A-LevelBiologyTransport in plants9700/32 · May/June 2019 · Q219 Marks

M1 is a slide of a stained transverse section through a plant organ. You are not expected to be familiar with this specimen.

(a)(i)Select a field of view so that you can observe: • the epidermis • at least three vascular bundles. Use a sharp pencil for drawings. You are expected to draw the correct shape and proportions of the different tissues. Draw a large plan diagram from the selected field of view which has: • part of the epidermis • only three vascular bundles • any other observable tissues. Use one ruled label line and label to identify the epidermis.[5]
(a)(ii)Observe the epidermis of the organ on M1. Select two epidermal cells and two adjacent, touching cells on the layer below the epidermis. Each cell must touch at least two other cells. Make a large drawing of this group 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 an organ from a different species. You are not expected to be familiar with this specimen. [Figure 2.1] magnification x20 Identify the organ shown in Fig. 2.1. Describe one observable feature that supports your identification. name of organ.. feature..[1]
(b)(ii)Use the magnification and the line Z on Fig. 2.1 to calculate the actual length of the vascular bundle. Show all the steps in your working and use appropriate units. actual length of the vascular bundle = [5]
(b)(iii)State the apparatus that you would use with a microscope to measure the actual length of a vascular bundle in the organ on M1.[1]
(c)Identify the observable differences between the organ on M1 and the organ shown in Fig. 2.1. Record the observable differences in Table 2.1. Table 2.1 feature M1 Fig. 2.1 [2]

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 2019). The mark or mark type is shown in brackets.

[5] 1. minimum size + at least two layers of tissue; 2. draws part of stem + only three vascular bundles ; 3. correct proportion of vascular tissue to the width of the plant organ; 4. draws at least three layers of tissue; 5. label line and label to identify the epidermis ;
[5] 1. minimum cell size + lines thin and continuous; 2. draws only four cells + each cell touching at least two others; 3. draws two epidermal cells + two adjacent cells on the layer below the epidermis ; 4. two lines drawn around each cell, three lines where cells touch; 5. label line and label to identify the cell wall;
[1] organ identified as a stem + one observable feature supporting identification e.g. vascular bundles located around outside/near the epidermis ;
[5] 1. uses line Z to measure the length of the vascular bundle within range; 2. show conversion from mm to μm (×1000); 3. shows division by 20; 4. decides to give answer in μm or mm ; 5. answer stated to the appropriate degree of accuracy;
[1] graticule or stage micrometer;
[2] records two observable differences between M1 and Fig. 2.1 ; ; e.g. M1 has fewer vascular bundles than Fig. 2.1 M1 has scattered vascular tissue while in Fig. 2.1 it is located towards the epidermis