Form 4 · Paper 2 essay guide

Support and Movement in Humans and Animals, Paper 2 essay guide

How Support and Movement in Humans and Animals appears in Paper 2 essays: themes, a planning grid, a model answer structure and the keyword list.

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Essay themes this chapter supports

The three types of skeleton compared: Define the role of a skeleton: support, shape and a framework for movement. → Describe the hydrostatic skeleton of the earthworm using fluid pressure. → Describe the exoskeleton of insects, its protective role and the need to moult. → Describe the endoskeleton of vertebrates and explain how it grows with the animal and anchors muscles.
How antagonistic muscles move a joint: State that a muscle can only pull by contracting, never push. → Explain the biceps and triceps pair bending and straightening the arm at the hinge joint. → Give the knee (quadriceps and hamstrings) as a second example. → Conclude that a joint needs an antagonistic pair because one muscle reverses the other.
Locomotion matched to habitat: State that locomotion suits the habitat and the medium the animal moves through. → Explain the fish: flexible vertebral column, myotomes, body waves and fins in water. → Explain the bird: hollow and fused bones and a keeled sternum for flight in air. → Compare with a land mammal swinging jointed limbs against solid ground.
Caring for the musculoskeletal system: Explain osteoporosis as falling bone density with its causes and effect. → Explain arthritis as joint inflammation affecting cartilage or the synovial membrane. → Distinguish a dislocation from a sprain as two injuries. → Recommend weight-bearing exercise, adequate calcium and vitamin D, and correct posture.

How to structure your essay

Open with one or two sentences that define the topic and set the scope.
Devote one paragraph to each key concept, in a logical order.
Use precise biological terms and, where relevant, a labelled diagram.
Give an example or state where the process happens in the body or plant.
Close by linking the ideas back to the question.

Planning grid

Question	Answer
Intro	Define support and movement and name the structures involved
Point 1	Describe the supporting structure (skeleton type or bone and joint)
Point 2	Explain how muscles produce the movement
Point 3	Relate the structure to how the animal actually moves or functions
Point 4	Add a comparison or a health issue to show depth
Conclusion	Summarise how structure suits function

Key terms to include

hydrostatic skeleton
exoskeleton
endoskeleton
moulting
tendon
ligament
antagonistic muscles
biceps and triceps
hinge joint
myotomes
keeled sternum
osteoporosis
arthritis
cartilage

A model essay outline

Types of skeleton, Hydrostatic skeleton (e.g. earthworm), exoskeleton (e.g. insects) and endoskeleton (e.g. humans) each support and allow movement.
Musculoskeletal system, Bones give support, joints allow movement, and muscles attached by tendons produce the force.
Joints, A hinge joint (elbow, knee) allows movement in one plane; a ball-and-socket joint (shoulder, hip) allows movement in many directions.
Antagonistic muscles, Muscles work in pairs: when the biceps contracts to bend the arm, the triceps relaxes, and the reverse straightens it.
Movement and locomotion, Muscle contraction pulls on bones across a joint to produce movement; locomotion is movement of the whole body.

Frequently asked questions

How do antagonistic muscles move the arm?

Muscles can only pull, not push, so they work in antagonistic pairs. To bend the arm, the biceps contracts and pulls the forearm up while the triceps relaxes. To straighten the arm, the triceps contracts and pulls the forearm down while the biceps relaxes. Because one muscle undoes the action of the other, the joint can move both ways.

What is the difference between a tendon and a ligament?

A tendon is a tough band that joins a muscle to a bone, so that when the muscle contracts it pulls the bone. A ligament joins one bone to another at a joint and holds the bones together while allowing controlled movement. Tendons connect muscle to bone; ligaments connect bone to bone.

What are the three types of skeleton?

A hydrostatic skeleton uses fluid pressure inside the body, as in an earthworm. An exoskeleton is a hard outer covering, as in insects and crabs, which also protects the body. An endoskeleton is an internal framework of bone or cartilage, as in humans and other vertebrates, which supports the body and provides attachment for muscles.