Primary 5 Science Systems Quiz

Primary 5 Science Quiz - Systems: Answer Key

Total Marks: 40 marks

Section A: Multiple Choice (1 mark each)

1. C — Producing red blood cells in the lungs

Explanation: Red blood cells are produced in the bone marrow, not the lungs. The circulatory system does transport oxygen (A), remove waste (B), and transport nutrients from digested food (D). Lungs are for gas exchange, not blood cell production.

2. B — Xylem

Explanation: Xylem vessels transport water and dissolved mineral salts from the roots up to the leaves and other parts of the plant. Phloem (A) transports food, not water. Stomata (C) are pores for gas exchange, not vessels. Vein (D) is a term used in animals, not plant transport tissue.

3. A — It lights up because the circuit is complete

Explanation: When the switch is closed, the circuit forms a complete loop from the positive terminal of the battery, through the switch and bulb, back to the negative terminal. Electric current can flow, so the bulb lights up. For a bulb to light, we need a complete circuit with a power source (battery), not just any closed loop.

4. C — Oxygen

Explanation: During respiration, humans take in oxygen from the air. This oxygen is absorbed into the blood in the lungs and transported by red blood cells to all body cells. Cells use oxygen to release energy from food. Carbon dioxide (A) is a waste product released, not taken in.

5. B — Condensation

Explanation: Condensation is the process where water vapour cools down and changes back into liquid water droplets, forming clouds. Evaporation (A) is when liquid water turns to vapour (happens at the surface of water bodies). Precipitation (C) is water falling as rain, snow, etc. Collection (D) is water gathering in oceans, lakes, etc.

6. C — Left atrium

Explanation: Blood returning from the lungs (oxygen-rich blood) enters the left atrium of the heart. From there it passes to the left ventricle and is pumped out to the body. The right side (A and B) receives deoxygenated blood returning from the body and pumps it to the lungs. Remember: "Left = Lungs return" helps recall this flow pattern.

7. B — Phloem

Explanation: Phloem transports food (sugar/glucose) made during photosynthesis in the leaves to all other parts of the plant, including roots, fruits, and growing areas. Xylem (A) carries water upward only. This transport of food in phloem is sometimes called translocation.

8. B — Beaker A; evaporation is faster at higher temperatures

Explanation: Beaker A in the sunny spot has a higher temperature. Higher temperature gives water particles more kinetic energy, so more particles can escape from the liquid surface as water vapour. Evaporation occurs at any temperature (not only in sunlight as C suggests), and shade does not prevent all evaporation (D is wrong) — it just slows it down.

9. B — To control whether the circuit is open or closed

Explanation: A switch is a control device. When open (off position), it breaks the circuit so current cannot flow. When closed (on position), it completes the circuit so current can flow. The battery (A) provides energy, not the switch. Voltage increase (C) and energy conversion (D) are functions of other components.

10. C — Circulatory system — Transports substances around the body

Explanation: The circulatory system (heart, blood, blood vessels) transports oxygen, nutrients, hormones, and waste products. A is wrong because digestion is the digestive system's role. B is wrong because gas exchange is the respiratory system. D is wrong because pumping blood is the heart's function within the circulatory system, not the nervous system's.

Section B: Short Answer (2 marks each)

11. (a) Water and mineral salts [1]

(b) Phloem transports food/sugars made in leaves to other parts of the plant [1]. Without this, roots and other non-photosynthetic parts would not receive the energy they need to grow and survive.

Note: Accept "food," "sugar," or "glucose." The explanation must mention transport to other parts of the plant.

12. (a) The muscles need more oxygen and nutrients/there is more carbon dioxide to remove [1]. The heart pumps faster to deliver more oxygenated blood and remove more waste products.

(b) Oxygen [1] (accept carbon dioxide, glucose, nutrients)

Explanation: During exercise, muscle cells respire faster and need more oxygen to release energy. The heart rate increases to pump blood faster around the body. Common mistake: saying "oxygen" alone without explaining why more is needed.

13. (a) Part C [1]

(b) It has villi / it is very long / it has thin walls / good blood supply [1]

Explanation: The small intestine (C) is the main site of absorption. Villi are tiny finger-like projections that massively increase the surface area for absorption. The walls are one-cell thick, allowing quick diffusion into blood. Long length (~6 metres in adults) provides more time and surface for absorption.

14. (a) Transpiration [1]

(b) Plant A has leaves with stomata through which water vapour escapes [1]. Plant B has no leaves, so no transpiration can occur / water cannot escape. The water vapour condenses on the cooler inside surface of the plastic bag.

Explanation: Transpiration is the loss of water vapour from plant leaves through stomata. The sealed bag traps this water vapour, which condenses into visible droplets. Without leaves, this process cannot happen.

15. (a) Circuit Y [1]

(b) In a parallel circuit, there are multiple paths for current [1]. If one bulb is removed/breaks, current can still flow through the other path. In series (Circuit X), there is only one path, so removing one bulb breaks the entire circuit.

Key concept: Parallel circuits provide independent paths; series circuits have dependent components.

16. (a) As body size increases, heart rate decreases / there is an inverse relationship [1]

(b) Smaller animals lose heat faster (have higher surface area to volume ratio) [1], so they need faster blood circulation to maintain body temperature / deliver more energy for heat production.

Alternative answer: Smaller animals have higher metabolic rates and need to transport oxygen and nutrients faster to supply their active cells.

17. (a) P: Evaporation [0.5]; R: Precipitation [0.5]

(b) The Sun provides heat energy [0.5] which causes water particles to gain kinetic energy and change from liquid to gas / water vapour [0.5].

Explanation: Evaporation requires energy input. The sun's thermal energy increases the kinetic energy of water molecules at the surface of water bodies, allowing them to escape into the air as water vapour.

18. (a) The biconcave (doughnut/disc) shape increases surface area [0.5] for absorbing oxygen / allows more oxygen to be carried [0.5]

(b) Red blood cells have no nucleus / red blood cells contain haemoglobin / white blood cells fight germs while red blood cells carry oxygen / there are more red blood cells than white blood cells [1]

Note: Any valid difference other than shape is acceptable. The no-nucleus feature allows more space for haemoglobin, the iron-containing protein that binds oxygen.

Section C: Application and Analysis (4 marks each)

19. (a) More batteries in series provide higher total voltage [1]. The voltage adds up (1.5V + 1.5V + 1.5V = 4.5V in Circuit 3 vs 1.5V in Circuit 1) [1]. Higher voltage pushes more current through the bulb, making it brighter. Note: Accept conceptual explanation without calculation.

Marking breakdown: [1] for recognising voltage increases with more batteries; [1] for linking higher voltage to more current/brightness.

(b) Both bulbs would be dimmer than the single bulb in Circuit 3 [1]. In a series circuit, the voltage is shared between components / there is only one path so resistance increases / current decreases through each bulb [1].

Explanation: With two bulbs in series, the total resistance increases and each bulb gets only part of the total voltage. The current through both bulbs is the same but less than with one bulb, so both glow less brightly. This is a key difference between series and parallel arrangements.

20. (a) Plant Y had petroleum jelly only on the upper surface, leaving the lower surface with stomata uncovered [1]. Water vapour could still escape through stomata on the lower surface / more stomata are on the lower surface, so water loss was greatest [1].

Explanation: The petroleum jelly blocks stomata and prevents transpiration. By only covering the upper surface, Plant Y still had functional stomata on the lower surface where most stomata are located.

(b) Plant X (upper surface covered) lost little water, while Plant Y (lower surface covered) lost much water [1]. This shows that most stomata must be on the lower surface / if stomata were mainly on top, Plant X would have lost the most water [1].

Explanation: The experimental results provide evidence: minimal water loss when upper surface is blocked (Plant X) but major water loss when lower surface is blocked (Plant Y). Therefore, the lower surface must have more stomata. This is an adaptation to reduce water loss — lower stomata are shaded from direct sun and wind.

Note: Accept answers that correctly interpret the pattern even if phrased differently. The key is using the data pattern to infer stomata location.

END OF ANSWER KEY