SCGS Prelim 2025 Biology P2 QP

1 SINGAPORE CHINESE GIRLS’ SCHOOL PRELIMINARY EXAMINATION CANDIDATE NAME CLASS REGISTER NUMBER CENTRE NUMBER INDEX NUMBER BIOLOGY 6093/02 Paper 2 Friday, 22 August 2025 1 hour 45 minutes Candidates answer on the Question Paper. No Additional Materials are required. READ THESE INSTRUCTIONS FIRST Write your class, register number, centre number and index number and name 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. Do not use staples, paper clips, glue or correction fluid/tape. Section A Answer all questions. Write your answers in the spaces provided. Section B Answer one question. Write your answers in the spaces provided. The use of an approved scientific calculator is expected, where appropriate. The number of marks is given in brackets [ ] at the end of each question or part question. This question paper consists of 21 printed pages and 1 blank page. For Examiner’s Use Section A 70 Section B 10 Total 80

2 Section A Answer all questions. 1 Fig. 1.1 is a diagram of the alimentary canal in the human body. Letters A to K represent structures. Fig. 1.1 (a) State the letter from Fig. 1.1 that identifies the structure where [3] (i) alcohol is broken down .................................. (ii) egestion occurs .................................. (iii) most absorption of water occurs .................................. (b) Outline the role of structure H in the digestion of a named nutrient. [2] ……………………………………………………………………………………………... ……………………………………………………………………………………………... ……………………………………………………………………………………………...

3 (c) Disease-causing bacteria may enter the alimentary canal through contaminated food. State a letter from Fig. 1.1 to indicate the structure which acts as a barrier to these bacteria. Explain your answer. [2] ……………………………………………………………………………………………... ……………………………………………………………………………………………... ……………………………………………………………………………………………... [Total : 7]

4 2 Large quantities of plastic waste are polluting the oceans. A survey published in March 2018 showed the increase in plastic waste in the Pacific Ocean. One area of the Pacific Ocean is known as the Great Pacific Garbage Patch (GPGP). Data were collected from areas inside and outside the GPGP from 1965 to 2015 to estimate the quantity of plastic waste. The results are shown in Fig. 2.1. Fig. 2.1 (a) Describe the results of the survey from 1965 to 2015 as shown in Fig. 2.1. [3] ……………………………………………………………………………………………... ……………………………………………………………………………………………... ……………………………………………………………………………………………... ……………………………………………………………………………………………... ……………………………………………………………………………………………... ……………………………………………………………………………………………... ……………………………………………………………………………………………... ……………………………………………………………………………………………...

5 (b) The green turtle, Chelonia mydas, is a species of marine animal that is harmed by plastic waste. Fig. 2.2 shows a green turtle swimming past a plastic bag in the Pacific Ocean. Fig. 2.2 (i) Outline the dangers of non-biodegradable plastic waste to marine animals, such as green turtles. [2] …………………………………………………………………………………….. …………………………………………………………………………………….. …………………………………………………………………………………….. …………………………………………………………………………………….. (ii) Suggest two ways to reduce the quantity of plastic waste. [2] …………………………………………………………………………………….. …………………………………………………………………………………….. …………………………………………………………………………………….. …………………………………………………………………………………….. [Total : 7]

6 3 Antibodies are proteins that are produced by white blood cells. Antitoxins are antibodies which neutralise the toxins released by some bacteria. The transmissible disease diphtheria is caused by a bacterium that releases a toxin that can cause serious damage to the body. A person is suspected of having caught diphtheria. At a clinic, the person is given an injection of antitoxin antibodies that provide protection against the diphtheria toxin. She is also given an injection of the vaccine for diphtheria. A few weeks later she is given a second injection of the diphtheria vaccine. Fig. 3.1 shows the changes in concentration of the antitoxin antibodies and the antibodies produced in response to the vaccine. Fig. 3.1 (a) State the name of white blood cells that produce antibodies. [1] ……………………………………………………………………………………………... (b) List two advantages of giving the person an injection of antitoxin antibodies. [2] 1 …………………………………………………………………………………….. …………………………………………………………………………………….. 2 …………………………………………………………………………………….. ……………………………………………………………………………………..

7 (c) Suggest how the two injections of the vaccine result in better protection against diphtheria than the injection of antitoxin antibodies. [3] ……………………………………………………………………………………………... ……………………………………………………………………………………………... ……………………………………………………………………………………………... ……………………………………………………………………………………………... ……………………………………………………………………………………………... [Total : 6]

8 4 Enzymes are used in genetic engineering. (a) Define the term enzyme. [2] ……………………………………………………………………………………………... ……………………………………………………………………………………………... ……………………………………………………………………………………………... (b) The process of genetic engineering often starts with the steps shown in Fig. 4.1. Fig. 4.1 (i) Complete the sequence of bases on the lower strand of the DNA molecule in step 1. [1] upper DNA strand G A A T T C lower DNA strand (ii) State the name of enzyme 1 and describe its importance in genetic engineering. [3] …………………………………………………………………………………….. …………………………………………………………………………………….. …………………………………………………………………………………….. ……………………………………………………………………………………..

9 (c) Another enzyme, enzyme 2, is used later in the process of genetic engineering. Fig. 4.2 is a diagram showing the action of enzyme 2. Fig. 4.2 Using Fig. 4.2, explain the function of enzyme 2 in step 7 and describe the result seen in step 8. [2] ……………………………………………………………………………………………... ……………………………………………………………………………………………... ……………………………………………………………………………………………... [Total : 8]

10 5 (a) Events in the menstrual cycle related to the uterine lining are shown. Hormones play a part in these events. A uterine lining is shed out of the body B thickness of uterine lining remains constant C thickness of uterine lining continues to increase Using A to C, identify the events which involve named hormones in the menstrual cycle and describe their roles. [2] ……………………………………………………………………………………………... ……………………………………………………………………………………………... ……………………………………………………………………………………………... (b) Fig. 5.1 shows part of the female human reproductive system. Fig. 5.1 (i) State the names of the structures labelled X and Y on Fig. 5.1. [2] X ………………………………………………. Y ………………………………………………. (ii) Describe the early development of the zygote after fertilisation has occurred. [2] …………………………