A-LevelBiologyTransport in plants9700/33 · May/June 2024 · Q218 Marks

L1 is a slide of a stained transverse section through a plant stem.

(a)(i)Draw a large plan diagram of the whole section on L1. Use a sharp pencil. Use one ruled label line and label to identify the cortex.[5]
(a)(ii)Observe the cells in the cortex on the section of the stem on L1. Select a group of four adjacent cortex cells. Each cell must touch at least two other cells. • Make a large drawing of this group of four cortex cells. • Use one ruled label line and label to identify the cell wall of one cortex cell.[5]
(b)Fig. 2.1 is a photomicrograph of a stained transverse section through a different plant. [Figure 2.1] Identify three observable features, other than colour, that are different between the section on L1 and the section in Fig. 2.1. Record the differences between these three observable features in Table 2.1. Table 2.1 feature L1 Fig. 2.1[4]
(c)Fig. 2.2 is the same photomicrograph as that shown in Fig. 2.1. [Figure 2.2] magnification ×40 Determine the mean actual diameter of the stem in Fig. 2.2. Show your working. mean actual diameter ...........................................................[4]

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Mark scheme

Marking points from the official mark scheme (May/June 2024). The mark or mark type is shown in brackets.

[1] uses most of the available space and no shading ;
[2] draws the correct shape of the whole section and no cells included ;
[3] draws a correct number of tissue layers ;
[4] draws the epidermis as two lines;
[5] label line and label to the cortex ;
[1] uses most of the available space and lines continuous, thin and sharp ;
[2] draws only four cortex cells and each cell touches at least two other cells ;
[3] two lines around each cell and three lines where cells touch ;
[4] detailed shapes of the cortex cells ;
[5] label line and label to the cell wall;
[1] records only observable differences ;
[2] three correct differences between L1 and Fig. 2.1 ;;; e.g. feature L1 Fig. 2.1 shape of section oval wavy number of tissue layers more fewer position of vascular bundles arranged in a circle scattered size of vascular bundles all the same size some large and some small
[1] takes at least two measurements and uses appropriate units ;
[2] shows addition of least two measurements and division by the number of measurements ;
[3] shows the mean measurement divided by the magnification (× 40) ;
[4] correct answer and uses appropriate units ;

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