IB Biology IA: 60 Examples and Guidance (2025)

The International Baccalaureate (IB) program offers a variety of assessments for students, including Internal Assessments (IAs), which are pieces of coursework marked by students’ teachers. The Biology IA is an assessment designed to test students' understanding of the material they have learned in their biology course, their ability to conduct independent research, and their competence in applying their knowledge to real-world biological issues.

What is the IA?

The IA consists of a laboratory report that students must complete during their IB biology course. For assessments before May 2025, the report should be 6 to 12 pages in length, but after May 2025, the length requirement is updated to a maximum of 3,000 words.

What should the IA contain?

The research question for the internal assessment should be a testable question that is related to the biology curriculum. It's essential that the question is relevant to the biology curriculum, specific and clearly defined. The methodology section should explain how the research was conducted, including the materials and methods used. The methodology should be detailed and well-explained, and should include information on the materials and methods used, as well as any ethical considerations.

Data analysis is an important aspect of the IA. Professional IB Biology tutors recommend that students should present their data in a clear and organized manner, and should use appropriate statistical analysis to interpret their results. They should also make sure to include a discussion of the limitations of their study and the implications of their findings.

The conclusion should summarise the main findings of the study, relate the results back to the research question, and address the relevance of these findings to the broader context of the biological field.

In addition to the laboratory report, students must complete a reflective statement, which is mandatory. This statement should be around 500 words long and must include references to how the student has achieved specific learning objectives outlined in the IB Biology syllabus, and should reflect on the student’s learning during the internal assessment process. The reflective statement should include a description of the student’s personal learning process, including successes and challenges, as well as an evaluation of their performance on the internal assessment and the skills they have gained through the process.

Have a look at our comprehensive set of IB Biology 2025 SL resources and IB Biology 2025 HL resources, developed by expert IB teachers and examiners:

📚 View IB Biology 2025 SL Practice Questions
📚 View IB Biology 2025 HL Practice Questions
📚 View IB Biology 2025 SL Study Notes
📚 View IB Biology 2025 HL Study Notes
📚 View IB Biology 2025 SL Past Papers
📚 View IB Biology 2025 HL Past Papers

What are some example research questions?

Here are examples with details of potential research questions, written by expert IB Biology tutors and teachers, that could inspire your Biology IA:

1 - Investigating the effect of different types of sugars on the rate of fermentation by yeast.
Understanding how different sugars influence yeast fermentation can shed light on metabolic pathways and practical applications such as biofuel production. By testing various sugars, such as glucose, sucrose, and lactose, the experiment can reveal differences in fermentation efficiency.

• Prepare yeast solutions with equal concentrations.
• Use different sugar types at the same concentration in each setup.
• Measure fermentation rate via CO₂ production using a gas syringe or respirometer.
• Control variables like temperature, pH, and yeast concentration.

Analyse results to compare sugar utilisation rates.

2 - How does the pH of a solution affect the activity of an enzyme?
The relationship between pH and enzyme activity demonstrates the importance of maintaining optimal conditions for biological reactions. Enzyme activity can be systematically tested across a range of pH values to find its optimal working environment.

• Use a reaction where the enzyme catalyses a visible or measurable product (e.g., starch breakdown by amylase).
• Prepare buffered solutions of varying pH levels.
• Measure reaction rate by tracking product formation or substrate depletion.
• Maintain constant temperature, substrate concentration, and enzyme amount.
• Plot results to identify the enzyme’s optimal pH range.

3 - Can the concentration of vitamin C in different types of fruit juice be determined using titration?

Vitamin C content in fruit juices varies with type, storage, and processing. Titration with potassium permanganate offers an accurate method to quantify ascorbic acid concentration.

• Standardise the potassium permanganate solution for reliable titration.
• Perform titration with juice samples, adding permanganate until a faint pink endpoint persists.
• Record the volume of titrant used and calculate vitamin C concentration using stoichiometry.
• Test multiple juice types for comparative analysis.
• Ensure equipment and environmental conditions are consistent.

4 - Investigating the effect of light intensity on the rate of photosynthesis in aquatic plants.

Photosynthesis depends heavily on light intensity, a factor that can be easily manipulated to explore its direct impact on oxygen production in aquatic plants like Elodea.

• Set up containers with plants exposed to varying light intensities by altering the distance of the light source.
• Measure oxygen production using a dissolved oxygen probe or bubble count.
• Maintain constant temperature, water type, and plant species.
• Collect and analyse data to determine the light intensity threshold for optimal photosynthesis.
• Repeat trials for reliability.

5 - How does the concentration of carbon dioxide affect the rate of photosynthesis in terrestrial plants?

Carbon dioxide concentration plays a pivotal role in photosynthesis rates, making it essential to study its effects in a controlled environment to understand plant efficiency and growth potential.

• Grow plants in sealed chambers with controlled CO₂ levels.
• Use a dissolved oxygen probe to measure oxygen output as an indicator of photosynthesis.
• Keep light, temperature, and watering conditions constant across chambers.
• Compare oxygen production at different CO₂ concentrations.
• Ensure replicates for statistical accuracy.

6 - Can the presence of glucose in urine be determined using Benedict's test?

The investigation explores the effectiveness of Benedict's test in detecting glucose levels in urine samples. By using Benedict's reagent and assessing the resulting colour change, it provides a visual and quantitative means to determine glucose concentration. This is particularly useful in diagnosing conditions like diabetes.

• Procedure: Add Benedict’s reagent to a urine sample and heat in a water bath.
• Observation: A colour change indicates the presence of glucose, ranging from green (low) to red (high).
• Quantification: Use a standardised colour chart to estimate glucose concentration.
• Repetition: Conduct multiple tests to ensure reliability and account for variability in samples.

7 - Investigating the effect of temperature on the respiration rate of germinating seeds.

This experiment examines how varying temperatures influence the rate of respiration in germinating seeds. Oxygen consumption or carbon dioxide production serves as measurable indicators of respiration under controlled environmental conditions.

• Setup: Expose germinating seeds to different temperatures (e.g., 10°C, 20°C, 30°C).
• Measurement: Monitor oxygen consumed or CO₂ released using respirometers or gas sensors.
• Control variables: Ensure uniformity in seed type, water availability, and nutrient levels.
• Comparison: Analyse respiration rates across temperature groups to determine trends.

8 - How does the concentration of salt in a solution affect the growth of bacteria?

This investigation determines the impact of salt concentration on bacterial growth. By preparing salt solutions of varying concentrations and incubating bacterial cultures, the study highlights the relationship between salinity and microbial proliferation.

• Preparation: Create solutions with increasing salt concentrations (e.g., 0%, 2%, 5%, 10%).
• Inoculation: Add a fixed bacterial culture to each solution.
• Incubation: Maintain constant temperature and pH for all samples.
• Measurement: Assess growth through colony counts or optical density using a spectrophotometer.
• Comparison: Identify the salt concentration that inhibits or promotes bacterial growth.

9 - Can the concentration of nitrogen compounds in soil be determined using colorimetry?

This study uses colorimetry to quantify nitrogen compounds in soil, offering insight into soil fertility and agricultural suitability. Extracted nitrogen reacts with a reagent to produce a measurable colour whose intensity correlates with concentration.

• Sample collection: Obtain soil samples from various locations.
• Extraction: Isolate nitrogen compounds using methods like Kjeldahl digestion.
• Reaction: Add a reagent that reacts with nitrogen to produce a colour.
• Measurement: Use a spectrophotometer to quantify the absorbance of the coloured solution.
• Calculation: Determine nitrogen concentration using a standard curve.

10 - Investigating the effect of different types of plant hormones on the growth of seedlings.

This experiment evaluates how plant hormones influence seedling growth by applying different hormone treatments and measuring the resulting changes in height, mass, and other growth characteristics.

• Hormone treatments: Prepare solutions with varying concentrations of hormones such as auxins or gibberellins.
• Control variables: Maintain consistent light exposure, temperature, and watering for all seedlings.
• Measurement: Record height, mass, and additional traits such as root development and leaf size.
• Observation: Assess differences in growth patterns between treated and control groups.
• Analysis: Determine the specific effects of each hormone type and concentration.

11 - How does the concentration of salt in water affect the hatching rate of brine shrimp?

This experiment investigates the relationship between salt concentration and the hatching rate of brine shrimp. It provides insights into the salinity levels optimal for the development of these organisms, which are commonly used in ecological and aquaculture studies.

• Setup: Prepare containers with varying salt concentrations (e.g., 0%, 5%, 10%, 15%).
• Consistency: Ensure constant temperature, light levels, and aeration for all containers.
• Observation: Count hatched brine shrimp at regular intervals (e.g., every 24 hours).
• Calculation: Compute hatching rates as the percentage of eggs hatched in each condition.
• Comparison: Analyse trends across different salinity levels to identify optimal conditions.

12 - Can the rate of mitosis be determined using microscopy techniques?

This investigation focuses on measuring the mitotic rate in cells using microscopy. By observing and timing the stages of mitosis, the experiment quantifies cell division rates, providing key insights into biological growth and development.

• Preparation: Collect samples from rapidly dividing tissues (e.g., onion root tips).
• Staining: Use a mitotic stain (e.g., aceto-orcein) to enhance visibility of chromosomes.
• Observation: Record the duration of each mitotic stage (prophase, metaphase, etc.) under a microscope.
• Replication: Examine multiple cells to ensure statistical reliability.
• Calculation: Determine the average mitotic rate by summing times for all stages.

13 - Investigating the effect of different types of antibiotics on the growth of bacteria.

This study evaluates the efficacy of various antibiotics in inhibiting bacterial growth. It determines which antibiotics are most effective against specific bacterial strains by measuring zones of inhibition in a controlled environment.

• Culture: Grow bacteria on nutrient agar plates.
• Antibiotics: Apply discs soaked in different antibiotics at standardised concentrations.
• Incubation: Maintain plates at a consistent temperature (e.g., 37°C) for 24-48 hours.
• Measurement: Measure the diameter of inhibition zones around each antibiotic disc.
• Comparison: Analyse results to determine the relative effectiveness of each antibiotic.

14 - How does the concentration of oxygen affect the respiration rate of crickets?

This experiment examines how varying oxygen levels influence the metabolic activity of crickets. By measuring gas exchange, the study provides insights into the physiological adaptations of insects to environmental conditions.

• Chambers: Prepare sealed chambers with different oxygen concentrations (e.g., 10%, 15%, 20%).
• Monitoring: Use gas sensors to measure oxygen consumption and carbon dioxide production.
• Controls: Maintain consistent temperature, humidity, and number of crickets per chamber.
• Duration: Record data over a fixed time period (e.g., 1 hour per trial).
• Analysis: Compare respiration rates across oxygen levels to identify trends.

15 - Can the concentration of glucose in blood be determined using glucose oxidase and spectrophotometry?

This experiment quantifies glucose levels in blood by leveraging the enzymatic activity of glucose oxidase. The process combines biochemical reactions with spectrophotometric analysis, offering precise measurements of glucose concentration.

• Reagents: Mix blood samples with glucose oxidase to initiate the enzymatic reaction.
• Measurement: Use a spectrophotometer to measure absorbance at a specific wavelength.
• Standard curve: Prepare a calibration curve using known glucose concentrations.
• Calculation: Determine glucose levels in the sample based on absorbance readings.
• Repetition: Test multiple samples for accuracy and reproducibility.

16 - Investigating the effect of different types of pesticides on the growth of bean plants.

This investigation assesses how various pesticides and their concentrations influence the growth and health of bean plants. By measuring growth metrics and observing plant health indicators, the experiment highlights the potential effects of pesticide use on plant development.

• Setup: Grow bean plants in soil treated with varying concentrations of different pesticides.
• Controls: Maintain consistent light, temperature, water supply, and soil type for all plants.
• Measurements: Record plant height and mass periodically over the study period.
• Observation: Examine leaves for signs of discolouration or structural damage.
• Analysis: Compare growth rates and health indicators across groups to determine the effects.

17 - How does the concentration of light affect the growth of algae?

This experiment investigates the relationship between light intensity and the growth of algae. By exposing algae to different light conditions, it aims to identify the optimal light level for algal biomass production and chlorophyll synthesis.

• Containers: Prepare multiple containers with controlled light intensities (e.g., 10%, 50%, 100%).
• Algal samples: Use the same initial volume of algal culture in each container.
• Measurements: Track growth using biomass (dry weight) or chlorophyll content analysis.
• Controls: Keep nutrient levels, temperature, and water quality consistent across all groups.
• Duration: Monitor and measure growth rates over a fixed period (e.g., 7-10 days).

18 - Can the presence of starch in leaves be determined using iodine solution?

This study explores the use of iodine as a simple and effective method to detect starch in plant leaves. By examining the colour change upon adding iodine, the experiment determines starch presence and potentially its distribution in different leaves.

• Preparation: Grind leaf samples into a fine powder to increase surface area for reaction.
• Test: Add iodine solution to the leaf powder and observe for a blue-black colour change.
• Repetition: Test multiple leaves from different plants to ensure reliable results.
• Variables: Control for leaf age, time of collection, and environmental factors.

19 - Investigating the effect of different types of plant nutrients on the growth of tomatoes.

This study evaluates how varying concentrations of essential nutrients—nitrogen, phosphorus, and potassium—impact the growth of tomato plants. The experiment also explores the potential correlation between soil nutrient concentration and the nutrient content of the tomatoes produced.

• Setup: Grow tomato plants in soil with controlled levels of nitrogen, phosphorus, and potassium.
• Controls: Maintain consistent light, temperature, and watering conditions.
• Measurements: Monitor growth by recording plant height, mass, and fruit yield over time.
• Nutrient analysis: Test the nutrient content of plant tissues to examine correlations.
• Comparison: Analyse growth and nutrient uptake differences across treatments.

20 - How does the concentration of carbon dioxide affect the growth of marine plants?

This experiment investigates how varying levels of carbon dioxide influence the growth of marine plants. By controlling CO₂ concentrations in water, it examines the impact on plant biomass, height, and chlorophyll content while ensuring other factors remain constant.

• CO₂ control: Bubble specific amounts of carbon dioxide into water to create different concentrations.
• Marine plants: Use a uniform species of plant to ensure comparable results.
• Measurements: Record changes in plant height, biomass, and chlorophyll content over a fixed period.
• Controls: Standardise light exposure, water temperature, and nutrient availability.
• Analysis: Compare growth rates and physiological changes across varying CO₂ levels.

21 - Can the concentration of protein in an egg be determined using the Biuret method?

This investigation explores how the Biuret method can quantify the protein concentration in egg samples. By observing the colour intensity resulting from the protein-Biuret reagent reaction, the protein content can be measured against a standard curve of known protein concentrations.

• Sample preparation: Homogenise the egg and extract protein in a liquid phase.
• Reagent reaction: Add Biuret reagent to the extract to induce a colour change.
• Standard curve: Prepare a calibration curve using known protein concentrations.
• Measurement: Use a spectrophotometer to quantify the absorbance of the colour.
• Repetition: Test multiple eggs to ensure consistency and reliability of results.

22 - Investigating the effect of different types of plant hormones on the root growth of seedlings.

This study examines how different plant hormones influence root growth in seedlings. The focus is on quantifying root length or biomass while controlling environmental variables to ensure accurate comparisons.

• Hormone treatments: Use varying concentrations of hormones such as auxins or gibberellins.
• Control variables: Standardise light exposure, soil type, watering, and temperature.
• Measurement: Record root length or mass at regular intervals.
• Observation: Assess any additional changes, such as root branching or discolouration.
• Analysis: Compare growth metrics across treatments to evaluate hormone effects.

23 - How does the concentration of oxygen affect the respiration rate of goldfish?

This experiment investigates how oxygen concentration affects the metabolic rate of goldfish by measuring their gas exchange. The results provide insights into the physiological limits of the species in varying oxygen levels.

• Setup: Prepare tanks with different oxygen levels, adjusted by aeration or chemical means.
• Measurements: Track oxygen consumption or carbon dioxide production using sensors.
• Control variables: Maintain consistent water temperature, tank size, and feeding schedule.
• Duration: Conduct observations over a fixed period (e.g., 1 hour).
• Comparison: Analyse respiration rates across groups to identify oxygen-dependent trends.

24 - Can the concentration of a specific hormone in blood be determined using ELISA?

This experiment uses the ELISA technique to measure the concentration of a specific hormone in blood. The method employs antigen-antibody interactions and enzyme reactions to produce a quantifiable colour signal.

• Plate preparation: Coat a microplate with antibodies specific to the hormone.
• Sample addition: Add blood samples, allowing the hormone to bind to the antibodies.
• Signal amplification: Introduce a secondary antibody linked to an enzyme.
• Detection: Measure the colour intensity produced by the enzyme reaction using a spectrophotometer.
• Standard curve: Use known hormone concentrations for accurate quantification.

25 - Investigating the effect of different types of pollutants on the growth of watercress.

This study evaluates how varying types and concentrations of pollutants impact the growth of watercress. The experiment simulates real-world pollution scenarios to assess the plant’s tolerance and adaptability.

• Pollutants: Select pollutants such as heavy metals, pesticides, or detergents.
• Concentrations: Prepare a gradient of pollutant concentrations for testing.
• Controls: Standardise light exposure, water temperature, and nutrient availability.
• Measurements: Track growth through height, mass, or visual health indicators.
• Analysis: Compare growth data to determine the toxicity threshold for each pollutant.

26 - How does the concentration of light affect the rate of respiration in germinating seeds?

This experiment investigates how light intensity influences the respiration rate in germinating seeds. By measuring oxygen consumption or carbon dioxide production under different light conditions, it explores the potential link between light and metabolic activity.

• Setup: Expose germinating seeds to varying light intensities (e.g., low, medium, high).
• Measurement: Use gas sensors to track oxygen consumption or CO₂ production.
• Controls: Maintain constant temperature, humidity, and seed type.
• Duration: Record respiration rates over a standardised time period.
• Analysis: Compare data to identify trends related to light intensity.

27 - Can the concentration of nitrates in water be determined using colorimetry?

This investigation evaluates how colorimetry can quantify nitrate concentrations in water. By comparing the colour intensity of nitrate reactions with standard solutions, the method provides an efficient way to assess water quality.

• Standard curve: Prepare solutions with known nitrate concentrations.
• Reagent reaction: Add a reagent that produces a coloured compound with nitrates.
• Measurement: Use a colorimeter to determine the absorbance of each sample.
• Calculation: Compare sample absorbance to the standard curve to calculate nitrate levels.
• Repetition: Test multiple water samples for reliability and accuracy.

28 - Investigating the effect of different types of disinfectants on the growth of bacteria.

This study compares the effectiveness of various disinfectants in inhibiting bacterial growth. By measuring growth rates in treated and untreated cultures, it identifies the most effective disinfectants for bacterial control.

• Cultures: Divide a bacterial culture into groups for testing.
• Disinfectant application: Treat each group with a different disinfectant, leaving a control untreated.
• Growth monitoring: Measure growth by colony counts or culture turbidity using a spectrophotometer.
• Controls: Standardise temperature, nutrient availability, and incubation time.
• Analysis: Compare growth inhibition across disinfectant types.

29 - How does the concentration of salt in water affect the growth of duckweed?

This experiment investigates how salt concentration impacts the growth of duckweed, focusing on physiological limits and adaptations. Growth metrics such as surface area or biomass are used to assess the effect of salinity.

• Salt gradients: Prepare containers with different salt concentrations (e.g., 0%, 2%, 5%, 10%).
• Plant samples: Add a consistent number of duckweed fronds to each container.
• Measurements: Track growth by measuring surface area or biomass over time.
• Controls: Maintain uniform light, temperature, and nutrient levels.
• Comparison: Analyse growth data to identify salt concentration thresholds.

30 - Can the concentration of ethanol in different types of alcoholic beverages be determined using gas chromatography?

This investigation uses gas chromatography (GC) to quantify ethanol concentrations in alcoholic beverages. The method involves separating ethanol from other components and measuring its abundance with a flame ionisation detector.

• Sample preparation: Dilute alcoholic beverages as required for GC analysis.
• GC process: Inject samples into the chromatograph to separate components.
• Detection: Measure ethanol peaks using a flame ionisation detector.
• Quantification: Calculate ethanol concentration using the peak area or height and a calibration curve.
• Repetition: Test multiple beverages for consistent and reliable results.

31 - Investigating the effects of different types of exercise on heart rate and blood pressure.

This experiment explores how different forms of exercise—running, cycling, and weightlifting—affect heart rate and blood pressure. By analysing pre- and post-exercise data, the study highlights the physiological responses to various physical activities.

• Participants: Recruit a diverse group and randomise them into exercise groups.
• Measurements: Record heart rate and blood pressure before and after each session.
• Exercise types: Include activities such as aerobic (running, cycling) and anaerobic (weightlifting).
• Controls: Standardise exercise duration, participant age, gender, and fitness level.
• Analysis: Use statistical tests to compare changes across exercise types.

32 - How does the level of noise pollution affect the behavior and communication of animals?

This field study examines the impact of noise pollution on animal behaviour and communication. Observing vocalisation changes, movement patterns, and social interactions in different noise environments can reveal correlations between noise levels and behavioural adaptations.

• Study areas: Select locations with varying noise pollution levels (e.g., urban, rural, and quiet reserves).
• Data collection: Record animal vocalisations, movement, and group interactions over set time periods.
• Controls: Account for factors like weather, time of day, and species.
• Comparison: Analyse differences in behaviour and communication across noise gradients.
• Statistical analysis: Correlate noise intensity with observed behavioural changes.

33 - Investigating the effects of different types of fertilizers on plant growth and nutrient uptake.

This experiment explores how different fertilisers affect plant growth and nutrient absorption. By measuring growth rates and nutrient content, the study evaluates the effectiveness of each fertiliser type in promoting healthy plant development.

• Setup: Grow identical plants in soil treated with various fertilisers (e.g., organic, synthetic, or balanced).
• Growth tracking: Measure plant height and mass at regular intervals.
• Nutrient analysis: Assess plant tissues for nitrogen, phosphorus, and potassium content.
• Controls: Maintain uniform light, watering, and temperature conditions.
• Comparison: Evaluate growth and nutrient uptake across fertiliser types.

34 - How does exposure to light pollution affect the migration and behavior of nocturnal animals?

This study investigates the influence of light pollution on nocturnal animals' behaviour and migration. Using GPS or radio telemetry to track movement patterns, the research assesses how artificial lighting impacts these animals' natural activities and habitats.

• Study areas: Select locations with low, moderate, and high light pollution.
• Tracking methods: Use GPS or radio tags to monitor animal movement and activity.
• Data collection: Record migration routes, habitat usage, and activity levels over time.
• Controls: Account for species type, season, and weather conditions.
• Analysis: Compare behavioural and migration data across different light pollution levels.

35 - Investigating the effects of different types of water pollution on aquatic ecosystems and organisms.

This experiment examines how various pollutants affect aquatic ecosystems. By populating tanks with organisms and exposing them to different pollution types, the study evaluates the impact on health, reproduction, and survival.

• Pollutant selection: Use types such as oil, chemical runoff, or excess nutrients.
• Tank setup: Maintain separate tanks with controlled pollution levels and clean water as a control.
• Organisms: Populate tanks with fish, algae, and invertebrates to simulate an ecosystem.
• Monitoring: Track growth, reproduction, behaviour, and mortality rates over time.
• Comparison: Analyse the ecological effects of each pollution type.

36 - How does exposure to electromagnetic radiation affect the growth and development of plants?

This experiment investigates the impact of electromagnetic radiation, such as UV light or radio waves, on plant growth and development. By measuring growth metrics and observing health changes, the study explores how radiation exposure affects plants at various levels.

• Radiation exposure: Use sources like UV lamps or radio wave generators at varying intensities.
• Plant setup: Grow plants in a controlled environment with consistent light, temperature, and watering.
• Measurements: Track plant height, leaf size, and health indicators over time.
• Control group: Include plants not exposed to radiation for baseline comparison.
• Analysis: Compare growth and health data across radiation levels to identify trends.

37 - Investigating the effects of different types of air pollution on respiratory function and lung health.

This study evaluates how various types of air pollution, such as traffic emissions and industrial fumes, affect respiratory health. By conducting lung function tests on participants from diverse environments, the investigation provides insights into the health impacts of polluted air.

• Participant recruitment: Select individuals from areas with varying pollution levels (e.g., urban, industrial, rural).
• Baseline tests: Conduct spirometry or other respiratory function tests to establish initial lung health.
• Follow-up: Repeat tests after a set duration to measure changes in function.
• Controls: Account for variables such as age, smoking status, and pre-existing conditions.
• Analysis: Compare respiratory outcomes to correlate pollution type with lung health effects.

38 - How does the level of acidity affect the growth and survival of aquatic organisms?

This experiment examines the impact of water pH on the growth, survival, and behaviour of aquatic organisms. By exposing organisms to a range of pH levels, the study investigates tolerance thresholds and ecological implications.

• pH levels: Prepare tanks with pH gradients (e.g., acidic, neutral, alkaline).
• Organisms: Use species such as fish, invertebrates, or algae for a broad analysis.
• Observations: Track survival rates, growth metrics, and behavioural changes.
• Control variables: Standardise temperature, light, and food supply.
• Additional data: Include observations on reproduction and stress responses for deeper analysis.

39 - Investigating the effects of different types of food additives on human health and metabolism.

This study explores the metabolic and health impacts of food additives through controlled dietary experiments. By measuring biomarkers and analysing health outcomes, it aims to identify potential risks associated with specific additives.

• Literature review: Identify additives of interest and their known or suspected health effects.
• Controlled diet: Design diets with varying levels of selected additives.
• Sample collection: Take blood and urine samples at regular intervals to measure biomarkers.
• Participant controls: Ensure a diverse participant pool, controlling for age, gender, and activity levels.
• Analysis: Use statistical tools to identify significant differences in metabolic and health markers.

40 - How does the level of UV radiation affect the growth and survival of plants?

This experiment assesses the effects of UV radiation on plant growth and survival. By using UV lamps or varying sun exposure, it quantifies changes in growth rates, leaf size, and chlorophyll content across radiation levels.

• UV intensity: Expose plants to controlled UV levels using lamps or distance-based sunlight exposure.
• Growth metrics: Measure height, leaf size, survival rate, and chlorophyll content.
• Control group: Include plants shielded from UV exposure as a baseline.
• Environmental consistency: Maintain uniform temperature, humidity, and watering for all groups.
• Comparison: Analyse data to determine how UV intensity influences plant health and development.

41 - Investigating the effects of different types of drugs on human physiology and behavior.

This investigation explores how various drugs influence human physiology and behaviour through a double-blind, randomised controlled trial. By measuring physical and cognitive outcomes, the study assesses the safety and potential side effects of each drug.

• Trial design: Conduct a double-blind, randomised trial with participants divided into drug and placebo groups.
• Measurements: Assess blood pressure, heart rate, cognitive function, and mood using standardised tests.
• Control variables: Ensure similar demographics (e.g., age, health status) across groups.
• Data analysis: Identify significant physiological and behavioural changes linked to each drug.
• Safety assessment: Monitor participants for adverse effects throughout the study.

42 - How does the level of carbon dioxide affect the growth and development of plants?

This experiment investigates how varying carbon dioxide levels influence plant growth and development. By monitoring growth metrics in controlled environments, the study provides insights into the effects of CO₂ on biomass production and development.

• CO₂ control: Use sealed growth chambers with different CO₂ concentrations (e.g., 300 ppm, 600 ppm, 1000 ppm).
• Growth metrics: Measure height, leaf area, and biomass over a set period.
• Control variables: Maintain consistent light intensity, temperature, and watering across groups.
• Analysis: Compare growth data to identify trends in CO₂-dependent development.
• Long-term impact: Observe any morphological or physiological changes in plants.

43 - Investigating the effects of different types of pesticides on non-target organisms and ecosystems.

This study evaluates the ecological risks of pesticides by examining their impact on non-target species and ecosystem dynamics. By tracking survival and reproductive success, the experiment highlights the broader consequences of pesticide application.

• Organism selection: Include ecologically significant species such as pollinators, earthworms, or microbes.
• Exposure: Treat organisms with varying pesticide concentrations in a controlled environment.
• Measurements: Monitor survival, reproduction, and behavioural changes over time.
• Ecosystem impact: Assess species diversity and abundance in pesticide-exposed areas.
• Comparison: Analyse results to determine which pesticides pose the greatest ecological risks.

44 - How does the level of atmospheric pollutants affect the growth and development of plants?

This experiment studies the impact of pollutants such as nitrogen dioxide and ozone on plant health. By measuring growth metrics and physiological changes, the investigation provides insights into the effects of air pollution on vegetation.

• Pollutant exposure: Use chambers with controlled pollutant levels (e.g., low, medium, high concentrations).
• Growth metrics: Measure plant height, leaf area, and chlorophyll content regularly.
• Control variables: Ensure consistent temperature, light exposure, and watering across groups.
• Observations: Track visible signs of stress such as leaf damage or discolouration.
• Analysis: Compare growth rates and health indicators to evaluate pollutant effects.

45 - Investigating the effects of different types of microorganisms on the digestive system and gut microbiome.

This study examines how exposure to specific microorganisms influences the gut microbiome and digestive health. By analysing microbial diversity and physiological changes, it explores the role of gut bacteria in animal health.

• Exposure methods: Introduce microorganisms through diet or direct exposure in controlled animal groups.
• Monitoring: Analyse faecal samples for bacterial composition and measure gut pH.
• Health indicators: Observe changes in digestion, nutrient absorption, or immune responses.
• Control variables: Standardise animal diet, environment, and age across groups.
• Data analysis: Compare microbial diversity and health outcomes to identify microorganism effects.

46 - How does the level of humidity affect the growth and survival of insects?

This investigation explores the influence of humidity on insect growth and survival. By exposing insects to various humidity levels in a controlled setting, the study examines how environmental moisture affects physiological development and lifespan.

• Humidity levels: Create environments with controlled relative humidity (e.g., low, moderate, high).
• Insect species: Use a consistent species for uniformity in results.
• Measurements: Monitor survival rates, growth (e.g., size or mass), and developmental time over a set period.
• Controls: Maintain consistent temperature, food availability, and lighting across groups.
• Analysis: Compare data across humidity conditions to determine its impact on growth and survival.

47 - Investigating the effects of different types of radiation on the genetic material and DNA replication.

This experiment examines how exposure to various types of radiation affects DNA integrity and replication in cells. By comparing radiation-treated cells with untreated controls, the study evaluates mutation rates and potential long-term impacts on genetic material.

• Radiation types: Use UV light, gamma rays, or X-rays for testing.
• Cell cultures: Cultivate cells in identical conditions to ensure consistency.
• DNA analysis: Assess changes such as mutations, replication errors, or structural damage.
• Control group: Include cells not exposed to radiation for baseline comparisons.
• Long-term effects: Extend observations to explore delayed genetic consequences.

48 - How does the level of soil salinity affect the growth and survival of plants?

This investigation evaluates how different salinity levels in soil influence plant growth and survival. By measuring growth metrics and ion concentrations, the study explores the physiological responses of plants to salt stress.

• Salinity gradients: Prepare soils with varying salt concentrations (e.g., 0%, 2%, 5%, 10%).
• Plant species: Select a species tolerant to a range of salinity levels.
• Measurements: Track plant height, mass, leaf count, and survival rate.
• Controls: Standardise light, temperature, and watering across all groups.
• Ion analysis: Measure soil ion concentrations to correlate with plant growth.

49 - Investigating the effects of different types of antibiotics on bacterial growth and antibiotic resistance.

This study investigates the effectiveness of antibiotics on bacterial growth and the development of resistance. By testing different antibiotics at varying concentrations, the experiment identifies the most potent inhibitors and examines resistance patterns.

• Setup: Prepare petri dishes with bacterial cultures and antibiotic discs at varying concentrations.
• Incubation: Grow cultures in a controlled environment (e.g., 37°C) for a set duration.
• Measurements: Measure inhibition zones or bacterial density using optical density.
• Resistance analysis: Observe any reduced efficacy of antibiotics over multiple generations.
• Controls: Standardise temperature, humidity, and bacterial species across all dishes.

50 - How does the level of soil pH affect the growth and survival of plants?

This experiment explores the relationship between soil pH and plant growth by testing various pH levels in controlled conditions. Growth and survival metrics are tracked to identify optimal pH ranges and potential pH-induced stress.

• pH levels: Prepare soil with adjusted pH ranges (e.g., acidic, neutral, alkaline).
• Plant species: Select plants suitable for testing across diverse pH levels.
• Growth metrics: Measure plant height, biomass, and leaf health over time.
• Controls: Keep light, temperature, and watering uniform across groups.
• Nutrient analysis: Assess soil nutrient availability to identify any pH-related changes.

51 - Investigating the effects of different types of hormones on animal behavior and physiology.

This study explores how specific hormones influence animal behaviour and physiology. By monitoring animals exposed to different hormones in controlled settings, the experiment identifies potential behavioural changes and physiological effects.

• Hormone treatments: Expose groups of animals to different hormones at standardised doses.
• Measurements: Monitor changes in behaviour (e.g., activity levels, social interactions) and physiology (e.g., weight, heart rate).
• Controls: Standardise diet, environment, age, and species across all groups.
• Duration: Observe animals over a set period to identify short- and long-term effects.
• Analysis: Use statistical tools to determine the significance of observed changes.

52 - How does the level of water availability affect the growth and survival of plants?

This experiment investigates how varying water availability impacts plant growth and survival. By simulating conditions from drought to optimal watering, the study highlights the effects of water stress on plant health.

• Water levels: Grow plants under controlled watering regimes (e.g., drought, moderate, optimal).
• Growth metrics: Measure plant height, biomass, and health indicators (e.g., leaf wilting or colour).
• Controls: Maintain consistent light, temperature, and soil type for all groups.
• Duration: Monitor growth and survival over a standard period (e.g., 4-6 weeks).
• Comparison: Analyse the relationship between water availability and plant performance.

53 - Investigating the effects of different types of plant extracts on bacterial growth and antibiotic resistance.

This study evaluates how plant extracts influence bacterial growth and resistance to antibiotics. By testing extracts at varying concentrations, the experiment identifies their antimicrobial properties and potential resistance impacts.

• Preparation: Create petri dishes with bacterial cultures and plant extracts at different concentrations.
• Measurements: Monitor bacterial growth using inhibition zones or spectrophotometry.
• Resistance testing: Assess if extracts reduce or enhance antibiotic resistance.
• Controls: Keep temperature, nutrient medium, and bacterial strains consistent.
• Analysis: Compare growth patterns to evaluate the effectiveness of each extract.

54 - How does the level of nutrients affect the growth and development of microorganisms?

This experiment examines how nutrient availability influences microbial growth and development. By comparing populations in nutrient-rich and nutrient-poor environments, the study identifies the conditions required for optimal growth.

• Nutrient gradients: Grow microorganisms in media with varying nutrient concentrations.
• Growth tracking: Measure population size using optical density or colony counts.
• Morphology: Observe structural differences under a microscope.
• Controls: Standardise temperature, pH, and oxygen levels across all groups.
• Analysis: Evaluate the relationship between nutrient availability and microbial development.

55 - Investigating the effects of different types of pollution on the reproductive systems and fertility of animals.

This investigation studies the impact of pollution, such as air or water pollutants, on animal reproduction. By analysing fertility metrics, the study evaluates how exposure affects reproductive health and offspring viability.

• Pollution types: Expose animals to specific pollutants, such as heavy metals or particulates.
• Reproductive metrics: Monitor offspring count, health, and abnormalities during development.
• Controls: Include a pollution-free group for baseline comparisons.
• Long-term effects: Assess changes in fertility or reproductive health over multiple generations.
• Analysis: Correlate pollution exposure with reproductive outcomes and abnormalities.

56 - How does the level of light intensity affect the growth and development of microorganisms?

This investigation explores the effect of light intensity on microbial growth by culturing microorganisms under controlled light conditions. By analysing colony size or turbidity, the study evaluates how light influences microbial development and activity.

• Light conditions: Use a range of intensities, from complete darkness to bright light.
• Culture setup: Inoculate identical strains of microorganisms onto agar in petri dishes.
• Measurements: Quantify growth using colony counts or turbidity readings.
• Controls: Maintain consistent temperature, nutrient availability, and humidity.
• Analysis: Compare growth data to identify optimal and inhibitory light levels.

57 - Investigating the effects of different types of food on the metabolism and energy balance of humans.

This study examines how various food types influence human metabolism and energy balance. By monitoring changes in weight, energy intake, and metabolic rates, the research identifies dietary effects on overall energy balance.

• Study design: Conduct a randomised controlled trial with participants divided into diet groups.
• Measurements: Track weight, energy expenditure, and metabolic markers pre- and post-intervention.
• Duration: Ensure the trial spans a sufficient period to observe measurable changes.
• Controls: Monitor and standardise physical activity, sleep, and other lifestyle factors.
• Analysis: Compare results to determine the metabolic impact of each diet type.

58 - How does the level of nutrients affect the growth and development of plants?

This experiment investigates how varying levels of essential nutrients, such as nitrogen, phosphorus, and potassium, impact plant growth. By measuring growth metrics, the study identifies optimal nutrient levels for plant health and development.

• Nutrient solutions: Prepare solutions with different nutrient concentrations (e.g., low, medium, high).
• Plant growth: Monitor height, mass, and leaf count over a set period.
• Controls: Keep light intensity, temperature, and watering consistent.
• Additional data: Test soil nutrient levels to confirm uptake by plants.
• Analysis: Determine the relationship between nutrient availability and plant development.

59 - Investigating the effects of different types of hormones on plant growth and development.

This study examines the influence of plant hormones, such as auxins and gibberellins, on growth and development. By varying hormone types and concentrations, the experiment explores how specific hormones affect plant morphology and health.

• Hormone treatments: Apply varying concentrations of hormones to groups of plants.
• Growth metrics: Measure plant height, mass, and growth rate over time.
• Additional observations: Assess root length, leaf size, and flower production.
• Controls: Maintain uniform light, temperature, and watering for all groups.
• Analysis: Compare plant responses to determine the effects of each hormone.

60 - How does the level of water quality affect the growth and survival of aquatic organisms?

This investigation evaluates how water quality parameters, such as pollutants or pH, impact the growth and survival of aquatic organisms. By tracking survival and health metrics, the study identifies key environmental stressors.

• Water quality: Prepare aquariums with varying pH levels or pollutant concentrations.
• Organism selection: Use a single species for consistent results (e.g., fish, invertebrates).
• Measurements: Track growth rates, survival rates, and behaviour changes over time.
• Controls: Keep temperature, oxygen levels, and feeding schedules consistent.
• Analysis: Compare data to identify water quality thresholds critical for organism survival.

Remember to come up with your own original IA topic and check it with your teacher. It should be practical to conduct and relevant to the syllabus. Even A-Level Biology tutors say that this is a great opportunity to develop your personal interests, while advancing your knowledge of the Biology curriculum.

How can I prepare for the IA?

To prepare for the IA, students should ensure that they understand the material covered in their biology course and should practice writing lab reports. They should also seek feedback from their teachers on their writing skills and their understanding of the research process. IB tutors provide personalized guidance and can help students understand complex topics and achieve higher grades as well.

TutorChase's IB resources, including IB Biology Q&A Revision Notes, are perfect for students who want to get a 7 in their IB Biology exams and also prepare for the internal assessment. They are completely free, cover all topics in depth, also have IB Biology past papers and are structured by topic so you can easily keep track of your progress.

How is the IA graded?

The IA is worth 20% of the final grade for the IB biology course, whether you are studying at Higher or at Standard Level. It is graded by the student’s teacher, who is trained and certified by the International Baccalaureate organization. The report is then sent to a moderator, who will check that the report adheres to the IB guidelines and that the grade awarded is appropriate.

Online Biology tutors emphasise that it is important for students to be familiar with the assessment criteria for the biology internal assessment. These criteria are used to grade the laboratory report and reflective statement, and include aspects such as the quality of the research question, the methodology used, the data analysis, and the conclusion. Students should also make sure that their report is well-written and properly formatted, and that it includes all the required sections.

Recent Changes to the IB Biology IA Guidelines

The IB has recently updated the guidelines for the Biology IA to better reflect the evolving nature of biological research and education. These changes include a greater focus on the application of biological principles to real-world situations, a more structured approach to reflective statements, and updated word count and grading criteria. It is important for students to familiarize themselves with these changes to ensure they meet the new expectations.

Source: IB Biology Subject Guide, pre-May 2025

Conclusion

In summary, the IA in the IB is an opportunity for students to demonstrate their understanding of the biology curriculum, as well as their ability to conduct independent research. It consists of a laboratory report and a reflective statement, and is worth 20% of the final grade for the course. To prepare for the assessment, students should ensure that they understand the material covered in their IB Biology.