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 47 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 44 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 42 ideas · 14 questions What a leaf does with its sugar 28 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 38 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 33 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 39 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 37 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 30 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 30 ideas · 30 questions How many kinds of gamete? 21 ideas · 12 questions Swapped segments 33 ideas · 14 questions New combinations of old alleles 33 ideas · 14 questions Which egg fuses with which sperm 22 ideas · 22 questions A question you could test 16 ideas · 12 questions When a pair fails to separate 27 ideas · 27 questions Which division failed? 12 ideas · 8 questions Three copies of one chromosome 22 ideas · 24 questions Practice questions 10 multiple choice · 2 free response End-of-topic test: Meiosis and Genetic Diversity 18 multiple choice · 2 free response Topic 5.3 · Mendelian Genetics The white flower that came back 25 ideas · 24 questions Two alleles, one on each homolog 24 ideas · 21 questions Which allele shows 20 ideas · 23 questions One allele per gamete 35 ideas · 38 questions Why three to one, and why not exactly 26 ideas · 31 questions Rules of chance 21 ideas · 33 questions PP or Pp? 17 ideas · 22 questions Which allele is dominant? 10 ideas · 8 questions The twenty-two matching pairs and the one odd pair 14 ideas · 14 questions Who is who on a family tree 22 ideas · 21 questions Fix the genotypes; dominant or recessive? 23 ideas · 33 questions The next child 11 ideas · 13 questions Two genes at once 24 ideas · 22 questions The sixteen-cell square 16 ideas · 22 questions Multiply the one-gene answers 10 ideas · 12 questions Does the data fit? Stating the null, finding chi-square 22 ideas · 33 questions Does the data fit? Reading the verdict 21 ideas · 28 questions When chi-square is the wrong tool 18 ideas · 11 questions From the cross to the verdict 9 ideas · 10 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 34 ideas · 24 questions Two pinks crossed 12 ideas · 8 questions Three alleles, two per person 17 ideas · 15 questions Whose child is this? 17 ideas · 24 questions Genes that travel together 45 ideas · 29 questions How far apart are the genes? 24 ideas · 22 questions Putting genes in order 21 ideas · 20 questions Linked, or just chance? 15 ideas · 14 questions Where the X and the Y go 14 ideas · 15 questions One X is enough 21 ideas · 21 questions Predict an X-linked cross 21 ideas · 23 questions Swap the parents 16 ideas · 6 questions Birds, bees and the Y 19 ideas · 19 questions One gene, many effects 19 ideas · 7 questions Genes outside the nucleus 16 ideas · 10 questions Traits that come only from the mother 21 ideas · 16 questions Which pattern is this? 31 ideas · 28 questions Which deviation is this? Decide from the counts 17 ideas · 17 questions Practice questions 10 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 53 ideas · 35 questions Six cases 16 ideas · 10 questions How to test one 29 ideas · 22 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 Topic 6.1 · DNA and RNA Structure Where the instructions are kept 41 ideas · 31 questions Extra circles 31 ideas · 11 questions Instructions written in RNA 45 ideas · 18 questions Two rings with one: the pairing rules 55 ideas · 41 questions Use the rules 40 ideas · 36 questions Practice questions 10 multiple choice · 2 free response End-of-topic test: DNA and RNA Structure 17 multiple choice · 2 free response Topic 6.2 · DNA Replication Half old, half new 39 ideas · 29 questions The bands in the tube 59 ideas · 21 questions The fork opens 59 ideas · 32 questions Only at the 3′ end 39 ideas · 28 questions One strand in pieces 52 ideas · 31 questions The whole fork, and what breaks it 50 ideas · 29 questions Practice questions 10 multiple choice · 2 free response End-of-topic test: DNA Replication 18 multiple choice · 2 free response Topic 6.3 · Transcription and RNA Processing A message leaves the nucleus 28 ideas · 29 questions Three RNAs, three jobs 47 ideas · 36 questions One strand is read 56 ideas · 42 questions Write the transcript 36 ideas · 25 questions A cap and a tail 42 ideas · 24 questions Where did 1,500 nucleotides go? 56 ideas · 37 questions From gene to mature message 38 ideas · 29 questions Practice questions 10 multiple choice · 2 free response End-of-topic test: Transcription and RNA Processing 17 multiple choice · 2 free response Unit 7 · Natural Selection Topic 7.1 · Introduction to Natural Selection One field of dandelions 43 ideas · 24 questions Why the plants differ 37 ideas · 31 questions More seeds than space 28 ideas · 17 questions We call it natural selection 32 ideas · 28 questions Populations evolve, individuals do not 33 ideas · 23 questions A wet year and a dry year 35 ideas · 25 questions Practice questions 10 multiple choice · 2 free response End-of-topic test: Introduction to Natural Selection 16 multiple choice · 2 free response Topic 7.2 · Natural Selection What selection can see 34 ideas · 24 questions Good here, bad there 39 ideas · 27 questions Resistance was already there 39 ideas · 25 questions Explain the numbers 18 ideas · 16 questions Three ways a trait can move 32 ideas · 13 questions Practice questions 10 multiple choice · 2 free response End-of-topic test: Natural Selection 16 multiple choice · 2 free response Topic 7.3 · Artificial Selection When people choose the parents 50 ideas · 28 questions Draw the heights 31 ideas · 26 questions Before and after, in one picture 48 ideas · 39 questions Practice questions 10 multiple choice · 2 free response End-of-topic test: Artificial Selection 18 multiple choice · 2 free response Topic 7.4 · Population Genetics Counting alleles, not rabbits 33 ideas · 37 questions Has it evolved, and was it luck? 45 ideas · 27 questions New alleles, and lucky ones 49 ideas · 30 questions A crash, or a small group leaving 59 ideas · 34 questions Alleles that travel 54 ideas · 31 questions Which force was it? 32 ideas · 23 questions Practice questions 10 multiple choice · 2 free response End-of-topic test: Population Genetics 18 multiple choice · 2 free response Topic 7.5 · Hardy–Weinberg Equilibrium Two shares of two different things 32 ideas · 24 questions p, q and two draws from the pool 44 ideas · 30 questions Start from the ones you can be sure of 26 ideas · 7 questions Five things that must be true, and never are 53 ideas · 29 questions Read the frequency over time 58 ideas · 31 questions How big was the change? 23 ideas · 8 questions Does the census fit? 42 ideas · 22 questions From the census to the verdict 49 ideas · 16 questions Practice questions 10 multiple choice · 2 free response End-of-topic test: Hardy–Weinberg Equilibrium 18 multiple choice · 2 free response Topic 7.6 · Evidence of Evolution Five kinds of evidence, and the oldest kind 53 ideas · 33 questions Decay is a clock 48 ideas · 30 questions Where they live, and what came before 37 ideas · 27 questions Same bones, look-alikes, leftovers 60 ideas · 36 questions Count the differences 46 ideas · 25 questions Practice questions 10 multiple choice · 2 free response End-of-topic test: Evidence of Evolution 18 multiple choice · 2 free response Topic 7.7 · Common Ancestry One ancestor for every eukaryote 42 ideas · 20 questions Two more shared features, and a test 53 ideas · 29 questions Practice questions 8 multiple choice · 2 free response End-of-topic test: Common Ancestry 16 multiple choice · 2 free response Topic 7.8 · Continuing Evolution Still happening 38 ideas · 23 questions Resistance: selection we can watch 58 ideas · 22 questions The next disease 37 ideas · 17 questions Counts that climb by tens 37 ideas · 18 questions Plot the counts 26 ideas · 13 questions What was wrong with the study, and what to do next 51 ideas · 19 questions Practice questions 8 multiple choice · 2 free response End-of-topic test: Continuing Evolution 16 multiple choice · 2 free response Unit 8 · Ecology Topic 8.1 · Responses to the Environment The pill bug and the damp side 39 ideas · 31 questions A change inside, a change outside, and why the answer helps 37 ideas · 18 questions Turning toward, speeding up: taxis, kinesis and the plant that leans 43 ideas · 33 questions Testing the pill bug 41 ideas · 23 questions Nine to one, or chance? 31 ideas · 21 questions A call in the grass 33 ideas · 26 questions What the signal is for 32 ideas · 18 questions Who leaves offspring 36 ideas · 14 questions Born knowing it, or learned it 39 ideas · 25 questions Safety in numbers 60 ideas · 31 questions Capstone: a change in the environment, a change in behavior, a change in the population 23 ideas · 20 questions Practice questions 10 multiple choice · 2 free response End-of-topic test: Responses to the Environment 17 multiple choice · 2 free response Topic 8.2 · Energy Flow Through Ecosystems What the energy is used for 36 ideas · 20 questions Gain or loss: the energy budget 25 ideas · 13 questions Warm from inside, warm from outside 49 ideas · 28 questions Breeding when the energy is there 29 ideas · 13 questions From a pond to a biome, and the two things that pass through it 43 ideas · 22 questions Boxes and arrows: how every cycle is drawn 44 ideas · 34 questions Where the rain came from 29 ideas · 26 questions Where your carbon has been 58 ideas · 25 questions Surrounded by nitrogen, and unable to use it 38 ideas · 27 questions Four more steps, by what goes in and what comes out 43 ideas · 19 questions The cycle that starts in rock 57 ideas · 29 questions Who makes the food 56 ideas · 38 questions Net primary productivity 23 ideas · 13 questions Who eats the food 52 ideas · 27 questions Levels, chains and the direction of the arrow 47 ideas · 26 questions Build the web 52 ideas · 26 questions Ten percent 43 ideas · 35 questions Measuring the loss, and why the chain stops 30 ideas · 17 questions Less sun, fewer hawks, and why maize beats beef 36 ideas · 15 questions Explain the result by following the energy 41 ideas · 7 questions Practice questions 10 multiple choice · 2 free response End-of-topic test: Energy Flow Through Ecosystems 19 multiple choice · 2 free response Topic 8.3 · Population Ecology Counting frogs 45 ideas · 20 questions More births, more deaths 32 ideas · 21 questions The equation: births minus deaths 31 ideas · 20 questions How many next year? 21 ideas · 11 questions Each one makes more 36 ideas · 26 questions The equation for unchecked growth 36 ideas · 32 questions The J and the straight line 53 ideas · 33 questions Draw the growth graph 32 ideas · 15 questions Practice questions 10 multiple choice · 2 free response End-of-topic test: Population Ecology 18 multiple choice · 2 free response Built from the College Board AP Biology Course and Exam Description V.1 (2025).