A-LevelBiologyTransport in plants9700/31 · May/June 2019 · Q218 Marks

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

(a)(i)Draw a large plan diagram of the whole root. Use one ruled label line and label to identify the epidermis.[5]
(a)(ii)Observe the cells in the cortex of the root on J1. Select four adjacent, touching cells which show observable features of the cortex tissue. Each cell must touch at least two 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)Annotate Fig. 2.1 to describe three observable differences between the root in Fig. 2.1 and the root on J1. • Draw label lines to three features of the root in Fig. 2.1 that are different from the root on J1. • Label one line Q, label one line R and label one line S. • Next to each letter, describe how each feature of the root in Fig. 2.1 differs from the root on J1.[3]
(b)(ii)Use the scale bar and the line Z on Fig. 2.1 to calculate the actual width of the root. Show all the steps in your working and use appropriate units. actual width of the root = .......................................................................[5]

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Mark scheme

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

J1 is TS Maize root
[5] 1. minimum size + no shading + no cells ;
2. whole root drawn + at least 3 lines;
3. correct root shape + at least 5 lines across width of section from the centre of drawing;
4. correct proportion of the diameter of the central region to the total diameter of the root ;
5. label line and label to epidermis ;
[5] 1. lines continuous, thin and sharp + minimum size ;
2. draws only 4 whole cells + each cell touching at least two of the other cells ;
3. cell wall drawn as two lines + 3 lines where two cells touch;
4. shows an air space between cells ;
5. label line and label to cell wall;
[3] annotates 3 correct features on Fig 2.1 using labels Q, R and S ; ; ;
e.g. Fig 2.1 xylem tissue arranged in a cross shape, J1 arranged in a ring
[5] 1. correct measurement of the scale bar + units ;
2. correct measurement of length of line Z + units ;
method A mp 3 scale bar measurement multiplied by 1000 + divided by 273; mp 4 displays measurement of line Z + divided by magnification ;
method B mp 3 length of line Z divided by length of the scale bar; if line Z or the scale bar has been converted it must be shown mp 4 answer to mp3 multiplied by 273;
method C mp 3 (1 mm =) 273 divided by scale bar length ; if a conversion of units is done it must be shown mp 4 answer to mp3 multiplied by length of Z;
5. correct answer + units ;

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