Primary 6 PSLE Science Systems Quiz

Primary 6 PSLE Science Quiz - Systems

Answer Key

Section A: Multiple Choice Questions (10 marks)

1. C — A single plastic ruler [1]
Reasoning: A system is made up of parts that work together to carry out a function. A single plastic ruler is one object with no interacting parts. A bicycle, digestive system, and water cycle all have multiple components working together.

2. B — taking in oxygen and removing carbon dioxide from the body [1]
Reasoning: The respiratory system is specifically for gas exchange — inhaling oxygen and exhaling carbon dioxide. Transporting oxygen is the role of the circulatory system.

3. C — Xylem [1]
Reasoning: Xylem tissue transports water and mineral salts upward from roots to leaves. Phloem transports food (glucose).

4. B — pump to push blood around the body [1]
Reasoning: The heart's primary function is to act as a muscular pump that circulates blood throughout the body.

5. A — Heart → Lungs → Body → Heart [1]
Reasoning: Deoxygenated blood goes from the heart to the lungs (pulmonary circulation), becomes oxygenated, returns to the heart, then is pumped to the body (systemic circulation), and returns to the heart.

6. D — All of the above [1]
Reasoning: A lever system can change the direction of force, reduce effort needed, and increase the distance a load moves, depending on the class of lever.

7. B — The solar system [1]
Reasoning: The solar system is a natural system consisting of the sun, planets, moons, and other celestial bodies that interact through gravitational forces. The other options are man-made systems.

8. C — Small intestine [1]
Reasoning: The small intestine is the main site of nutrient absorption due to its large surface area (villi). The mouth and stomach are involved in digestion; the large intestine absorbs water.

9. C — Phloem [1]
Reasoning: Phloem is the plant tissue responsible for transporting food (glucose/sucrose) from the leaves (where photosynthesis occurs) to other parts of the plant.

10. B — work together to carry out a function [1]
Reasoning: By definition, a system is a group of related components that work together to perform a specific function.

Section B: Short Answer Questions (20 marks)

11. (a) Mouth [1]
Marking note: Accept "oral cavity". Do not accept "oesophagus" or "stomach".

(b) Any two of the following [1 mark each, total 2]:

• Digestion of food (completion of chemical digestion)
• Absorption of digested food / nutrients into the blood
• Absorption of nutrients through villi

Marking note: "Absorption" alone is acceptable. "Digestion" alone is acceptable. Do not award marks for "absorption of water" — that is the function of the large intestine.

12. (i) To transport oxygen, nutrients, and waste products around the body (or similar) [1]
Marking note: Accept any correct description of circulatory system function. "Pump blood" alone is too vague — must mention transport of substances.

(ii) Xylem [1]
Marking note: Must be spelt correctly. Accept "xylem tissue".

(iii) Diaphragm (or windpipe / trachea) [1]
Marking note: Accept any correct component of the respiratory system. "Nose" or "bronchi" also acceptable.

13. (a) Xylem [1]
Marking note: Must be spelt correctly.

(b) [2 marks]

• The xylem tissues are arranged in vessels/tubes that run up the stem in lines/columns. [1]
• Since the red-coloured water is transported only through the xylem vessels, the red colour appears in lines (where the xylem is located) rather than being spread throughout the stem. [1]

Marking note: Students must mention xylem AND explain that xylem is arranged in lines/vessels. Award 1 mark for mentioning xylem only without explanation of arrangement.

14. (a) Any one of the following [1]:

• Reduces the effort needed to lift the load
• Makes it easier to lift heavy objects
• Changes the direction of the applied force

(b) [2 marks]
Using the principle of moments:
Clockwise moment = Anticlockwise moment
Load × Load arm = Effort × Effort arm
200 N × 0.5 m = Effort × 2 m
100 = Effort × 2
Effort = 50 N [1 for correct working, 1 for correct answer with unit]

Marking note: Award 1 mark for correct substitution even if final answer is wrong. Unit (N) must be stated for full marks.

15. [3 marks]
During running, the body needs more energy, so:

• The respiratory system takes in more oxygen and removes more carbon dioxide. [1]
• The circulatory system transports the oxygen from the lungs to the muscles more quickly (heart beats faster). [1]
• The circulatory system also carries carbon dioxide from the muscles back to the lungs for removal. [1]

Marking note: Award 1 mark for each valid point linking the two systems. Students must show how the two systems interact, not just describe each system separately. Award a maximum of 2 marks if only one system is described.

16. (a) Left ventricle [1]

(b) [2 marks]

• The left ventricle has a thicker muscular wall because it needs to pump blood to all parts of the body (systemic circulation). [1]
• The right ventricle only pumps blood to the lungs (pulmonary circulation), which is a shorter distance and requires less force/pressure. [1]

Marking note: Award 1 mark for identifying the longer distance/greater force needed, and 1 mark for contrasting with the right ventricle. "Pumps blood further" alone earns 1 mark.

Section C: Structured / Application Questions (10 marks)

17. (a) [2 marks]
Advantage: Changes the direction of the applied force (allows you to pull down to lift the load up) [1]
Disadvantage: Does not reduce the effort needed (effort = load for a single fixed pulley) [1]

Marking note: Accept any valid advantage/disadvantage. Common wrong answer: "reduces effort" — this is incorrect for a single fixed pulley.

(b) 100 N [1]
A single fixed pulley only changes the direction of force; it does not provide any mechanical advantage. Therefore, the effort required equals the load (100 N).

Marking note: Award the mark for the correct value with or without explanation. If the student writes "100 N because there is no mechanical advantage", award the mark.

18. (a) Producer: Grass [1]
Top consumer: Eagle [1]

(b) [2 marks]

• If the number of snakes increases, more frogs will be eaten/consumed by the snakes. [1]
• The population of frogs will decrease. [1]

Marking note: Award 1 mark for identifying the predator-prey relationship and 1 mark for stating the decrease. "Frogs will die" is acceptable but less precise.

(c) [1]
An ecosystem is a system because it is made up of living organisms and the physical environment that interact and work together to maintain a balanced cycle of energy flow and nutrient cycling.

Marking note: Accept any answer that refers to parts working together. Key idea: multiple components interacting.

19. (a) Evaporation [1]
Marking note: Must be spelt correctly. Do not accept "transpiration" — that refers to water vapour from plants.

(b) [3 marks]

• The water cycle is a system because it consists of multiple processes/parts (evaporation, condensation, precipitation, runoff, transpiration) that are interconnected. [1]
• Each part depends on and affects the others — for example, evaporation provides water vapour for condensation, and condensation leads to precipitation. [1]
• Together, these parts work to continuously move and recycle water through the environment, maintaining a balanced water supply on Earth. [1]

Marking note: Award 1 mark for identifying multiple parts, 1 mark for explaining how parts are linked/interdependent, and 1 mark for stating the overall function. Answers that only list processes without explaining how they work together earn a maximum of 1 mark.

20. (a) Chemical energy → Light energy (and Heat energy) [1]
Marking note: Must mention both the input (chemical) and output (light/heat) energy forms. "Electrical energy to light energy" is also acceptable if the student considers the battery as the source of electrical energy.

(b) [2 marks]

• When the switch is open, the circuit is incomplete/broken. [1]
• For a system to function, all its parts must be connected and working together. Since the circuit is broken, electrical energy cannot flow through the system, and the bulb will not light up. [1]

Marking note: Award 1 mark for identifying the broken/incomplete circuit and 1 mark for linking it to the concept of a system (parts must be connected to function).

(c) Any one of the following [1]:

• Variable resistor / Rheostat
• Resistor

Marking note: Accept "dimmer switch". Do not accept "another battery" — this changes the energy source rather than controlling brightness within the same system.

Total: 40 marks