Primary 6 PSLE Science Practice Paper 3

TuitionGoWhere Practice Paper — Science Primary 6 PSLE

Answer Key — Version 3

Subject: Science (Primary 6 PSLE) Topic: Diversity Total Marks: 100

Section A — Multiple Choice (10 × 2 marks = 20 marks)

1. Answer: B Explanation: Classification of living things is based on observable structural characteristics such as body coverings, number of legs, and methods of reproduction. The number of legs is a valid classification characteristic (e.g., insects have 6 legs, spiders have 8). Colour, diet, and habitat are not reliable classification features because they can vary within a group.

2. Answer: C Explanation: Plants are producers that can make their own food through photosynthesis using sunlight, carbon dioxide, and water. Animals, fungi, and most bacteria cannot make their own food and are consumers or decomposers.

3. Answer: C Explanation: A soft body with no backbone and a hard shell describes a mollusc (e.g., a snail). Insects have an exoskeleton and six legs. Fish have backbones (vertebrates). Mammals have fur/hair and backbones.

4. Answer: D Explanation: All mammals have hair or fur at some stage of their life. Feathers are characteristic of birds. Most mammals give birth to live young (exceptions: platypus and echidna lay eggs). Mammals breathe through lungs, not gills.

5. Answer: B Explanation: Ferns are non-flowering plants that reproduce using spores, whereas flowering plants reproduce using seeds formed in flowers. Ferns do have roots, stems (called rhizomes), and leaves (called fronds), and they need sunlight for photosynthesis.

6. Answer: C Explanation: Moss is a non-flowering plant that reproduces by spores. Rose, orchid, and sunflower are all flowering plants.

7. Answer: C Explanation: A food chain always begins with a producer (an organism that can make its own food, usually a plant). Producers convert light energy into chemical energy, which is then passed on to consumers.

8. Answer: A Explanation: A food chain must start with a producer and flow from prey to predator. Only option A (Grass → Rabbit → Fox → Eagle) follows this correct order. The other options start with consumers or reverse the energy flow.

9. Answer: C Explanation: An ecosystem includes all the living (biotic) and non-living (abiotic) components in a given area, interacting together. This includes plants, animals, microorganisms, water, soil, air, and sunlight.

10. Answer: B Explanation: A polar bear's white fur provides camouflage in the snowy Arctic environment, helping it hunt prey. Polar bears have thick fur (not thin) to keep warm, small ears (not large) to reduce heat loss, and large, broad paws to distribute their weight on ice.

Section B — Structured / Short-Answer Questions (40 marks)

11. (a) (4 marks — 1 mark each)

• W: Bird — has feathers and can fly.
• X: Fish — has scales and fins, lives in water.
• Y: Amphibian (frog) — has moist skin and no scales.
• Z: Insect (butterfly) — has six legs and wings covered in tiny scales.

Marking note: Accept "frog" for Y and "butterfly" for Z. Full marks only if all four are correct.

11. (b) (2 marks — 1 mark each) Any two of the following (or other valid characteristics of living things):

• They need food / energy to survive.
• They can reproduce.
• They can grow.
• They respond to changes in their surroundings.
• They can excrete / remove waste.
• They can breathe / respire.

Marking note: "They can move" alone is not accepted as a defining characteristic of all living things (e.g., plants are living but do not move from place to place).

12. (a) (2 marks) Plant P is most likely a fern. (1 mark) It has roots, stems, and leaves but does not have flowers or seeds, which are the characteristics of ferns. (1 mark)

12. (b) (2 marks) Plant R is most likely an algae. (1 mark) It has no roots, stems, leaves, flowers, or seeds, which are the characteristics of algae — the simplest plants. (1 mark)

12. (c) (1 mark) Plant S is a gymnosperm (or conifer). Marking note: Accept "conifer" or "non-flowering seed plant."

13. (a) (2 marks — 1 mark each)

1. Grass
2. Grass is the only producer listed. (Note: If the question expects two, only "Grass" is available from the food web described. Award 1 mark for "Grass." If the student writes "plants" as a second answer, accept it for the second mark.)

Marking note: Since only one producer (grass) is explicitly described in the food web, award 1 mark for naming "Grass." If the student identifies any other valid producer (e.g., "plants" in general), award the second mark.

13. (b) (1 mark) Any one of the following: Grasshopper, Rabbit, Frog, Lizard, Fox Marking note: The organism must be both eaten by something and eats something. Eagle and snake are only predators (top of the described chain), so they are not accepted.

13. (c) (2 marks) The number of frogs would decrease (1 mark) because grasshoppers are a food source for frogs, so frogs would have less food available. (1 mark)

Marking note: Award 1 mark for stating "decrease" and 1 mark for the reason linking food availability.

13. (d) (2 marks) Grass → Grasshopper → Frog → Snake (2 marks) Alternative: Grass → Grasshopper → Lizard → Eagle (2 marks) Alternative: Grass → Rabbit → Fox → Eagle (2 marks)

Marking note: Award 2 marks for a correct 4-organism food chain starting with a producer and following the correct energy flow. Deduct 1 mark if the chain does not start with a producer or if the order is reversed.

14. (a) (1 mark) Vertebrates

14. (b) (1 mark) Invertebrates

14. (c) (4 marks — 1 mark for each correct example + 1 mark for each correct group)

Example 1: Butterfly — Group: Insect (or Insecta) Example 2: Snail — Group: Mollusc (or Mollusca)

Other acceptable examples:

• Spider — Arachnid
• Crab — Crustacean
• Earthworm — Annelid
• Jellyfish — Cnidarian
• Starfish — Echinoderm

Marking note: The example and group must match. Award 1 mark for a correct example and 1 mark for the correct group, up to 4 marks.

15. (a) (2 marks — 1 mark each) Any two of the following:

• Water availability / moisture — the pond has abundant water; the desert is dry.
• Temperature — the desert has extreme temperatures (very hot days, cold nights); the pond habitat has more moderate temperatures.
• Type of soil — the pond has wet, muddy soil; the desert has dry, sandy soil.
• Amount of rainfall — the pond area receives more rainfall; the desert receives very little rainfall.

Marking note: Accept any valid abiotic factor that differs between the two habitats.

15. (b) (4 marks — 2 marks each)

Thick, fleshy stems: The thick, fleshy stems store water (1 mark), allowing the cactus to survive during long periods without rain in the desert. (1 mark)

Spines instead of leaves: The spines reduce the surface area of the plant (1 mark), which reduces water loss through transpiration, helping the cactus conserve water in the hot, dry desert. (1 mark)

Marking note: For each feature, award 1 mark for identifying the adaptation and 1 mark for explaining how it helps survival.

16. (a) (2 marks) The Rafflesia is a flowering plant (1 mark) because it produces a flower (the largest flower in the world). (1 mark)

Marking note: The key evidence is that it produces a flower. Award 1 mark for the correct classification and 1 mark for the reason.

16. (b) (2 marks) A parasite is an organism that lives on or inside another organism (called the host) (1 mark) and obtains its food and nutrients from the host, harming the host in the process. (1 mark)

Marking note: Award 1 mark for the concept of living on/in another organism and 1 mark for obtaining food/nutrients from it (and causing harm).

16. (c) (2 marks) The Rafflesia produces a smell like rotting flesh to attract flies (1 mark) which help to pollinate the flower by carrying pollen from one Rafflesia flower to another. (1 mark)

Marking note: Award 1 mark for identifying that the smell attracts flies/insects and 1 mark for linking this to pollination.

Section C — Open-Ended / Explanation Questions (40 marks)

17. (a) (6 marks — 1 mark per correctly placed organism)

Marking note:

• Producers (2 marks): Water lilies and Algae — both make their own food by photosynthesis.
• Herbivores (2 marks): Water beetles (eat algae/plant matter), Dragonflies (larvae may feed on algae; accept as herbivore or omnivore depending on life stage — award mark if placed in either herbivore or carnivore/omnivore column).
• Carnivores/Omnivores (2 marks): Fish (eat algae, insects, and small organisms — omnivore), Herons (eat fish — carnivore), Frogs (eat insects — carnivore).

Alternative acceptable classification:

• Dragonfly larvae are carnivorous (eat small aquatic organisms), so placing dragonflies in the carnivore column is also acceptable.
• Some fish are herbivores, but in this context, fish are likely omnivores.

Award 1 mark for each correctly placed organism, up to 6 marks.

17. (b) (3 marks) Producers are important because:

• They make their own food through photosynthesis using sunlight (1 mark).
• They are the first organism in a food chain / they provide food (energy) for all other organisms (consumers) in the ecosystem (1 mark).
• Without producers, there would be no energy entering the ecosystem, and all other organisms would not be able to survive (1 mark).

Marking note: Award 1 mark for each valid point, up to 3 marks. Key ideas: photosynthesis, base of food chain, energy source for ecosystem.

17. (c) (3 marks) If the fish population decreased significantly, the heron population would also decrease (1 mark) because herons depend on fish as their main source of food (1 mark). With less food available, herons would struggle to survive and reproduce, leading to a decline in their population (1 mark).

Marking note: Award 1 mark for stating the heron population would decrease, 1 mark for identifying the food relationship, and 1 mark for explaining the consequence (less food → struggle to survive/reproduce).

18. (a) (3 marks) Organism A is most likely a fish. (1 mark) Reason 1: It has gills for breathing, which is a characteristic of fish. (1 mark) Reason 2: It has scales as its body covering and lives in water, which are characteristics of fish. (1 mark) Alternative reason: It lays eggs in water.

Marking note: Award 1 mark for correctly identifying Organism A and 2 marks for any two valid reasons from the table.

18. (b) (3 marks) Organism E is most likely an amphibian. (1 mark) Reason 1: It has moist skin and can breathe through its skin, which is a characteristic of amphibians. (1 mark) Reason 2: It lives on both land and water, which is a characteristic of amphibians (dual habitat). (1 mark) Alternative reason: It lays eggs and uses both skin and lungs for breathing.

Marking note: Award 1 mark for correctly identifying Organism E and 2 marks for any two valid reasons.

18. (c) (3 marks — 1 mark each) Three characteristics of insects:

1. They have six legs (three pairs of legs).
2. They have an exoskeleton (hard outer covering).
3. Their body is divided into three parts: head, thorax, and abdomen. Alternative: They breathe through spiracles (tiny holes along the body). Alternative: Most insects have wings (at least at some stage).

Marking note: Award 1 mark for each correct characteristic, up to 3 marks.

19. (a) (3 marks) Bala is correct. (1 mark) Classification of animals is based on their structural characteristics (body features), not their behaviour or habitat. (1 mark) A penguin has feathers, lays eggs, and has a beak — all of which are characteristics of birds. Although a penguin swims like a fish, it does not have the characteristics of a fish (such as gills, fins, and scales). (1 mark)

Marking note: Award 1 mark for identifying Bala, 1 mark for the principle of classification by structural features, and 1 mark for applying the principle to the penguin example.

19. (b) (3 marks — 1 mark each) Three characteristics of birds:

1. They have feathers.
2. They have wings (even if some cannot fly).
3. They lay eggs with hard shells. Alternative: They have a beak (no teeth). Alternative: They are warm-blooded (endothermic). Alternative: They have hollow bones to reduce weight.

Marking note: Award 1 mark for each correct characteristic, up to 3 marks.

19. (c) (3 marks) The ability to fly is not the most important characteristic for classifying a bird because:

• Some birds, such as penguins, ostriches, and kiwis, cannot fly but are still classified as birds (1 mark).
• The defining characteristics of birds are structural features such as having feathers, a beak, wings, and laying eggs — not their ability to fly (1 mark).
• If we used the ability to fly as the main criterion, flightless birds would be incorrectly classified, and some flying animals (like bats, which are mammals) might be incorrectly grouped with birds (1 mark).

Marking note: Award 1 mark for each valid point, up to 3 marks. Key ideas: existence of flightless birds, structural features are more important, risk of misclassification.

20. (a) (3 marks) Clearing the rainforest led to a decrease in the number of species because:

• The habitats of many organisms were destroyed when the trees were cut down (1 mark).
• Organisms lost their sources of food, shelter, and nesting sites, making it difficult for them to survive (1 mark).
• Many organisms could not adapt to the new conditions or migrate to other areas, leading to a decline in biodiversity (1 mark).

Marking note: Award 1 mark for each valid point, up to 3 marks. Key ideas: habitat destruction, loss of food/shelter, reduced biodiversity.

20. (b) (3 marks) The loss of trees caused the soil to become drier and more prone to erosion because:

• Tree roots hold the soil together, preventing it from being washed or blown away. Without roots, the soil is easily eroded by wind and rain (1 mark).
• Trees provide shade, which reduces the direct heating of the soil by the sun and slows down the evaporation of water from the soil. Without shade, the soil loses moisture more quickly and becomes drier (1 mark).
• Fallen leaves from trees add organic matter to the soil, helping it retain moisture. Without this, the soil becomes less fertile and drier (1 mark).

Marking note: Award 1 mark for each valid point, up to 3 marks. Key ideas: roots hold soil, shade reduces evaporation, leaf litter retains moisture.

20. (c) (2 marks — 1 mark each) Any two of the following:

1. Plant new trees / reforestation — to restore habitats and prevent soil erosion.
2. Create nature reserves / protected areas — to conserve remaining forest and protect species from further habitat loss.
3. Practice selective logging instead of clear-cutting — to reduce the extent of forest destruction.
4. Enforce laws against illegal logging — to prevent further deforestation.
5. Educate the public about the importance of biodiversity — to encourage conservation efforts.
6. Use sustainable farming practices — such as agroforestry, which integrates trees with crops.

Marking note: Award 1 mark for each valid suggestion, up to 2 marks.

Mark Summary

This practice paper was generated as syllabus-aligned content. It is not derived from any specific past-year examination paper. Questions are designed to reflect the style and difficulty of PSLE Science examinations based on the interpreted MOE syllabus for Primary 6.