AP Biology
Self-paced lessons — an introduction plus 126 lessons · 2125 ideas · 1262 questions. Work through at your own rate; each
part ends with a check you must pass to move on.
Introduction · Life at every scale What biology studies, and at what scales 11 ideas · 3 parts · 2 questions Zooming in on a living thing: cells, molecules and atoms 28 ideas · 5 parts · 8 questions Zooming out from one organism: populations, communities and ecosystems 19 ideas · 4 parts · 8 questions The four questions AP Biology asks at every level 26 ideas · 4 parts · 7 questions Unit 1 · Chemistry of Life Topic 1.1 · Structure of Water and Hydrogen Bonding Bonds and partial charges 27 ideas · 6 questions The hydrogen bond 23 ideas · 9 questions Water sticks to itself and to other things 21 ideas · 8 questions Slow to warm 16 ideas · 6 questions Cooling by evaporation 23 ideas · 6 questions Why ice floats 14 ideas · 4 questions How AP Biology asks you questions Four options, one answer 14 ideas · 4 questions What the verb is asking for: Describe, Explain, Predict 28 ideas · 10 questions What the verb is asking for: Justify, Identify, Represent 26 ideas · 8 questions How a point is earned 29 ideas · 8 questions A free-response question, step by step 13 ideas · 2 questions Topic 1.1 · Structure of Water and Hydrogen Bonding (continued) Practice questions 10 multiple choice · 2 free response End-of-topic test: Structure of Water and Hydrogen Bonding 18 multiple choice · 2 free response Topic 1.3 · Introduction to Biological Macromolecules Chains: build and break 22 ideas · 7 questions Counting the water 29 ideas · 16 questions Practice questions 9 multiple choice · 2 free response End-of-topic test: Introduction to Biological Macromolecules 18 multiple choice · 2 free response Topic 1.4 · Carbohydrates One sugar, many chains 20 ideas · 7 questions Starch, glycogen and cellulose 17 ideas · 5 questions Practice questions 9 multiple choice · 2 free response End-of-topic test: Carbohydrates 18 multiple choice · 2 free response Topic 1.5 · Lipids Why oil and water don't mix 26 ideas · 6 questions Butter or olive oil 31 ideas · 9 questions Where the energy in a food store comes out 16 ideas · 5 questions Building a fat 10 ideas · 3 questions Steroids and hormones 13 ideas · 7 questions The membrane around every cell 28 ideas · 4 questions Cholesterol, cold water and the membrane 24 ideas · 5 questions Practice questions 10 multiple choice · 2 free response End-of-topic test: Lipids 18 multiple choice · 2 free response Topic 1.7 · Proteins: Structure and Function Inside one amino acid 28 ideas · 5 questions From amino acids to a chain 23 ideas · 6 questions Coils and sheets in the chain 13 ideas · 3 questions What the R groups do 11 ideas · 3 questions Why the nonpolar R groups end up inside 10 ideas · 2 questions Shape is the job 21 ideas · 5 questions Change one amino acid 15 ideas · 3 questions Practice questions 10 multiple choice · 2 free response End-of-topic test: Proteins: Structure and Function 18 multiple choice · 2 free response Topic 1.6 · Nucleic Acids The nucleotide 27 ideas · 14 questions Joining nucleotides into a strand 21 ideas · 16 questions The second strand 23 ideas · 16 questions Counting the bases 14 ideas · 8 questions One strand, no partner 9 ideas · 4 questions Antiparallel strands and the double helix 21 ideas · 10 questions Writing a strand from its 5 end 13 ideas · 4 questions DNA or RNA? 11 ideas · 4 questions Reading a model of DNA 12 ideas · 4 questions Practice questions 10 multiple choice · 2 free response End-of-topic test: Nucleic Acids 18 multiple choice · 2 free response Topic 1.2 · Elements of Life Where the atoms in you come from 27 ideas · 8 questions Practice questions 9 multiple choice · 2 free response End-of-topic test: Elements of Life 18 multiple choice · 2 free response Unit 2 · Cells Topic 2.3 · Plasma Membrane Two watery worlds and the film between them 28 ideas · 9 questions A mosaic that flows 20 ideas · 7 questions Practice questions 9 multiple choice · 2 free response End-of-topic test: Plasma Membrane 17 multiple choice · 2 free response Topic 2.4 · Membrane Permeability What gets through the hydrophobic interior 34 ideas · 10 questions Topic 2.5 · Membrane Transport A drop of dye spreads 35 ideas · 10 questions Topic 2.6 · Facilitated Diffusion Doors for ions and sugars 35 ideas · 12 questions Practice questions 9 multiple choice · 2 free response End-of-topic test: Facilitated Diffusion 16 multiple choice · 2 free response Topic 2.8 · Mechanisms of Transport Pumping uphill 21 ideas · 4 questions Why the inside of a cell is negative 24 ideas · 8 questions Practice questions 10 multiple choice · 2 free response End-of-topic test: Mechanisms of Transport 17 multiple choice · 2 free response Topic 2.5 · Membrane Transport (continued) Too big for any door 23 ideas · 7 questions Practice questions 10 multiple choice · 2 free response End-of-topic test: Membrane Transport 17 multiple choice · 2 free response Topic 2.7a · Tonicity and Osmoregulation Red cells in three beakers 32 ideas · 8 questions Topic 2.4 · Membrane Permeability (continued) Why celery goes limp 28 ideas · 10 questions Practice questions 10 multiple choice · 2 free response End-of-topic test: Membrane Permeability 17 multiple choice · 2 free response Topic 2.7a · Tonicity and Osmoregulation (continued) Keeping water in balance 19 ideas · 4 questions Practice questions 9 multiple choice · 2 free response End-of-topic test: Tonicity and Osmoregulation 19 multiple choice · 2 free response Topic 2.7b · Water Potential Water potential: a number for which way water goes 26 ideas · 16 questions Solute potential from a concentration 27 ideas · 20 questions The potato lab 20 ideas · 18 questions Practice questions 10 multiple choice · 2 free response End-of-topic test: Water Potential 19 multiple choice · 2 free response Topic 2.2 · Cell Size Why a cell can't just grow bigger 29 ideas · 19 questions Folded surfaces 15 ideas · 3 questions Mouse and elephant: heat and fuel per gram 14 ideas · 6 questions Spheres, rods and slabs 11 ideas · 12 questions Practice questions 10 multiple choice · 2 free response End-of-topic test: Cell Size 17 multiple choice · 2 free response Topic 2.1 · Cell Structure and Function Two kinds of cell 38 ideas · 10 questions A folded network with ribosomes on it 17 ideas · 3 questions A stack of sacs that finishes and packs 11 ideas · 2 questions Sacs that digest 17 ideas · 3 questions Three cells, three jobs 38 ideas · 10 questions Practice questions 10 multiple choice · 2 free response End-of-topic test: Cell Structure and Function 18 multiple choice · 2 free response Topic 2.9 · Cell Compartmentalization Rooms with their own rules 26 ideas · 7 questions Practice questions 9 multiple choice · 2 free response End-of-topic test: Cell Compartmentalization 16 multiple choice · 2 free response Topic 2.10 · Origins of Cell Compartmentalization The cell that moved in 26 ideas · 7 questions Practice questions 9 multiple choice · 2 free response End-of-topic test: Origins of Cell Compartmentalization 16 multiple choice · 2 free response Unit 3 · Cellular Energetics Topic 3.1 · Enzymes The fizz on a cut 32 ideas · 18 questions Used again and again 17 ideas · 6 questions Why catalase ignores sugar 22 ideas · 19 questions Potato or liver? Designing a fair test 23 ideas · 8 questions Practice questions 10 multiple choice · 2 free response End-of-topic test: Enzymes 18 multiple choice · 2 free response Topic 3.2a · Environmental Impacts Warm the tube 27 ideas · 17 questions Too sour, too bitter: pH 18 ideas · 14 questions Sometimes the fold comes back 16 ideas · 4 questions More substrate, more product? 19 ideas · 6 questions Blocking the door, or bending the frame 29 ideas · 5 questions Practice questions 10 multiple choice · 2 free response End-of-topic test: Environmental Impacts 18 multiple choice · 2 free response Topic 3.2b · Statistics: Mean, Standard Deviation and Error Bars Ten tubes, one number 18 ideas · 18 questions How far off might the mean be? 12 ideas · 8 questions Draw the error bar, read the caption 14 ideas · 6 questions Do the bars overlap? 13 ideas · 9 questions Practice questions 9 multiple choice · 2 free response End-of-topic test: Statistics 18 multiple choice · 2 free response Topic 3.3 · Cellular Energy How a cell pays for work 29 ideas · 8 questions Order costs energy 24 ideas · 8 questions One big step or dozens of small ones 23 ideas · 6 questions Practice questions 10 multiple choice · 2 free response End-of-topic test: Cellular Energy 18 multiple choice · 2 free response Topic 3.5 · Cellular Respiration Where sugar’s energy goes 37 ideas · 8 questions From glucose to carbon dioxide 27 ideas · 8 questions Downhill electrons, uphill protons 34 ideas · 8 questions Break the machine and see 21 ideas · 6 questions When oxygen runs out 21 ideas · 16 questions Graph the yeast 25 ideas · 20 questions Practice questions 10 multiple choice · 2 free response End-of-topic test: Cellular Respiration 17 multiple choice · 2 free response Topic 3.4 · Photosynthesis Where a tree’s mass comes from 29 ideas · 8 questions A plant in a sealed jar, day and night 17 ideas · 11 questions Inside a chloroplast 34 ideas · 18 questions One electron’s journey 33 ideas · 6 questions Building sugar in the stroma 24 ideas · 14 questions One machine, one ancestry 24 ideas · 5 questions Practice questions 10 multiple choice · 2 free response End-of-topic test: Photosynthesis 19 multiple choice · 2 free response Unit 4 · Cell Communication and Cell Cycle Topic 4.1 · Cell Communication A pounding heart 24 ideas · 11 questions Touching, nearby, far away 20 ideas · 8 questions Single cells counting their neighbors 12 ideas · 4 questions Which way did the message travel? 10 ideas · 3 questions Practice questions 10 multiple choice · 2 free response End-of-topic test: Cell Communication 19 multiple choice · 2 free response Topic 4.2 · Introduction to Signal Transduction The message crosses, the molecule stays outside 28 ideas · 15 questions Where the receptor waits 20 ideas · 13 questions One molecule outside, a million inside 35 ideas · 20 questions Two kinds of door 24 ideas · 5 questions What the cell does with the message 24 ideas · 17 questions Practice questions 10 multiple choice · 2 free response End-of-topic test: Introduction to Signal Transduction 19 multiple choice · 2 free response Topic 4.3 · Signal Transduction Pathways Bananas in a paper bag 29 ideas · 17 questions One broken link 25 ideas · 15 questions Stuck on, switched off 27 ideas · 16 questions Practice questions 9 multiple choice · 2 free response End-of-topic test: Signal Transduction Pathways 18 multiple choice · 2 free response Topic 4.4 · Feedback Why your blood sugar comes back down 37 ideas · 18 questions Contractions that get stronger 32 ideas · 16 questions Practice questions 9 multiple choice · 2 free response End-of-topic test: Feedback 18 multiple choice · 2 free response Topic 4.5 · Cell Cycle A scraped knee closes 27 ideas · 19 questions The long quiet stretch 30 ideas · 21 questions Watching a cell split 27 ideas · 20 questions Name the stage, draw the stage 23 ideas · 15 questions Counting frozen moments 21 ideas · 19 questions Practice questions 10 multiple choice · 2 free response End-of-topic test: Cell Cycle 19 multiple choice · 2 free response Topic 4.6 · Regulation of Cell Cycle Division has to be switched on 15 ideas · 6 questions What each checkpoint checks 11 ideas · 6 questions Cyclins rise and fall; CDKs wait for them 20 ideas · 8 questions A lump that should not be there 30 ideas · 18 questions Practice questions 9 multiple choice · 2 free response End-of-topic test: Regulation of Cell Cycle 18 multiple choice · 2 free response Unit 5 · Heredity Topic 5.1 · Meiosis Twenty-three pairs 15 ideas · 2 questions Forty-six, not ninety-two 18 ideas · 7 questions Which division halves the count? 15 ideas · 3 questions The pairs find each other 13 ideas · 2 questions Pulled apart, still doubled 10 ideas · 2 questions Which stage of meiosis I? 8 ideas · 3 questions The second division 12 ideas · 2 questions Count the DNA, not the chromosomes 8 ideas · 7 questions Meiosis I or meiosis II? 7 ideas · 4 questions Count the chromosomes and chromatids 5 ideas · 6 questions Two divisions, side by side 14 ideas · 2 questions Practice questions 9 multiple choice · 2 free response End-of-topic test: Meiosis 19 multiple choice · 2 free response Topic 5.2 · Meiosis and Genetic Diversity Shuffled pairs 10 ideas · 2 questions How many kinds of gamete? 6 ideas · 6 questions Swapped segments 14 ideas · 3 questions Which egg meets which sperm 10 ideas · 7 questions A question you could test 7 ideas · 3 questions When a pair fails to separate 12 ideas · 3 questions Which division failed? 6 ideas · 3 questions Three copies of one chromosome 7 ideas · 3 questions Practice questions 9 multiple choice · 2 free response End-of-topic test: Meiosis and Genetic Diversity 17 multiple choice · 2 free response Topic 5.3 · Mendelian Genetics The white flower that came back 15 ideas · 5 questions Which allele shows 11 ideas · 9 questions One allele per gamete 20 ideas · 4 questions Why three to one, and why not exactly 12 ideas · 13 questions Rules of chance 15 ideas · 15 questions PP or Pp? 11 ideas · 10 questions Which allele is dominant? 7 ideas · 3 questions Reading a family tree 15 ideas · 8 questions The next child 5 ideas · 5 questions Two genes at once 10 ideas · 4 questions The sixteen-cell square 9 ideas · 5 questions Multiply the one-gene answers 6 ideas · 6 questions Does the data fit? Stating the null, finding chi-square 17 ideas · 12 questions Does the data fit? Reading the verdict 11 ideas · 8 questions When chi-square is the wrong tool 6 ideas · 3 questions From the cross to the verdict 6 ideas · 4 questions Practice questions 10 multiple choice · 2 free response End-of-topic test: Mendelian Genetics 19 multiple choice · 2 free response Topic 5.4 · Non-Mendelian Genetics Pink between red and white 13 ideas · 4 questions Two pinks crossed 6 ideas · 6 questions Three alleles, two per person 15 ideas · 5 questions Genes that travel together 16 ideas · 4 questions How far apart are the genes? 10 ideas · 8 questions Putting genes in order 13 ideas · 4 questions Linked, or just chance? 8 ideas · 7 questions Traits on the X 17 ideas · 4 questions One X is enough 11 ideas · 3 questions Predict an X-linked cross 18 ideas · 8 questions Birds, bees and the Y 7 ideas · 3 questions One gene, many effects 11 ideas · 3 questions Genes outside the nucleus 14 ideas · 4 questions Traits that come only from the mother 15 ideas · 5 questions Which pattern is this? 21 ideas · 11 questions Which deviation is this? Decide from the counts 14 ideas · 10 questions Practice questions 9 multiple choice · 2 free response End-of-topic test: Non-Mendelian Genetics 19 multiple choice · 2 free response Topic 5.5 · Environmental Effects on Phenotype Same plant, two pots 18 ideas · 10 questions Six cases 9 ideas · 4 questions How to test one 13 ideas · 9 questions Practice questions 9 multiple choice · 2 free response End-of-topic test: Environmental Effects on Phenotype 16 multiple choice · 2 free response Unit 6 · Gene Expression and Regulation PLACEHOLDER ONLY · DEMO COMING SOON · NOT READY FOR REVIEW DNA and RNA Structure (part 1 of 2) 18 ideas · 2 parts · 10 questions DNA and RNA Structure (part 2 of 2) 17 ideas · 3 parts · 10 questions DNA Replication (part 1 of 2) 12 ideas · 2 parts · 10 questions DNA Replication (part 2 of 2) 11 ideas · 1 parts · 10 questions Transcription and RNA Processing (part 1 of 2) 19 ideas · 2 parts · 10 questions Transcription and RNA Processing (part 2 of 2) 18 ideas · 1 parts · 10 questions Translation (part 1 of 2) 20 ideas · 2 parts · 10 questions Translation (part 2 of 2) 17 ideas · 1 parts · 10 questions Regulation of Gene Expression (part 1 of 2) 18 ideas · 2 parts · 10 questions Regulation of Gene Expression (part 2 of 2) 17 ideas · 3 parts · 10 questions Gene Expression and Cell Specialization 18 ideas · 4 parts · 10 questions Mutations (part 1 of 3) 21 ideas · 2 parts · 10 questions Mutations (part 2 of 3) 20 ideas · 4 parts · 10 questions Mutations (part 3 of 3) 20 ideas · 3 parts · 10 questions Biotechnology (part 1 of 2) 14 ideas · 2 parts · 10 questions Biotechnology (part 2 of 2) 12 ideas · 1 parts · 10 questions Unit 7 · Natural Selection PLACEHOLDER ONLY · DEMO COMING SOON · NOT READY FOR REVIEW Introduction to (part 1 of 2) 16 ideas · 1 parts · 10 questions Introduction to (part 2 of 2) 14 ideas · 2 parts · 10 questions Natural Selection 19 ideas · 3 parts · 10 questions Artificial Selection 6 ideas · 1 parts · 10 questions Population Genetics (part 1 of 2) 14 ideas · 2 parts · 10 questions Population Genetics (part 2 of 2) 13 ideas · 3 parts · 10 questions Hardy-Weinberg Equilibrium (part 1 of 2) 18 ideas · 2 parts · 10 questions Hardy-Weinberg Equilibrium (part 2 of 2) 11 ideas · 3 parts · 10 questions Evidence of Evolution (part 1 of 2) 18 ideas · 3 parts · 10 questions Evidence of Evolution (part 2 of 2) 14 ideas · 1 parts · 10 questions Common Ancestry 10 ideas · 2 parts · 10 questions Continuing Evolution 17 ideas · 2 parts · 10 questions Phylogeny (part 1 of 2) 17 ideas · 2 parts · 10 questions Phylogeny (part 2 of 2) 15 ideas · 2 parts · 10 questions Speciation (part 1 of 2) 19 ideas · 2 parts · 10 questions Speciation (part 2 of 2) 17 ideas · 2 parts · 10 questions Variations in Populations 21 ideas · 2 parts · 10 questions Origins of Life on Earth 17 ideas · 2 parts · 10 questions Unit 8 · Ecology PLACEHOLDER ONLY · DEMO COMING SOON · NOT READY FOR REVIEW Responses to the Environment (part 1 of 4) 18 ideas · 2 parts · 10 questions Responses to the Environment (part 2 of 4) 18 ideas · 3 parts · 10 questions Responses to the Environment (part 3 of 4) 18 ideas · 2 parts · 10 questions Responses to the Environment (part 4 of 4) 12 ideas · 3 parts · 10 questions Energy Flow Through Ecosystems (part 1 of 6) 22 ideas · 2 parts · 10 questions Energy Flow Through Ecosystems (part 2 of 6) 22 ideas · 4 parts · 10 questions Energy Flow Through Ecosystems (part 3 of 6) 22 ideas · 2 parts · 10 questions Energy Flow Through Ecosystems (part 4 of 6) 22 ideas · 4 parts · 10 questions Energy Flow Through Ecosystems (part 5 of 6) 22 ideas · 5 parts · 10 questions Energy Flow Through Ecosystems (part 6 of 6) 20 ideas · 3 parts · 10 questions Population (part 1 of 2) 20 ideas · 2 parts · 10 questions Population (part 2 of 2) 13 ideas · 2 parts · 10 questions Effect of Density on Populations (part 1 of 2) 13 ideas · 4 parts · 10 questions Effect of Density on Populations (part 2 of 2) 8 ideas · 3 parts · 10 questions Community (part 1 of 2) 16 ideas · 4 parts · 10 questions Community (part 2 of 2) 14 ideas · 3 parts · 10 questions Biodiversity 15 ideas · 3 parts · 10 questions Disruptions in Ecosystems (part 1 of 3) 16 ideas · 5 parts · 10 questions Disruptions in Ecosystems (part 2 of 3) 16 ideas · 5 parts · 10 questions Disruptions in Ecosystems (part 3 of 3) 13 ideas · 3 parts · 10 questions Built from the College Board AP Biology Course and Exam Description V.1 (2025).