T3W5 ZHSS 4E BIO Prelim P2 2023 A4 Final

[Turn over ZHONGHUA SECONDARY SCHOOL PRELIMINARY EXAMINATION 2023 SECONDARY 4 EXPRESS Candidate Name Class Register Number 4E5 BIOLOGY 6093 /02 14 September 2023 1 hour 45 minutes Additional Materials: Nil READ THESE INSTRUCTIONS FIRST Write your name, index number and class in the spaces at the top of this page. Write in dark blue or black pen. You may use a pencil for any diagrams, graphs or rough working. Do not use staples, paper clips, highlighters, glue or correction fluid. Section A Answer all questions. Write your answers in the spaces provided on the question paper. Section B For Examiner’s Use Answer all three questions, the last question is in the form Either/Or. Write your answers in the spaces provided. Section A 50 B7 10 You are advised to spend no longer than one hour on Section A and no longer than 45 minutes on Section B. B8 10 B9 E / O 10 The number of marks is given in brackets [ ] at the end of each question or part question. All essential working must be shown clearly. Total 80 This document consists of 20 printed pages.

2 Section A Answer all questions. Write your answers in the spaces provided. 1 A contractile vacuole is found in some unicellular organisms. It is a structure that periodically expands, filling with water, and then contracts, expelling its contents out of the cell. In an experiment, a marine unicellular organism was placed in several dilutions of seawater. The output rate of its contractile vacuole and changes in its body volume were measured and recorded. Fig. 1.1 shows the data collected during the experiment. Fig. 1.1 (a) Besides water, name another substance that can also enter the contractile vacuole. [1]

3 [Turn over (b) Describe and explain the effect on the rate of contractile vacuole output as the percentage of seawater increases from 20% to 100%. [3] (c) Describe one other relationship observed in Fig. 1.1 as the percentage of seawater increases from 20% to 100%. [1] (d) Suggest and explain what has happened to the marine unicellular organism at 10% seawater. [2] [Total: 7]

4 2 Fig. 2.1 shows the oxygen uptake before, during and after strenuous exercise. Fig. 2.1 Fig. 2.2 shows the lactic acid concentration in blood samples taken at different time intervals during and after exercise. Fig. 2.2 (a) (i) On Fig. 2.1, mark with the letter D, the area that shows oxygen deficit. [1] lactic acid / mMl-1 time / min

5 [Turn over (ii) State a reason for this oxygen deficit. [1] (b) With reference to Fig. 2.1 and Fig. 2.2, explain the rise in concentration of lactic acid in the blood. [3] (c) (i) On Fig. 2.2, draw a line to show the change in muscle glycogen concentration during the period of exercise. [1] (ii) Explain the graph drawn in (c)(i). [2] (d) Suggest how the curve in Fig. 2.2 might be different if the person suffers from emphysema. [1] [Total: 9]

6 3 The kidney is an organ with the second highest mitochondrial content and oxygen consumption after the heart. Fig. 3.1 is an electron micrograph section of the proximal convoluted tubule. Microvilli form the brush border on the surface facing the lumen. Mitochondria are present closer to the plasma membrane of the cells. Fig. 3.1 (a) Suggest why proximal tubular cells have many mitochondria. [2] (b) Suggest a purpose for microvilli in the proximal tubular cells. [2]

7 [Turn over Fig. 3.2 shows the process of kidney dialysis. Fig. 3.2 (c) Compare and contrast the mechanism of kidney dialysis to the structure and function of the proximal tubular cells and its microvilli in the kidney. [4] [Total: 8] dialysis fluid out arterial blood venous blood filter dialyser dialysis fluid in urea diffuses through the dialysis membrane and into the dialysis fluid a pump keeps the blood moving through the dialyser and at a higher pressure than the dialysis fluid a shunt is added to allow arterial blood to enter a vein and then be withdrawn for dialysis

8 4 Fig. 4.1 shows the cross-section of the human skin. Fig. 4.1 (a) (i) Identify the structures labelled C and D. C D [2] (ii) The thickness of layer D may undergo changes over several months. Suggest and explain one reason for a decrease in the thickness. [2]

9 [Turn over (b) Structure A can be unevenly distributed in human skin. Name structure A and suggest a reason for this uneven distribution in the human skin. [3] (c) Describe how B is involved in thermoregulation when there is a decrease in the external temperature. [3] [Total: 10]

10 5 Guinea pigs are small mammals that are produced for food or bred as pets in different parts of the world. (a) Guinea pigs can have either straight hair or curly hair. The allele for straight hair, T, is dominant to the allele for curly hair, t. (i) Distinguish between a gene and an allele. [2] (ii) A breeder mated a pair of male and female straight -haired guinea pigs and was surprised when this pair produced an offspring with curly hair. Complete the genetic diagram to explain the observation. genotype of parents x gametes offspring genotypes offspring phenotypes [4]