Edexcel A Level Biology Paper 2 Mark Scheme June 2022: GCE In Biology B (9BI0/02) Paper 2 | Advanced Physiology, Evolution and Ecology

Edexcel A Level Biology Paper 2 Mark Scheme June 2022: GCE In Biology B (9BI0/02) Paper 2 | Advanced Physiology, Evolution and Ecology. A calculation that makes reference to the following points: • correct calculation of percentage cytosine (1) • correct calculation of number of nucleotides (1) 15 % cytosine 15 % of 10 000 = 1500 Correct answer with no working gains full marks One mark for 15 % (2) Question Number Answer Additional Guidance Mark 2 (a)(i) The only correct answer is: C low auxin, high cytokinin A is incorrect as high auxin inhibits lateral shoots B is incorrect as high auxin inhibits lateral shoots D is incorrect as low cytokinin inhibits lateral shoots (1) 6 Question Number Answer Additional Guidance Mark 2(a)(ii) An explanation that makes reference to three of the following points: • auxin binds with {receptor / transcription factor} (inside cell / in cytoplasm / in nucleus) (1) • transcription factor becomes active / is activated (1) • transcription factor binds to {DNA / promoter} (1) • switches on / causes {transcription / production of RNA} (1) Accept forms auxin-receptor complex Accept forms hormone-receptor complex Do not accept if receptor on cell membrane Accept transcription factor changes shape Accept auxin-receptor complex becomes a transcription factor Accept auxin-receptor complex binds to DNA / promoter (1) (3) 7 Question Number Answer Additional Guidance Mark 2(b) An answer that makes reference to four of the following points: • more seeds germinate when last colour is red (1) • number of exposures to light makes no difference (1) • significant difference when last colours are different as standard deviations do not overlap (1) • red light converts PR into PFR / far red light converts PFR into PR (1) • {PFR stimulates/ PR inhibits} {germination / gibberellin release / activation of amylase / abscisic acid} Allow converse for FR light Accept no significant difference when last colours are same as standard deviations overlap (1) Accept P725 or P730 for PFR / P665 or P660 for PR Accept high PFR : low PR ratio stimulates germination (4) Question Number Answer Additional Guidance Mark 8 3 (a) (i) The only correct answer is: D smooth endoplasmic reticulum A is incorrect as centriole has microtubules B is incorrect as a nucleus has a nucleolus C is incorrect as there are no ribosomes (1) Question Number Answer Additional Guidance Mark 3 (a)(ii) The only correct answer is: D P S R A is incorrect because the SER is not involved in protein synthesis B is incorrect because Golgi should be after the RER C is incorrect because the SER is not involved in protein synthesis