AP Biology Units: Full List, Explained

This article will discuss the units required for AP Biology. You will develop an understanding of the key learning and assessment points for AP Biology. This will ensure you have a full course overview ready to delve deeper into each unit as part of your studies.

Unit 1: Chemistry of Life

This first unit in AP Biology sets the foundation for understanding the chemical basis of life. This is needed for understanding future learning areas and an overview of the elements necessary for carbon-based systems to function. Exam coverage for this unit is 8–11%  of all questions in the AP exam.

Topics included in this unit:

• Structure of Water and Hydrogen Bonding

• Elements of Life

• Properties of Biological Macromolecules

• Structure and Function of Biological Macromolecules

• Nucleic Acids

Unit 2: Cell Structure and Function

This unit covers the cell as the basic unit of life. Cells contribute to the organisation of life and provide the environment in which organelles function. Organelles in turn provide compartmentalisation and organise cellular products for dispersal and waste for disposal. Exam coverage for this unit is 10–13% of all questions in the AP exam.

Topics included in this unit:

• Cell Structure: Subcellular Components

• Cell Structure and Function

• Cell Size

• Plasma Membranes

• Membrane Permeability

• Membrane Transport

• Facilitated Diffusion

• Tonicity and Osmoregulation

• Mechanisms of Transport

• Cell Compartmentalisation

• Origins of Cell Compartmentalization

Unit 3: Cellular Energetics

In Unit 3, knowledge gained in Unit 2 is built upon now focusing on cellular energetics. Living systems are complex in their organisation and require constant energy input. This unit will provide the knowledge to understand the concepts of energy capture and its use in living organisms. Exam coverage for this unit is 12–16%  of all questions in the AP exam.

Topics included in this unit:

• Enzyme Structure

• Enzyme Catalysis

• Environmental Impacts on Enzyme Function

• Cellular Energy

• Photosynthesis

• Cellular Respiration

• Fitness

Unit 4: Cell Communication and Cell Cycle

In this unit, students continue to learn about the role of cells, focusing on how cells use energy and information transmission to communicate and replicate. Exam coverage for this unit is 10–15%  of all questions in the AP exam.

Topics included in this unit:

• Cell Communication

• Introduction to Signal Transduction

• Signal Transduction

• Changes in Signal Transduction Pathways

• Feedback

• Cell Cycle

• Regulation of Cell Cycle

Unit 5: Heredity

Unit 5 focuses on heredity and the biological concepts and processes involved in ensuring the continuity of life. Learning includes the storage and transmission of genetic information via chromosomes from generation to generation through meiosis and Mendelian genetics. Exam coverage for this unit is 8–11%  of all questions in the AP exam.

Topics included in this unit:

• Meiosis

• Meiosis and Genetic Diversity

• Mendelian Genetics

• Non-Mendelian Genetics

• Environmental Effects on Phenotype

• Chromosomal Inheritance

Unit 6: Gene Expression and Regulation

Unit 6 covers in-depth knowledge about nucleic acids and their role in gene expression. This includes a comparison between the structures of DNA and RNA. This unit explains how an individual’s genotype is physically expressed through that individual’s phenotype. Exam coverage for this unit is 12–16%  of all questions in the AP exam.

Topics included in this unit:

• DNA and RNA Structure

• Replication

• Transcription and RNA Processing

• Translation

• Regulation of Gene Expression

• Gene Expression and Cell Specialization

• Mutations

• Biotechnology

Unit 7: Natural Selection

The concepts in this unit allow the discovery of natural selection, a mechanism of evolution. The evidence for and mechanisms of evolutionary change are also covered. In addition, you will learn to calculate and draw conclusions about the evolution of a population from data related to allele frequencies. Exam coverage for this unit is 13–20%  of all questions in the AP exam.

Topics included in this unit:

• Introduction to Natural Selection

• Natural Selection

• Artificial Selection

• Population Genetics

• Hardy-Weinberg Equilibrium

• Evidence of Evolution

• Common Ancestry

• Continuing Evolution

• Phylogeny

• Speciation

• Extinction

• Variations in Populations

• Origin of Life on Earth

Unit 8: Ecology

Unit 8 brings together all the previous units and shows how a system’s interactions are directly related to its energy and ability to evolve and respond to environmental changes. Exam coverage for this unit is 10–15%  of all questions in the AP exam.

Topics included in this unit:

• Responses to the Environment

• Energy Flow Through Ecosystems

• Population Ecology

• Effect of Density of Populations

• Community Ecology

• Biodiversity

• Disruptions to Ecosystems

Frequently Asked Questions

How Many Units are in AP Biology?

There are eight units in AP Biology. Unit 1 starts off looking at elements and biological molecules; from there, each unit builds on the next until the final unit covers ecosystems and whole populations. Each unit is broken down into learnable segments called topics. The number of topics within each unit ranges from five to thirteen.

What are the Hardest AP Biology Units?

There is no single objective measurement of how 'hard' each unit is. This will depend on several factors and variables including your learning styles and interests, your unique skills and abilities. Each unit tends to build on learning from the previous unit so it is useful to learn the units in order, (although this may be out of your control). Also, even your teacher's teaching style can affect how hard a unit is, or how hard it appears to be.

What Units are Most Common on the AP Biology Exam?

Each unit has a different weighting as to how it is assessed with the AP Biology exam. There is no single common AP Biology unit. Each unit will be assessed in the exam and it is important to ensure a thorough understanding of each unit to be as successful as possible in the AP Biology exam. 

Ace Your AP Exams with Save My Exams

Here at Save My Exams we have a great range of resources to help you to ace your AP exams. Our in-depth study guides on each unit and topic will guide you through key learning points with helpful diagrams, worked examples and examiner hints and tips. Each unit and topic has a set of exam questions written by our AP Biology team; these questions carefully match the real AP Biology exam experience. Past papers for the Free Response section of the exam can be found helpfully all in one place too, to ensure you have everything you need for successful studying.

Explore Our AP Biology Study Resources

References 

AP Biology  Course and Exam Description