Primary 3 Science Semestral Assessment 2 (End of Year) Paper 2

Primary 3 Science Quiz - Diversity (Answer Key)

Total Marks: 40
Version: 2 of 5

Section A: Multiple Choice (Questions 1–8)

8 marks

Section B: Fill in the Blanks and Matching (Questions 9–14)

12 marks

Question 9 (4 marks)

Marking: 1 mark per correct row. Total: 4 marks

Teaching note:

• A dog is living: it needs food/water/air, grows, moves by itself, reproduces, responds to stimuli.
• A mango tree is living: plants grow, make their own food, reproduce (seeds), respond to light/water.
• A river is non-living: water flows due to gravity, not because it is alive; it does not need food or reproduce.
• A glass bottle is non-living: made by humans from sand; no life processes.

Common error: Students sometimes think rivers are living because water "moves" — emphasize that living things move by themselves, not due to external forces.

Question 10 (2 marks)

(a) B — A baby monkey grows into an adult monkey (growth)

(b) A — A vine climbs towards light (responding to change/stimulus)

Marking: 1 mark each. Total: 2 marks

Teaching note:

• Growth means increasing in size or developing into a more mature form over time. Weight gain in animals includes growth, but "growth" specifically refers to development, not just getting bigger temporarily.
• Responding to changes (also called "sensitivity" or "irritability") means reacting to stimuli like light, touch, temperature, or danger.

Question 11 (2 marks)

Based on the visual:

• (a) Living (goldfish — real, living animal)
• (b) Non-living (toy fish — plastic, artificial)
• (c) Living (real rose — real plant)
• (d) Non-living (paper rose — crafted decoration)

Marking: 0.5 mark each. Total: 2 marks

Teaching note: This tests the common misconception that "looking like" a living thing means it is living. The key is to check for life processes, not appearance. Both pairs show real vs. artificial versions — students must look beyond surface similarity.

Question 12 (2 marks)

reproduce

Marking: 2 marks for correct word; 1 mark if "grow" or "respond" is given (wrong word but correct concept of life processes)

Teaching note:

• Reproduce means to produce offspring (young) of the same kind. This ensures the species continues.
• Dogs have puppies, cats have kittens, birds lay eggs, plants produce seeds.
• Non-living things cannot reproduce — a chair does not make smaller chairs!

Question 13 (2 marks)

Answer: False

Reason: The balloon is not a living thing. While it gets bigger, this is not growth in the living sense. Living things grow by building new cells and developing. A balloon just stretches because air pushes against it — there are no cells, no food being used, and the balloon cannot grow by itself (a person pumps air in).

Marking: 1 mark for "False"; 1 mark for clear explanation distinguishing living growth from physical expansion. Total: 2 marks (Note: Original was 1 mark — adjusting to 2 for complete answer, or give 1 mark total: 0.5 for False, 0.5 for reason)

Revised marking for 1 mark: 0.5 for "False", 0.5 for any reasonable explanation.

Question 14 (1 mark)

Answer: Animals (or Fungi / Bacteria)

Marking: 1 mark for any correct group

Teaching note:

• Plants can make their own food through photosynthesis (using sunlight, water, carbon dioxide, and chlorophyll).
• Animals must eat other living things to get food.
• Fungi and bacteria also cannot make their own food — fungi absorb nutrients, bacteria breakdown matter or live as parasites.

Section C: Classification and Short Answer (Questions 15–20)

20 marks

Question 15 (3 marks)

(a) Cow and Pigeon (or any two correctly identified mammals)

Marking: 1 mark each, maximum 2 marks

Teaching note:

• Mammals have hair or fur, give birth to live young (mostly), and feed their young with milk.
• Cow: fur, live young, milk
• Pigeon: Wait — pigeons are birds, not mammals!

Correction: Looking at the animal list: pigeon (bird), salmon (fish), frog (amphibian), python (reptile), cow (mammal), ant (insect).

Correct answer: Only Cow is clearly a mammal from this set. If pigeon was intended as an error-check, full marks only for cow.

Revised acceptable answer: Cow (2 marks if only one mammal); if student writes "cow and pigeon" — 1 mark for cow, note that pigeon is a bird.

(b) Frog (1 mark)

Teaching note: Frogs are amphibians — they have moist skin, live in water as young (tadpoles with gills), and on land as adults (with lungs).

Question 16 (4 marks)

Marking: 1 mark per correct "Yes"; 1 mark per clear explanation with two valid points. Total: 4 marks (1+1+1+1 or 2 marks per row if holistic)

Question 17 (4 marks)

(a) Mammal (1 mark)

Path: Cannot make own food → No feathers → No scales → Mammal

(b) Bird (1 mark)

Path: Cannot make own food → Has feathers → Bird

(c) Plant (1 mark)

Path: Can make own food → Plant

(d) Reptile (1 mark)

Path: Cannot make own food → No feathers → Has scales → Reptile

Teaching note: The flow chart works through key distinguishing features:

• Making own food separates plants (autotrophs) from animals/fungi (heterotrophs)
• Feathers are unique to birds among this set — no other animal group has feathers
• Scales help separate fish/reptiles from mammals/amphibians. Note: Fish also have scales, so additional特征 (gills/fins vs. lungs/limbs) may be needed for finer distinction.

Question 18 (3 marks)

Answer: The object is non-living.

Explanation: The object is non-living because:

• It does not need food — living things need food for energy and growth, but this object stayed the same for a week with no food (1 mark)
• It does not grow — living things grow and develop, but this object stayed the same size (1 mark)
• (Alternative) It cannot move by itself — it only moves with wind; living things move on their own (1 mark)
• (Alternative) It cannot reproduce — no young were seen; living things reproduce (1 mark)

Marking: 1 mark for "non-living"; 1 mark per valid characteristic cited with evidence from the table. Maximum: 3 marks

Teaching note: This is a data interpretation question. Students must use evidence from the table, not just state characteristics generally. The observation-result pairs are designed to show that the object fails multiple life tests.

Question 19 (3 marks)

Marking: 1 mark per correct column (both items correct); 0.5 mark if one item correct in mixed column. Total: 3 marks

Teaching note:

• Hibiscus flower & banana tree: Plants — make own food through photosynthesis, have roots/stems/leaves, reproduce by seeds
• Cat & butterfly: Animals — cannot make own food, move by themselves, have senses, reproduce by eggs/live young
• Bread mould & mushroom: Fungi — cannot make own food, absorb nutrients, reproduce by spores (not seeds). Bread mould is specifically mentioned to test that students don't classify all "plant-like" things as plants.

Common error: Bread mould is often mistaken for a plant because it "grows" on bread. Emphasize that mould is a fungus — it does not photosynthesize and spreads through spores.

Question 20 (3 marks)

(a) Responding to changes / Sensitivity / Irritability (1 mark)

The plant stem bends towards the light — this is phototropism, a response to light stimulus.

(b) Any valid example:

• "A cat runs away when it hears a loud noise" (1 mark)
• "A mimosa plant closes its leaves when touched" (1 mark)
• "A sunflower turns to face the sun" (1 mark)
• "A person pulls hand away from hot water" (1 mark)

(c) No, a plastic plant would not show the same response. (0.5 mark)

A plastic plant is non-living — it has no cells, cannot carry out life processes, and cannot detect or respond to light. It might bend if physically pushed, but not by itself towards light. (0.5 mark)

Marking: (a) 1 mark; (b) 1 mark; (c) 1 mark (0.5 for "No", 0.5 for explanation). Total: 3 marks

Teaching note: The image shows positive phototropism — growth towards light, which helps plants get more sunlight for photosynthesis. This is an active, energy-requiring process. Non-living things may appear to "respond" (a sponge absorbs water) but this is passive physical change, not true sensitivity.

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