Biology Extended Essay Exemplar: How do aqueous and ethanolic… | RevisionDojo

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IB Biology SL Extended Essay Example

How do aqueous and ethanolic extracts of garlic (Allium sativum), neem (Azadirachta indica), and turmeric (Curcuma longa) differ in their antibacterial activity against Lactobacillus casei after incubation for 24 hours at 25°C, as measured by the mean radius of the zone of inhibition using the agar well diffusion method?SL

Official IB Result

IB Grade: A

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

Excellent

Criteria Feedback

The student communicates the investigation clearly and with strong biological context, so the reader can immediately understand what is being tested and why.
The student's research question is precise, operationally measurable, and tightly aligned with the method and data analysis.
The student justifies the methodological choices well, including the use of different solvents, solvent controls, and the agar diffusion approach.

The method is strong, but a few limitations reduce the very top level of completeness, such as the lack of inoculum standardization and unclear independence of replicate extract preparation.
The hypothesis is incomplete where it cuts off, so the expected pattern is not fully stated for all three plants.
Some procedural details, such as how comparable cultures were maintained across plates, could be explained more explicitly.

Criteria B: Knowledge and Understanding

5/6

Criteria StrandsPro

B.1Application of source material

Excellent

B.2Use of terminology and concepts

Excellent

Criteria Feedback

The student uses scientific source material in a relevant way to explain antibacterial mechanisms, solvent effects, and assay limitations.
The student's terminology is mostly accurate and consistently applied, including key terms related to diffusion, polarity, inhibition zones, and statistical analysis.
The student connects source material to the actual investigation instead of listing background information in isolation.

A few explanations are more confident than the evidence allows, especially where the report implies chemical composition has been verified without direct analysis.
Some biological claims would be stronger with an extra sentence linking structure and function more explicitly.
A small number of source-related claims would benefit from slightly more cautious wording.

Criteria C: Critical Thinking

10/12

Criteria StrandsPro

C.1Research analysis

Good

C.2Discussion and evaluation

Good

C.3Argument development

Good

Criteria Feedback

Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.
Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.

Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur.
Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.

Criteria D: Presentation

4/4

Criteria StrandsPro

D.1Structure appropriateness

Excellent

D.2Layout and formatting

Moderate

Criteria Feedback

Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.
Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.

Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur.
Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.

Loading scores...

Official IB Result

IB Grade: A

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

Excellent

Criteria Feedback

The student communicates the investigation clearly and with strong biological context, so the reader can immediately understand what is being tested and why.
The student's research question is precise, operationally measurable, and tightly aligned with the method and data analysis.
The student justifies the methodological choices well, including the use of different solvents, solvent controls, and the agar diffusion approach.

The method is strong, but a few limitations reduce the very top level of completeness, such as the lack of inoculum standardization and unclear independence of replicate extract preparation.
The hypothesis is incomplete where it cuts off, so the expected pattern is not fully stated for all three plants.
Some procedural details, such as how comparable cultures were maintained across plates, could be explained more explicitly.

Criteria B: Knowledge and Understanding

5/6

Criteria StrandsPro

B.1Application of source material

Excellent

B.2Use of terminology and concepts

Excellent

Criteria Feedback

The student uses scientific source material in a relevant way to explain antibacterial mechanisms, solvent effects, and assay limitations.
The student's terminology is mostly accurate and consistently applied, including key terms related to diffusion, polarity, inhibition zones, and statistical analysis.
The student connects source material to the actual investigation instead of listing background information in isolation.

A few explanations are more confident than the evidence allows, especially where the report implies chemical composition has been verified without direct analysis.
Some biological claims would be stronger with an extra sentence linking structure and function more explicitly.
A small number of source-related claims would benefit from slightly more cautious wording.

Criteria C: Critical Thinking

10/12

Criteria StrandsPro

C.1Research analysis

Good

C.2Discussion and evaluation

Good

C.3Argument development

Good

Criteria Feedback

Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.
Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.

Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur.
Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.

Criteria D: Presentation

4/4

Criteria StrandsPro

D.1Structure appropriateness

Excellent

D.2Layout and formatting

Moderate

Criteria Feedback

Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.
Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.

Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur.
Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.