6093 Hua Yi 2024 Paper 3

[Turn Over HUA YI SECONDARY SCHOOL PRELIMINARY EXAM 2024 4-G3 NAME CLASS INDEX NUMBER BIOLOGY 6093/03 PAPER 3 (XX) 27 August 2024 1 hour 50 mins Additional Materials: Nil READ THESE INSTRUCTIONS FIRST Write your Name, Class, and Index Number on all the work you hand in. Write in dark blue or black pen. You may use an HB pencil for any diagrams, graphs or rough working. The use of an approved scientific calculator is expected, where appropriate. Do not use staples, paper clips, highlighters, glue, or correction fluid. Answer all questions. The number of marks is given in brackets [ ] at the end of each question or part question. The use of an approved scientific calculator is expected, where appropriate. You may lose marks if you do not show your working or if you do not use appropriate units. Total 40 This document consists of 12 printed pages. © HYSS 2024 No part of this document may be reproduced in any form or transmitted in any form or by any means without the prior permission of Hua Yi Secondary School. Setter: Mr Edwin Khoo

2 2024_4-G3_ PRELIMS_ BIOLOGY _PAPER 3 You are advised to read the whole question before you start. 1 Fig. 1.1 shows an African elephant. African elephants do not sweat and do not pant. Under the savanna sun , one main cooling mechanism for African elephants occurs through their large ear. Fig. 1.1 Blood flow to the elephant’s ears is changed in response to its body temperature, similar to the way that blood flow towards the skin of a human is changed during thermoregulation. You will investigate how this cooling mechanism affects the rate of heat loss. The ears of the elephant are represented by two plastic droppers. Step 1 Set up the apparatus as shown in Fig. 1.2 using the glass beaker provided. Step 2 Collect 200 cm3 of hot water in the glass beaker. Step 3 Measure and record the initial temperature of the water in the beaker. Step 4 Start the stopwatch. Step 5 Begin to squeeze and release the droppers so that they are emptied and filled with hot water. Continue to do this throughout the experiment. Step 6 Measure and record in (a) the temperature of the water in the beaker every minute for a total of eight minutes. beaker water thermometer plastic droppers with ‘ears’ Fig. 1.2 without ‘ears’ Fig. 1.3

3 2024_4-G3_ PRELIMS_ BIOLOGY _PAPER 3 Step 7 Repeat Steps 1 to 6 for the beaker without ears by setting up the apparatus as shown in Fig. 1.3. (a) Record your results in a table. [3]

4 2024_4-G3_ PRELIMS_ BIOLOGY _PAPER 3 (b) Plot a graph to show how the temperature of each set up changed over time. Draw lines of best fit for your graph. [4] (c) (i) Suggest what the gradient of the graph represents. ………………………………………………………………………………………... [1] (ii) Using the graph in (b), comment on the effectiveness of the droppers as a cooling mechanism. ………………………………………………………………………………………... ………………………………………………………………………………………... ………………………………………………………………………………………... [2]

5 2024_4-G3_ PRELIMS_ BIOLOGY _PAPER 3 (d) Suggest how this experiment may not accurately reflect how elephants lose heat through their ears. ……………………………………………………………………………………………….. ……………………………………………………………………………………………….. [1] (e) Fig.1.4 is a picture of an adult elephant with a juvenile elephant. Fig. 1.4 (i) Using the grid provided, estimate the area of the ear of the juvenile and the adult. Assume the area of one square to be 1 unit2. ear area (juvenile): …………………….. unit2 ear area (adult): …………………….. unit2 [1] (ii) Using the grid provided, estimate the area of the entire juvenile and adult elephant. Assume the area of one square to be 1 unit2. ear area (juvenile): …………………….. unit2 ear area (adult): …………………….. unit2 [1]

6 2024_4-G3_ PRELIMS_ BIOLOGY _PAPER 3 (iii) Express the proportion of ear area to body area as a percentage for the juvenile and adult elephant. percentage of ear to body area (juvenile): …………………….. % percentage of ear to body area (adult): …………………….. % [1] (iv) Using the information in (iii), predict the ability of the juvenile elephant to cool down its body as compared to the adult elephant. ………………………………………………………………………………………... [1] (v) Make modifications to the experiment shown in Fig. 1.1 and 1.2 so that it can test the prediction that you made in (f)(iv). Clearly show how it can test your prediction. ………………………………………………………………………………………... ………………………………………………………………………………………... ………………………………………………………………………………………... ………………………………………………………………………………………... ………………………………………………………………………………………... ………………………………………………………………………………………... ………………………………………………………………………………………... ………………………………………………………………………………………... ………………………………………………………………………………………... ………………………………………………………………………………………... ………………………………………………………………………………………... ………………………………………………………………………………………... ………………………………………………………………………………………... [5] [Total: 25]

7 2024_4-G3_ PRELIMS_ BIOLOGY _PAPER 3 2 Aquatic plants live in water and exchange gases with the water around them. When carbon dioxide dissolves in water, the solution becomes more acidic. Hydrogencarbonate indicator (bicarbonate indicator) can be used to detect changes in the pH of a solution. It changes colour as follows: most acidic most alkaline yellow red purple You will be investigating the gas exchange of two pieces of an aquatic plant using hydrogencarbonate indicator. Step 1 Add 5 cm3 of hydrogencarbonate indicator into a measuring cylinder. Step 2 Add 30 cm3 of distilled water into the measuring cylinder. Stir the solution with the glass rod. The resulting solution is the dilute hydrogencarbonate indicator that will be used for the experiment. Fig. 2.1 Step 3 Place one piece of the plant in a test tube and carefully push it down so that one end touches the bottom of the test tube as shown in the Fig. 2.1. Label this test tube A. Step 4 Pour the dilute hydrogencarbonate indicator prepared in Step 2 into test tube A. Ensure that the plant is completely submerged in the indicator. Record the volume of indicator added into test tube A. volume of indicator added = ………………….. cm3 Step 5 Place the second piece of plant in another test tube and carefully push it down so that one end touches the bottom of the test tube. Label this test tube B. Step 6 Add the same volume of indicator that you added to test tube A, ensuring the plant is completely submerged. Step 7 Wrap aluminium foil around test tube B completely to prevent any light from entering.

8 2024_4-G3_ PRELIMS_ BIOLOGY _PAPER 3 Step 8 Place both test tubes together on a test tube rack, approximately 10 cm away from a lamp. Turn on the lamp and start the stopwatch. Step 9 Leave test tubes A and B for 30 minutes. Step 10 Set up a control by adding the same volume of hydrogencarbonate indicator into test tube C. Place test tube C on the test tube rack. Step 11 At the end of 30 minutes, decant the indicator solutions in A and B into clean test tubes. Record observations of the colour of the indicator in these two test tubes in Table 2.1. (a) Record your results for test tube A and B in Table 2.1. Table 2.1 test tube initial colour of hydrogen carbonate indicator final colour of hydrogen carbonate indicator A B [1] (b) Explain the difference in results for test tubes A and B. ………………………………………………………………………………………………..