12 IB Biology IA ideas

How does temperature (10–50 °C) affect the rate of catalase activity in potato extract, measured as volume of O₂ produced in 60 s?

Difficulty:

medium

Time:

1 week

Equipment:

school lab

Analysis:

ANOVA or correlation

Feasibility:

5/5

Overused:

Often seen

Biggest trap:

H₂O₂ not kept fresh between trials

Variables · IV: water-bath temperature. DV: O₂ volume via gas syringe. Control: [H₂O₂], extract mass, pH.

Note · Denaturation above ~40 °C gives a clear optimum curve. Keep H₂O₂ fresh and cold between trials.

How does external NaCl concentration (0–1.0 mol dm⁻³) affect the percentage change in mass of potato tissue cylinders over 24 h?

Difficulty:

easy

Time:

1 week

Equipment:

basic

Analysis:

Linear regression

Feasibility:

5/5

Overused:

Often seen

Biggest trap:

Cylinders not cut to identical dimensions

Variables · IV: solution molarity. DV: % mass change. Control: cylinder dimensions, immersion time, temperature.

Note · Lets you estimate the tissue's water potential from the x-intercept — a strong analysis point.

How does light intensity (lamp distance 10–60 cm) affect the rate of photosynthesis in Elodea, measured by O₂ bubble count per minute?

Difficulty:

medium

Time:

1 week

Equipment:

school lab

Analysis:

1/distance² vs rate

Feasibility:

4/5

Overused:

Often seen

Biggest trap:

Lamp heat confounding light intensity

Variables · IV: 1/distance² as a proxy for intensity. DV: bubbles min⁻¹. Control: NaHCO₃ concentration, temperature, plant segment.

Note · A heat-sink (water tank) between lamp and plant stops temperature confounding the result.

How does caffeine concentration (0–0.5%) affect the heart rate of Daphnia magna?

Difficulty:

medium

Time:

1 week

Equipment:

school lab

Analysis:

t-test on heart rate

Feasibility:

4/5

Overused:

Less common

Biggest trap:

Ethics approval for live organisms

Variables · IV: caffeine solution %. DV: heartbeats in 15 s under a microscope. Control: acclimatisation time, temperature, Daphnia size.

Note · Use cotton-wool fibres to restrain the Daphnia; count from a slowed video rather than live.

How does pH (3–9) affect the time for salivary amylase to fully hydrolyse a starch solution, judged by iodine colour change?

Difficulty:

easy

Time:

1 week

Equipment:

basic

Analysis:

t-test on reaction time

Feasibility:

5/5

Overused:

Often seen

Biggest trap:

pH range where enzyme is inactive

Variables · IV: buffer pH. DV: time to no colour change. Control: [amylase], [starch], temperature.

Note · Amylase activity is very low below pH 4 — cap the timer so an outlier does not distort the mean.

How does storage temperature (4 °C, 20 °C, 35 °C) affect the rate of vitamin C loss in orange juice over 6 days, measured by DCPIP titration?

Difficulty:

hard

Time:

multi-week

Equipment:

school lab

Analysis:

Rate vs time regression

Feasibility:

3/5

Overused:

Less common

Biggest trap:

DCPIP standardisation skipped

Variables · IV: storage temperature. DV: mg vitamin C per cm³ per day. Control: juice batch, container type, light exposure.

Note · Standardise the DCPIP against a known ascorbic acid solution first.

How does soil water content (10–40% by mass) affect the germination percentage of Lepidium sativum seeds after 5 days?

Difficulty:

easy

Time:

1 week

Equipment:

basic

Analysis:

Chi-squared on germination %

Feasibility:

5/5

Overused:

Less common

Biggest trap:

Uneven watering between pots

Variables · IV: % water in soil. DV: % of seeds germinated. Control: seed batch, temperature, light, seed depth.

How does antibacterial mouthwash dilution (neat to 1:64) affect the zone of inhibition on a lawn of cultured non-pathogenic oral bacteria?

Difficulty:

medium

Time:

1 week

Equipment:

school lab

Analysis:

ANOVA on zone diameter

Feasibility:

3/5

Overused:

Less common

Biggest trap:

Non-pathogenic culture protocol not followed

Variables · IV: mouthwash dilution. DV: inhibition zone diameter (mm). Control: agar depth, incubation time and temperature, inoculum density.

Note · Use an approved non-pathogenic culture and seal plates; do not open after incubation.

Is there a correlation between stomatal density and leaf surface area across a vertical light gradient within a single tree?

Difficulty:

hard

Time:

multi-week

Equipment:

specialized

Analysis:

Pearson correlation

Feasibility:

2/5

Overused:

Less common

Biggest trap:

Leaf age varies with height

Variables · IV: canopy height / light level. DV: stomatal density (nail-varnish peel count). Control: species, aspect, leaf age.

Note · Correlation IA — report r and r² and test its significance rather than a mean comparison.

How does exercise intensity (step-test cadence 15–35 steps min⁻¹) affect the time for an individual's heart rate to return to resting?

Difficulty:

easy

Time:

1 day

Equipment:

basic

Analysis:

Paired t-test

Feasibility:

5/5

Overused:

Less common

Biggest trap:

Same subject — order effects

Variables · IV: metronome cadence. DV: recovery time (s). Control: step height, exercise duration, rest between trials, same subject.

How does sucrose concentration (0–15%) affect pollen tube growth length in Impatiens over 2 h?

Difficulty:

hard

Time:

multi-week

Equipment:

school lab

Analysis:

ANOVA on tube length

Feasibility:

2/5

Overused:

Less common

Biggest trap:

Pollen viability varies by flower

Variables · IV: sucrose %. DV: mean tube length (µm) under a microscope. Control: incubation time, temperature, pollen source.

How does music tempo (60–160 BPM) affect an individual's mean reaction time to a visual stimulus?

Difficulty:

easy

Time:

1 day

Equipment:

basic

Analysis:

Repeated-measures t-test

Feasibility:

5/5

Overused:

Often seen

Biggest trap:

Practice effects on reaction time

Variables · IV: track tempo. DV: reaction time (ms) from a ruler-drop or app test. Control: same subject, volume, number of trials, time of day.