Question 1
Paper 1A style
HL only (what this means)
HL only: additional Higher Level content, only for HL students. SL students can skip it. What the labels meanWhat happens to the bands of a sarcomere during muscle contraction?
- The A band shortens and the I band stays the same length
- The I band shortens and the A band stays the same length
- Both the A band and the I band shorten
- The actin and myosin filaments both shorten
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Answer: B [1]
Question 2
Paper 1A style
HL only (what this means)
HL only: additional Higher Level content, only for HL students. SL students can skip it. What the labels meanWhich statement about skeletons is correct?
- Arthropods have endoskeletons with muscles attached to the outer surface
- Vertebrates have exoskeletons made of chitin
- Arthropods have exoskeletons with muscles attached to the inner surface
- Skeletons act as levers but do not provide anchorage for muscles
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Answer: C [1]
Question 3
Paper 2A style
HL only (what this means)
HL only: additional Higher Level content, only for HL students. SL students can skip it. What the labels meanExplain how the internal and external intercostal muscles act as an antagonistic pair.
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- muscles can only exert force/pull when they contract [1]
- muscle fibres in the two layers have different orientations [1]
- external intercostals move ribcage up and out; internal move it down and in [1]
- contraction of one layer stretches the other [1]
- potential energy stored in titin (of stretched sarcomeres) helps recoil [1]
- max 3
Question 4
Paper 2A style
HL only (what this means)
HL only: additional Higher Level content, only for HL students. SL students can skip it. What the labels meanOutline the structure and function of a motor unit.
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- one motor neuron and the muscle fibres it stimulates [1]
- connected by neuromuscular junctions/synapses [1]
- acetylcholine released at junctions stimulates fibres [1]
- all fibres in the unit contract together [1]
- more motor units recruited for greater force / small units for fine control [1]
- max 3
Question 5
Paper 1B style
HL only (what this means)
HL only: additional Higher Level content, only for HL students. SL students can skip it. What the labels meanStudents used a goniometer to measure the range of motion of the hip in three dimensions. (a) Calculate the mean range of hip flexion. (b) Identify the movement with the smallest range. (c) Suggest one reason why the measurements varied between trials. (d) Suggest why the hip has a larger range of motion in more dimensions than the knee.
| Movement | Trial 1 | Trial 2 | Trial 3 |
|---|---|---|---|
| Flexion | 118 | 122 | 120 |
| Abduction | 42 | 45 | 39 |
| Extension | 18 | 22 | 20 |
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- (a) (118 + 122 + 120) ÷ 3 = 120° [1]
- (b) extension [1]
- (c) goniometer not placed exactly on the joint centre/arms not aligned with bones the same way each time / student moved by different amounts [1]
- (d) hip is a ball-and-socket joint (allowing movement in several planes) whereas the knee is a hinge joint [1]
Question 6
Paper 2A style
HL only (what this means)
HL only: additional Higher Level content, only for HL students. SL students can skip it. What the labels meanOutline four reasons for locomotion in animals, giving a named example of each.
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- foraging for food, e.g. honeybees flying to flowers for nectar [1]
- escaping from danger, e.g. squid using jet propulsion to escape predators [1]
- searching for a mate, e.g. male moths following female pheromones [1]
- migration, e.g. Arctic terns between Arctic and Antarctic [1]
- Accept other valid named examples. Reason and example both required for each mark.
Question 7
Paper 2B style
HL only (what this means)
HL only: additional Higher Level content, only for HL students. SL students can skip it. What the labels meanExplain how skeletal muscle contracts and how it returns to its resting length.
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- muscle fibre/myofibril made of repeating sarcomeres between Z lines [1]
- actin (thin) filaments attached to Z lines; myosin (thick) filaments in centre [1]
- calcium ions released expose binding sites on actin [1]
- myosin heads bind to actin forming cross-bridges [1]
- heads swivel/power stroke pulls actin towards centre of sarcomere [1]
- ATP binds causing myosin to detach [1]
- hydrolysis of ATP re-cocks/re-energises myosin head [1]
- filaments slide past each other; sarcomere shortens/Z lines closer [1]
- I band and H zone shorten, A band unchanged [1]
- muscle can only pull so an antagonistic muscle stretches it back [1]
- titin stores potential energy when stretched and recoils [1]
- titin prevents overstretching [1]
- max 7
Question 8
Paper 2A style
HL only (what this means)
HL only: additional Higher Level content, only for HL students. SL students can skip it. What the labels mean(a) State the roles of cartilage and synovial fluid in the hip joint. (b) Describe two adaptations of the tail and airways of a dolphin for swimming.
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- (a) cartilage reduces friction/absorbs shock between femur and pelvis [1]
- (a) synovial fluid lubricates the joint/reduces friction [1]
- (b) tail forms a (horizontal) fluke moved up and down for propulsion [1]
- (b) blowhole on top of head closes during dives / allows rapid breathing at surface between dives [1]