A-LevelBiologyCell structure9700/33 · May/June 2021 · Q221 Marks

L1 is a slide of a stained transverse section through a plant leaf. (a) Set up the microscope so that you can observe the section on L1. Use a sharp pencil for drawing.

(a)(i)Draw a large plan diagram of the whole section of the leaf on L1. Your drawing should show the correct shapes and proportions of the different tissues. Use one ruled label line and label to identify the palisade layer.[5]
(a)(ii)Observe the cells in the layer just below the epidermis of the section on L1. Select a line of four adjacent cells that make up this tissue. Each cell you draw must touch at least one of the other cells. • Make a large drawing of this line of four cells. • Use one ruled label line and label to identify the cell wall of one cell.[5]
(b)(i)Fig. 2.1 is a photomicrograph of a stained transverse section through a leaf of a different type of plant. [Figure 2.1] The leaf sections on L1 and in Fig. 2.1 are from plants that are adapted to grow in dry environments (xerophytic plants). Observe the leaf sections on L1 and in Fig. 2.1. • State one xerophytic feature that is visible on L1. • State one xerophytic feature visible in Fig. 2.1 that is a different feature from the one you have identified for L1.[2]
(b)(ii)Observe the vascular tissue on L1 and in Fig. 2.1. Identify one observable difference between the vascular tissue on L1 and in Fig. 2.1. Record the observable difference in Table 2.1. Table 2.1 feature, L1, Fig. 2.1 vascular tissue[1]
(c)(i)A scientist identifies five different types of tree in a forest, as shown in Table 2.2. Table 2.2 type of tree, percentage of total trees in the forest Juniperus excelsa (E), 10.5 Pinus pinea (P), 37.0 Cedrus libani (L), 5.0 Juniperus drupacea (D), 3.0 Pinus brutia (B), 44.5 Plot a bar chart of the data in Table 2.2 on the grid in Fig. 2.2. Use a sharp pencil for drawing bar charts. [Figure 2.2][4]
(c)(ii)The forest has a total of 2344 trees. Calculate the total number of Juniperus trees in the forest using the data in Table 2.2. Show your working. total number of Juniperus trees = .....................................................[4]

This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.

Mark scheme

Marking points from the official mark scheme (May/June 2021). The mark or mark type is shown in brackets.

[5] 1 uses most of the available space and at least three layers of tissue ;
[5] 2 draws whole leaf and no cells;
[5] 3 correct shape of leaf;
[5] 4 correct proportion of vascular tissue to width of leaf ;
[5] 5 label line and label to identify the palisade layer;
[5] 1 uses most of the available space and lines thin and continuous;
[5] 2 draws only four cells in a line and each cell touching at least one other cell ;
[5] 3 two lines drawn around each cell and three lines where cells touch ;
[5] 4 cells with thick walls;
[5] 5 label line and label to identify the cell wall ;
[2] (L1) thick cuticle or thick epidermal cell wall;
[2] (Fig.2.1) trichomes or sunken stomata ;
[1] any one from:
[1] feature: vascular tissue L1: one central in location circular in shape Fig.2.1: many in mid-rib and in a line V-shaped;
[4] 1 x-axis: type of tree and y-axis: percentage of total trees in the forest ;
[4] 2 x-axis has bars of the same width, evenly spaced and scale on y-axis: 10 to 2 cm, labelled at least every 2 cm ;
[4] 3 correct plotting of five bars;
[4] 4 five separate bars, with ruled horizontal lines and labelled correctly;
[4] 1 uses 13.5 (10.5 + 3.0);
[4] 2 shows division by 100;
[4] 3 shows multiplication by 2344 ;
[4] 4 correct answer to whole number ;