Malaria is a disease caused by the protoctist, Plasmodium. The organism has a very complex life cycle as it has two hosts, a human and a mosquito. [Figure 3.1 is a transmission electron micrograph showing the developing Plasmodium cells inside a protective structure known as an oocyst. In this stage of the life cycle the oocysts are found in the mosquito gut. When mature, the Plasmodium cells are released and travel to the salivary glands of the mosquito. 20 μm]

Mark scheme

Marking points from the official mark scheme (May/June 2017). The mark or mark type is shown in brackets.

1. [1] (Plasmodium) falciparum/malariae / ovale / vivax ;
2. [1] Anopheles; I female / male I specific epithet e.g. gambiae
3. [1] higher / better / AW, resolution / resolving power ;
4. [1] 0.5nm (A 0.2–1 nm) compared to, 200nm 0.2m (A range 100–300nm) or electrons have shorter wavelength ; or R electron microscope has a shorter wavelength idea that cell structures too small to interfere with light waves ora
5. [1] better able to distinguish between two points ; A as a definition if mp 1 achieved
6. [1] (can see) more detail ; treat ‘clearer' as neutral
7. [1] able to make thinner sections / able to see inside (oocyst);
8. [1] can continue to obtain higher magnifications and see more detail;
9. [1] (magnification =) image/scale bar (length) actual/object (length) ; A triangle / letters only
10. [2] (x) 500 ;; using 10mm as measured length A calculated values for measured length of 9mm or 11mm allow one mark if correct answer given with units allow one mark if incorrect answer and correct measurement and correct working correct measurement and formula but incorrect conversion measurement ±2mm and correct working
11. [1] vector;
12. [1] ref. to feeding / taking / AW, blood (from a person); e.g. taking blood meals / Plasmodium enters blood during feeding
13. [1] infective cells / Plasmodium / pathogen / parasite / AW, enter (person) with, anticoagulant/ saliva; I malaria / disease, enters A idea that, infective cells / Plasmodium, in saliva / salivary glands
14. [1] AVP; e.g. ref. to providing correct conditions for, part of Plasmodium life cycle / sexual reproduction in Plasmodium