Circulatory & Respiratory Systems — Practice · Grade 7 Science

Chapter: Body Organization, Transport & Movement

What this practice covers

By the end of Circulatory & Respiratory Systems you should be able to:

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

Vocabulary used: ventilation, gas exchange, capillary, artery, vein.

Problem 1

Is exhaled air pure carbon dioxide?
Answer and explanation

No. It remains a mixture including nitrogen, oxygen, carbon dioxide, and water vapor in different proportions.

Problem 2

Why are thin surfaces relevant?
Answer and explanation

They shorten the distance materials must cross and support exchange under suitable conditions.

Problem 3

Why is “every artery carries oxygen-rich blood” inaccurate?
Answer and explanation

Arteries are defined by direction from the heart; the lung-circuit artery carries blood toward gas exchange before it becomes oxygen-rich.

Problem 4

Why is inhalation alone not the whole oxygen pathway?
Answer and explanation

Oxygen must cross exchange surfaces, travel in blood, and reach cells; inhalation is only one step.

Problem 5

Illustrative draft: air enters lungs; oxygen then moves directly from lungs to every muscle cell; no vessels or heart are drawn. Repair the pathway, label gas exchanges, and distinguish the pathway from cellular respiration.
Answer and explanation

Oxygen enters lung air spaces, crosses into blood, is transported through the heart and vessels, and reaches tissues by exchange. Carbon dioxide can follow a return pathway toward lung release. Cellular respiration occurs in cells and uses food and oxygen in the aerobic model; it is not simply the act of breathing. The diagram is simplified and does not show every anatomical detail.

Add lung exchange into blood.

Add heart and transport vessels.

Add tissue exchange and cellular use.

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 vessel carries blood from the heart toward the lungs. Is it an artery or vein under the directional definition?
Answer and explanation

It is an artery because it carries blood away from the heart, regardless of its oxygen content before lung exchange.

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

Which structure supplies the pumping action in circulation?
  1. Heart
  2. Food molecule
  3. Lung air alone
  4. Microscope lens
Answer and explanation

Heart

The heart pumps blood; lungs supply gas exchange and ventilation functions.

Problem 8

Why do respiratory and circulatory systems both matter to oxygen delivery?
Answer and explanation

Respiration-related surfaces exchange gases, while circulation moves oxygen-containing blood toward tissues. Cells also require exchange at the destination.

Browse all courses