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Primary 6 PSLE Science Semestral Assessment 2 (End of Year) Paper 2
Free P6 PSLE Science SA2 Paper 2, Nemo3 Exam version, with questions, answers, and PSLE-focused practice for Singapore students.
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TuitionGoWhere Practice Paper - Science Primary 6 PSLE (Answer Key)
Subject: Science
Level: Primary 6 PSLE
Paper: SA2 Version 2
Total Marks: 100
SECTION A (56 marks)
Question 1
Answer: (4)
Explanation: Not all living things can make their own food. Only plants (producers) can make their own food through photosynthesis. Animals and fungi are consumers/decomposers that obtain food by eating other organisms.
Key concept: Living things need air, food, water; can reproduce; respond to changes. Only plants are autotrophic.
Question 2
Answer: (4)
Explanation: Whales are mammals, not fish. They breathe with lungs, give birth to live young, feed young with milk, and have hair (though minimal). Mushrooms are fungi (not plants), but the chart classifies them under non-flowering plants which is a common simplification in primary science. Bats are mammals. Penguins are birds.
Key concept: Vertebrate classification - whales are marine mammals.
Question 3
Answer: (2)
Explanation: The cell has a cell wall and chloroplasts, which are characteristic of plant cells. Animal cells lack cell walls and chloroplasts. Bacterial cells are prokaryotic (no nucleus). Fungal cells have cell walls made of chitin, not cellulose, and lack chloroplasts.
Key concept: Plant cell identification - cell wall (cellulose) and chloroplasts are key distinguishing features.
Question 4
Answer: (2)
Explanation: Bala is correct - yeast is a microorganism (fungus) that reproduces by budding. Cindy is correct - bacteria are microscopic and require a microscope to be seen. Ali is incorrect - not all microorganisms are harmful (e.g., yeast in bread, bacteria in yogurt, decomposers). Devi is incorrect - mould is a fungus, not a bacterium.
Key concept: Microorganism classification and beneficial/harmful roles.
Question 5
Answer: (2)
Explanation: Organism X has a backbone (vertebrate), feathers → Bird. Organism Y has no backbone (invertebrate), 8 legs → Arachnid (spiders, scorpions). Insects have 6 legs.
Key concept: Using dichotomous keys/flowcharts for classification.
Question 6
Answer: (2)
Explanation: Bacteria and mushrooms (fungi) are both decomposers. Earthworms are detritivores (consume dead matter but are animals). Yeast is a fungus but is a microorganism, not typically classified as a decomposer in the same ecological role. Ferns are plants (producers).
**
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TuitionGoWhere Practice Paper - Science Primary 6 PSLE (Answer Key)
Subject: Science
Level: Primary 6 PSLE
Paper: SA2 Version 2
SECTION A (56 marks)
| Question | Answer | Explanation |
|---|---|---|
| 1 | (4) | Not all living things can make their own food. Only plants (producers) can photosynthesise. Animals and fungi are consumers/decomposers. |
| 2 | (1) and (4) | Mushroom is a fungus, not a non-flowering plant. Whale is a mammal, not a fish. |
| 3 | (2) | The cell has a cell wall and chloroplasts, which are characteristic of plant cells. |
| 4 | (2) | Bala: Yeast is a microorganism that reproduces (by budding). Cindy: Bacteria are microscopic. Ali is wrong (some microorganisms are beneficial). Devi is wrong (mould is a fungus, not bacteria). |
| 5 | (2) | Organism X has backbone + feathers = Bird. Organism Y has no backbone + 8 legs + 2 body parts = Arachnid. |
| 6 | (2) | Bacteria and mushroom (fungi) are both decomposers. Earthworm is a detritivore, yeast is a fungus but often classified separately, mould is a fungus (decomposer) but fern is a plant. |
| 7 | (2) | Organism Q: Has cell wall, no chloroplasts, cannot move freely, reproduces by spores → Fungus. P is a plant, R and S are animals. |
| 8 | (3) | Food chains with exactly 4 organisms: Plant→Grasshopper→Frog→Snake; Plant→Grasshopper→Bird→Hawk; Plant→Caterpillar→Bird→Hawk; Plant→Rabbit→Snake→Hawk. (4 chains) |
| 9 | (3) | Structural adaptation: physical feature (thick fleshy stems). Others are behavioural adaptations. |
| 10 | (3) | Egg, larva, and pupa stages live in water. Adult is terrestrial/flying. |
| 11 | (2) | Bacteria reproduce asexually by binary fission. Not all cause diseases; they are unicellular; they lack a nucleus (prokaryotes). |
| 12 | (1) | Group A: Frog = amphibian (moist skin, breathes through lungs/skin/gills, lays eggs in water). |
| 13 | (2) | Ferns reproduce by spores produced in sori on the underside of fronds. |
| 14 | (3) | Yeast is a fungus, not a bacterium. |
| 15 | (2) | Fewer caterpillars → less eaten plants → plant population increases. Fewer caterpillars → less food for birds → bird population decreases. |
| 16 | (4) | Insects have six legs, not eight. Eight legs is characteristic of arachnids. |
| 17 | (2) | Small intestine is the main site for absorption of digested nutrients (villi increase surface area). |
| 18 | (1) | Correct taxonomic hierarchy: Kingdom → Phylum → Class → Order → Family → Genus → Species. |
| 19 | (1) | Organism W: Nucleus + cellulose cell wall + chloroplasts + autotrophic = Plant. X = Fungus (chitin), Y = Bacteria (peptidoglycan, no nucleus), Z = Animal (no cell wall). |
| 20 | (2) | Viruses are obligate intracellular parasites; they replicate only inside living host cells. They are non-living outside host; antibiotics don't work on them; they are smaller than bacteria. |
| 21 | (2) | Zooplankton eats phytoplankton (predator) and is eaten by small fish/jellyfish (prey). Phytoplankton is producer only; Shark and Turtle are top predators only. |
| 22 | (3) | Chloroplasts are present in plant cells (for photosynthesis) but absent in animal cells. |
| 23 | (1) | Fern (spores), moss (spores), mushroom (spores) all reproduce by spores. Yeast buds; bacteria binary fission; mould spores but yeast/bacteria not spores. |
| 24 | (2) | Dolphins are mammals: breathe air with lungs, give live birth, produce milk. Fish have gills, lay eggs (mostly). |
| 25 | (2) | Has chlorophyll → cannot move freely → Plant. (Euglena moves freely; fungi/bacteria/protozoa lack chlorophyll). |
| 26 | (3) | Behavioural adaptation: action/behaviour (flying in V-formation). Others are structural (fur, hump, spines). |
| 27 | (2) | Budding is a form of asexual reproduction (offspring genetically identical to parent). |
| 28 | (4) | Organisms in the same genus have the same genus name but different species names (e.g., Panthera leo, Panthera tigris). |
SECTION B (44 marks)
Question 29
(a) Structure A: Cell wall
Structure B: Chloroplasts
[2]
(b) Function of cell wall: Provides shape and support to the plant cell / Protects the cell / Prevents cell from bursting when water enters.
Function of chloroplasts: Contains chlorophyll to trap light energy for photosynthesis / Site of photosynthesis.
[2]
(c) The animal cell does not have a cell wall, so it cannot maintain a fixed shape and is irregular/round. The plant cell has a rigid cell wall giving it a fixed, rectangular shape.
[1]
Question 30
(a) Group X: Fungi
Group Y: Bacteria
[1]
(b) Fungi: Cell wall made of chitin (accept: reproduce by spores, saprotrophic nutrition, eukaryotic).
Bacteria: No nucleus / Prokaryotic / Cell wall made of peptidoglycan (accept: reproduce by binary fission, unicellular).
[2]
(c) Yeast is a fungus (unicellular fungus) but is microscopic like bacteria. It reproduces by budding (asexual), not binary fission. It has a nucleus (eukaryotic) and cell wall made of chitin, not peptidoglycan.
[2]
Question 31
(a) Food chain: Plant → Grasshopper → Frog → Snake → Hawk
(or Plant → Caterpillar → Bird → Hawk; Plant → Rabbit → Snake → Hawk, etc.)
[1]
(b) Energy is lost as heat at each trophic level (through respiration, movement, undigested waste). Only about 10% is transferred. There is insufficient energy to support another trophic level.
[2]
(c) Decomposers (bacteria and fungi) break down dead organisms and waste, recycling nutrients back into the environment for plants to reuse.
[1]
Question 32
(a) Stage A: Egg
Stage B: Larva
Stage C: Pupa
Stage D: Adult
[2]
(b) Complete metamorphosis (four distinct stages: egg, larva, pupa, adult; larva looks very different from adult).
[1]
(c) Mosquito: Larva and pupa live in water, breathe air through siphon/trumpet.
Frog: Tadpole lives in water, breathes through gills (later lungs).
Difference: Mosquito larvae/pupae are air-breathers (come to surface); frog tadpoles are water-breathers (gills).
[2]
Question 33
(a) Structural adaptation: Thick, waxy cuticle / Sunken stomata / Reduced leaves (spines) / Extensive shallow roots / Succulent stems.
(Any one)
[1]
(b) Behavioural adaptation: Stomata open at night (CAM photosynthesis) to reduce water loss / Dormancy during extreme drought.
(Any one)
[1]
(c) The adaptation reduces water loss (transpiration) and stores water, allowing the cactus to survive long periods without rain in the desert.
[1]
Question 34
(a) Bacteria and Fungi (mould/yeast)
[1]
(b) Decomposers break down dead organic matter and waste products into simpler substances (nutrients/mineral salts), returning them to the soil/air for producers (plants) to reuse. This recycles nutrients in the ecosystem.
[2]
(c) Without decomposers, dead matter and waste would accumulate, nutrients would be locked up and not recycled, plants would lack essential minerals, and the entire food web would collapse.
[2]
Question 35
(a) Vertebrates have a backbone (vertebral column); Invertebrates do not have a backbone.
[1]
(b) Animal P: Fish (gills, scales, fins, lay eggs in water)
Animal Q: Mammal (hair/fur, lungs, give birth to live young, produce milk)
[2]
(c) Bat (mammal) → has hair, gives birth to live young, feeds young milk, breathes with lungs.
Penguin (bird) → has feathers, lays eggs, breathes with lungs, beak.
Difference: Bat has hair/fur and gives live birth; Penguin has feathers and lays eggs.
[2]
Question 36
(a) Photosynthesis
[1]
(b) Carbon dioxide + Water → (Light + Chlorophyll) → Glucose + Oxygen
[1]
(c) Light intensity: Rate increases with light intensity until a maximum (saturation point).
Carbon dioxide concentration: Rate increases with CO₂ concentration until a maximum.
Temperature: Rate increases with temperature up to an optimum (~35°C), then decreases as enzymes denature.
(Any two factors with correct trend)
[2]
(d) Oxygen is released as a by-product, which animals and other organisms need for respiration to release energy from food.
[1]
Question 37
(a) Pollination: Transfer of pollen grains from anther to stigma.
Fertilisation: Fusion of male gamete (in pollen) with female gamete (in ovule) to form a zygote.
[2]
(b) Wind-pollinated: Small, dull petals; no nectar/scent; large feathery stigma; light, smooth pollen; long exposed stamens.
Insect-pollinated: Large, colourful petals; nectar/scent; sticky stigma; heavy, sticky pollen; stamens inside flower.
(Any two differences)
[2]
(c) After fertilisation, the ovary develops into the fruit and the ovules develop into seeds. The fruit protects the seeds and aids in seed dispersal.
[1]
Question 38
(a) Circulatory system: Transports oxygen, nutrients, hormones to cells and carbon dioxide, waste away from cells.
Respiratory system: Gaseous exchange – takes in oxygen, removes carbon dioxide.
Digestive system: Breaks down food into simple substances (nutrients) for absorption into the blood.
[3]
(b) Digested nutrients (glucose, amino acids) are absorbed in the small intestine into the bloodstream (circulatory system) and transported to all cells for respiration (with oxygen from respiratory system) to release energy.
[2]
(c) Exercise increases demand for energy → heart beats faster (circulatory) and breathing rate increases (respiratory) to supply more oxygen and glucose to muscles and remove more carbon dioxide.
[1]
MARKING GUIDELINES
- Section A: 2 marks per question (28 × 2 = 56 marks)
- Section B: Marks as indicated (Total 44 marks)
- Total: 100 marks
Key Concepts Tested:
- Diversity of Living Things (Classification, Characteristics)
- Cells (Plant vs Animal, Microorganisms)
- Life Cycles & Reproduction
- Adaptations (Structural vs Behavioural)
- Food Chains/Webs & Energy Flow
- Decomposers & Nutrient Cycling
- Plant Systems (Photosynthesis, Transport, Reproduction)
- Human Systems (Digestive, Circulatory, Respiratory)
- Interactions (Environment, Ecosystems)
End of Answer Key