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Primary 4 Science Systems Quiz

Free P4 Science Systems quiz, Nemo3 AI version, with questions, answers, and syllabus-aligned practice for Singapore students.

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Primary 4 Science AI Generated Generated by NVIDIA Nemotron 3 Ultra 550B A55B Free Updated 2026-08-17

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Questions

Primary 4 Science Quiz - Systems

Name: ___________________________
Class: Primary 4 _______
Date: ___________________________
Score: ______ / 40

Duration: 45 minutes
Total Marks: 40

Instructions:

Answer all questions.
Write your answers in the spaces provided.
For multiple-choice questions, write the letter (A, B, C, or D) in the bracket provided.
For open-ended questions, write your answers clearly in complete sentences.
Diagrams are not drawn to scale unless stated.

Section A: Multiple-Choice Questions (10 × 1 mark = 10 marks)

For each question, choose the correct answer and write its letter in the bracket provided.

1. Which of the following is the main function of the roots of a plant?
A. Makes food for the plant
B. Transports water and food
C. Absorbs water and minerals from the soil
D. Supports the plant upright

[ ]

2. In the human digestive system, where does digestion first begin?
A. Stomach
B. Small intestine
C. Mouth
D. Large intestine

[ ]

3. The stem of a plant has two main functions. Which of the following pairs correctly states these functions?
A. Absorbs water and makes food
B. Transports water and food; supports the plant
C. Anchors the plant and absorbs minerals
D. Makes food and supports the plant

[ ]

4. Which organ in the human digestive system produces digestive juices that break down food into simpler substances?
A. Oesophagus
B. Stomach
C. Large intestine
D. Anus

[ ]

5. A plant is placed in a dark cupboard for a week. Which part of the plant will be most affected in its function?
A. Roots
B. Stem
C. Leaves
D. Flowers

[ ]

6. Food moves from the mouth to the stomach through which tube?
A. Trachea
B. Oesophagus
C. Small intestine
D. Large intestine

[ ]

7. Which of the following statements about the human digestive system is correct?
A. The large intestine digests proteins.
B. The small intestine absorbs water from undigested food.
C. The stomach absorbs most of the nutrients from digested food.
D. The small intestine absorbs nutrients from digested food into the blood.

[ ]

8. The diagram below shows a plant.

Image pending generation: diagram for Q8.

Which part (P, Q, R, or S) makes food for the plant?
A. P
B. Q
C. R
D. S

[ ]

9. Which of the following shows the correct order of the digestive system from start to end?
A. Mouth → Stomach → Oesophagus → Small intestine → Large intestine → Anus
B. Mouth → Oesophagus → Stomach → Small intestine → Large intestine → Anus
C. Mouth → Oesophagus → Small intestine → Stomach → Large intestine → Anus
D. Mouth → Stomach → Small intestine → Oesophagus → Large intestine → Anus

[ ]

10. A student observes that a plant's leaves have turned yellow and the plant looks weak. Which part of the plant system is likely not functioning properly?
A. Roots cannot absorb water
B. Stem cannot transport water
C. Leaves cannot make food
D. Flowers cannot produce seeds

[ ]

Section B: Short-Answer Questions (5 × 2 marks = 10 marks)

Write your answers in the spaces provided. Answer in complete sentences where appropriate.

11. State the function of the leaves in a plant system.

12. Name the organ in the human digestive system where most nutrients are absorbed into the bloodstream.

13. The diagram below shows the human digestive system.

Diagram for Q13 (P4 Science)

Generated diagram for Q13.

(a) Write the letter of the organ where digestion of food first begins.

(b) Write the letter of the organ that absorbs water from undigested food.

14. Explain why the roots are important for the survival of a plant.

15. A potted plant is watered only at the base of the stem, not on the leaves. After a few days, the leaves are still green and healthy. Explain how water reaches the leaves.

Section C: Structured / Open-Ended Questions (5 × 4 marks = 20 marks)

Answer all questions in the spaces provided. Show your working or reasoning clearly.

16. The diagram below shows a cross-section of a stem.

Diagram for Q16 (P4 Science)

Generated diagram for Q16.

(a) Name the two types of transport tubes found in the stem.

(b) State the function of each type of tube.

Water-carrying tubes: __________________________________________________________
Food-carrying tubes: __________________________________________________________

(c) If the food-carrying tubes are removed in a ring around the stem (ringing), the upper part of the stem swells after some time. Explain why this happens.

17. Study the flowchart below about the human digestive system.

Diagram for Q17 (P4 Science)

Generated diagram for Q17.

(a) Fill in the two missing organs in the flowchart.

(b) In which organ does the digestion of proteins begin?

(d) Why is the small intestine coiled and very long?

18. Two similar plants, Plant X and Plant Y, are used in an experiment. Plant X has all its leaves removed. Plant Y is left unchanged. Both plants are watered daily and placed in sunlight. After two weeks, Plant Y grows taller and healthier, while Plant X withers and dies.

(a) Explain why Plant X died.

(b) What does this experiment show about the function of leaves?

19. The table below shows the time taken for food to pass through different parts of the digestive system.

Part of Digestive System	Time Taken (hours)
Mouth	0.1
Oesophagus	0.01
Stomach	3
Small intestine	5
Large intestine	15

(a) In which part does food spend the longest time?

(b) Calculate the total time taken for food to pass through the entire digestive system.

(d) Suggest one reason why food stays in the large intestine for the longest time.

20. A student wants to investigate whether the number of leaves on a plant affects the amount of water absorbed by the roots. She sets up the following experiment:

Plant A: 10 leaves
Plant B: 5 leaves
Plant C: No leaves (all removed)

All three plants are of the same type, same size, planted in the same type of soil, and given the same amount of water daily. The amount of water left in the soil is measured each day.

(a) What is the changed variable (independent variable) in this experiment?

(b) What is the measured variable (dependent variable)?

(d) Predict which plant will absorb the most water and explain why.

End of Quiz

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Answers

Primary 4 Science Quiz - Systems (Answer Key)

Total Marks: 40

Section A: Multiple-Choice Questions (10 × 1 mark = 10 marks)

1. C — Roots absorb water and minerals from the soil. They also anchor the plant, but their primary physiological function is absorption.
Marking note: 1 mark for correct answer.

2. C — Digestion begins in the mouth where teeth mechanically break down food and saliva (containing amylase) starts chemical digestion of starch.
Marking note: 1 mark for correct answer.

3. B — The stem transports water and food (via xylem and phloem) and supports the plant upright.
Marking note: 1 mark for correct answer.

4. B — The stomach produces gastric juices (including hydrochloric acid and pepsin) that break down proteins.
Marking note: 1 mark for correct answer.

5. C — Leaves make food through photosynthesis, which requires light. In darkness, leaves cannot photosynthesise.
Marking note: 1 mark for correct answer.

6. B — The oesophagus (food pipe) connects the mouth to the stomach. The trachea is the windpipe for air.
Marking note: 1 mark for correct answer.

7. D — The small intestine is the main site of nutrient absorption. Its inner walls have villi that increase surface area for absorption into the bloodstream.
Marking note: 1 mark for correct answer. Common mistake: confusing large intestine's water absorption with small intestine's nutrient absorption.

8. C — Part R is the leaves, which make food for the plant through photosynthesis.
Marking note: 1 mark for correct answer.

9. B — Correct order: Mouth → Oesophagus → Stomach → Small intestine → Large intestine → Anus.
Marking note: 1 mark for correct answer.

10. C — Yellow leaves indicate the plant cannot make food (chlorophyll breaks down). Leaves are the food-making organs.
Marking note: 1 mark for correct answer.

Section B: Short-Answer Questions (5 × 2 marks = 10 marks)

11. The leaves make food for the plant through photosynthesis, using sunlight, carbon dioxide, and water.
Marking: 1 mark for "make food" or "photosynthesis"; 1 mark for mentioning sunlight/light energy.

12. The small intestine.
Marking: 2 marks for correct answer. Accept "small intestine" only.

13. (a) A (Mouth)
(b) E (Large intestine)
Marking: 1 mark each. The mouth is where digestion begins (mechanical and chemical). The large intestine absorbs water from undigested food matter.

14. Roots absorb water and mineral salts from the soil, which are transported to other parts of the plant for photosynthesis and growth. Roots also anchor the plant firmly to the ground, providing support.
Marking: 1 mark for absorption of water/minerals; 1 mark for anchoring/support. Both functions needed for full marks.

15. Water is absorbed by the roots and transported upwards through the water-carrying tubes (xylem) in the stem to reach the leaves.
Marking: 1 mark for "roots absorb water"; 1 mark for "transported through stem/water-carrying tubes/xylem to leaves".

Section C: Structured / Open-Ended Questions (5 × 4 marks = 20 marks)

16. (a) Water-carrying tubes (xylem) and food-carrying tubes (phloem).
Marking: 1 mark for both correct names.

(b) Water-carrying tubes: Transport water and mineral salts from roots to all parts of the plant.
Food-carrying tubes: Transport food (sugar) made by the leaves to all parts of the plant.
Marking: 1 mark each (2 marks total). Must match function to correct tube.

(c) When food-carrying tubes are removed, food made by the leaves cannot be transported downwards past the cut. Food accumulates above the cut, causing the upper stem to swell.
Marking: 1 mark for "food cannot be transported down"; 1 mark for "food accumulates above cut causing swelling".

17. (a) Oesophagus (between Mouth and Stomach); Small intestine (between Stomach and Large intestine).
Marking: 1 mark each (2 marks total). Order must be correct.

(b) Stomach.
Marking: 1 mark. Proteins are first chemically digested in the stomach by pepsin in acidic conditions.

(c) Water is absorbed from the undigested food, and the remaining waste is formed into faeces.
Marking: 1 mark for water absorption; 1 mark for faeces formation/waste removal.

(d) The small intestine is long and coiled to increase the surface area for absorption of digested nutrients into the bloodstream.
Marking: 1 mark for "increase surface area"; 1 mark for "for absorption of nutrients".

18. (a) Plant X died because its leaves were removed. Without leaves, the plant cannot make food through photosynthesis. Without food, the plant cannot carry out life processes (growth, repair, respiration) and eventually dies.
Marking: 1 mark for "no leaves → no photosynthesis"; 1 mark for "no food made"; 1 mark for "plant dies without food".

(b) Leaves are essential for making food (photosynthesis) for the plant. Without leaves, the plant cannot survive.
Marking: 1 mark for "leaves make food"; 1 mark for "essential for survival".

(c) Plant X would grow more slowly than Plant Y but may survive. With half the leaves, it can still make some food, but less than Plant Y, so growth is reduced.
Marking: 1 mark for "grow slower/survive"; 1 mark for "less food made with fewer leaves".

19. (a) Large intestine (15 hours).
Marking: 1 mark.

(b) Total time = 0.1 + 0.01 + 3 + 5 + 15 = 23.11 hours.
Marking: 1 mark for correct addition; 1 mark for correct answer with unit (hours).

(c) Food stays in the stomach for several hours because the stomach churns food mechanically and mixes it with gastric juices to break it down into a semi-liquid mixture (chyme), especially digesting proteins.
Marking: 1 mark for "churning/mechanical breakdown"; 1 mark for "chemical digestion of proteins / mixing with gastric juices".

(d) The large intestine absorbs water from undigested food, which is a slow process. It also stores waste temporarily before removal.
Marking: 1 mark for "water absorption is slow"; 1 mark for "stores waste / forms faeces".

20. (a) Number of leaves on the plant.
Marking: 1 mark.

(b) Amount of water absorbed by the roots (or amount of water left in the soil).
Marking: 1 mark.

(c) Any two: Type of plant, size of plant, type of soil, amount of water given daily, amount of sunlight, temperature, pot size.
Marking: 1 mark each (2 marks total). Must be relevant controlled variables.

(d) Plant A (10 leaves) will absorb the most water. More leaves mean more transpiration (water loss through stomata), creating a stronger "pull" (transpiration pull) that draws more water up from the roots.
Marking: 1 mark for "Plant A"; 1 mark for "more leaves → more transpiration → more water absorbed"; 1 mark for explaining transpiration pull or water loss through leaves.

End of Answer Key