Dunman 6093 Prelims Paper 3 MS 2026

DUNMAN SECONDARY SCHOOL PRELIMINARY EXAMINATION 2026 - SECONDARY 4 EXPRESS BIOLOGY 6093/03 (MARKING SCHEME) Question Marking scheme 1 (a) (i) 2% x 2.5 = 0.05 0.05 / 10 * 100 = 0.5 % [1] (ii) beaker percentage concentration of amylase solution / % time taken for start to be broken down / minutes A 2.0 5 B 1.5 6 C 1.0 8 D 0.5 > 8 U 1.5 [1] 6 • suitable table with minimum two columns (ie. beaker or percentage concentration amylase AND time / minutes) [1] • suitable headings with correct units [1] • five results recorded [1] • trend: A is faster than U [1] (iii) iodine solution added to the mixture remained yellow-brown / did not change to blue- black [1] (iv) value of U in the table [1] (v) method: • To a volume of sample, add equal volume of Benedict’s solution [1] • Place it in a boling water bath for 2 - 3 minutes [1] positive test result: • green / yellow / orange / brick-red / red precipitate is formed in the presence of reducing sugar [1] U

(b) independent variable: 1 select at least five different temperatures in which seeds are allowed to germinate (i.e. 20°C, 30°C, 40°C, 50°C, 60°C) method: 2 method of maintaining a constant temperature (i.e. greenhouse / enclosed room etc) 3 allow time for seeds to germinate (i.e. 1 week) 4 description of making seed extract (i.e. grinding seeds / AW) dependant variable: 5 test the seed extract with Benedict’s solution and record the time taken for reducing sugar to appear Accept: alternative method for data collection (i.e. use iodine solution AND record time taken for starch to be broken down / colour change of reagent instead of time taken / time taken for germination of seeds 6 and 7 are variables kept constant (max 2): • age / type / species, of seed • time of germination allowed • growing conditions / environmental factors • volume / mass, of extract / seeds • concentration of extract / amylase • volume / concentration of Benedict’s / iodine solution • pH of soil results analysis: 8 Plot a graph of time taken against temperature and draw a trend line to see the relationship between temperature and activity of amylase in germinating seeds. 9 repeat the experiment 3 times / allow 3 seeds to germinate at each temperature to increase reliability of results Any six points [6]

(c) (i) • Scale: appropriate scale – [1] • Line: line of best fit or points joined with ruled lines [1] • Axes: correct title and units [1] • Plot: correct plotting of data points [1] (ii) • As time increases day 0 to 12, activity of amylase increases from 0 to 240 arbitrary units. From day 12 to 16, activity of amylase decreases from 240 to 65 arbitrary units. [1] • Between day 16 and 24, activity of amylase remains constant at 240 arbitrary units. [1] (d) (i) • no peak in the graph • values at day 12 and day 16 are the same • the intervals between recordings were too large • there are no readings on day 13, 14 and 15 any one point [1] (ii) measure activity of amylase daily / at narrower intervals / between day 12 and day 16 / measure on day 13, 14 and 15 [1] 2 (a) (i) • clear, continuous outlines; no broken / sketchy lines [1] • correct proportion and large size (at least the width of the image) [1] • detail 1: six seeds shown and two openings without seeds [1] • detail 2: indents in external shape at the top and on both sides [1] (ii) 84.5 mm [1] (±1 mm) (iii) actual diameter = 84.5 / 2.2 = 38.4 mm (to 3sf) [1] magnification = actual diameter of the persimmon fruit length of line PQ in Fig. 2.1 2.2 x = [1] 84.5 actual diameter

(b) (i) structure part of leaf function A stoma / stomata controls diffusion of gases between the atmosphere and air spaces inside the leaf B palisade mesophyll layer that carries out the highest rate of photosynthesis C cuticle reduces water loss from leaf surface D xylem transports water and ions to leaf cells E phloem transports sucrose by translocation every two correct [1] (ii) every two correct [1] (iii) • Stomata will be found on the upper surface of the leaf, [1] • so that they are exposed to air for gaseous exchange to occur. [1] OR • There will be more / larger intercellular air spaces. [1] • so that the leaf can be more buoyant and float. [1] (iv) • During the day, guard cells carry out photosynthesis as they contain chloroplasts to produce glucose. [1] • This lowers the water potential of guard cells causing water to enter by osmosis. [1] • Guard cells swell and become turgid pulling open the stoma as they have a thicker cell wall facing the stoma. [1] E A B C D