Biology IA Exemplar: How does exposure to varying concentrations of… | RevisionDojo

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IB Biology HL Internal Assessment Example

How does exposure to varying concentrations of sucrose solution, 0.00M, 0.25M, 0.50M, 0.75M, and 1.00M (±0.01) influence the mass change of 2.00 g ± 0.01 g of powdered domestic hen (Gallus gallus domesticus) eggshells during 12 hours of fermentation by 0.50 g ± 0.01 g of active Lactococcus lactis bacteria?HL

Official IB Result

17/24

Criteria A: Research Design

5/6

Criteria StrandsPro

A.1Research question context

Excellent

A.2Methodological considerations

Good

A.3Methodology description

Moderate

Criteria Feedback

The student's research question is highly focused and clearly framed within a specific biological context.
The student justifies the investigation with a coherent rationale and shows awareness of the model system’s relevance and limits.
The student's method includes several important controls, repeats, and a logical sequence that mostly allows the investigation to be followed.
The student shows thoughtful refinement from preliminary testing, which strengthens the design.

Some important procedural details are still missing, especially around the bacterial culture, particle size, and drying procedure.
There is an internal inconsistency in the stated incubation temperature.
A few design choices are described but not fully explained, which leaves some ambiguity about reproducibility.

1.1·Strength

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The research question is impressively specific: it names the independent variable levels, dependent variable, time frame, sample mass, and bacterial mass. That level of precision gives the investigation a clear scope and makes it much easier to evaluate whether the method and data actually answer the question.

1.2·Strength

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The student establishes a relevant biological context by explaining why eggshells are a reasonable model for enamel erosion. This helps justify the chosen system rather than presenting the investigation as an isolated laboratory exercise.

1.3·Suggestion

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The variable description would be stronger if the student explicitly stated whether the concentration values refer to final prepared solutions by volume or whether the sucrose mass was adjusted to keep total volume constant. That clarification would help the reader judge the validity of the independent variable.

1.4·Strength

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This is a strong contextual link because the student identifies a gap in prior work and shows how the present investigation responds to it. That makes the research aim purposeful and academically framed, not just descriptive.

1.5·Weakness

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The explanation here is a good start, but it stays generic. The student should connect this control more directly to the actual organism and reaction being studied, and explain why holding temperature near the chosen value matters for the reliability of the fermentation outcome.

1.6·Weakness

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This control is relevant, but it is not sufficiently precise to be reproducible. The student should specify the drying method more carefully, because “high heat for 3 minutes” does not guarantee consistent moisture removal or a measurable endpoint.

1.7·Weakness

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This creates an internal inconsistency with the earlier controlled-variable target of 35 °C. The student should align the control table and procedure so the method clearly identifies one incubation temperature; otherwise the investigation is not fully reproducible.

1.8·Suggestion

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It would strengthen the method to describe the bacterial culture more fully, including source, strain, and whether the cells were actively growing or pre-cultured to a standard density. That detail matters because bacterial viability can strongly affect acid production.

1.9·Weakness

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“Fine powder” is too vague for reproducibility. The student should define what counts as sufficiently fine, or use a standard sieve size, because particle-size variation would affect surface area and therefore the rate of dissolution.

1.10·Question

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How will the student ensure that the filter paper is fully dry before this weighing step? If moisture remains, the final mass could be inflated, which would weaken the validity of the mass-loss measurement.

1.11·Weakness

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The repetition is helpful, but the method still leaves some ambiguity about whether each trial uses freshly prepared solution and newly standardized eggshell powder. The student should clarify this, because reusing materials could introduce carryover effects.

1.12·Suggestion

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The qualitative observations are useful, but the student could make them more scientific by linking them to measurable indicators such as pH change, gas production, or visible precipitate. That would make the observations easier to interpret alongside the quantitative results.

Criteria B: Data Analysis

4/6

Criteria StrandsPro

B.1Communication of data recording and processing

Good

B.2Consideration of uncertainties

Moderate

B.3Data processing quality

Good

Criteria Feedback

The student's raw data are clearly organized and easy to follow across all trials and concentrations.
The student processes the data in a relevant way by calculating mass loss, means, standard deviations, and a graph with error bars.
The student includes a statistical test that is appropriate for comparing multiple groups.

Some values are reported with more precision than the measurement system justifies.
The treatment of uncertainty is only partly accurate, especially for derived mass-loss values.
The analysis does not fully address assumptions, measurement bias, or the limitations of using a final mass only.

2.1·Strength

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The raw-data summary is clear and easy to follow: the student identifies the extreme values and immediately interprets what they mean. This is effective because it helps the reader see the trend before moving into processed data.

2.2·Weakness

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This claim is too strong. Small, orderly data do suggest consistency, but they do not automatically prove reliability, especially when the measurement process may include filtration or moisture-residue effects. The student should distinguish between low spread in the data and true validity of the method.

2.3·Strength

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Including the definitions before the calculations makes the processing easier to follow for the reader. It shows that the student is trying to communicate the statistical steps rather than simply presenting final numbers.

2.4·Weakness

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The trend is communicated well, but this conclusion overstates what the graph alone can prove. Non-overlapping standard-deviation bars suggest separation between groups, yet they do not by themselves establish reliability or eliminate measurement bias.

2.5·Weakness

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This interpretation is incorrect: standard deviation measures spread or precision, not accuracy. The student should rewrite this to say the data are tightly clustered, then discuss accuracy separately using the balance resolution and the possibility of systematic error.

2.6·Weakness

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This is an appropriate test for comparing multiple group means, but the report should also acknowledge the assumptions behind ANOVA and whether they were checked. Without that, the statistical processing is only partly justified.

2.7·Suggestion

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The statistical result is correctly interpreted at the overall level, but the analysis would be stronger with post-hoc comparisons. That would show which specific concentration pairs differ, rather than only proving that at least one group is different.

Criteria C: Conclusion

4/6

Criteria StrandsPro

C.1Conclusion relevance and consistency

Good

C.2Scientific context comparison

Moderate

Criteria Feedback

The student's conclusion directly answers the research question and follows the overall trend in the results.
The student makes a relevant comparison to the accepted scientific context and uses it to support their interpretation.
The student shows some caution by acknowledging that small changes at low concentrations may have alternative explanations.

Some mechanistic claims go beyond what the student's data directly measure.
The comparison to human enamel is too strong unless it is more carefully qualified.
The conclusion is consistent with the data overall, but not every interpretive step is fully supported by the evidence the student collected.

3.1·Strength

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The conclusion is well linked to the analysis because it restates the observed trend and offers a biologically plausible mechanism. This helps the reader see how the data were interpreted rather than merely repeated.

3.2·Weakness

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This comparison goes beyond what the evidence supports. The student did not measure reaction rate directly or demonstrate a saturation curve, so the Michaelis-Menten claim should be presented more cautiously, or removed unless supported by additional data.

3.3·Suggestion

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The scientific-context comparison would be stronger if the student also compared other design features, such as fermentation time, bacterial conditions, and how mass was measured. That would make the contrast with the cited study more evidence-based and less general.

3.4·Weakness

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The leap from eggshell dissolution to human enamel erosion is too strong here. The student should qualify the claim by emphasizing the model limitation: the investigation suggests a relationship in powdered eggshells under fermentation, but it does not directly measure enamel erosion.

3.5·Question

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If these smallest changes are close to the method’s measurement limits, how confident can the student be that they represent real dissolution rather than procedural loss? This is worth reflecting on when judging how strongly the conclusion should be stated.

3.6·Strength

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This is a thoughtful qualification because it shows awareness of alternative explanations for the low-concentration results. That kind of caution strengthens the conclusion by preventing overinterpretation of small mass changes.

Criteria D: Evaluation

4/6

Criteria StrandsPro

D.1Methodological weaknesses

Good

D.2Improvements

Moderate

Criteria Feedback

The student identifies several specific limitations rather than relying on generic comments.
The student connects multiple weaknesses to likely effects on the results, which shows real evaluative thinking.
The student's improvement suggestions are realistic and often linked to the issues they identified.

The relative importance of the limitations is not always made clear.
Some improvements need more detail to show exactly how they would reduce error.
A few limitations that could strongly affect the measurements are not explored deeply enough.

4.1·Weakness

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This limitation is relevant, but the evaluation should explain its relative impact more clearly. The student should state whether the short duration mainly reduced fermentation, limited dissolution, or simply compressed the observable differences, so the reader can judge its seriousness.

4.2·Strength

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The evaluation is anchored by specific weaknesses rather than generic statements, which is a strong start. This gives the student a clear basis for improvement and shows that the evaluation is tied to the actual method used.

4.3·Weakness

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This is a useful limitation, but the discussion is still incomplete because it does not connect the likely mass loss to the size of the error. The student should explain whether the missing powder would systematically lower every final mass and therefore bias the trend.

4.4·Suggestion

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The extension is interesting, but it would be more valuable if it were framed as a direct follow-up to the current limitations and findings. The student should show how the new investigation would build on the present data rather than just introducing a new topic.

4.5·Suggestion

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This improvement is relevant, but it needs to be more specific to be useful. The student should state how the filtrate would be handled, whether the residue would be dried to constant mass, and what filter pore size would be appropriate to prevent loss of fine powder.

4.6·Suggestion

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This is a realistic improvement, and it would be even stronger if the student explained how the stirring time or speed would be standardized across all trials. That would make the proposed fix clearly tied to reducing random variation.

4.7·Weakness

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The issue is identified well, but the student should say how much this matters relative to the other limitations. Uneven stirring could change exposure to fermentation products, yet its effect may be smaller than filtration loss or wet-mass error, so prioritizing the limitations would improve the evaluation.

Loading scores...

Official IB Result

17/24

Criteria A: Research Design

5/6

Criteria StrandsPro

A.1Research question context

Excellent

A.2Methodological considerations

Good

A.3Methodology description

Moderate

Criteria Feedback

The student's research question is highly focused and clearly framed within a specific biological context.
The student justifies the investigation with a coherent rationale and shows awareness of the model system’s relevance and limits.
The student's method includes several important controls, repeats, and a logical sequence that mostly allows the investigation to be followed.
The student shows thoughtful refinement from preliminary testing, which strengthens the design.

Some important procedural details are still missing, especially around the bacterial culture, particle size, and drying procedure.
There is an internal inconsistency in the stated incubation temperature.
A few design choices are described but not fully explained, which leaves some ambiguity about reproducibility.

1.1·Strength

Page 1• Click to view

1.2·Strength

Page 2• Click to view

1.3·Suggestion

Page 6• Click to view

1.4·Strength

Page 6• Click to view

1.5·Weakness

Page 7• Click to view

1.6·Weakness

Page 8• Click to view

1.7·Weakness

Page 11• Click to view

1.8·Suggestion

Page 11• Click to view

1.9·Weakness

Page 11• Click to view

1.10·Question

Page 12• Click to view

1.11·Weakness

Page 12• Click to view

1.12·Suggestion

Page 13• Click to view

Criteria B: Data Analysis

4/6

Criteria StrandsPro

B.1Communication of data recording and processing

Good

B.2Consideration of uncertainties

Moderate

B.3Data processing quality

Good

Criteria Feedback

The student's raw data are clearly organized and easy to follow across all trials and concentrations.
The student processes the data in a relevant way by calculating mass loss, means, standard deviations, and a graph with error bars.
The student includes a statistical test that is appropriate for comparing multiple groups.

Some values are reported with more precision than the measurement system justifies.
The treatment of uncertainty is only partly accurate, especially for derived mass-loss values.
The analysis does not fully address assumptions, measurement bias, or the limitations of using a final mass only.

2.1·Strength

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2.2·Weakness

Page 14• Click to view

2.3·Strength

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2.4·Weakness

Page 17• Click to view

2.5·Weakness

Page 17• Click to view

2.6·Weakness

Page 18• Click to view

2.7·Suggestion

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Criteria C: Conclusion

4/6

Criteria StrandsPro

C.1Conclusion relevance and consistency

Good

C.2Scientific context comparison

Moderate

Criteria Feedback

The student's conclusion directly answers the research question and follows the overall trend in the results.
The student makes a relevant comparison to the accepted scientific context and uses it to support their interpretation.
The student shows some caution by acknowledging that small changes at low concentrations may have alternative explanations.

Some mechanistic claims go beyond what the student's data directly measure.
The comparison to human enamel is too strong unless it is more carefully qualified.
The conclusion is consistent with the data overall, but not every interpretive step is fully supported by the evidence the student collected.

3.1·Strength

Page 19• Click to view

3.2·Weakness

Page 19• Click to view

3.3·Suggestion

Page 20• Click to view

3.4·Weakness

Page 20• Click to view

3.5·Question

Page 20• Click to view

3.6·Strength

Page 20• Click to view

Criteria D: Evaluation

4/6

Criteria StrandsPro

D.1Methodological weaknesses

Good

D.2Improvements

Moderate

Criteria Feedback

The student identifies several specific limitations rather than relying on generic comments.
The student connects multiple weaknesses to likely effects on the results, which shows real evaluative thinking.
The student's improvement suggestions are realistic and often linked to the issues they identified.

The relative importance of the limitations is not always made clear.
Some improvements need more detail to show exactly how they would reduce error.
A few limitations that could strongly affect the measurements are not explored deeply enough.

4.1·Weakness

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4.2·Strength

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4.3·Weakness

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4.4·Suggestion

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4.5·Suggestion

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4.6·Suggestion

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4.7·Weakness

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