PLMGS S4Exp 5NA Sc Bio Prelim P4 2025 Answer

1 Preliminary Examination 2025 (Term 3) Secondary 4 Express & 5 Normal Academic Science Biology 5088 Qn Answer Marks Remarks Learning Outcome 1(a) (i) (ii) mark awarded only if structure is in a plausible position nucleus / mitochondrion / vacuole (shown in both cells); Ignore: cytoplasm Any 2 from: chloroplast / cell wall / one large central vacuole in plant cell + many small vacuoles in animal cell; 1 1 nucleus: large, round mitochondrion: bean-shaped ignore: size of organelles cell wall: even thickness around cell membrane 1 Cell (c) compare the structure of typical animal and plant cells vacuoles vacuole

2 1(b) (i) (some plant tissues) carry out photosynthesis + produces / manufactures glucose [or] excess glucose is converted to starch for storage / starch storage [or] presence of cellulose in the cell wall; 1 (ii) 1. liver / muscles; 2. storage of glycogen; 2 (iii) Any 1 from (proteins): 1. to synthesize new cytoplasm; 2. to build and repair tissues; 3. to synthesize enzymes; 4. to synthesize hormones; ignore: to synthesize antibodies (antibodies are only found in animal cells, not in plant tissues) Any 1 from (fats) 5. energy storage; 6. component of cell membrane; 7. to reduce water loss (e.g: oily substance found on the skin surface / waxy layer on the epidermis of leaves) ignore: insulation (less relevant in plant tissues) max: 2 MP5: seeds contain fats 3 Biological Molecules: (a) state the main roles of carbohydrates, fats and proteins in living organisms. [Total: 7 marks]

3 2(a) Any 2 from: 1. net movement of water molecules; 2. from a region of high water potential to a region of low water potential 3. across a partially permeable membrane; 2 2 Movement of Substances (b) define osmosis, investigate and describe the effects of osmosis on plant and animal tissues 2(b) 1. (water molecules) move by osmosis; 2. from large intestine, higher water potential + to blood plasma, lower water potentia l + down the water potential gradient; 3. large intestine membrane is a partially permeable membrane; 3 2(c) (i) 2 1 mark for each correct line; 2(c) (ii) as surface area to volume ratio decreases + time taken for diffusion increases + rate of diffusion decreases; 1

4 2(d) Any 2 from: 1. many / numerous alveoli + to increase surface area; 2. surrounded by many blood capillaries + to maintain diffusion gradient + to remove absorbed materials; 3. one-cell thick alveolar wall and blood capillary wall + to shorten the diffusion distance; max: 2 6 Respiration in humans (b) explain how the structure of an alveolus is suited for its function of gaseous exchange [Total: 10 marks]

5 3(a) nucleus / chromosomes; 1 3(b) (i) 1. Dd + Dd; 2. correctly shown gametes; 3. correctly shown gamete linkage + offspring genotype and offspring phenotype; 3 12 Inheritance (d) predict the results of simple crosses with expected ratio of 3 :1 and 1:1, using the terms homozygous, heterozygous, F1 generation and F2 generation (ii) Non- cystic fibrosis: cystic fibrosis 3:1 phenotype ratio correctly expressed and identified; Accept: 75% non-cystic fibrosis and 25% cystic fibrosis ¼ cystic fibrosis + ¾ non-cystic fibrosis 1

6 3(c) (i) duodenum / small intestine; 1 4 Nutrition in humans (a) describe the functions of the various parts of the digestive system, in relation to ingestion, digestion, absorption, assimilation and egestion of food, as appropriate (ii) Any 3 from: 1. reduction in enzyme lipase in pancreatic juice entering duodenum; 2. reduction of bile (from gall bladder) entering duodenum; 3. less emulsification of fat + slower / reduced digestion of fats; [or] fat droplets remain large [or] fat droplets has small surface area to volume ratio; correct ref. to reduce bile action 4. fewer fatty acids and glycerol absorbed into the bloodstream + lower assimilation into large molecules; 5. e.g. of assimilation: ref. less fat molecules can be used in growth; ref. less fat stored, e.g. less excess fats can be stored as adipose tissues; max: 3 [Total: 9 marks]

7 4(a) (i) bacteria; 1 (ii) Human immunodeficiency virus; Accept: HIV 1 4(b) 1. From 2000 to 2012, percentage of pathogens sampled that show resistance to all three antibiotics is increasing; 2. In 2000, percentage of pathogens sampled that show resistance to antibiotics A and B starts at 0%; + percentage of pathogens sampled that show resistance to antibiotic C starts at 5.5%; 3. From 2012 to 2013, percentage of pathogens sampled that show resistance to antibiotic C decreases + from 17% to 16.5% / decreases by 0.5%; 4. Between 2009 and 2012, percentage of pathogens sampled that show resistance to antibiotics B and C are the same + increases from 13.5% to 17%; 5. Between 2000 and 2001, percentage of pathogens sampled that show resistance to antibiotics A rises very steeply + from 0% to 9%; 6. From 2001 to 2013, the percentage of pathogens sampled that show resistance to antibiotic A is always higher than antibiotics B and C; Accept: from second half of 2000 to 2013 max:3

8 4(c) Any 1 from: 1. did not complete the full course of antibiotics prescribed by doctors + not all the bacterial are killed; 2. misusing or overusing antibiotics / or described Accept: alternative wordings max: 1 7 Infectious Diseases in Humans (f) state that antibiotics kill bacteria and are ineffective against viruses/ 4(d) (antibiotics are ineffective against viruses) because viruses do not have cell walls, cell membranes or ribosomes; 1 7 Infectious Diseases in Humans (g) explain that the misuse and overuse of antibiotics may accelerate the emergence of antibiotic – resistant bacteria [Total: 7 marks]

9 5(a) (i) (oak) tree / primrose 1 9 Organisms and their Environment (b) describe the toles of producers, consumers and decomposers in food chains and food webs. (ii) oak tree → flies → spiders → blue tits → owl; 1 5(b) (i) group of organisms of the same species + living in the same area at the same time; 1 (ii) position of an organism in a food chain / food web + example from food web in Fig. 5.1 e.g. flies ate at second trophic level 1 5(c) (i) decomposers / bacteria / fungi; 1 (ii) Any 2 from: 1. releases minerals from leaves; ignore: nutrients 2. minerals absorbed into plant from soil; 3. (decomposers) carry out respiration / decomposition + releases carbon dioxide; 4. carbon dioxide absorbed by leaves from photosynthesis; max: 2 [Total: 7 marks]

10 6(a) (i) (ii) Label line + fallopian tube / oviduct Label line + ovary 1 1 11 Reproduction in Humans (c) identify the female reproductive system and state the functions of: ovaries, oviduct, uterus, cervix and vagina ovary oviduct / fallopian tube