A-LevelBiologyCell structure9700/31 · Oct/Nov 2019 · Q219 Marks

J1 is a slide of a stained transverse section of a plant stem. You are not expected to be familiar with this specimen. Use a sharp pencil for drawing. You are expected to draw the correct shape and proportions of the different tissues.

(a)(i)Draw a large plan diagram of the sector shown in Fig. 2.1. Use one ruled label line and label to identify the epidermis. [Figure 2.1][5]
(a)(ii)Observe the cells from the central region (the pith) of the stem of J1. Select four adjacent, touching cells. Each cell must touch at least two of the other cells. Make a large drawing of this group of four touching cells. Use one ruled label line and label to identify the cell wall of one cell.[5]
(b)(i)Fig. 2.2 is a photomicrograph of a stained transverse section through a stem of a different type of plant. You are not expected to be familiar with this specimen. [Figure 2.2] Use the lines C–D, E–F and G–H to determine: • the mean diameter of the whole stem, as seen in the photomicrograph in Fig. 2.2. • the mean depth of the outer layer, as seen in the photomicrograph in Fig. 2.2. Show all the steps in your working. mean diameter of whole stem ............................................ mm mean depth of outer layer ............................................ mm[4]
(b)(ii)Use your answers to (b)(i) to determine the simplest whole number ratio of the mean diameter of the whole stem to the mean depth of the outer layer. simplest whole number ratio =[1]
(c)Prepare an appropriate table so that it is suitable for you to record observable differences between the stem on J1 and the stem in Fig. 2.2. Record the observable differences in your table.[4]

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Mark scheme

Marking points from the official mark scheme (Oct/Nov 2019). The mark or mark type is shown in brackets.

[5] 1. suitable size and no shading and no cells ;
[5] 2. draws correct sector ;
[5] 3. correct shape and distribution of tissues ;
[5] 4. correct proportions of tissues ;
[5] 5. label line and label to epidermis ;
[5] 1. lines continuous, thin and sharp ;
[5] 2. draws only four whole cells and each cell touches at least two other cells ;
[5] 3. two lines around each cell and three lines where cells touch ;
[5] 4. at least one cell with three or more angles ;
[5] 5. label line and label to one cell wall ;
[4] 1. measures and records length of C-D, E-F and G-H;
[4] 2. measures and records depth of six outer layers;
[4] 3. (for diameter) shows addition of three values and shows division by three and (for depth of outer layer) shows addition of six values and shows division by six ;
[4] 4. answers to correct degree of accuracy ;
[1] states answer as larger whole number to smaller whole number and simplest whole number ratio ;
[4] 1. organises comparison into three columns with one column for features and collects only differences ;
[4] any three from: Feature | J1 | Fig. 2.2
[4] size of vascular bundles | smaller | larger ;
[4] xylem | fewer | more ;
[4] phloem | fewer | more ;
[4] layers of cells around vascular tissue | two layers | one layer ;
[4] air spaces | present / more / larger | absent / less / smaller ;
[4] thickened layer beneath epidermis | present | absent ;
[4] cortex cells | fewer | more ;
[4] gaps in outer surface | present / more | absent / fewer ;
[4] AVP | described | described ;

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