IB Biology HL B3.3 Muscle and motility [HL only] Questions

Practise IB Biology HL B3.3 by linking sarcomere contraction and joint mechanics with ventilation, migration and marine-mammal swimming adaptations.

89 questions in this syllabus scope, with question parts counted together.

Syllabus
First assessment 2025
Course
Biology HL
Level
HL

Exam analysis

HL · 2010–2025
Papers with this topic53 / 117in the analysed sample
Latest appearanceNovember 2025
Tagged question parts81
Paper types5

Most tested objectives

  1. B3.3.2 (HL)—Sliding filament model32 papers
  2. B3.3.3 (HL)—Titin and antagonistic muscles10 papers
  3. B3.3.5 (HL)—Skeletons as anchorage and levers7 papers
  4. B3.3.6 (HL)—Synovial joint movement7 papers
  5. B3.3.10 (HL)—Swimming adaptations in marine mammals5 papers

Common question formats

  • Diagram interpretation
  • Process explanation
  • Comparison
  • Definition or recall
  • Structured response

Recent exam appearances

November 2025Paper 2 HL · TZ1Q1(b)(ii), 3(b), 3(c)[ 7 ]
November 2025Paper 1A HL · TZ3Q23[ 1 ]
November 2025Paper 1A HL · TZ1Q1[ 1 ]

117 papers analysed · Tagging incomplete

Exam points

  • Identify muscle, fibre, myofibril and sarcomere organisation, then interpret Z-line and band changes as actin and myosin slide.
  • Trace motor-end-plate excitation and sarcoplasmic-reticulum calcium release to troponin binding and exposed actin sites.
  • Explain how ATP enables myosin detachment and reset during repeated cross-bridge cycling and sarcomere shortening.
  • Explain how titin centres myosin, recoils after stretching and limits sarcomere overstretching.
  • Apply contracting and relaxing antagonist pairs to predict flexion or extension in elbow and insect-joint diagrams.
  • Compare vertebrate endoskeletons with arthropod exoskeletons and use muscle attachments to explain support, lever action and movement.
  • Relate cartilage and synovial fluid to cushioning and low-friction movement, and distinguish tendon attachment from ligament stabilisation.
  • Compare hinge and ball-and-socket movement, then calculate range-of-motion changes from joint-angle or age-group data.
  • Explain how intercostal muscles move the ribs during inhalation or forced expiration and alter thoracic volume and pressure.
  • Interpret migration evidence and relate locomotion to seasonal access to food and suitable habitats.
  • Relate marine-mammal streamlining, flipper propulsion and tissue oxygen stores to swimming and dive-duration evidence.

Covered syllabus points

B3.3.1 (HL)—Movement adaptationsB3.3.2 (HL)—Sliding filament modelB3.3.3 (HL)—Titin and antagonistic musclesB3.3.4 (HL)—Motor unitsB3.3.5 (HL)—Skeletons as anchorage and leversB3.3.6 (HL)—Synovial joint movementB3.3.7 (HL)—Range of motionB3.3.8 (HL)—Intercostal musclesB3.3.9 (HL)—Reasons for locomotionB3.3.10 (HL)—Swimming adaptations in marine mammals

Exam points

  • State adaptive advantages of bird migration, including access to food, tolerable temperatures or suitable habitat.
  • Interpret migration data for direction or timing, variation, and innate versus learned behaviour.

Question 1

[Maximum number: 2]

The bird known as the blackcap (Sylvia atricapilla) traditionally migrates from its summer breeding grounds in Central Europe to Spain and Portugal for the winter. State two adaptive advantages of bird migration.

Exam points

  • Identify sarcomeres between Z lines, thin actin and thick myosin filaments, and interpret band or micrograph changes as filaments slide and the sarcomere shortens.
  • Explain that calcium released from the sarcoplasmic reticulum binds troponin, moves tropomyosin and exposes myosin-binding sites on actin.
  • Explain the ATP cross-bridge cycle: myosin attachment, power stroke, ATP-driven detachment and ATP hydrolysis/reset, repeated to shorten sarcomeres.

Question 1

[Maximum number: 1]

The diagram shows a contracted sarcomere. Which part will vary in length in response to relaxation of a muscle?

Figure for Question 1 — IB Biology HL

Exam points

  • Explain how titin centres myosin in a sarcomere, stores elastic potential energy, recoils after stretching and limits overstretching.
  • Explain why antagonistic muscles are required: one muscle actively contracts to pull a joint while the opposing muscle relaxes, producing opposite movements.
  • Apply flexor-extensor opposition to elbow or insect-joint diagrams by identifying biceps/triceps actions, attachment and the resulting flexion or extension.

Question 1

[Maximum number: 1]

A titinopathy is a muscle disorder caused by titin abnormalities. What could be a consequence of abnormal titin in muscles?

A

Muscles would detach from tendons.

B

Muscles would stretch too much during relaxation.

C

Muscles would have less ATP for contraction.

D

Antagonistic muscles would contract the same time.

Exam points

  • Identify a motor unit as a motor neuron and the skeletal muscle fibres it controls, joined at neuromuscular junctions.
  • Explain that acetylcholine released at the motor end plate after a motor-neuron action potential excites the muscle-fibre sarcolemma.
  • Trace excitation from the motor end plate to calcium-ion release from the sarcoplasmic reticulum, initiating skeletal-muscle contraction.

Question 1

[Maximum number: 1]

What happens when an action potential reaches motor end plates?

A

Calcium ions are absorbed by the muscle fibres.

B

The sarcomeres relax.

C

Neurotransmitter is released.

D

Action potential is passed to the neuron.

Exam points

  • Explain how vertebrate bones provide support and act as levers, with skeletal muscles transmitting force to them through tendons at joints.
  • Compare vertebrate endoskeletons and arthropod exoskeletons by position, material and the side on which muscles attach.
  • Use joint or skeleton diagrams to identify tendon or muscle attachment and relate the arrangement to force production and movement.

Question 1

[Maximum number: 1]

What is a role of one of the structures at a synovial joint such as the hip?

A

Ligaments attach muscle to bone.

B

Tendons transmit force of contraction to bone.

C

Cartilage holds bones together at the joint.

D

Muscles stretch and contract to move bones.

Exam points

  • Explain how cartilage-covered bone ends and synovial fluid reduce friction and absorb shock in a synovial joint.
  • Distinguish tendon attachment of muscle to bone from ligament connection of bone to bone, and relate both to joint stability and movement.

Question 1

[Maximum number: 1]

What is the role of the joint capsule in an elbow joint?

A

It seals the joint to retain the synovial fluid.

B

It provides a point of attachment for muscles.

C

It produces cartilage to reduce friction during movement.

D

It directs the formation of bone tissue during growth and development.

Exam points

  • Compare ball-and-socket joints such as the hip with hinge joints such as the knee by identifying planes and directions of movement, including circumduction versus mainly flexion and extension.
  • Measure or calculate joint range of motion from a goniometer, calibrated image or age-group data, reporting angles or percentage change.

Question 1

[Maximum number: 4]

Physical therapists used goniometers to obtain range of motion measurements for different joints from a total of 674 healthy, normal subjects aged 2-69 years. The male and female subjects were grouped into four age groups: 2-8, 9-19, 20-44 and 45-69 years.

The table shows mean range of motion values for hip and knee joints.

Table for Question 1 — IB Biology HL

Question (a)

(a)

Calculate the percentage decrease in mean range of motion for hip extension in males from the youngest to the oldest group.

[ 1 ]

Question (b)

(b)

Describe how to measure the range of motion of a joint.

[ 3 ]

Exam points

  • Explain that external intercostal muscles contract to lift the ribs up and out during inspiration, increasing thoracic volume and lowering pressure.
  • Explain that internal intercostal muscles contract to pull the ribs down and in during forced expiration, reducing thoracic volume and raising pressure.
  • Distinguish the antagonistic external- versus internal-intercostal actions and use rib direction or pressure evidence to identify inspiration or forced expiration.

Question 1

[Maximum number: 4]

Emergent properties exist when many different components, such as cells, tissues, organs and body systems, integrate in a multicellular living organism.

Describe how muscles interact to carry out inhalation in the lungs.

Exam points

  • Relate a streamlined body and buoyancy or blubber-associated streamlining to reduced drag and efficient swimming in marine mammals.
  • Explain how flippers steer or propel and tail flukes moving up and down provide propulsion in water.
  • Explain diving adaptations including breath-holding or closed airways and increased oxygen storage that support prolonged dives and surface breathing.

Question 1

[Maximum number: 1]

Which characteristic of the ringed seal (Pusa hispida) is a consequence of the viscosity of water?

A

Streamlined body

B

Sharp teeth

C

Claws

D

Lungs