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Primary 3 Science Human System Quiz

Free P3 Science Human System quiz, Exam version, with questions, answers, and syllabus-aligned practice for Singapore students.

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Primary 3 Science From Real Exams Generated by DeepSeek V4 Flash Sample 02 Updated 2026-08-17

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Questions

Primary 3 Science Quiz - Human System

Name: __________________________________________ Class: ___________ Date: ___________

Score: ___________ / 30

Duration: 30 minutes

Total Marks: 30

Instructions:

This quiz has 20 questions on the Human System.
Answer all questions in the spaces provided.
For multiple-choice questions, circle the correct option (A, B, C, or D).
For open-ended questions, write your answers clearly.
Each question is worth 1 or 2 marks as shown.

Section A: Multiple-Choice Questions (Questions 1 to 10)

Circle the correct answer. Each question is worth 1 mark.

1. Which of the following is the main function of the human heart? A) To pump blood around the body B) To help us breathe air C) To digest the food we eat D) To help us think and learn

2. The lungs are part of which human body system? A) Digestive system B) Respiratory system C) Circulatory system D) Skeletal system

3. Which organ is responsible for breaking down food into smaller pieces so that our body can absorb the nutrients? A) Heart B) Brain C) Stomach D) Lungs

4. A boy touches a hot pan and quickly pulls his hand away. Which body system is mainly responsible for this action? A) Muscular system B) Nervous system C) Digestive system D) Respiratory system

5. Which of the following is NOT a function of the human skeleton? A) Protecting our internal organs B) Helping us to move C) Pumping blood around the body D) Giving our body shape and support

6. The image below shows a model of the human body.

Diagram for Q6 (P3 Science)

Generated diagram for Q6.

Which organ is labelled as the brain? A) The organ in the head B) The organ in the chest C) The organ in the abdomen D) The organ in the arms

7. When we exercise, our breathing rate increases. This is because our body needs more __________. A) food B) oxygen C) carbon dioxide D) water

8. Which of the following organs is part of the digestive system? A) Heart B) Lungs C) Intestines D) Brain

9. The human body has many bones. What is the main function of the ribcage? A) To help us bend our arms B) To protect the heart and lungs C) To help us digest food D) To help us think

10. Which of the following actions is controlled by the brain? A) The heart beating B) The lungs breathing C) Reading a book D) The stomach digesting food

Section B: Matching and Fill-in-the-Blanks (Questions 11 to 15)

Write your answers in the spaces provided. Each question is worth 2 marks.

11. Match each organ in Column A to its correct function in Column B. Write the letter of the correct function in the box.

Column A (Organ)	Function	Answer
(a) Heart	A) Helps us to breathe	(a) _____
(b) Lungs	B) Pumps blood around the body	(b) _____
(c) Stomach	C) Controls our thoughts and actions	(c) _____
(d) Brain	D) Breaks down food	(d) _____

12. Complete the sentence by filling in the blanks with the correct words from the box below.

oxygen	carbon dioxide	blood	food

The heart pumps __________ to all parts of the body. The lungs take in __________ from the air and remove __________ from the body.

13. The diagram below shows the human skeleton.

Diagram for Q13 (P3 Science)

Generated diagram for Q13.

(a) Name the part of the skeleton that protects the brain. (1 mark)

(b) Name the part of the skeleton that protects the heart and lungs. (1 mark)

14. Arrange the following parts of the digestive system in the correct order that food passes through them. Write the numbers 1 to 4 in the boxes.

Part of Digestive System	Order (1 to 4)
Mouth
Stomach
Intestines
Gullet (Oesophagus)

15. Look at the picture below.

Diagram for Q15 (P3 Science)

Generated diagram for Q15.

(a) Which body system is the child using most when running? (1 mark)

(b) Name one organ in this system. (1 mark)

Section C: Open-Ended Questions (Questions 16 to 20)

Write your answers in the spaces provided. Each question is worth 2 marks.

16. Explain why it is important for the human body to have a skeleton. Give one reason.

17. A doctor tells a patient that his heart is not working properly. What could be one effect of this on the patient's body?

18. The brain is often called the "control centre" of the body. Give one example of an action that the brain controls.

19. When you eat a sandwich, it goes through several organs before the nutrients are absorbed. Name the organ where most of the nutrients are absorbed into the body.

20. A person holds their breath for 30 seconds. After that, they start breathing quickly. Why does the person need to breathe quickly after holding their breath?

--- End of Quiz ---

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Answers

Answer Key: Primary 3 Science Quiz - Human System

Total Marks: 30

Section A: Multiple-Choice Questions (Questions 1 to 10)

Each question is worth 1 mark.

1. A) To pump blood around the body

Explanation: The heart is a muscular organ that acts as a pump. Its main job is to pump blood, which carries oxygen and nutrients, to all parts of the body. Option B is the function of the lungs, C is the function of the stomach and intestines, and D is the function of the brain.
Marking: 1 mark for A.

2. B) Respiratory system

Explanation: The respiratory system is responsible for breathing. It includes the nose, windpipe (trachea), and lungs. The lungs are the main organs where oxygen from the air is exchanged for carbon dioxide from the blood.
Marking: 1 mark for B.

3. C) Stomach

Explanation: The stomach is a part of the digestive system. It receives food from the gullet and uses strong muscles and digestive juices to break the food down into a liquid mixture. This process is called digestion. The heart pumps blood, the brain controls thoughts, and the lungs help us breathe.
Marking: 1 mark for C.

4. B) Nervous system

Explanation: The nervous system, which includes the brain, spinal cord, and nerves, is responsible for sensing the environment and sending signals to the muscles. When the boy touches the hot pan, nerves in his hand send a signal to his brain (or spinal cord for a reflex), which then sends a signal to his arm muscles to pull his hand away. This is a very fast response.
Marking: 1 mark for B.

5. C) Pumping blood around the body

Explanation: The skeleton provides support, protects organs (like the skull protecting the brain and the ribcage protecting the heart and lungs), and works with muscles to help us move. Pumping blood is the function of the heart, not the skeleton.
Marking: 1 mark for C.

6. A) The organ in the head

Explanation: The brain is located inside the skull, which is in the head. The diagram shows the brain in the head area. The organs in the chest are the heart and lungs, and the organ in the abdomen is the stomach.
Marking: 1 mark for A.

7. B) oxygen

Explanation: When we exercise, our muscles work harder and need more energy. To produce this energy, our cells need more oxygen. Our breathing rate increases to take in more oxygen from the air and to remove the extra carbon dioxide that is produced.
Marking: 1 mark for B.

8. C) Intestines

Explanation: The digestive system is a long tube that runs from the mouth to the anus. The intestines (small and large) are a major part of this system where nutrients are absorbed and waste is formed. The heart, lungs, and brain are part of other systems.
Marking: 1 mark for C.

9. B) To protect the heart and lungs

Explanation: The ribcage is a cage-like structure made of bones (ribs) that surrounds the chest cavity. Its main function is to protect the delicate organs inside, especially the heart and lungs, from injury.
Marking: 1 mark for B.

10. C) Reading a book

Explanation: The brain controls voluntary actions, which are actions we choose to do, like reading, writing, and talking. The heart beating, lungs breathing, and stomach digesting are involuntary actions (they happen automatically without us thinking about them), but they are also controlled by the brain (specifically the brainstem).
Marking: 1 mark for C.

Section B: Matching and Fill-in-the-Blanks (Questions 11 to 15)

11. Matching Organs and Functions (2 marks)

(a) Heart → B) Pumps blood around the body
(b) Lungs → A) Helps us to breathe
(c) Stomach → D) Breaks down food
(d) Brain → C) Controls our thoughts and actions
Explanation: Each organ has a specific main job. The heart is a pump, the lungs are for gas exchange, the stomach is for digestion, and the brain is the control centre.
Marking: 1 mark for two correct matches. 2 marks for all four correct.

12. Fill-in-the-Blanks (2 marks) The heart pumps blood to all parts of the body. The lungs take in oxygen from the air and remove carbon dioxide from the body.

Explanation: The blood is the transport medium. Oxygen is the gas we need from the air. Carbon dioxide is the waste gas we produce.
Marking: 1 mark for "blood" and "oxygen" correct. 2 marks for all three correct.

13. The Human Skeleton (2 marks) (a) The part of the skeleton that protects the brain is the skull (or cranium). (b) The part of the skeleton that protects the heart and lungs is the ribcage (or ribs).

Explanation: The skull is a hard, bony case that surrounds the brain. The ribcage is a bony basket that surrounds the chest cavity.
Marking: 1 mark for each correct answer. Accept "skull" for (a) and "ribcage" or "ribs" for (b).

14. Order of the Digestive System (2 marks)

Part of Digestive System	Order (1 to 4)
Mouth	1
Gullet (Oesophagus)	2
Stomach	3
Intestines	4

Explanation: Food enters the mouth, travels down the gullet to the stomach, and then goes to the intestines.
Marking: 1 mark for the first two (Mouth and Gullet) in the correct order. 2 marks for all four in the correct order.

15. The Respiratory System (2 marks) (a) The body system the child is using most when running is the respiratory system (or breathing system). (b) One organ in this system is the lungs (or nose, mouth, windpipe/trachea).

Explanation: Running requires more energy, which needs more oxygen. The respiratory system works harder to bring in oxygen and remove carbon dioxide.
Marking: 1 mark for each correct answer. Accept "respiratory system" or "breathing system" for (a). Accept "lungs", "nose", "mouth", or "windpipe" for (b).

Section C: Open-Ended Questions (Questions 16 to 20)

Each question is worth 2 marks.

16. Importance of the Skeleton (2 marks)

Answer: The skeleton is important because it gives our body shape and support (1 mark). It also protects our internal organs (e.g., the skull protects the brain) (1 mark). Accept any one valid reason for full marks.
Explanation: Without a skeleton, our body would be a soft, shapeless bag. The skeleton is a strong framework that holds us up and keeps our soft organs safe.
Marking: 1 mark for a correct reason. 2 marks for a clear and correct explanation.

17. Effect of a Faulty Heart (2 marks)

Answer: If the heart is not working properly, it may not be able to pump enough blood to the rest of the body (1 mark). This could make the patient feel tired, weak, or short of breath because the body's cells are not getting enough oxygen and nutrients (1 mark).
Explanation: The heart's main job is to pump blood. If it fails, the delivery of oxygen and food to the body's cells is reduced.
Marking: 1 mark for identifying a general effect (e.g., "blood not pumped properly"). 2 marks for a more specific effect (e.g., "body won't get enough oxygen").

18. The Brain as a Control Centre (2 marks)

Answer: The brain controls actions like reading a book (1 mark), writing, walking, talking, or thinking (1 mark). Accept any one clear example of a voluntary action.
Explanation: The brain receives information from our senses and sends signals to our muscles to perform actions. It also controls involuntary actions like heartbeat and breathing.
Marking: 1 mark for a correct example. 2 marks for a clear and correct example.

19. Absorption of Nutrients (2 marks)

Answer: Most of the nutrients are absorbed into the body in the small intestines (or intestines).
Explanation: After the stomach breaks down food, it goes into the small intestine. The walls of the small intestine have tiny finger-like projections that absorb the nutrients into the bloodstream.
Marking: 1 mark for "intestines". 2 marks for "small intestines" or "small intestine".

20. Breathing After Holding Breath (2 marks)

Answer: When a person holds their breath, the level of oxygen in their body drops and the level of carbon dioxide rises (1 mark). The person needs to breathe quickly to take in more oxygen and to get rid of the extra carbon dioxide (1 mark).
Explanation: The body needs a constant supply of oxygen for its cells to function. Holding your breath stops this supply. The build-up of carbon dioxide is a signal for the brain to force you to breathe.
Marking: 1 mark for mentioning the need for oxygen or removal of carbon dioxide. 2 marks for a complete explanation mentioning both gases or the body's need for oxygen.

--- End of Answer Key ---