Temasek Sec 2024_Prelim_4E_BIO_P3_ANS

2024 TMS Biology Practical Prelims Mark Scheme (6093/03) Qn Description Marks 1a Time/ min Height of markings/mm Average height of markings/ mm First reading Second reading 0 0 0 0 1 11 13 12 2 18 19 19 3 22 24 23 4 26 29 28 5 29 32 31 6 32 35 34 Note: Trend to be observed: Curve/ not straight line 1)Heads/ unit = 1m 2)7 data sets = 1m 3)Nearest mm = 1m 4)2 sets of readings = 1m 1b Axis =1m Plots = 1m Scale = 1m Best fit line = 1m 1c Rate of uptake of coloured water at t = 1.5m R = 25.5 – 6.5 / 2.9-0.1 = 19/2.8 = 6.79mm/min (3sf) or (6.8mm/min (1d.p) Working = 1m Final answer =1m

• Show coordinates on graph • Working 1d Coloured water travelled up the whole chalk but in xylem vessels of celery stem. 1m 1e(i) Source of error: Uneven horizontal level of coloured water; Explanation: subjective decision in marking the level of coloured water, leading to inaccurate readings. Source of error: chalk particles may not be evenly packed Explanation: rate of water uptake in the chalk is uneven, resulting in inaccurate readings. 1m 1m 1m 1m 1f To ensure reliability of the results. 1m 1g Independent Variable: different fan speed • fan speed (5 different speeds)/ • place fan at varying distance to the apparatus (5 variations – 20cm intervals x 5 distances within fixed fan speed.) Dependent Variable: height of water in the test tube after a fixed duration. Constant variable: • same set up as in Fig. 1.3, • duration of experiment (fixed time) e.g. 30 mins/ 1 hour Method: 1. Set up the apparatus as in Fig.1.3 and place the electric fan at a fixed distance (1.2m) from the leafy twig. 2. Measure the initial height of water in the tube. 3. Measure the water loss water loss after 30 min. 4. Repeat Step 1 to 4 for 4 other distances (each at 20 cm distance apart i.e. 1.0m, 0.8m, 0.6m, 0.4m) 5. Calculate the rate of water loss by taking difference in height of water per min. 6. Plot a graph of rate of water loss against distance. 7. Draw a conclusion on how difference distances would affect the rate of transpiration via rate of water loss from twig. E.g. the higher the rate of water loss, the higher the rate of transpiration. 1 m for correct variable IV/DV / Constant variables can also be picked up from procedures, as long as clear description of how IV is varied. 2 m for correct design/procedure 1 m to show how the interpretation of results would be.

Reliability: Repeat the investigation and take average of the readings. Alternative: • Set up as in Fig. 1.3 • A fan is positioned at the same distance to the twig (e.g. 1m) for varying fan speeds. • The speed of fan at which gives the greatest rate of water loss, would have the highest rate of transpiration. Other suggestions: IV: 1 with fan, 1 without fan, 1 in enclosed area 1 m to show how to ensure reliability 2a(i) Drawing of eye