AP Biology Lab Review: Every Investigation You Need to Know
Lab-based questions account for roughly 25% of the AP Biology exam. You won't be asked to recite lab procedures step by step, but you will need to interpret exp...
Key Takeaways
- What you did: Used organisms (commonly Wisconsin Fast Plants) to selectively breed for specific traits across generations, collecting data on how traits shifted over time.
- What you did: Used dialysis tubing or potato cores to measure water movement across semipermeable membranes.
- What you did: Observed and counted cells in different stages of mitosis (using onion root tip slides) to calculate the relative duration of each phase.
- What you did: Measured energy flow through a model ecosystem, calculating net primary productivity and analyzing energy transfer between trophic levels.
- Beyond specific investigations, the AP Biology exam tests general lab skills that cut across all investigations:.
Need Personalised Guidance?
Active recall and spaced repetition are the most effective methods. Create flashcards for key terms, practice diagram labeling regularly, and work through past paper questions to reinforce understanding. This guide covers every key aspect you need to understand. (This guide has been for the 2025-26 syllabus.)
Frequently Asked Questions
What is the best way to study IB Biology?
Active recall and spaced repetition are the most effective methods. Create flashcards for key terms, practice diagram labeling regularly, and work through past paper questions to reinforce understanding.
For more on this topic, explore our guide on Things No One Will Tell You About What to Expect at University Part Ii.
How many hours should I study Biology per week?
Aim for 3-5 hours weekly outside of class for SL, and 5-7 hours for HL. Break this into short focused sessions rather than long cramming sessions for better retention.
What are the hardest topics in IB Biology?
Genetics, biochemistry (especially HL topics like protein synthesis), and ecology data analysis tend to be the most challenging. Dedicate extra revision time to these areas.
How do I improve at Biology data-based questions?
Practice interpreting graphs and tables regularly. Focus on identifying trends, calculating percentage changes, and drawing evidence-based conclusions. Past papers are the best preparation tool for these questions.
Lab-based questions account for roughly 25% of the AP Biology exam. You won't be asked to recite lab procedures step by step, but you will need to interpret experimental setups, analyze data, identify variables and controls, and apply lab concepts to unfamiliar scenarios. Every year, at least one long FRQ and one or two short FRQs reference lab investigations directly.
The AP Biology curriculum includes 13 required investigations organized around the four Big Ideas. This review covers each investigation: what you did, what it tests, and the key concepts that appear on the exam. Use it as your lab-focused study guide in the weeks leading up to May.
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Big Idea 1: Evolution
Investigation 1: Artificial Selection
What you did: Used organisms (commonly Wisconsin Fast Plants) to selectively breed for specific traits across generations, collecting data on how traits shifted over time.
For more on this topic, explore our guide on All You Need to Know About the Ib Results Remark Procedure.
Key exam concepts: Natural selection vs artificial selection. How selective pressure changes allele frequency in a population. Phenotypic variation as raw material for selection. Connection between artificial selection evidence and Darwin's theory.
FRQ tip: Be prepared to design an experiment testing how selection affects a measurable trait. Identify independent variable (selection criteria), dependent variable (trait measurement), and controls (unselected population).
Investigation 2: Mathematical Modeling — Hardy-Weinberg
What you did: Used mathematical models and simulations to track allele frequencies across generations. Tested what happens when Hardy-Weinberg equilibrium conditions are violated.
Key exam concepts: Hardy-Weinberg equations: p + q = 1 and p² + 2pq + q² = 1. The five conditions for equilibrium (large population, no migration, no mutation, random mating, no selection). How violating each condition drives evolution. Calculating allele and genotype frequencies from population data.
FRQ tip: Hardy-Weinberg calculations appear on nearly every AP Biology exam. Practice using observed phenotype data to calculate allele frequencies and predict genotype ratios. Know how to determine if a population is in equilibrium.
Investigation 3: Comparing DNA Sequences (BLAST)
What you did: Used bioinformatics tools (BLAST database) to compare DNA or protein sequences across species and construct evolutionary relationships.
Key exam concepts: Molecular evidence for evolution. How DNA sequence similarity indicates common ancestry. Constructing and interpreting cladograms using molecular data. More closely related species share more sequence similarities.
FRQ tip: You may be given sequence data and asked to determine which organisms are most closely related. Count the number of differences between sequences — fewer differences means more recent common ancestor.
Big Idea 2: Cellular Processes — Energy and Communication
Investigation 4: Diffusion and Osmosis
What you did: Used dialysis tubing or potato cores to measure water movement across semipermeable membranes. Calculated water potential and observed how solute concentration affects osmosis.
Key exam concepts: Water potential equation: Ψ = Ψs + Ψp (water potential = solute potential + pressure potential). Water moves from high water potential to low water potential. Hypertonic, hypotonic, and isotonic solutions. How cell size and surface area affect diffusion rates.
FRQ tip: Water potential calculations are commonly tested on the AP exam. Know how to calculate solute potential using the equation Ψs = -iCRT, and determine which direction water will flow between two solutions.
Investigation 5: Photosynthesis
What you did: Measured the rate of photosynthesis using leaf disk assays (floating leaf disk method) or a photosynthesis sensor. Tested variables like light intensity, light color, or CO₂ concentration.
Key exam concepts: Light-dependent reactions (in thylakoid membrane) and the Calvin cycle (in stroma). How light intensity, wavelength, and CO₂ concentration affect photosynthesis rate. The role of chlorophyll and accessory pigments. Interpreting absorption spectra and action spectra.
FRQ tip: Be ready to interpret graphs showing photosynthesis rate vs light intensity, noting the plateau where light saturation occurs. Explain why the rate levels off (another factor becomes limiting).
Investigation 6: Cellular Respiration
What you did: Used respirometers to measure oxygen consumption in germinating vs non-germinating seeds. Compared respiration rates at different temperatures.
Key exam concepts: Glycolysis, Krebs cycle, and oxidative phosphorylation (electron transport chain). How temperature affects enzyme-mediated respiration rates. Aerobic vs anaerobic respiration. Net ATP production across all stages.
FRQ tip: Data analysis questions may present respirometry data and ask you to explain rate differences between experimental conditions. Connect temperature effects to enzyme kinetics — too high denatures enzymes, too low reduces molecular motion.
Big Idea 3: Information Storage and Transmission
Investigation 7: Cell Division — Mitosis and Meiosis
What you did: Observed and counted cells in different stages of mitosis (using onion root tip slides) to calculate the relative duration of each phase. Modeled meiosis using chromosome beads to understand crossing over and independent assortment.
Key exam concepts: Stages of mitosis (prophase, metaphase, anaphase, telophase) and what happens in each. Difference between mitosis (identical daughter cells) and meiosis (genetically unique gametes). How crossing over and independent assortment create genetic variation. Cell cycle regulation and checkpoints.
FRQ tip: You may be given cell count data for each mitotic phase and asked to determine which phase lasts longest (the phase with the most cells observed takes the longest proportionally). Calculate percentage of time in each phase.
Investigation 8: Biotechnology — Bacterial Transformation
What you did: Transformed E. coli bacteria with a plasmid containing an antibiotic resistance gene and/or GFP (green fluorescent protein). Compared growth on plates with and without antibiotic.
Key exam concepts: How plasmids transfer genes between organisms. Role of restriction enzymes and ligases. Gene expression in transformed vs non-transformed bacteria. Applications of genetic engineering.
FRQ tip: Expect questions about experimental controls. The plate without antibiotic serves as a positive control (bacteria should grow). The non-transformed bacteria on the antibiotic plate is the negative control (bacteria should not grow).
Investigation 9: Biotechnology — Restriction Enzyme Analysis of DNA
What you did: Used restriction enzymes to cut DNA at specific recognition sequences, then separated fragments by size using gel electrophoresis.
Key exam concepts: How restriction enzymes recognize specific palindromic DNA sequences. Gel electrophoresis separates fragments by size (smaller fragments move farther). Interpreting banding patterns to compare DNA samples. Applications in forensics, paternity testing, and genetic research.
FRQ tip: If given a gel image, you must be able to estimate fragment sizes using a DNA ladder (standard). Smaller bands travel farther from the well. Matching band patterns between samples indicates identical DNA sequences at those cut sites.
Big Idea 4: System Interactions
Investigation 10: Energy Dynamics
What you did: Measured energy flow through a model ecosystem, calculating net primary productivity and analyzing energy transfer between trophic levels.
You might also find these guides helpful: How to Master Biology Data Based Questions a Student Proven Guide and How to Study Biology Like a Top Student the Science Backed Method.
Key exam concepts: Gross primary productivity vs net primary productivity (NPP = GPP - respiration). Energy transfer efficiency between trophic levels (roughly 10% rule). Why food chains rarely exceed 4-5 levels. Biomass and energy pyramids.
FRQ tip: Be prepared to calculate productivity from experimental data. If given dry mass measurements before and after a growth period, you can determine NPP. Understand why only ~10% of energy transfers to the next trophic level.
Investigation 11: Transpiration
What you did: Used a potometer to measure water loss from plant cuttings under different environmental conditions (light, humidity, wind, temperature).
Key exam concepts: How stomata regulate gas exchange and water loss. Environmental factors affecting transpiration rate. Cohesion-tension theory of water transport in xylem. The trade-off between CO₂ uptake for photosynthesis and water loss through transpiration.
FRQ tip: Questions may ask you to predict how changing an environmental variable affects transpiration rate. Higher temperature, lower humidity, more wind, and more light all increase transpiration. Explain the mechanism for each.
Investigation 12: Fruit Fly Behavior
What you did: Observed Drosophila (fruit fly) responses to environmental stimuli in a choice chamber. Used chi-square analysis to determine whether observed behavior differed significantly from random movement.
Key exam concepts: Taxis (directed movement toward or away from stimulus) vs kinesis (change in movement speed). Chi-square statistical test: χ² = Σ (observed - expected)² / expected. Using degrees of freedom and critical values to determine statistical significance. Null hypothesis testing.
FRQ tip: Chi-square calculations appear frequently on the AP Biology exam, not just in behavioral contexts. Practice the formula, know how to use a chi-square table, and understand what it means when χ² exceeds the critical value (reject the null hypothesis).
Investigation 13: Enzyme Activity
What you did: Measured the rate of an enzyme-catalyzed reaction (commonly catalase or peroxidase) under different conditions of pH, temperature, and substrate concentration.
Key exam concepts: How enzyme structure relates to function (active site, substrate specificity). Effects of temperature, pH, and substrate concentration on reaction rate. Enzyme denaturation. Competitive vs non-competitive inhibition. Michaelis-Menten kinetics (Vmax and Km).
FRQ tip: Enzyme questions are among the most common on the AP Biology exam. Be ready to interpret reaction rate graphs showing the effect of changing one variable while holding others constant. Explain plateaus in rate vs substrate concentration graphs (all active sites are saturated at Vmax).
Lab Skills the Exam Tests
Beyond specific investigations, the AP Biology exam tests general lab skills that cut across all investigations:
Experimental design: Identify independent, dependent, and controlled variables. Explain why controls are necessary. Describe how to set up a proper control group.
Data analysis: Interpret graphs and data tables. Calculate means, standard deviations, and standard error. Understand what error bars represent.
Statistical analysis: Apply chi-square tests. Understand p-values and statistical significance. Know when to reject a null hypothesis.
Graphing: Construct appropriate graphs from data (bar graphs for categorical data, line graphs for continuous data). Label axes correctly with units. Draw best-fit lines or curves.
How to Study Lab Content Effectively
Don't re-read lab procedures — instead, practice applying lab concepts to new scenarios. For each investigation, make sure you can explain the biological concept being tested, identify what data was collected and how, describe what the results showed and why, design a modified version of the experiment to test a different variable, and interpret data presented in an unfamiliar format.
Released College Board FRQs are the single most valuable practice resource. Many past FRQs reference specific lab investigations — work through these under timed conditions and score yourself against the rubric.
Need help connecting lab concepts to exam questions? Our AP Biology tutors can review your understanding of all 13 investigations and identify which lab skills you need to strengthen before exam day. They focus practice on the specific question types that appear most frequently.
Related: AP Biology FRQ: How to Score Full Marks on Every Question Type | AP Biology Subject Page
