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  1. Preface
  2. Unit 1
    1. 1 The Study of Life
      1. Introduction
      2. 1.1 The Science of Biology
      3. 1.2 Themes and Concepts of Biology
      4. Key Terms
      5. Chapter Summary
      6. Review Questions
      7. Critical Thinking Questions
      8. Test Prep for AP® Courses
    2. 2 The Chemical Foundation of Life
      1. Introduction
      2. 2.1 Atoms, Isotopes, Ions, and Molecules: The Building Blocks
      3. 2.2 Water
      4. 2.3 Carbon
      5. Key Terms
      6. Chapter Summary
      7. Review Questions
      8. Critical Thinking Questions
      9. Test Prep for AP® Courses
      10. Science Practice Challenge Questions
    3. 3 Biological Macromolecules
      1. Introduction
      2. 3.1 Synthesis of Biological Macromolecules
      3. 3.2 Carbohydrates
      4. 3.3 Lipids
      5. 3.4 Proteins
      6. 3.5 Nucleic Acids
      7. Key Terms
      8. Chapter Summary
      9. Review Questions
      10. Critical Thinking Questions
      11. Test Prep for AP® Courses
      12. Science Practice Challenge Questions
  3. Unit 2
    1. 4 Cell Structure
      1. Introduction
      2. 4.1 Studying Cells
      3. 4.2 Prokaryotic Cells
      4. 4.3 Eukaryotic Cells
      5. 4.4 The Endomembrane System and Proteins
      6. 4.5 Cytoskeleton
      7. 4.6 Connections between Cells and Cellular Activities
      8. Key Terms
      9. Chapter Summary
      10. Review Questions
      11. Critical Thinking Questions
      12. Test Prep for AP® Courses
      13. Science Practice Challenge Questions
    2. 5 Structure and Function of Plasma Membranes
      1. Introduction
      2. 5.1 Components and Structure
      3. 5.2 Passive Transport
      4. 5.3 Active Transport
      5. 5.4 Bulk Transport
      6. Key Terms
      7. Chapter Summary
      8. Review Questions
      9. Critical Thinking Questions
      10. Test Prep for AP® Courses
      11. Science Practice Challenge Questions
    3. 6 Metabolism
      1. Introduction
      2. 6.1 Energy and Metabolism
      3. 6.2 Potential, Kinetic, Free, and Activation Energy
      4. 6.3 The Laws of Thermodynamics
      5. 6.4 ATP: Adenosine Triphosphate
      6. 6.5 Enzymes
      7. Key Terms
      8. Chapter Summary
      9. Review Questions
      10. Critical Thinking Questions
      11. Test Prep for AP® Courses
      12. Science Practice Challenge Questions
    4. 7 Cellular Respiration
      1. Introduction
      2. 7.1 Energy in Living Systems
      3. 7.2 Glycolysis
      4. 7.3 Oxidation of Pyruvate and the Citric Acid Cycle
      5. 7.4 Oxidative Phosphorylation
      6. 7.5 Metabolism without Oxygen
      7. 7.6 Connections of Carbohydrate, Protein, and Lipid Metabolic Pathways
      8. 7.7 Regulation of Cellular Respiration
      9. Key Terms
      10. Chapter Summary
      11. Review Questions
      12. Critical Thinking Questions
      13. Test Prep for AP® Courses
      14. Science Practice Challenge Questions
    5. 8 Photosynthesis
      1. Introduction
      2. 8.1 Overview of Photosynthesis
      3. 8.2 The Light-Dependent Reaction of Photosynthesis
      4. 8.3 Using Light to Make Organic Molecules
      5. Key Terms
      6. Chapter Summary
      7. Review Questions
      8. Critical Thinking Questions
      9. Test Prep for AP® Courses
      10. Science Practice Challenge Questions
    6. 9 Cell Communication
      1. Introduction
      2. 9.1 Signaling Molecules and Cellular Receptors
      3. 9.2 Propagation of the Signal
      4. 9.3 Response to the Signal
      5. 9.4 Signaling in Single-Celled Organisms
      6. Key Terms
      7. Chapter Summary
      8. Review Questions
      9. Critical Thinking Questions
      10. Test Prep for AP® Courses
      11. Science Practice Challenge Questions
    7. 10 Cell Reproduction
      1. Introduction
      2. 10.1 Cell Division
      3. 10.2 The Cell Cycle
      4. 10.3 Control of the Cell Cycle
      5. 10.4 Cancer and the Cell Cycle
      6. 10.5 Prokaryotic Cell Division
      7. Key Terms
      8. Chapter Summary
      9. Review Questions
      10. Critical Thinking Questions
      11. Test Prep for AP® Courses
      12. Science Practice Challenge Questions
  4. Unit 3
    1. 11 Meiosis and Sexual Reproduction
      1. Introduction
      2. 11.1 The Process of Meiosis
      3. 11.2 Sexual Reproduction
      4. Key Terms
      5. Chapter Summary
      6. Review Questions
      7. Critical Thinking Questions
      8. Test Prep for AP® Courses
      9. Science Practice Challenge Questions
    2. 12 Mendel's Experiments and Heredity
      1. Introduction
      2. 12.1 Mendel’s Experiments and the Laws of Probability
      3. 12.2 Characteristics and Traits
      4. 12.3 Laws of Inheritance
      5. Key Terms
      6. Chapter Summary
      7. Review Questions
      8. Critical Thinking Questions
      9. Test Prep for AP® Courses
      10. Science Practice Challenge Questions
    3. 13 Modern Understandings of Inheritance
      1. Introduction
      2. 13.1 Chromosomal Theory and Genetic Linkages
      3. 13.2 Chromosomal Basis of Inherited Disorders
      4. Key Terms
      5. Chapter Summary
      6. Review Questions
      7. Critical Thinking Questions
      8. Test Prep for AP® Courses
      9. Science Practice Challenge Questions
    4. 14 DNA Structure and Function
      1. Introduction
      2. 14.1 Historical Basis of Modern Understanding
      3. 14.2 DNA Structure and Sequencing
      4. 14.3 Basics of DNA Replication
      5. 14.4 DNA Replication in Prokaryotes
      6. 14.5 DNA Replication in Eukaryotes
      7. 14.6 DNA Repair
      8. Key Terms
      9. Chapter Summary
      10. Review Questions
      11. Critical Thinking Questions
      12. Test Prep for AP® Courses
      13. Science Practice Challenge Questions
    5. 15 Genes and Proteins
      1. Introduction
      2. 15.1 The Genetic Code
      3. 15.2 Prokaryotic Transcription
      4. 15.3 Eukaryotic Transcription
      5. 15.4 RNA Processing in Eukaryotes
      6. 15.5 Ribosomes and Protein Synthesis
      7. Key Terms
      8. Chapter Summary
      9. Review Questions
      10. Critical Thinking Questions
      11. Test Prep for AP® Courses
      12. Science Practice Challenge Questions
    6. 16 Gene Regulation
      1. Introduction
      2. 16.1 Regulation of Gene Expression
      3. 16.2 Prokaryotic Gene Regulation
      4. 16.3 Eukaryotic Epigenetic Gene Regulation
      5. 16.4 Eukaryotic Transcriptional Gene Regulation
      6. 16.5 Eukaryotic Post-transcriptional Gene Regulation
      7. 16.6 Eukaryotic Translational and Post-translational Gene Regulation
      8. 16.7 Cancer and Gene Regulation
      9. Key Terms
      10. Chapter Summary
      11. Review Questions
      12. Critical Thinking Questions
      13. Test Prep for AP® Courses
      14. Science Practice Challenge Questions
    7. 17 Biotechnology and Genomics
      1. Introduction
      2. 17.1 Biotechnology
      3. 17.2 Mapping Genomes
      4. 17.3 Whole-Genome Sequencing
      5. 17.4 Applying Genomics
      6. 17.5 Genomics and Proteomics
      7. Key Terms
      8. Chapter Summary
      9. Review Questions
      10. Critical Thinking Questions
      11. Test Prep for AP® Courses
      12. Science Practice Challenge Questions
  5. Unit 4
    1. 18 Evolution and Origin of Species
      1. Introduction
      2. 18.1 Understanding Evolution
      3. 18.2 Formation of New Species
      4. 18.3 Reconnection and Rates of Speciation
      5. Key Terms
      6. Chapter Summary
      7. Review Questions
      8. Critical Thinking Questions
      9. Test Prep for AP® Courses
      10. Science Practice Challenge Questions
    2. 19 The Evolution of Populations
      1. Introduction
      2. 19.1 Population Evolution
      3. 19.2 Population Genetics
      4. 19.3 Adaptive Evolution
      5. Key Terms
      6. Chapter Summary
      7. Review Questions
      8. Critical Thinking Questions
      9. Test Prep for AP® Courses
      10. Science Practice Challenge Questions
    3. 20 Phylogenies and the History of Life
      1. Introduction
      2. 20.1 Organizing Life on Earth
      3. 20.2 Determining Evolutionary Relationships
      4. 20.3 Perspectives on the Phylogenetic Tree
      5. Key Terms
      6. Chapter Summary
      7. Review Questions
      8. Critical Thinking Questions
      9. Test Prep for AP® Courses
      10. Science Practice Challenge Questions
  6. Unit 5
    1. 21 Viruses
      1. Introduction
      2. 21.1 Viral Evolution, Morphology, and Classification
      3. 21.2 Virus Infection and Hosts
      4. 21.3 Prevention and Treatment of Viral Infections
      5. 21.4 Other Acellular Entities: Prions and Viroids
      6. Key Terms
      7. Chapter Summary
      8. Review Questions
      9. Critical Thinking Questions
      10. Test Prep for AP® Courses
      11. Science Practice Challenge Questions
    2. 22 Prokaryotes: Bacteria and Archaea
      1. Introduction
      2. 22.1 Prokaryotic Diversity
      3. 22.2 Structure of Prokaryotes
      4. 22.3 Prokaryotic Metabolism
      5. 22.4 Bacterial Diseases in Humans
      6. 22.5 Beneficial Prokaryotes
      7. Key Terms
      8. Chapter Summary
      9. Review Questions
      10. Critical Thinking Questions
      11. Test Prep for AP® Courses
      12. Science Practice Challenge Questions
  7. Unit 6
    1. 23 Plant Form and Physiology
      1. Introduction
      2. 23.1 The Plant Body
      3. 23.2 Stems
      4. 23.3 Roots
      5. 23.4 Leaves
      6. 23.5 Transport of Water and Solutes in Plants
      7. 23.6 Plant Sensory Systems and Responses
      8. Key Terms
      9. Chapter Summary
      10. Review Questions
      11. Critical Thinking Questions
      12. Test Prep for AP® Courses
      13. Science Practice Challenge Questions
  8. Unit 7
    1. 24 The Animal Body: Basic Form and Function
      1. Introduction
      2. 24.1 Animal Form and Function
      3. 24.2 Animal Primary Tissues
      4. 24.3 Homeostasis
      5. Key Terms
      6. Chapter Summary
      7. Review Questions
      8. Critical Thinking Questions
      9. Test Prep for AP® Courses
    2. 25 Animal Nutrition and the Digestive System
      1. Introduction
      2. 25.1 Digestive Systems
      3. 25.2 Nutrition and Energy Production
      4. 25.3 Digestive System Processes
      5. 25.4 Digestive System Regulation
      6. Key Terms
      7. Chapter Summary
      8. Review Questions
      9. Critical Thinking Questions
      10. Test Prep for AP® Courses
      11. Science Practice Challenge Questions
    3. 26 The Nervous System
      1. Introduction
      2. 26.1 Neurons and Glial Cells
      3. 26.2 How Neurons Communicate
      4. 26.3 The Central Nervous System
      5. 26.4 The Peripheral Nervous System
      6. 26.5 Nervous System Disorders
      7. Key Terms
      8. Chapter Summary
      9. Review Questions
      10. Critical Thinking Questions
      11. Test Prep for AP® Courses
      12. Science Practice Challenge Questions
    4. 27 Sensory Systems
      1. Introduction
      2. 27.1 Sensory Processes
      3. 27.2 Somatosensation
      4. 27.3 Taste and Smell
      5. 27.4 Hearing and Vestibular Sensation
      6. 27.5 Vision
      7. Key Terms
      8. Chapter Summary
      9. Review Questions
      10. Critical Thinking Questions
      11. Science Practice Challenge Questions
    5. 28 The Endocrine System
      1. Introduction
      2. 28.1 Types of Hormones
      3. 28.2 How Hormones Work
      4. 28.3 Regulation of Body Processes
      5. 28.4 Regulation of Hormone Production
      6. 28.5 Endocrine Glands
      7. Key Terms
      8. Chapter Summary
      9. Review Questions
      10. Critical Thinking Questions
      11. Test Prep for AP® Courses
      12. Science Practice Challenge Questions
    6. 29 The Musculoskeletal System
      1. Introduction
      2. 29.1 Types of Skeletal Systems
      3. 29.2 Bone
      4. 29.3 Joints and Skeletal Movement
      5. 29.4 Muscle Contraction and Locomotion
      6. Key Terms
      7. Chapter Summary
      8. Review Questions
      9. Critical Thinking Questions
      10. Science Practice Challenge Questions
    7. 30 The Respiratory System
      1. Introduction
      2. 30.1 Systems of Gas Exchange
      3. 30.2 Gas Exchange across Respiratory Surfaces
      4. 30.3 Breathing
      5. 30.4 Transport of Gases in Human Bodily Fluids
      6. Key Terms
      7. Chapter Summary
      8. Review Questions
      9. Critical Thinking Questions
      10. Test Prep for AP® Courses
      11. Science Practice Challenge Questions
    8. 31 The Circulatory System
      1. Introduction
      2. 31.1 Overview of the Circulatory System
      3. 31.2 Components of the Blood
      4. 31.3 Mammalian Heart and Blood Vessels
      5. 31.4 Blood Flow and Blood Pressure Regulation
      6. Key Terms
      7. Chapter Summary
      8. Review Questions
      9. Critical Thinking Questions
      10. Test Prep for AP® Courses
      11. Science Practice Challenge Questions
    9. 32 Osmotic Regulation and Excretion
      1. Introduction
      2. 32.1 Osmoregulation and Osmotic Balance
      3. 32.2 The Kidneys and Osmoregulatory Organs
      4. 32.3 Excretion Systems
      5. 32.4 Nitrogenous Wastes
      6. 32.5 Hormonal Control of Osmoregulatory Functions
      7. Key Terms
      8. Chapter Summary
      9. Review Questions
      10. Critical Thinking Questions
      11. Test Prep for AP® Courses
    10. 33 The Immune System
      1. Introduction
      2. 33.1 Innate Immune Response
      3. 33.2 Adaptive Immune Response
      4. 33.3 Antibodies
      5. 33.4 Disruptions in the Immune System
      6. Key Terms
      7. Chapter Summary
      8. Review Questions
      9. Critical Thinking Questions
      10. Test Prep for AP® Courses
      11. Science Practice Challenge Questions
    11. 34 Animal Reproduction and Development
      1. Introduction
      2. 34.1 Reproduction Methods
      3. 34.2 Fertilization
      4. 34.3 Human Reproductive Anatomy and Gametogenesis
      5. 34.4 Hormonal Control of Human Reproduction
      6. 34.5 Fertilization and Early Embryonic Development
      7. 34.6 Organogenesis and Vertebrate Formation
      8. 34.7 Human Pregnancy and Birth
      9. Key Terms
      10. Chapter Summary
      11. Review Questions
      12. Critical Thinking Questions
      13. Test Prep for AP® Courses
      14. Science Practice Challenge Questions
  9. Unit 8
    1. 35 Ecology and the Biosphere
      1. Introduction
      2. 35.1 The Scope of Ecology
      3. 35.2 Biogeography
      4. 35.3 Terrestrial Biomes
      5. 35.4 Aquatic Biomes
      6. 35.5 Climate and the Effects of Global Climate Change
      7. Key Terms
      8. Chapter Summary
      9. Review Questions
      10. Critical Thinking Questions
      11. Test Prep for AP® Courses
      12. Science Practice Challenge Questions
    2. 36 Population and Community Ecology
      1. Introduction
      2. 36.1 Population Demography
      3. 36.2 Life Histories and Natural Selection
      4. 36.3 Environmental Limits to Population Growth
      5. 36.4 Population Dynamics and Regulation
      6. 36.5 Human Population Growth
      7. 36.6 Community Ecology
      8. 36.7 Behavioral Biology: Proximate and Ultimate Causes of Behavior
      9. Key Terms
      10. Chapter Summary
      11. Review Questions
      12. Critical Thinking Questions
      13. Test Prep for AP® Courses
      14. Science Practice Challenge Questions
    3. 37 Ecosystems
      1. Introduction
      2. 37.1 Ecology for Ecosystems
      3. 37.2 Energy Flow through Ecosystems
      4. 37.3 Biogeochemical Cycles
      5. Key Terms
      6. Chapter Summary
      7. Review Questions
      8. Critical Thinking Questions
      9. Test Prep for AP® Courses
      10. Science Practice Challenge Questions
    4. 38 Conservation Biology and Biodiversity
      1. Introduction
      2. 38.1 The Biodiversity Crisis
      3. 38.2 The Importance of Biodiversity to Human Life
      4. 38.3 Threats to Biodiversity
      5. 38.4 Preserving Biodiversity
      6. Key Terms
      7. Chapter Summary
      8. Review Questions
      9. Critical Thinking Questions
      10. Test Prep for AP® Courses
  10. A | The Periodic Table of Elements
  11. B | Geological Time
  12. C | Measurements and the Metric System
  13. Index

Welcome to Biology for AP® Courses, an OpenStax resource. This textbook was written to increase student access to high-quality learning materials, maintaining highest standards of academic rigor at little to no cost.

About OpenStax

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About Biology for AP® Courses

Biology for AP® Courses covers the scope and sequence requirements of a typical two-semester Advanced Placement® biology course. The text provides comprehensive coverage of core biology concepts and foundational research through an evolutionary lens. Biology for AP® Courses was designed to meet and exceed the requirements of the College Board’s AP® Biology framework while allowing significant flexibility for instructors. Each section of the book includes an introduction based on the AP® curriculum as well as rich features that engage students in scientific practice and AP® test preparation. It also highlights careers and research opportunities in the biological sciences.

This content features enhancements from TEA AP® Biology by TEA (Texas Education Agency).

Coverage and scope

In developing Biology for AP® Courses, we relied on experts in the goals and approach of the AP® curriculum, carefully considered the AP® framework design, and listened to the advice of hundreds of high school and college biology instructors.

The result is a book that provides excellent coverage of the AP® framework while addressing the sheer breadth of biology topics in the modern age. We provide a thorough treatment of biology’s foundational concepts while condensing selected topics. We also strive to make biology, as a discipline, interesting and accessible to students. In addition to a comprehensive coverage of core concepts and foundational research, we have incorporated features that draw learners into the discipline in meaningful ways.

  • Unit 1: The Chemistry of Life. Our opening unit introduces students to the sciences, including scientific methods and the fundamental concepts of chemistry and physics that provide a framework within which learners comprehend biological processes.
  • Unit 2: The Cell. Students will gain solid understanding of the structures, functions, and processes of the most basic unit of life: the cell.
  • Unit 3: Genetics. Our comprehensive genetics unit takes learners from the earliest experiments that revealed the basis of inheritance through the intricacies of DNA’s structure, replication, and expression, to current applications in the studies of biotechnology and genomics.
  • Unit 4: Evolutionary Processes. The core concepts of evolution are discussed in this unit with examples illustrating evolutionary processes. Additionally, the evolutionary basis of biology reappears throughout the textbook in general discussion and is also reinforced through special call-out features highlighting specific topics in evolution.
  • Unit 5: Biological Diversity. The diversity of life is explored through detailed study of all phyla of organisms as well as discussion of their phylogenetic relationships. The unit begins with viruses and then moves through prokaryotes and eukaryotes, ending with a discussion of vertebrates and, finally, humans.
  • Unit 6: Plant Structure and Function. Our plant anatomy and physiology unit thoroughly covers the fundamental structure and function of plant cells, tissues, and organs. It also covers important plant physiological functions such as tissue differentiation, material transport, and the roles of plant hormones.
  • Unit 7: Animal Structure and Function. An introduction to the form and function of the animal body is followed by detailed chapters on specific body systems and their physiological function. This unit touches on the biology of all organisms while maintaining an engaging focus on human anatomy and physiology that helps students connect to the topics.
  • Unit 8: Ecology. Ecological concepts are broadly covered in this unit, beginning with the small-scale relationships of population ecology and gradually building to the large-scale processes of ecosystem ecology. Localized, real-world issues of conservation and biodiversity are presented at numerous points along the way.

AP® Connections

Every section of the textbook — over 200 total — begins with a “Connection for AP® Courses.” Section. Written by Julianne Zedalis, the College Board’s AP® Biology Curriculum Committee Co-Chair, these valuable overviews provide meaningful support for students and instructors.

  • Each Connection highlights the key concepts of the section in the context of the AP® Biology Curriculum Framework and explains their importance in brief, engaging language.
  • The explanations build upon the knowledge gained in previous sections, reinforcing the most significant concepts and alerting students of the foundational basis of upcoming material. This helps students build a more comprehensive understanding and helps instructors reference prior explanations.
  • Direct references to the relevant sections of the AP® Curriculum Framework are first explained and then outlined in table format emphasizing their importance and relating them to the overall design of the course. Students and teachers using these reference tables can easily see their progression through and coverage of the required curriculum.

Scientific practices

The AP® Biology Science Practices are presented to students through several active learning features.

Science Practice Connections for AP® Courses provide a context and suggested activity linking the concepts with the relevant science practices. Students are often asked to build representations, undertake brief research, or answer critical thinking questions.

Science Practice Questions, designed and authored by John Eggebrecht and Julianne Zedalis, present a complex scenario or data set and ask students a series of multiple-choice and open-ended questions based on a complex scenario or data set. These robust activities hone students’ scientific thinking skills and prepare them for similar questions on the AP® Examination.

Pedagogical foundation and features

Biology for AP® Courses® is grounded in a solid scientific base, with features that engage the students in scientific inquiry:

  • Evolution Connection features highlight the importance and relevance of evolutionary theory to all biological study. Through discussions like “The Evolution of Metabolic Pathways” and “Algae and Evolutionary Paths to Photosynthesis,” the student is able to see how evolution pervades all aspects of biology.
  • Scientific Methods Connection call-outs walk students through actual or thought experiments that elucidate scientific processes and procedures for a variety of topics. Features include “Determining the Time Spent in Cell Cycle Stages” and “Testing the Hypothesis of Independent Assortment.”
  • Career Connection features present information on a variety of careers in the biological sciences. They are meant to introduce students to professions and day-to-day work related to the current section content. Examples include microbiologist, ecologist, neurologist, and forensic scientist.
  • Everyday Connection features tie biological concepts to students’ everyday lives as well as emerging world issues related to biology. Topics include “Chesapeake Bay” and “Can Snail Venom Be Used as a Pharmacological Pain Killer?”

Illustrations and animations that engage

Illustrations within the book are designed to help students visualize the concepts of biology using figures with simple, clear, designs and color schemes that go side-by-side with vivid photos and micrographs. Biology for AP® Courses also incorporates links to relevant animations and interactive exercises that help bring biology to life.

  • Visual Connection features identify core figures in each chapter for student study. Questions about key figures, including clicker questions that can be used in the classroom, engage students’ critical thinking to ensure genuine understanding.
  • Link to Learning features direct students to online interactive exercises and animations that add greater context to core content.

Additional resources

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About the authors

Senior contributing authors

Julianne Zedalis, Bishop’s School, La Jolla, California
Julianne Zedalis has taught AP® Biology for over twenty years. She served on the College Board’s committee to rewrite and test the revised AP® Curriculum Framework, working with other high school AP® teachers and college faculty as well as the National Science Foundation. She was later selected to chair the College Board’s Curriculum Development and Assessment Committee.

Dr. John Eggebrecht, Brooklyn Technical High School (retired), Brooklyn, New York
John Eggebrecht taught AP® Physics and Biology courses for over thirty years. He was instrumental in the development and revision of various AP® curriculum frameworks over an extended collaboration with the College Board and other educational organizations. Under his guidance, Brooklyn Tech was repeatedly selected by the College Board as an exemplary AP® program, and its practices and students outcomes were featured in several publications. In addition to his writing role, John regularly evaluates course materials and programs for alignment and quality.

Contributing authors

Connie Rye, East Mississippi Community College
Robert Wise, The University of Wisconsin Oshkosh
Vladimir Jurukovski, Suffolk County Community College
Jean DeSaix, The University of North Carolina at Chapel Hill
Jung Choi, Georgia Institute of Technology
Yael Avissar, Rhode Island College

Curriculum Framework for AP® Biology

Big Idea 1: The process of evolution drives the diversity and unity of life.
Enduring understanding 1.A. Change in the genetic makeup of a population over time is evolution. Chapter/Key Concepts
1.A.1. Natural selection is a major mechanism of evolution. 5.3, 18.1, 18.2, 19.1, 19.2, 19.3, 21.2, 23.5
1.A.2. Natural selection acts on phenotypic variations in populations. 7.3, 7.6, 18.2, 19.2, 19.3, 36.5
1.A.3. Evolutionary change is also driven by random processes. 19.1, 19.2
1.A.4. Biological evolution is supported by scientific evidence from many disciplines, including mathematics. 2.1, 5.2, 8.2, 11.1, 14.1, 17.1 18.1, 19.3
Enduring understanding 1.B. Organisms are linked by lines of descent from common ancestry. Chapter/Key Concepts
1.B.1. Organisms share many conserved core processes and features that evolved and are widely distributed among organisms today. 3.4, 4.3, 4.6, 8.2, 15.3, 13.2, 14.1, 15.5, 18.1, 20.1, 20.2
1.B.2. Phylogenetic trees and cladograms are graphical representations (models) of evolutionary history that can be tested. 14.4, 20.1, 20.2, 20.3
Enduring understanding 1.C. Life continues to evolve within a changing environment. Chapter/Key Concepts
1.C.1. Speciation and extinction have occurred throughout the Earth's history. 14.4, 18.2, 20.1, 38.1
1.C.2. Speciation may occur when two populations become reproductively isolated from each other. 18.2, 19.2, 23.5
1.C.3. Populations of organisms continue to evolve. 7.3, 7.6, 18.1, 18.3, 19.1, 19.2, 20.1, 20.2, 23.5
Enduring understanding 1.D. The origin of living systems is explained by natural processes. Chapter/Key Concepts
1.D.1. There are several hypotheses about the natural origin of life on Earth, each with supporting scientific evidence. 8.2, 18.1, 20.1, 21.1, 20.3
1.D.2. Scientific evidence from many different disciplines supports models of the origin of life. 8.2, 18.1, 20.2, 28.1

Big Idea 2: Biological systems utilize free energy and molecular building blocks to grow, to reproduce and to maintain dynamic homeostasis.
Enduring understanding 2.A. Growth, reproduction and maintenance of the organization of living systems require free energy and matter. Chapter/Key Concepts
2.A.1. All living systems require constant input of free energy 6.1, 6.2, 6.3, 6.4, 6.7, 7.1, 7.2, 7.3, 7.4, 7.5, 7.6, 8.2, 23.1, 23.5, 36.3, 37.2
2.A.2. Organisms capture and store free energy for use in biological processes. 3.2, 4.3, 6.1, 6.4, 6.5, 7.1, 7.2, 7.3, 7.4, 7.4, 7.5, 7.6, 8.1, 8.2, 8.3, 9.2, 22.1, 22.2, 23.1, 23.5, 37.2
2.A.3. Organisms must exchange matter with the environment to grow, reproduce and maintain organization. 2.1, 2.2, 3.3, 4.2, 4.6, 6.1, 6.8, 22.4, 22.5, 23.5, 25.8, 37.3
Enduring understanding 2.B. Growth, reproduction and dynamic homeostasis require that cells create and maintain internal environments that are different from their external environments. Chapter/Key Concepts
2.B.1. Cell membranes are selectively permeable due to their structure. 3.2, 3.3, 5.1, 5.2, 5.3, 5.4, 8.3
2.B.2. Growth and dynamic homeostasis are maintained by the constant movement of molecules across membranes. 2.3, 3.3, 5.2, 5.3, 5.4
2.B.3. Eukaryotic cells maintain internal membranes that partition the cell into specialized regions. 3.3, 4.2, 4.3, 4.4
Enduring understanding 2.C. Organisms use feedback mechanisms to regulate growth and reproduction, and to maintain dynamic homeostasis. Chapter/Key Concepts
2.C.1. Organisms use feedback mechanisms to maintain their internal environments and respond to external environmental changes. 5.2, 5.3, 7.1, 7.2, 7.3, 7.4, 7.5, 7.6, 8.2, 10.1, 11.1, 21.1, 23.5, 24.3, 28.3
2.C.2. Organisms respond to changes in their external environments. 2.1, 6.4, 7.5, 7.6, 22.5, 23.5, 26.3, 26.5
Enduring understanding 2.D. Growth and dynamic homeostasis of a biological system are influenced by changes in the system's environment. Chapter/Key Concepts
2.D.1. All biological systems from cells and organisms to populations, communities and ecosystems are affected by complex biotic and abiotic interactions involving exchange of matter and free energy. 2.1, 2.2, 7.1, 7.4, 7.5, 7.6, 8.2, 15.2, 15.3, 17.3, 21.1, 22.4, 35.1, 37.1
2.D.2. Homeostatic mechanisms reflect both common ancestry and divergence due to adaptation in different environments. 4.3, 5.2, 6.1, 18.2, 21.1, 25.1, 32.1, 32.3, 34.1
2.D.3. Biological systems are affected by disruptions to their dynamic homeostasis. 3.2, 22.3, 22.5, 23.1, 28.3, 38.2
2.D.4. Plants and animals have a variety of chemical defenses against infections that affect dynamic homeostasis. 23.6, 33.1, 33.2
Enduring understanding 2.E. Many biological processes involved in growth, reproduction and dynamic homeostasis include temporal regulation and coordination. Chapter/Key Concepts
2.E.1. Timing and coordination of specific events are necessary for the normal development of an organism, and these events are regulated by a variety of mechanisms. 10.2, 10.3, 14.3, 23.5, 30.1, 32.3, 34.1, 34.6
2.E.2. Timing and coordination of physiological events are regulated by multiple mechanisms. 6.8, 10.1, 10.2, 15.3, 22.3, 23.2, 24.1, 30.6, 36.1, 36.2, 36.3, 36.4, 36.5, 43.6, 43.7
2.E.3. Timing and coordination of behavior are regulated by various mechanisms and are important in natural selection. 11.1, 21.2, 23.5, 30.6, 35.2, 45.7

Big Idea 3: Living systems store, retrieve, transmit and respond to information essential to life processes.
Enduring understanding 3.A. Heritable information provides for continuity of life. Chapter/Key Concepts
3.A.1. DNA, and in some cases RNA, is the primary source of heritable information. 3.5, 10.3, 13.1, 13.2, 14.1, 14.2, 14.3, 14.5, 15.1, 15.2, 15.3, 15.4, 15.5, 16.1, 16.2, 16.3, 17.1, 17.3, 21.1, 21.2, 22.4
3.A.2. In eukaryotes, heritable information is passed to the next generation via processes that include the cell cycle and mitosis or meiosis plus fertilization. 10.1, 10.2, 10.3, 11.1, 11.2, 13.1
3.A.3. The chromosomal basis of inheritance provides an understanding of the pattern of passage (transmission) of genes from parent to offspring. 11.2, 12.1, 12.2, 13.1, 14.2, 17.1, 17.4
3.A.4. The inheritance pattern of many traits cannot be explained by simple Mendelian genetics. 4.3, 12.2, 13.1
Enduring understanding 3.B. Expression of genetic information involves cellular and molecular mechanisms. Chapter/Key Concepts
3.B.1. Gene regulation results in differential gene expression, leading to cell specialization. 7.3, 7.6, 16.1, 16.2, 16.3, 16.4, 16.5, 17.3
3.B.2. A variety of intercellular and intracellular signal transmissions mediate gene expression. 9.1, 9.2, 9.3, 15.3, 17.1
Enduring understanding 3.C. The processing of genetic information is imperfect and is a source of genetic variation. Chapter/Key Concepts
3.C.1. Changes in genotype can result in changes in phenotype. 5.3, 11.2, 13.1, 13.2, 14.6, 15.1, 17.1, 18.1, 19.1, 19.3
3.C.2. Biological systems have multiple processes that increase genetic variation. 11.2, 13.1, 14.1, 14.6, 15.2, 17.1, 20.3, 21.2, 22.4
3.C.3. Viral replication results in genetic variation, and viral infection can introduce genetic variation into the hosts. 21.1, 21.2
Enduring understanding 3.D. Cells communicate by generating, transmitting and receiving chemical signals Chapter/Key Concepts
3.D.1. Cell communication processes share common features that reflect a shared evolutionary history. 4.6, 9.1, 9.2, 9.3, 9.4, 10.4, 37.2, 37.3
3.D.2. Cells communicate with each other through direct contact with other cells or from a distance via chemical signaling. 9.1, 9.3
3.D.3. Signal transduction pathways link signal reception with cellular response. 9.1, 9.2
3.D.4. Changes in signal transduction pathways can alter cellular response. 9.2, 9.3, 9.4
Enduring understanding 3.E. Transmission of information results in changes within and between biological systems. Chapter/Key Concepts
3.E.1. Individuals can act on information and communicate it to others. 9.2, 9.4, 21.2, 36.1, 36.2, 36.3, 36.4, 36.5
3.E.2. Animals have nervous systems that detect external and internal signals, transmit and integrate information, and produce responses. 6.1, 35.1, 35.2, 35.3, 35.4

Big Idea 4: Biological systems interact, and these systems and their interactions possess complex properties.
Enduring understanding 4.A Interactions within biological systems lead to complex properties. Chapter/Key Concepts
4.A.1. The subcomponents of biological molecules and their sequence determine the properties of that molecule. 3.1, 3.2, 3.3, 3.4, 3.5, 5.2, 6.2, 14.1, 14.3, 14.4, 17.1
4.A.2. The structure and function of subcellular components, and their interactions, provide essential cellular processes. 3.4, 4.3, 4.4, 4.6, 10.3, 15.3
4.A.3. Interactions between external stimuli and regulated gene expression result in specialization of cells, tissues and organs. 16.1, 22.3, 43.6, 43.7
4.A.4. Organisms exhibit complex properties due to interactions between their constituent parts. 15.2, 17.1, 18.1, 22.3, 22.5, 30.5, 33.3, 34.3
4.A.5. Communities are composed of populations of organisms that interact in complex ways. 22.5, 23.5, 45.5, 45.6
4.A.6. Interactions among living systems and with their environment result in the movement of matter and energy. 3.2, 3.3, 6.2, 6.3, 6.6, 7.5, 7.6, 8.2, 10.3, 18.1, 23.1, 22.4, 45.2, 45.6, 46.2, 47.3
Enduring understanding 4.B Competition and cooperation are important aspects of biological systems. Chapter/Key Concepts
4.B.1. Interactions between molecules affect their structure and function. 3.5, 5.2, 6.2, 6.5, 8.3
4.B.2. Cooperative interactions within organisms promote efficiency in the use of energy and matter. 4.3, 7.3, 7.6, 45.6
4.B.3. Interactions between and within populations influence patterns of species distribution and abundance. 45.4, 45.6
4.B.4. Distribution of local and global ecosystems changes over time. 22.4, 23.1, 46.1, 47.1, 47.3
Enduring understanding 4.C. Naturally occurring diversity among and between components within biological systems affects interactions with the environment. Chapter/Key Concepts
4.C.1. Variation in molecular units provides cells with a wider range of functions. 3.4, 9.2, 10.3, 13.1, 15.5, 42.2, 49.1
4.C.2. Environmental factors influence the expression of the genotype in an organism. 14.2, 19.3, 22.3, 30.4, 43.1
4.C.3. The level of variation in a population affects population dynamics. 7.5, 7.6, 19.1, 45.6, 47.1
4.C.4. The diversity of species within an ecosystem may influence the stability of the ecosystem. 45.6, 46.1
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