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 22 ideas · 10 questions Water sticks to itself and to other things 20 ideas · 15 questions Slow to warm 16 ideas · 6 questions Cooling by evaporation 22 ideas · 7 questions Why ice floats 13 ideas · 5 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 What the verb is asking for: Make a claim, Support a claim, Evaluate, Determine 57 ideas · 25 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 28 ideas · 17 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 · 8 questions Starch, glycogen and cellulose 16 ideas · 6 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 25 ideas · 8 questions Butter or olive oil 30 ideas · 17 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 26 ideas · 5 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 · 6 questions From amino acids to a chain 22 ideas · 7 questions Coils and sheets in the chain 12 ideas · 3 questions What the R groups do 10 ideas · 4 questions Why the nonpolar R groups end up inside 9 ideas · 3 questions Shape is the job 21 ideas · 6 questions Change one amino acid 14 ideas · 4 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 22 ideas · 17 questions Counting the bases 14 ideas · 9 questions One strand, no partner 8 ideas · 5 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 35 ideas · 11 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 42 ideas · 16 questions Topic 2.5 · Membrane Transport A drop of dye spreads 42 ideas · 15 questions Millimoles: counting in thousandths 10 ideas · 6 questions Topic 2.6 · Facilitated Diffusion Doors for ions and sugars 41 ideas · 26 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 43 ideas · 18 questions Why the inside of a cell is negative 31 ideas · 15 questions Practice questions 10 multiple choice · 2 free response End-of-topic test: Mechanisms of Transport 16 multiple choice · 2 free response Topic 2.5 · Membrane Transport (continued) Too big for any door 27 ideas · 15 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 39 ideas · 23 questions Topic 2.4 · Membrane Permeability (continued) Why celery goes limp 37 ideas · 27 questions Practice questions 10 multiple choice · 2 free response End-of-topic test: Membrane Permeability 16 multiple choice · 2 free response Topic 2.7a · Tonicity and Osmoregulation (continued) Keeping water in balance 25 ideas · 9 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 · 25 questions Solute potential from a concentration 29 ideas · 27 questions The potato lab 22 ideas · 19 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 32 ideas · 26 questions Folded surfaces 21 ideas · 11 questions Mouse and elephant: heat and fuel per gram 15 ideas · 10 questions Spheres, rods and slabs 12 ideas · 8 questions Which cell exchanges faster? 8 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 50 ideas · 19 questions Where a cell makes the proteins it sends out 11 ideas · 3 questions A folded network with ribosomes on it 20 ideas · 10 questions Where the bubbles from the ER go 37 ideas · 16 questions A sac that digests 32 ideas · 13 questions Where lysosomes come from, and what else they take apart 25 ideas · 12 questions The endomembrane system 34 ideas · 16 questions The cell that ships protein 26 ideas · 11 questions Where a cell gets its energy 44 ideas · 20 questions The cell that catches light 33 ideas · 16 questions Read a cell’s job from its parts 19 ideas · 15 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 50 ideas · 16 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 A cell inside a cell 22 ideas · 7 questions Five pieces of evidence that mitochondria came from bacteria 36 ideas · 16 questions The chloroplast’s story 28 ideas · 9 questions Two ways to organize a cell’s inside 14 ideas · 3 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 How fast: the rate of reaction 35 ideas · 22 questions The energy hump 51 ideas · 28 questions Used again and again 70 ideas · 29 questions Why catalase ignores sugar 46 ideas · 29 questions What happens in the pocket 16 ideas · 19 questions What to change, measure and keep the same 41 ideas · 25 questions Writing the prediction down 35 ideas · 7 questions Practice questions 10 multiple choice · 2 free response End-of-topic test: Enzymes 19 multiple choice · 2 free response Topic 3.2a · Environmental Impacts Warm the tube 29 ideas · 16 questions Past the optimum 46 ideas · 14 questions pH: a scale for hydrogen ions 25 ideas · 16 questions Too sour, too bitter 36 ideas · 22 questions Sometimes the fold comes back 52 ideas · 19 questions More substrate 35 ideas · 17 questions More enzyme, more product? 40 ideas · 17 questions Blocking the door 23 ideas · 11 questions Bending the frame 29 ideas · 15 questions Practice questions 10 multiple choice · 3 free response End-of-topic test: Environmental Impacts 19 multiple choice · 2 free response Topic 3.2b · Statistics: Mean, Standard Deviation and Error Bars One number for five tubes 10 ideas · 6 questions How spread out: the standard deviation 17 ideas · 16 questions How far off might the mean be? 16 ideas · 14 questions Draw the error bar, read the caption 20 ideas · 14 questions Do the bars overlap? 14 ideas · 17 questions Practice questions 10 multiple choice · 2 free response End-of-topic test: Statistics 19 multiple choice · 2 free response Topic 3.3 · Cellular Energy Where ATP’s energy comes from 42 ideas · 27 questions How ATP drives the cell’s work 45 ideas · 27 questions Transformed, never made 22 ideas · 17 questions Order needs energy 32 ideas · 27 questions One big step or dozens of small ones 58 ideas · 38 questions Practice questions 10 multiple choice · 2 free response End-of-topic test: Cellular Energy 19 multiple choice · 2 free response Topic 3.5 · Cellular Respiration Where sugar’s energy goes 40 ideas · 20 questions Losing electrons, gaining electrons 29 ideas · 23 questions The cell with no mitochondria 30 ideas · 15 questions Every carbon breathed out 47 ideas · 20 questions Downhill to oxygen 25 ideas · 22 questions The one way back 27 ideas · 17 questions Break the machine and see 56 ideas · 22 questions When there is no oxygen 28 ideas · 25 questions Two ATP or thirty 28 ideas · 18 questions Graph the yeast 25 ideas · 25 questions From the gas back to the pathway 10 ideas · 4 questions Practice questions 10 multiple choice · 3 free response End-of-topic test: Cellular Respiration 19 multiple choice · 2 free response Topic 3.4 · Photosynthesis The reaction, written out 37 ideas · 19 questions Where a tree’s mass comes from 39 ideas · 14 questions What a leaf does with its sugar 26 ideas · 12 questions A plant in a sealed jar, day and night 26 ideas · 19 questions What a chloroplast is, and its six places 35 ideas · 14 questions Two rooms, two jobs 38 ideas · 21 questions Light and color 27 ideas · 19 questions Why leaves are green 36 ideas · 20 questions One electron’s journey 49 ideas · 20 questions The same machine, powered by light 28 ideas · 17 questions Building sugar in the stroma 27 ideas · 16 questions Break one room and the other fails 44 ideas · 19 questions One machine, three places 42 ideas · 19 questions Shared pathways, shared ancestry 33 ideas · 18 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 molecule released into the blood 38 ideas · 24 questions Predict from the receptor 28 ideas · 14 questions Cells that touch 18 ideas · 7 questions Nearby cells 28 ideas · 15 questions Far away 27 ideas · 17 questions Single cells counting their neighbors 36 ideas · 14 questions Which way did the message travel? 25 ideas · 13 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 ligand fits 48 ideas · 21 questions The message crosses, the molecule stays outside 53 ideas · 24 questions Stopped at the surface, or straight through 17 ideas · 13 questions The receptor goes to the DNA 22 ideas · 19 questions A phosphate as a switch 37 ideas · 34 questions A small molecule spreads the message 41 ideas · 41 questions Switching the signal off 23 ideas · 18 questions A door that opens 19 ideas · 12 questions A door that hands the message on 29 ideas · 23 questions Three kinds of response 24 ideas · 16 questions Same signal, different cells 35 ideas · 22 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 31 ideas · 16 questions From a changed cell to a changed organism 15 ideas · 13 questions A signal that says: dismantle 13 ideas · 7 questions A changed gene, a changed shape 31 ideas · 30 questions Find the break 26 ideas · 26 questions Stuck on, switched off 51 ideas · 33 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 A set point, a stimulus, a response 17 ideas · 20 questions The response cancels the stimulus 26 ideas · 15 questions The same loop at three levels 23 ideas · 18 questions Break one part of the loop 15 ideas · 17 questions Contractions that get stronger 36 ideas · 24 questions Predict what a disruption does 20 ideas · 24 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 New cells come from cells 21 ideas · 23 questions What must be handed on 16 ideas · 26 questions Copied and held together 20 ideas · 28 questions The cycle in order 17 ideas · 24 questions G1, S phase and G2 25 ideas · 21 questions Stepping out of the cycle 15 ideas · 8 questions Building the machine: prophase and metaphase 26 ideas · 24 questions Two cells from one: anaphase, telophase and cytokinesis 31 ideas · 44 questions Name the stage 28 ideas · 23 questions Why the two daughter cells match 13 ideas · 15 questions From counts to time 32 ideas · 27 questions Two tissues compared 31 ideas · 31 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 24 ideas · 14 questions Three checkpoints 18 ideas · 20 questions What each checkpoint checks 38 ideas · 19 questions Cyclins rise and fall; CDKs wait for them 50 ideas · 20 questions Cancer: division without the controls 25 ideas · 18 questions The other outcome 19 ideas · 8 questions Break a control and predict 36 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 25 ideas · 20 questions Two sets or one 12 ideas · 12 questions Forty-six, not ninety-two 16 ideas · 18 questions Which division halves the count? 30 ideas · 20 questions The pairs find each other 29 ideas · 21 questions Pulled apart, still doubled 23 ideas · 14 questions Which stage of meiosis I? 15 ideas · 7 questions The second division 26 ideas · 13 questions Count the DNA, not the chromosomes 21 ideas · 17 questions Meiosis I or meiosis II? 17 ideas · 11 questions Count the chromosomes and chromatids 12 ideas · 14 questions Two divisions, side by side 26 ideas · 8 questions Practice questions 10 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 · 6 questions How many kinds of gamete? 6 ideas · 10 questions Swapped segments 14 ideas · 10 questions Which egg fuses with which sperm 9 ideas · 12 questions A question you could test 6 ideas · 10 questions When a pair fails to separate 13 ideas · 5 questions Which division failed? 6 ideas · 7 questions Three copies of one chromosome 7 ideas · 9 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 · 12 questions Which allele shows 11 ideas · 17 questions One allele per gamete 20 ideas · 14 questions Why three to one, and why not exactly 12 ideas · 17 questions Rules of chance 15 ideas · 17 questions PP or Pp? 11 ideas · 15 questions Which allele is dominant? 8 ideas · 7 questions Reading a family tree 15 ideas · 23 questions The next child 5 ideas · 6 questions Two genes at once 10 ideas · 11 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 18 ideas · 18 questions Does the data fit? Reading the verdict 11 ideas · 19 questions When chi-square is the wrong tool 6 ideas · 9 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 · 9 questions Two pinks crossed 6 ideas · 7 questions Three alleles, two per person 15 ideas · 11 questions Genes that travel together 16 ideas · 17 questions How far apart are the genes? 10 ideas · 8 questions Putting genes in order 13 ideas · 6 questions Linked, or just chance? 8 ideas · 8 questions Traits on the X 17 ideas · 14 questions One X is enough 11 ideas · 7 questions Predict an X-linked cross 18 ideas · 11 questions Birds, bees and the Y 7 ideas · 3 questions One gene, many effects 11 ideas · 4 questions Genes outside the nucleus 14 ideas · 5 questions Traits that come only from the mother 16 ideas · 11 questions Which pattern is this? 22 ideas · 18 questions Which deviation is this? Decide from the counts 14 ideas · 12 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 · 14 questions Six cases 10 ideas · 10 questions How to test one 14 ideas · 15 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).