AQA · A-Level · Biology
Course version: 7402 · Version from Sept 2016
Students should be able to appreciate that there was a considerable period…
Full specification wording
Methods of studying cells: Students should be able to appreciate that there was a considerable period of time during which the scientific community distinguished between artefacts and cell organelles.
An artefact is a structure visible in a prepared specimen that was not present in the living cell.
Checked against the AQA 7402 specification (opens in a new tab) on .
- Point 4 of 4
- 3 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
An artefact is a structure visible in a prepared specimen that was not present in the living cell. Air bubbles, folds in a section, scratches, debris and material precipitated by the fixative or stain all qualify. Preparing tissue for microscopy means killing, fixing, dehydrating, embedding, sectioning and staining it, and every one of those steps can add something that was never there or destroy something that was. When electron microscopy was new, biologists were seeing structures nobody had seen before and had no way of telling the real from the manufactured, so the existence of several organelles stayed disputed for years.
What earns the marks
- Defining an artefact as a structure produced during preparation that was not present in the living cell.
- A named cause: fixing, staining, dehydration, sectioning, or air bubbles and debris on the slide.
- The idea that a structure is accepted as real when it is seen repeatedly using different preparation techniques or different microscopes.
- The delay being explained by the need for independent repetition and scrutiny by other scientists before a claim is accepted.
- Recognising that electron microscopy requires more preparation than light microscopy, so more artefacts can be introduced.
Common mistakes and how to put them right
Defining an artefact as a mistake made by the scientist rather than a structure created by the preparation process.
Saying the problem was solved by using a higher magnification instead of by repeating with different techniques.
Assuming only electron microscopy creates artefacts, when squashes and stained slides produce them too.
Claiming one very clear image is enough to prove a structure is genuine.
Describing artefacts as structures the scientist imagined rather than ones genuinely visible in the specimen.
Exam tips
- Anchor your answer in preparation: name the step (fixing, staining, sectioning) that could have created the structure.
- When asked how scientists became confident, use the language of repeatability, different techniques and independent workers.
- This idea returns in practical questions, so use it when asked whether an unexpected structure on a slide is real.
Try the lesson
The start of the Methods of studying cells: Students should be able to appreciate that there was a considerable period of time during which the scientific community distinguished between artefacts and cell organelles. lesson, made from checked teaching notes for this specification point.
Have a go first
What is an artefact in microscopy?
Listen
An artefact is a structure visible in a prepared specimen that was not present in the living cell. Air bubbles, folds in a section, scratches, debris and material precipitated by the fixative or stain all qualify. Preparing tissue for microscopy means killing, fixing, dehydrating, embedding, sectioning and staining it, and every one of those steps can add something that was never there or destroy something that was. When electron microscopy was new, biologists were seeing structures nobody had seen before and had no way of telling the real from the manufactured, so the existence of several organelles stayed disputed for years. A strong answer earns marks for these points. defining an artefact as a structure produced during preparation that was not present in the living cell. a named cause: fixing, staining, dehydration, sectioning, or air bubbles and debris on the slide. the idea that a structure is accepted as real when it is seen repeatedly using different preparation techniques or different microscopes. the delay being explained by the need for independent repetition and scrutiny by other scientists before a claim is accepted. Exam tip: Anchor your answer in preparation: name the step (fixing, staining, sectioning) that could have created the structure.
Key words
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artefact
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specimen preparation
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acceptance of scientific evidence
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See every definition
- artefact
- A structure visible in a prepared specimen that was not present in the living cell, such as air bubbles, folds in a section, scratches, debris or material precipitated by the fixative or stain.
- specimen preparation
- Killing, fixing, dehydrating, embedding, sectioning and staining tissue for microscopy, where every step can add something that was never there or destroy something that was.
- acceptance of scientific evidence
- A claim is accepted only after independent repetition and scrutiny by other scientists, which explains the delay in accepting structures as real.
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