New Senior Secondary Mastering Biology (Second Edition) Book 2 Ch 16 Coordination in humans Exercise Multiple-choice questions (p. 16-33) 1 A 6 C 11 A 2 7 D B 3 8 A B 4 9 A B 5 C 10 C Short questions (p. 16-35) 12 HKALE Biology 2009 I Q1 13 HKCEE Biology 2008 I Q2 (a) To harbour more neurones (1) (b) Y: * medulla oblongata (1) It acts as the reflex centre for some reflex actions / It controls involuntary actions (1) any one (c) Motor area (1) (d) Sensory area (1) Total: 5 marks 14 a b c d Correct drawing to show dendron of sensory neurone starts at receptor and travels through dorsal root; cell body is drawn inside dorsal root ganglion and axon enters grey matter of spinal cord (1) Muscle (1) Reflex action produces fast response / protects the body from danger / protects the body from damage. (1) Reflex arcs connect with other neurones to transmit nerve impulses to the brain. (1) - 24 -  Oxford University Press 2014 New Senior Secondary Mastering Biology (Second Edition) Book 2 15 HKDSE Biology 2013 IB Q1 B (1) C (1) A (1) (3 marks) Structured questions (p. 16-36) 16 a b 17 a b c P: mitochondrion (1) Q: nucleus (1) R: myelin sheath (1) i By diffusion (1) from a high concentration to a low concentration. (1) ii The chemicals may change the shape of the active sites of the enzymes, (1) or bind to the active sites of the enzymes. (1) Neurotransmitter molecules cannot bind to the active sites of the enzymes. (1) The breaking-down reaction of the neurotransmitter molecules cannot be catalysed. (1) The cerebral hemisphere is the site for intelligence / sight / hearing / enables us to think / make decisions / have memories / controls voluntary actions. (1) The cerebellum coordinates muscular movements / maintains body balance. (1) Death may result. (1) Part C controls involuntary actions / controls breathing / heart beat. (1) Spinal cord (1) There will be no impulses below the cut-position / at the lower body. / There will be no sensation below the cut-position. / There will be paralysis below the cut-position. (any 2) @(1) × 2 Essay (p. 16-36) 18 HKDSE Biology Practice Paper 2012 IB Q12 Positive phototropic response of the shoot (1) enables the leaves to be brought into positions that enable them to receive maximum sunlight for photosynthesis (1) OR Negative phototropic response of the root (1) enables the root to grow deep into the soil for firm anchorage / obtain water from deeper ground, (1) Any 1 set, Max. (2) Nature: Tropic response is a directional growth response of some parts of the plant to a unidirectional stimulus (1) whereas reflex action is a stereotyped response to a stimulus. (1) [i.e. growth response vs non-growth response; unidirectional stimulus vs stimulus not necessarily be unidirectional] - 25 -  Oxford University Press 2014 New Senior Secondary Mastering Biology (Second Edition) Book 2 Process: Tropic response is mediated by auxins / chemical substances while reflex action is mediated by nerve impulses which are electrochemical in nature. (1) The same stimulus can cause tropic responses in different parts of the plants (e.g. root tips and shoot tips), but the response in reflex action is localised. (1) The response in tropism is slow whereas the reflex response is always fast. (1) Different effectors (e.g. shoot tips / root tips) can show different responses (positive or negative) to the same stimulus (e.g. unidirectional light). However, the effectors in the reflex action always give the same response. (1) Nature + Process Max. (5) Communication (3) Mark award for communication: Clarity of expression and relevance to the Mark question Answers are easy to understand. They are fluent showing good command of 3 language. There is no or little irrelevant material. Language used is understandable but there is some inappropriate use of words. 2 A little relevant material is included, but does not mar the overall answer. Markers have to spend some time and effort on understanding the answer(s). 1 Irrelevant material obscures some minor ideas. Language used is incomprehensible. 0 Irrelevant material buries the major ideas required by the question. Logical and systematic presentation Answers are well structured showing coherence of thought and organisation of ideas. Answers are organised, but there is some repetition of ideas. Answers are a bit disorganised, but paragraphing is evident. Repetition is noticeable. Ideas are not coherent and systematic. Candidates show no attempt to organise thoughts. Reading to learn (p. 16-37) 1 2 3 The chicken would have bled to death due to a lack of oxygen carried by the blood. (1) The medulla oblongata is the reflex centre for many reflex actions in the head. (1) It also controls involuntary actions such as breathing and heart beat. (1) No (1) It is because the chicken had lost its cerebrum, which is the site for thinking and making decisions. (1) - 26 -  Oxford University Press 2014