DP Biology (last assessment 2024)

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Question 23M.3.SL.TZ1.6

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Date May 2023 Marks available [Maximum mark: 4] Reference code 23M.3.SL.TZ1.6
Level SL Paper 3 Time zone TZ1
Command term Explain, Outline Question number 6 Adapted from N/A
6.
[Maximum mark: 4]
23M.3.SL.TZ1.6

The fMRI scan shows a human brain.

[Source: DrOONeil, 2014. FMRI Brain Scan. [image online]
Available at: https://commons.wikimedia.org/wiki/File:FMRI_Brain_Scan.jpg
[Accessed 26 January 2022]. Public domain.]

(a)

On the diagram, label the cerebellum.

[1]

Markscheme

[Source: DrOONeil, 2014. FMRI Brain Scan. [image online]
Available at: https://commons.wikimedia.org/wiki/
File:FMRI_Brain_ Scan.jpg [Accessed 26 January 2022]. Public domain.]

Examiners report

Nearly all labelled the cerebellum correctly, several labelled the cerebral hemisphere.

(b)

Explain control of breathing rate by the structure labelled X.

[3]

Markscheme
  1. breathing centre in medulla (oblongata)/brain stem;
  2. operates via autonomic nervous system;
  3. blood pH reduced/more acidic (with increased carbon dioxide);
  4. (Medulla) causes deeper/faster breathing;
  5. expels more carbon dioxide from lungs/blood;
  6. raises pH of blood;

Accept inverse responses for decreased carbon dioxide (for mp c to f)

For mp d accept a valid mechanism

Examiners report

The medulla or brain stem was nearly always mentioned, but carbon dioxide receptors rather than pH. 3 marks were rarely awarded.