2025 NYJC H2 Bio 9744 P3 QP

NANYANG JUNIOR COLLEGE JC 2 PRELIMINARY EXAMINATION Higher 2 CANDIDATE NAME CLASS BIOLOGY 9744/03 Paper 3 Long Structured and Free-response Questions 19 September 2025 Additional Materials: Insert, Answer booklet 2 hours READ THESE INSTRUCTIONS FIRST Write your name and CT on all the work you hand in. Write in dark blue or black pen. You may use an HB pencil for any diagrams or graphs. Do not use staples, paper clips, highlighters, glue or correction fluid. Section A Answer all questions in the spaces provided on the Question Paper. Section B Answer any one question on the separate Answer Paper. 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 no use appropriate units. At the end of the examination, fasten all your work securely together. The number of marks is given in brackets [ ] at the end of each question or part question. For Examiner’s Use Section A 1 2 3 Section B Total This document consists of 17 printed pages and 1 blank page. [Turn over H

2 9744 / H2 Biology / 03 Section A Answer all the questions in this section. 1 Different types of respiratory substrate can have different energy values and therefore release different quantities of energy when they are respired. (a) Complete Table 1.1 to show the energy value of each of the three main types of respiratory substrate. Use one tick (√ ) to identify which of the two possible energy values is correct for each respiratory substrate. Table 1.1 [1] (b) Organic acids such as malic acid can also act as respiratory substrates. When respired aerobically, their repiratory quotient (RQ) values may be different to the RQ values of the main respiratory substrates. Fig. 1.1 shows the formula that is used to calulate RQ values. When malic acid is respired aerobically, the equation is: (i) Calculate how many molecules of oxygen are taken in when one molecule of malic acid is respired aerobically. number of molecules of oxygen = ......................................................... [1]

3 9744 / H2 Biology / 03 (ii) Calculate the RQ for malic acid. Give your answer to two decimal places. RQ = ......................................................... [1] (c) Determining the RQ of an organism can be used to indicate the main type of respiratory substrate that is being metabolised in respiration. This is because the different types of respiratory substrate have different RQ values. Table 1.2 shows typical RQ values for carbohydrate, lipid and protein. (i) State the name of the laboratory apparatus that can be used to determine the RQ value of organisms such as blowfly larvae. [1] (ii) When determining RQ values using the laboratory apparatus stated in (c)(i), chemicals such as soda lime or potassium hydroxide solution are used. State the reason for using chemicals such as soda lime or potassium hydroxide solution when measuring RQ values. [1]

4 9744 / H2 Biology / 03 (d) The deer mouse, Peromyscus maniculatus, lives in forests in North America. Fig. 1.2 shows a deer mouse. Fig 1.2 The deer mouse is active throughout the year and is much more active during the night than during the day. At certain times of the year, deer mice spend a number of hours during the day in a physiologically controlled state of inactivity (not active), known as torpor. During this time there is a decrease in metabolic rate. Fig. 1.3 is a graph showing the RQ of a deer mouse from 6:00 to 22:00 on a day that included time in torpor. Fig 1.3

5 9744 / H2 Biology / 03 (i) Describe the trend shown during torpor in Fig. 1.3 and suggest an explanation for this trend. [3] (ii) Deer mice have a daily period of torpor only at certain times of the year. Suggest reasons why a deer mouse enters torpor only at certain times of the year. [2]

6 9744 / H2 Biology / 03 Some deer mice may suffer from severe viral infections. (e) These deer mice have a genetic mutation in the gene Mx1/Mx2 which produces antiviral proteins to protect deer mice. With the deletion, mutated deer mice are prone to severe viral infections due to their inability to produce sufficient antiviral proteins. Polymerase chain reaction and electrophoresis are used to test whether the deer mouse has this mutation. If the mutation is found, a different treatment approach will be adopted. (i) Describe and explain the role of Taq polymerase in PCR. [4]

7 9744 / H2 Biology / 03 (ii) PCR with primers specific to the flanking sequences of Mx1/Mx2 genes are used to amplify DNA from the deer mouse that is being tested. The PCR primers are designed so that the amplified product of the normal allele of Mx1/Mx2 is longer than the amplified product of the mutant allele. Gel electrophoresis is used to separate the PCR products. Fig. 1.4 shows the results of gel electrophoresis after using this method of PCR on DNA samples collected from three deer mice. Fig. 1.4 State and explain which deer mouse/mice in Fig. 1.4 will probably die if infected with a severe viral infection. [2] Deer Deer Deer mouse 1 mouse 2 mouse 3

8 9744 / H2 Biology / 03 (iii) Explain how gel electrophoresis produces the pattern of results shown in Fig. 1. 4 from the PCR products of the Mx1/Mx2 genes. [4] Like the deer mouse, the orca (Orcinus orca) is an endotherm, maintaining a stable internal body temperature despite external fluctuations. The orca has a layer of blubber which is an energy rich fat layer with low thermal conductivity to conserve heat. The orca has the largest distribution of all aquatic mammals and is found in nearly all seas and oceans. Orcas are social mammals that usually live in groups. These groups can vary in size. Fig. 1.5 shows an orca. Fig 1.5 (f) There are two distinct types of orca in the Northeast Atlantic Ocean: Type 1 and Type 2. Type 1 orca feed mainly on fish. Type 2 orca feed mainly on aquatic mammals, such as seals. Fig. 1.6 shows the locations in the Northeast Atlantic Ocean where Type 1 orca and Type 2 orca have been observed. Orca do not occur only in these areas and some groups of orca travel great distances.

9 9744 / H2 Biology / 03 Fig 1.6 (i) With reference to Fig. 1.6, state and explain the type of speciation that is occuring among the orcas. [2] (ii) State the type of isolation mechanism and suggest two examples that would contribute to the type of speciation stated in f(i). [3]

10 9744 / H2 Biology / 03 (g) In the Southern Ocean, which surrounds Antarctica, there are three distinct types of orca: Type B, Type C and Type D. Fig. 1.7 shows the locations around Antarctica where Type B orca, Type C orca and Type D orca have been observed. • Type B orca and Type C orca are mainly seen near the coastline of Antarctica (inshore). • Type D orca are mainly seen in the Southern Ocean further away from the coastline of Antarctica (offshore). Fig 1.7