsTopic checklist
   • 4.4 Feedback Study guideRevision notesPractice questionsTopic checklist
   • 4.5 Cell Cycle Study guideRevision notesPractice questionsTopic checklist
   • 4.6 Regulation of Cell Cycle Study guideRevision notesPractice questionsTopic checklist
   • Cell Communication and Cell Cycle: Unit Diagnostic (Biology Unit 4)
   • Cell Communication and Cell Cycle: Mixed Unit Review (Biology Unit 4)
5. Unit 5: Heredity 8–11% of multiple choice · 5 topics

   • 5.1 Meiosis Study guideRevision notesPractice questionsTopic checklist
   • 5.2 Meiosis and Genetic Diversity Study guideRevision notesPractice questionsTopic checklist
   • 5.3 Mendelian Genetics Study guideRevision notesPractice questionsTopic checklist
   • 5.4 Non-Mendelian Genetics Study guideRevision notesPractice questionsTopic checklist
   • 5.5 Environmental Effects on Phenotype Study guideRevision notesPractice questionsTopic checklist
   • Heredity: Unit Diagnostic (Biology Unit 5)
   • Heredity: Mixed Unit Review (Biology Unit 5)
6. Unit 6: Gene Expression and Regulation 12–16% of multiple choice · 8 topics

   • 6.1 DNA and RNA Structure Study guideRevision notesPractice questionsTopic checklist
   • 6.2 DNA Replication Study guideRevision notesPractice questionsTopic checklist
   • 6.3 Transcription and RNA Processing Study guideRevision notesPractice questionsTopic checklist
   • 6.4 Translation Study guideRevision notesPractice questionsTopic checklist
   • 6.5 Regulation of Gene Expression Study guideRevision notesPractice questionsTopic checklist
   • 6.6 Gene Expression and Cell Specialization Study guideRevision notesPractice questionsTopic checklist
   • 6.7 Mutations Study guideRevision notesPractice questionsTopic checklist
   • 6.8 Biotechnology Study guideRevision notesPractice questionsTopic checklist
   • Gene Expression and Regulation: Unit Diagnostic (Biology Unit 6)
   • Gene Expression and Regulation: Mixed Unit Review (Biology Unit 6)
7. Unit 7: Natural Selection 13–20% of multiple choice · 12 topics

   • 7.1 Introduction to Natural Selection Study guideRevision notesPractice questionsTopic checklist
   • 7.2 Natural Selection Study guideRevision notesPractice questionsTopic checklist
   • 7.3 Artificial Selection Study guideRevision notesPractice questionsTopic checklist
   • 7.4 Population Genetics Study guideRevision notesPractice questionsTopic checklist
   • 7.5 Hardy–Weinberg Equilibrium Study guideRevision notesPractice questionsTopic checklist
   • 7.6 Evidence of Evolution Study guideRevision notesPractice questionsTopic checklist
   • 7.7 Common Ancestry Study guideRevision notesPractice questionsTopic checklist
   • 7.8 Continuing Evolution Study guideRevision notesPractice questionsTopic checklist
   • 7.9 Phylogeny Study guideRevision notesPractice questionsTopic checklist
   • 7.10 Speciation Study guideRevision notesPractice questionsTopic checklist
   • 7.11 Variations in Populations Study guideRevision notesPractice questionsTopic checklist
   • 7.12 Origins of Life on Earth Study guideRevision notesPractice questionsTopic checklist
   • Natural Selection: Unit Diagnostic (Biology Unit 7)
   • Natural Selection: Mixed Unit Review (Biology Unit 7)
8. Unit 8: Ecology 10–15% of multiple choice · 7 topics

   • 8.1 Responses to the Environment Study guideRevision notesPractice questionsTopic checklist
   • 8.2 Energy Flow Through Ecosystems Study guideRevision notesPractice questionsTopic checklist
   • 8.3 Population Ecology Study guideRevision notesPractice questionsTopic checklist
   • 8.4 Effect of Density on Populations Study guideRevision notesPractice questionsTopic checklist
   • 8.5 Community Ecology Study guideRevision notesPractice questionsTopic checklist
   • 8.6 Biodiversity Study guideRevision notesPractice questionsTopic checklist
   • 8.7 Disruptions in Ecosystems Study guideRevision notesPractice questionsTopic checklist
   • Ecology: Unit Diagnostic (Biology Unit 8)
   • Ecology: Mixed Unit Review (Biology Unit 8)

Exam skills

Guides that apply across every unit: what each task verb asks you to do, and how to set out answers so every step of your reasoning is visible.

• Experimental Design and Data Analysis: Exam Skills Guide (Biology)

  How to name variables and controls, state a null hypothesis, choose and draw the right graph, do the course calculations and write a claim backed by evidence and reasoning.

• Task Verbs and Free-Response Technique: Exam Skills Guide (Biology)

  What each free-response task verb asks for and how much to write, how to read multi-part questions, plan your time and set out calculations, with three worked answers shown weak and strong.

Science practices

1. Concept Explanation

Explain biological concepts, processes and models presented in written format.

2. Visual Representations

Analyze visual representations of biological concepts and processes.

3. Questions and Methods

Determine scientific questions and methods.

4. Representing and Describing Data

Represent and describe data.

5. Statistical Tests and Data Analysis

Perform statistical tests and mathematical calculations to analyze and interpret data.

6. Argumentation

Develop and justify scientific arguments using evidence.