Bones, Muscles & Structure-Function Models — Practice · Grade 7 Science

Chapter: Body Organization, Transport & Movement

What this practice covers

By the end of Bones, Muscles & Structure-Function Models you should be able to:

8 questions, written answer and multiple choice, each with a worked explanation.

Vocabulary used: skeletal muscle, tendon, joint, contraction, lever.

Problem 1

Why is listing bones alone not a structure-function explanation?
Answer and explanation

It identifies parts but does not explain how their arrangement contributes to support, protection, or movement.

Problem 2

Why are opposing muscle actions useful?
Answer and explanation

They allow movement in different directions because a contracting muscle pulls rather than actively pushes along the same attachment.

Problem 3

Can a paper lever determine someone’s safe lifting limit?
Answer and explanation

No. It omits biological and individual factors and is only a selected relationship model.

Problem 4

Why does movement depend on more than muscles?
Answer and explanation

Coordination, support, exchange, and cellular energy processes interact with muscle contraction.

Problem 5

Illustrative paper hinge: String A bends a joint when pulled; String B straightens it when pulled. The hinge and attachments are unchanged. Explain the represented mechanism, connect it with muscles, and state two limits of the analogy.
Answer and explanation

The strings represent pulls that can rotate the hinge in opposite directions, analogous to coordinated muscle actions. The model does not show nerves, living tissue, energy transfers, changing forces, or exact anatomical scale. It illustrates a mechanical relationship without establishing individual performance or health.

Identify the hinge as a turning point.

Connect each pull with an opposing action.

State missing tissues and cellular processes.

Response criteria

  • Explain the relevant biological process accurately.
  • Use the supplied evidence and show calculation steps with units where needed.
  • Connect a labeled model or mechanism with the claim.
  • State an assumption, evidence limitation, or useful next observation.

Problem 6

A diagram says one muscle contracts to bend and then pushes to straighten a joint. What needs correction?
Answer and explanation

Skeletal muscle contraction produces a pull. Opposing muscle action or another force can restore the movement; relaxation is not an active push along the same attachment.

Response criteria

  • Explain the relevant biological process accurately.
  • Use the supplied evidence and show calculation steps with units where needed.
  • Connect a labeled model or mechanism with the claim.
  • State an assumption, evidence limitation, or useful next observation.

Problem 7

What does a tendon connect in this model?
  1. Muscle and bone
  2. Only two air spaces
  3. A scale bar and nucleus
  4. Food and soil
Answer and explanation

Muscle and bone

Tendons transmit muscle forces to bones in the studied arrangement.

Problem 8

Name one omitted process in a paper joint model and why it matters.
Answer and explanation

Nervous coordination is omitted; actual movement depends on signals controlling muscle actions. Cellular energy processes and living tissue properties are other valid examples.

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