Mark Scheme (Results) Summer 2022 Pearson Edexcel GCSE In Biology (1SC0) Paper 1BH Edexcel and BTEC Qualifications

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Mark Scheme (Results) Summer 2022 Pearson Edexcel GCSE In Biology (1SC0) Paper 1BH Edexcel and BTEC Qualifications Edexcel and BTEC qualifications are awarded by Pearson, the UK’s largest awar... ding body. We provide a wide range of qualifications including academic, vocational, occupational and specific programmes for employers. For further information visit our qualifications websites at www.edexcel.com or www.btec.co.uk. Alternatively, you can get in touch with us using the details on our contact us page at www.edexcel.com/contactus. Pearson: helping people progress, everywhere Pearson aspires to be the world’s leading learning company. Our aim is to help everyone progress in their lives through education. We believe in every kind of learning, for all kinds of people, wherever they are in the world. We’ve been involved in education for over 150 years, and by working across 70 countries, in 100 languages, we have built an international reputation for our commitment to high standards and raising achievement through innovation in education. Find out more about how we can help you and your students at: www.pearson.com/uk Summer 2022 Publications Code 1SC0_1BH_2206_MS All the material in this publication is copyright © Pearson Education Ltd 2022 General Marking Guidance • All candidates must receive the same treatment. Examiners must mark the first candidate in exactly the same way as they mark the last. • Mark schemes should be applied positively. Candidates must be rewarded for what they have shown they can do rather than penalised for omissions. • Examiners should mark according to the mark scheme not according to their perception of where the grade boundaries may lie. • There is no ceiling on achievement. All marks on the mark scheme should be used appropriately. • All the marks on the mark scheme are designed to be awarded. Examiners should always award full marks if deserved, i.e. if the answer matches the mark scheme. Examiners should also be prepared to award zero marks if the candidate’s response is not worthy of credit according to the mark scheme. • Where some judgement is required, mark schemes will provide the principles by which marks will be awarded and exemplification may be limited. • When examiners are in doubt regarding the application of the mark scheme to a candidate’s response, the team leader must be consulted. • Crossed out work should be marked UNLESS the candidate has replaced it with an alternative response. Mark schemes have been developed so that the rubrics of each mark scheme reflects the characteristics of the skills within the AO being targeted and the requirements of the command word. So for example the command word ‘Explain’ requires an identification of a point and then reasoning/justification of the point. Explain questions can be asked across all AOs. The distinction comes whether the identification is via a judgment made to reach a conclusion, or, making a point through application of knowledge to reason/justify the point made through application of understanding. It is the combination and linkage of the marking points that is needed to gain full marks. When marking questions with a ‘describe’ or ‘explain’ command word, the detailed marking guidance below should be consulted to ensure consistency of marking. Assessment Objective Command Word Strand Element Describe Explain AO1 An answer that combines the marking points to provide a logical description An explanation that links identification of a point with reasoning/justification(s) as required AO2 An answer that combines the marking points to provide a logical description, showing application of knowledge and understanding An explanation that links identification of a point (by applying knowledge) with reasoning/justification (application of understanding) AO3 1a and 1b An answer that combines points of interpretation/evaluation to provide a logical description AO3 2a and 2b An explanation that combines identification via a judgment to reach a conclusion via justification/reasoning AO3 3a An answer that combines the marking points to provide a logical description of the plan/method/experiment AO3 3b An explanation that combines identifying an improvement of the experimental procedure with a linked justification/reasoning Paper 1SC0 1BH June 2022 Question number Answer Additional guidance Mark 1(a) A description linking two from: • weak (1) • hydrogen bonds (1) • complementary bases (1) • A – T / C – G (1) accept H bonds reject hydro bonds accept the names of the base pair (2) AO1 1 Question number Answer Additional guidance Mark 1(b)(i) T T G A T T G C G T A A A A C T A A C G C A T T award 1 mark for all the As and Ts in the top line correctly paired (1) award 1 mark for all the Cs and Gs in the top line correctly paired (1) accept lower case letters (2) AO2 1 Question number Answer Mark 1(b)(ii) B 4 The only correct answer is B A is incorrect because each 3 amino acids would need 9 bases to be present C is incorrect 6 amino acids would need 18 bases D is incorrect because 12 amino acids would need 36 bases (1) AO2 1 Question number Answer Mark 1(b)(iii) D double helix The only correct answer is D A is incorrect because a DNA molecule is not three separate strands B is incorrect because the DNA molecule consists of two strands C is incorrect because a DNA molecule is a double helix not a single helix (1) AO1 1 Question number Answer Additional guidance Mark 1(c)(i) An explanation linking two from: • (protease) breaks down proteins (1) • in the {cell/nuclear} membrane (1) • destroys enzymes (that may break down the DNA) (1) accept break down the {cell/nucleus/cell wall} (2) AO1 2 Question number Answer Additional Guidance Mark 1(c)(ii) to precipitate the DNA / because DNA is insoluble in ethanol accept to see the DNA (1) AO1 2 Total marks for question 1 = 9 marks Question number Answer Mark 2(a)(i) gonorrhoea (1) AO3 1a Question number Answer Additional guidance Mark 2(a)(ii) (66 000 000 ÷ 1000) = 66 000 (1) (66 000) x 3.7 =244 200 (people) or (3.7 ÷ 1000) = 0.0037 (1) (0.0037) x 66 000 000 = 244 200 (people) or (66 000 000 x 3.7) = 244 200 000 (1) (244 200 000 ÷ 1000) = 244200 award full marks for correct answer no working accept answers in standard form accept 244200 to any incorrect magnitude for one mark (2) AO2 1 Question number Answer Additional guidance Mark 2(a)(iii) Any one from: • it is {passed/spread} from person to person (1) • caused by bacteria (1) accept spread by {sexual contact / body fluids} accept pathogen ignore caused by a virus (1) AO1 1 Question number Answer Additional guidance Mark 2(a)(iv) Any one from: • avoid sexual contact (1) • use a {condom/femidom} (1) • screen people for an infection (1) • treat the infection/give antibiotics (1) accept use a barrier form of contraception ignore protection / contraception (1) AO2 1 Question number Answer Additional guidance Mark 2(a)(v) An explanation including the following: • it is {killed/inhibited} by antibiotics (1) • because chlamydia is caused by bacteria (1) accept disrupt cell processes (in bacteria) /prevent (bacteria) reproducing accept antibiotics are used to kill bacteria for 2 marks (2) AO2 1 Question number Answer Additional guidance Mark 2(b) An explanation linking the following: • HIV {destroys white blood cells / reduces the number of white blood cells} (1) • which compromises the immune system / making the person more susceptible to other {pathogens / infections / diseases} (1) accept named white blood cells accept weakens the immune system ignore more susceptible to AIDS (2) AO2 1 Total for question 2 = 9 marks Question number Answer Additional guidance Mark 3(a)(i) An explanation including four of the following: • by natural selection / evolution (1) • mutation in the bacterium /variation in the population (1) • only the resistant bacteria survived treatment by antibiotics / resistant bacteria survive when people don’t finish the course (1) • the resistant bacteria {reproduce / divide} (1) • offspring inherit the resistance / resistance passed onto future generations / process repeats increasing level of resistance (1) accept Klebsiella for bacteria accept they evolve accept some bacteria have a {gene/allele} for antibiotic resistance accept nonresistant bacteria killed by antibiotics ignore off [Show More]

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