Biology Extended Essay Exemplar: To what extent does temperature (5… | RevisionDojo

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IB Biology SL Extended Essay Example

To what extent does temperature (5 °C, 15 °C, 25 °C, 37 °C) affect the rate of lipase-mediated hydrolysis of milk triglycerides during neonatal hypothermia, quantified as the rate of change in absorbance per minute (ΔA/min) at 554 nm using spectrophotometry, and the Q₁₀ temperature coefficient across successive temperature intervals?SL

Official IB Result

27/34

Criteria A: Focus and Method

6/6

Criteria StrandsPro

A.1Topic communication and explanation

Excellent

A.2Research question formulation and focus

Excellent

A.3Methodology appropriateness and completeness

Moderate

Criteria Feedback

The student communicates the scientific topic clearly and builds a logical link between temperature, lipase activity, and milk triglyceride hydrolysis.
The student's research question is specific, measurable, and tied to an experimentally workable investigation.
The student includes a relevant range of methods and controls, showing purposeful planning rather than a loosely assembled procedure.
The student shows awareness of temperature sensitivity as a biological concept and uses it to give the investigation a clear direction.

The biological framing sometimes stretches beyond what the in-vitro model can directly support.
Some parts of the explanation become broader than the experiment itself, which reduces precision.
The methodological rationale is good, but it is not always fully aligned with the exact assay the student used.
A few procedural details are inconsistent, which weakens the overall focus of the design.

1.1·Strength

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The research question is specific, measurable, and experimentally grounded. The student identifies the independent variable, temperature levels, the dependent variable, and the intended kinetic comparison, which gives the investigation a clear methodological direction.

1.2·Suggestion

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Consider tightening the real-world framing here so the focus stays on neonatal digestion rather than shifting to harp seals. A shorter, more directly relevant motivation would keep the inquiry sharper and make the link between the biology and the assay easier to justify.

1.3·Weakness

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The method choice is reasonable, but the justification is incomplete. The student should explain why this indicator-based assay is valid for the specific substrate system and acknowledge its indirect nature more explicitly, since phenolphthalein does not measure fatty-acid production directly.

1.4·Strength

Page 10• Click to view

This gives the investigation a clear conceptual route beyond a simple temperature comparison. By introducing

Q_{10}

, the student shows an attempt to quantify temperature sensitivity rather than relying only on descriptive trends.

1.5·Weakness

Page 12• Click to view

This claim is too strong for a buffered whole-milk system. The absorbance change is an indirect proxy for hydrolysis, so the student should qualify it as an estimate of activity rather than a direct stoichiometric measure of fatty-acid production.

1.6·Weakness

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The temperature range is understandable, but the phrase 'physiologically relevant' is too broad without qualification. The student should state that the setup is an in-vitro model of neonatal hypothermia rather than implying that the entire temperature range directly represents neonatal physiology.

1.7·Weakness

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The preparation of the enzyme solution is not fully reproducible because the starting mass or volume used from the 50,000 U/g stock is not stated. The student should show the exact amount taken from the stock and the final dilution calculations so the concentration can be verified.

1.8·Weakness

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This is internally inconsistent: a 10–100 µL pipette cannot measure 5.00 mL accurately. The student should replace this with suitable volumetric equipment and correct the uncertainty, because equipment choice affects the validity of the controlled variables.

1.9·Suggestion

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Consider explaining how aliquot removal was handled without changing the reaction volume or temperature too much. A brief note on whether each reading was from a separate parallel tube or the same tube would improve methodological clarity.

Criteria B: Knowledge and Understanding

4/6

Criteria StrandsPro

B.1Application of source material

Good

B.2Use of terminology and concepts

Good

Criteria Feedback

The student uses a wide range of biological ideas and terminology accurately in most places.
The student draws on source material beyond background information and uses it to support the investigation’s scientific context.
The student shows a solid understanding of enzyme action, temperature effects, and the general relevance of lipase in digestion.
The student demonstrates awareness that the model is simplified compared with real neonatal digestion.

Some source use is broader than the specific assay or neonatal context, so the support is not always tightly matched to the claim being made.
The indicator-based method is sometimes treated as if it directly measures fatty-acid production, which overstates what the setup can show.
The use of Beer–Lambert reasoning and Q10 terminology is not always technically secure.
Several concepts are understood in outline, but the precision of their application drops in the analytical sections.

2.1·Strength

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The background shows strong biological understanding and uses correct terminology to establish why the topic matters. This gives the essay a clear scientific rationale and helps connect thermoregulation to metabolism.

2.2·Strength

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This is a strong use of source-based biology: the student links structure to function and then connects that function to neonatal thermogenesis. The explanation shows accurate conceptual understanding rather than isolated factual recall.

2.3·Weakness

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This statement is relevant, but it is later not fully integrated into the experimental model. The student should return to this limitation more consistently when interpreting the in-vitro results, because the assay does not include bile salts or pancreatic secretions.

2.4·Weakness

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The concept is only partly secure here. The student should distinguish between an indicator-based pH change and direct measurement of fatty-acid release, because the current wording overstates the precision of the method.

2.5·Weakness

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The use of Beer–Lambert here is not fully justified. The student should explain why a change in absorbance in this complex milk mixture can be treated as a concentration change, and should define the variables correctly; as written, the equation and explanation are not accurate enough.

2.6·Weakness

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The formula is incomplete as written because it does not show the required rate ratio clearly and consistently. The student should rewrite the definition cleanly and ensure the notation matches the temperatures actually compared.

2.7·Suggestion

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This is a strong place to deepen the biology by briefly explaining which specific physiological cofactors most change the outcome and why. That would help the reader see exactly how the model differs from neonatal digestion rather than only stating that it differs.

Criteria C: Critical Thinking

9/12

Criteria StrandsPro

C.1Research analysis

Moderate

C.2Discussion and evaluation

Moderate

C.3Argument development

Moderate

Criteria Feedback

The student processes the data in a meaningful way by calculating rates, comparing conditions, and using graphs and statistics to support their interpretation.
The student's argument generally stays connected to the research question and shows a clear line from temperature changes to changes in measured activity.
The student evaluates the investigation thoughtfully by acknowledging limitations, alternative explanations, and the difference between the model and real neonatal digestion.
The student's conclusions are usually grounded in the trend they observed rather than being purely descriptive.

Some claims go beyond what the dataset can firmly support, especially where the analysis treats a small number of temperature means as strong proof.
The initial-rate interpretation is not fully demonstrated, so the claim about the linear region is not fully secure.
The statistical treatment and data interpretation would be stronger if the student addressed independence, assumptions, and the indirect nature of the measure more carefully.
A few conclusions are more confident than the evidence warrants, particularly where the student generalizes from a simplified assay to broader biological outcomes.

3.1·Weakness

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The claim that the first five minutes represent the linear region is not sufficiently demonstrated. The student should show evidence for the linear interval, because calling the whole 0–5 minute change 'initial velocity' is only valid if linearity is established.

3.2·Strength

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The analysis begins appropriately by processing raw measurements into rates that can be compared across temperatures. This is a sound analytical step because it moves the work beyond description and toward testable interpretation.

3.3·Weakness

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This interpretation is plausible, but the explanation overstates the certainty of the pattern from only four temperature means. The student should avoid implying causation from the graph alone and instead describe the graph as supporting an association under the assay conditions.

3.4·Weakness

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This is not adequately supported. The student would need direct evidence that substrate remained effectively constant over the interval before making that claim; otherwise, it should be presented as an assumption of the method, not a proven conclusion.

3.5·Weakness

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The statistical conclusion is underexplained because it does not address whether the ANOVA assumptions were met or whether the reported replicates were truly independent. The student should discuss independence and normality more carefully, since those issues affect the validity of the inference.

3.6·Weakness

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This conclusion is too linear and too general for the dataset. With only four temperatures, the student should avoid presenting the slope as a universal rule and should instead discuss the observed change within the tested range.

3.7·Weakness

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The interpretation of

R^{2}

is too strong. A high

R^{2}

shows fit, not that temperature is the 'primary predictor' or that other factors are unimportant; the student should use more cautious language.

3.8·Weakness

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The conclusion broadly follows the data, but it should be more tightly tied to the assay’s indirect nature. The student should explain that the evidence supports reduced indicator change in this system, which is interpreted as reduced hydrolysis rather than measured directly.

3.9·Suggestion

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This is an effective evaluative statement, and it could be even stronger if the student explicitly weighed how much the model still tells us about neonatal digestion. A brief judgement on the limits of transferability would sharpen the evaluation.

Criteria D: Presentation

4/4

Criteria StrandsPro

D.1Structure appropriateness

Good

D.2Layout and formatting

Moderate

Criteria Feedback

The report has a clear extended structure that helps the reader follow the investigation from introduction through conclusion.
The student's graphs, tables, and sectioning generally support the flow of the work and make the argument easier to navigate.
Key presentation features such as numbering, captions, and a contents page are mostly present.
The main body is organized in a logical sequence rather than feeling fragmented.

Some numbering and captioning are inconsistent, which reduces polish.
A few tables and figures are awkwardly placed or separated from the text they support.
Formatting choices are not always applied consistently across the report.
The layout is understandable, but not always clean or fully professional.

4.1·Weakness

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The indexing is not fully polished here because the numbering skips and the heading lacks a space after 'vii)'. The student should correct these small structural inconsistencies so the contents page reads cleanly and professionally.

4.2·Strength

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The report is organized in a clear extended-essay structure, with sections that guide the reader from background through method, analysis, and evaluation. This makes the overall line of inquiry easy to follow.

4.3·Strength

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The analysis section is signposted clearly, which helps the reader distinguish between raw observation, processing, and statistical interpretation. That separation improves navigability and supports the logic of the report.

4.4·Weakness

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The table and graph naming becomes confusing later in the report, with repeated figure labels and inconsistent numbering. The student should standardize the labels so every table and graph can be identified unambiguously.

4.5·Weakness

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This note shows awareness of a structural issue in the analysis section, which is good. However, the explanation should be incorporated more clearly into the main text so the reader does not have to infer how the interval difference affects the comparison.

4.6·Weakness

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The student would benefit from separating pure description from interpretation more explicitly in this section. Several sentences immediately move from what the graph shows to what it proves, and a clearer structure would make the argument easier to follow.

4.7·Suggestion

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The evaluation is well signposted. To improve clarity further, the student could add a short concluding sentence after the table summarizing which limitation was most significant, so the reader can see the overall judgement more easily.

Loading scores...

Official IB Result

27/34

Criteria A: Focus and Method

6/6

Criteria StrandsPro

A.1Topic communication and explanation

Excellent

A.2Research question formulation and focus

Excellent

A.3Methodology appropriateness and completeness

Moderate

Criteria Feedback

The student communicates the scientific topic clearly and builds a logical link between temperature, lipase activity, and milk triglyceride hydrolysis.
The student's research question is specific, measurable, and tied to an experimentally workable investigation.
The student includes a relevant range of methods and controls, showing purposeful planning rather than a loosely assembled procedure.
The student shows awareness of temperature sensitivity as a biological concept and uses it to give the investigation a clear direction.

The biological framing sometimes stretches beyond what the in-vitro model can directly support.
Some parts of the explanation become broader than the experiment itself, which reduces precision.
The methodological rationale is good, but it is not always fully aligned with the exact assay the student used.
A few procedural details are inconsistent, which weakens the overall focus of the design.

1.1·Strength

Page 1• Click to view

1.2·Suggestion

Page 3• Click to view

1.3·Weakness

Page 4• Click to view

1.4·Strength

Page 10• Click to view

This gives the investigation a clear conceptual route beyond a simple temperature comparison. By introducing

Q_{10}

, the student shows an attempt to quantify temperature sensitivity rather than relying only on descriptive trends.

1.5·Weakness

Page 12• Click to view

1.6·Weakness

Page 12• Click to view

1.7·Weakness

Page 14• Click to view

1.8·Weakness

Page 14• Click to view

1.9·Suggestion

Page 15• Click to view

Criteria B: Knowledge and Understanding

4/6

Criteria StrandsPro

B.1Application of source material

Good

B.2Use of terminology and concepts

Good

Criteria Feedback

The student uses a wide range of biological ideas and terminology accurately in most places.
The student draws on source material beyond background information and uses it to support the investigation’s scientific context.
The student shows a solid understanding of enzyme action, temperature effects, and the general relevance of lipase in digestion.
The student demonstrates awareness that the model is simplified compared with real neonatal digestion.

Some source use is broader than the specific assay or neonatal context, so the support is not always tightly matched to the claim being made.
The indicator-based method is sometimes treated as if it directly measures fatty-acid production, which overstates what the setup can show.
The use of Beer–Lambert reasoning and Q10 terminology is not always technically secure.
Several concepts are understood in outline, but the precision of their application drops in the analytical sections.

2.1·Strength

Page 3• Click to view

2.2·Strength

Page 7• Click to view

2.3·Weakness

Page 9• Click to view

2.4·Weakness

Page 12• Click to view

2.5·Weakness

Page 19• Click to view

2.6·Weakness

Page 20• Click to view

2.7·Suggestion

Page 31• Click to view

Criteria C: Critical Thinking

9/12

Criteria StrandsPro

C.1Research analysis

Moderate

C.2Discussion and evaluation

Moderate

C.3Argument development

Moderate

Criteria Feedback

The student processes the data in a meaningful way by calculating rates, comparing conditions, and using graphs and statistics to support their interpretation.
The student's argument generally stays connected to the research question and shows a clear line from temperature changes to changes in measured activity.
The student evaluates the investigation thoughtfully by acknowledging limitations, alternative explanations, and the difference between the model and real neonatal digestion.
The student's conclusions are usually grounded in the trend they observed rather than being purely descriptive.

Some claims go beyond what the dataset can firmly support, especially where the analysis treats a small number of temperature means as strong proof.
The initial-rate interpretation is not fully demonstrated, so the claim about the linear region is not fully secure.
The statistical treatment and data interpretation would be stronger if the student addressed independence, assumptions, and the indirect nature of the measure more carefully.
A few conclusions are more confident than the evidence warrants, particularly where the student generalizes from a simplified assay to broader biological outcomes.

3.1·Weakness

Page 18• Click to view

3.2·Strength

Page 18• Click to view

3.3·Weakness

Page 24• Click to view

3.4·Weakness

Page 25• Click to view

3.5·Weakness

Page 25• Click to view

3.6·Weakness

Page 25• Click to view

3.7·Weakness

Page 28• Click to view

The interpretation of

R^{2}

is too strong. A high

R^{2}

shows fit, not that temperature is the 'primary predictor' or that other factors are unimportant; the student should use more cautious language.

3.8·Weakness

Page 29• Click to view

3.9·Suggestion

Page 31• Click to view

Criteria D: Presentation

4/4

Criteria StrandsPro

D.1Structure appropriateness

Good

D.2Layout and formatting

Moderate

Criteria Feedback

The report has a clear extended structure that helps the reader follow the investigation from introduction through conclusion.
The student's graphs, tables, and sectioning generally support the flow of the work and make the argument easier to navigate.
Key presentation features such as numbering, captions, and a contents page are mostly present.
The main body is organized in a logical sequence rather than feeling fragmented.

Some numbering and captioning are inconsistent, which reduces polish.
A few tables and figures are awkwardly placed or separated from the text they support.
Formatting choices are not always applied consistently across the report.
The layout is understandable, but not always clean or fully professional.

4.1·Weakness

Page 2• Click to view

4.2·Strength

Page 3• Click to view

4.3·Strength

Page 18• Click to view

4.4·Weakness

Page 20• Click to view

4.5·Weakness

Page 22• Click to view

4.6·Weakness

Page 24• Click to view

4.7·Suggestion

Page 32• Click to view