Primary 6 PSLE Science Practice Paper 5

TuitionGoWhere Practice Paper — Science Primary 6 PSLE

Answer Key — Diversity (Version 5 of 5)

Section A — Multiple Choice Questions (20 marks)

1. C [2]

• Explanation: Living things are classified based on observable body features and structures (e.g., body covering, method of reproduction, presence of backbone). Colour, size, and number of legs alone are not reliable classification criteria because they can vary within a group.
• Common mistake: Students may choose B (number of legs only), but this is insufficient — insects have 6 legs, spiders have 8, and crabs have 10, yet all are arthropods.

2. A (P) [2]

• Explanation: Birds are characterised by having feathers. Only Organism P has feathers and does not have fur (which would indicate a mammal). Organism S has both feathers and fur, which is not a real combination — this is a distractor.
• Common mistake: Choosing S because it has feathers, but no real organism has both feathers and fur.

3. B (Fern) [2]

• Explanation: Ferns are non-flowering plants that reproduce by spores. Rose plants, mango trees, and sunflowers are all flowering plants that reproduce by seeds.
• Common mistake: Students may confuse moss and fern — both reproduce by spores, but the question asks for a specific example and fern is the most commonly tested.

4. C (They breathe through lungs) [2]

• Explanation: Bats (mammals), whales (mammals), penguins (birds), and crocodiles (reptiles) all breathe through lungs. Bats and penguins can fly (not whales or crocodiles — eliminate A). Only penguins have feathers (eliminate B). Only whales live entirely in water (eliminate D).
• Common mistake: Choosing A because bats and penguins can fly, but whales and crocodiles cannot.

5. C [2]

• Explanation: A fern is a plant that does not produce flowers or seeds. It reproduces by spores and is classified as a non-flowering plant → Fern. Fungi are a separate kingdom, not plants.
• Common mistake: Choosing D (Moss) — moss is also a non-flowering spore-producing plant, but the question specifically asks about the classification of a fern.

6. A [2]

• Explanation: Monocots have parallel leaf veins and one cotyledon; dicots have network-like (reticulate) leaf veins and two cotyledons. Option B is reversed. Option C is reversed. Option D is incorrect because both monocots and dicots are flowering plants.
• Common mistake: Students often reverse the monocot/dicot features.

7. B (Mushroom) [2]

• Explanation: Mushrooms are fungi. They do not have chlorophyll and cannot make their own food. Algae are simple plant-like organisms; ferns and mosses are plants.
• Common mistake: Students may choose A (Algae) thinking it is a fungus because it is simple, but algae can photosynthesise and are classified as plant-like protists.

8. B (Molluscs) [2]

• Explanation: Molluscs (e.g., snails, slugs, clams) are characterised by a soft body, often with a hard shell, and movement via a muscular foot. Insects have jointed legs and exoskeletons. Fish have fins and scales. Amphibians have moist skin.
• Common mistake: Students may choose A (Insects) if they focus on "hard shell" without noting the muscular foot.

9. C (They feed their young with milk) [2]

• Explanation: All mammals have mammary glands and feed their young with milk. Not all mammals lay eggs (only monotremes like platypus — eliminate A). Scales are found on reptiles and fish (eliminate B). Some mammals live in water, e.g., whales (eliminate D).
• Common mistake: Choosing D — students may not know that whales and dolphins are mammals.

10. C (Invertebrate — Arthropod) [2]

• Explanation: A butterfly has no backbone (invertebrate) and has jointed legs (arthropod). Following the key: 1b (no backbone) → 4a (has jointed legs) → Arthropod.
• Common mistake: Choosing D if the student forgets that insects have jointed legs.

Section B — Short-Answer Questions (40 marks)

11. [5 marks]

(a) [3] — Accept any valid observable characteristic from the table. Full example:

Characteristic used: Body covering

Group 1 (Scales): Shark, Crocodile Group 2 (Not scales / Feathers, Fur, Moist skin): Eagle, Frog, Bat

Alternative acceptable answers:

• Characteristic: Reproduces by → Group 1 (Live young): Shark, Bat; Group 2 (Eggs): Eagle, Frog, Crocodile
• Characteristic: Habitat → Group 1 (Water): Shark; Group 2 (Not water-only / Air/Land, Water/Land): Eagle, Frog, Crocodile, Bat

Marking: 1 mark for valid characteristic, 1 mark for each correctly listed group.

(b) [2]

• Reason 1: Bats have fur/hair on their bodies, whereas birds have feathers.
• Reason 2: Bats give birth to live young and feed them with milk, whereas birds lay eggs.

Marking: 1 mark per valid reason. Accept equivalent phrasing.

12. [5 marks]

(a) [1] Moss and fern

(b) [2] Ferns reproduce by spores. The spores are produced in spore cases (sori) found on the undersides of their fronds/leaves. When the spores are released and land in a suitable moist environment, they grow into new fern plants.

Marking: 1 mark for "spores", 1 mark for describing where spores are found or how they develop.

(c) [2] The rose plant is a dicotyledonous plant.

• Feature: Rose plants have network-like (reticulate) leaf veins / two cotyledons in the seed / a tap root system / flower parts in multiples of 4 or 5.

Marking: 1 mark for identifying rose plant, 1 mark for a valid feature. (Pine trees are gymnosperms/non-flowering, so they are neither monocots nor dicots in the traditional sense.)

13. [5 marks]

(a) [1] Leaves W and Y (both have parallel veins and 1 cotyledon).

(b) [2] Any two of the following:

1. Root system — Monocots have fibrous roots; dicots have tap roots.
2. Flower parts — Monocots have flower parts in multiples of 3; dicots in multiples of 4 or 5.
3. Vascular bundle arrangement — Monocots have scattered vascular bundles; dicots have vascular bundles arranged in a ring.
4. Secondary growth — Monocots generally do not have secondary growth (no wood); dicots can have secondary growth.

Marking: 1 mark per valid feature.

(c) [2]

• Monocot: Grass / maize / rice / wheat / lily / orchid / palm / onion (any valid example)
• Dicot: Rose / mango / sunflower / bean / pea / hibiscus / balsam (any valid example)

Marking: 1 mark per valid example.

14. [5 marks]

(a) [2] Any two of the following:

1. They all have a backbone (vertebral column).
2. They all have an internal skeleton (endoskeleton).
3. They all have a well-developed brain protected by a skull.
4. They all have a closed circulatory system.

Marking: 1 mark per valid feature.

(b) [1] Arachnids

(c) [2] A penguin is classified as a bird because it has feathers, lays eggs, and has a beak — all of which are key characteristics of birds. The ability to fly is not a defining characteristic of birds (e.g., ostriches and emus also cannot fly but are birds).

Marking: 1 mark for stating key bird features (feathers/eggs/beak), 1 mark for explaining that flight is not a defining characteristic.

15. [5 marks]

(a) [2]

• Organism: P
• Reason: Organism P has fur as its body covering and gives birth to live young, which are characteristics of mammals.

Marking: 1 mark for correct organism, 1 mark for valid reason.

(b) [2]

• Organism: Q or S (both are invertebrates with jointed legs and exoskeletons; either is acceptable if reasoning is correct)
• Reason: Organism Q/S has no backbone, has jointed legs, and has an exoskeleton, which are characteristics of arthropods/insects.

Note: If the student chooses Q or S and gives valid reasoning, award full marks. If the student specifies "insect" and the organism has 6 legs (implied by context), accept. Spiders (8 legs) are arachnids, not insects, but at P6 level, grouping under arthropod is acceptable.

Marking: 1 mark for correct organism, 1 mark for valid reasoning.

(c) [1] Any one of: has a beak / lays eggs / has wings / has hollow bones / has a keel on the sternum (any valid bird feature not in the table).

16. [5 marks]

(a) [1] Molluscs

(b) [2]

1. It has a soft, unsegmented body.
2. It has a hard shell and moves using a muscular foot.

Marking: 1 mark per valid characteristic from the description.

(c) [1] Snail / slug / clam / oyster / mussel / octopus / squid (any valid mollusc).

(d) [1] This organism is not an arthropod because it does not have jointed legs or an exoskeleton. Arthropods (e.g., insects, spiders, crabs) have jointed appendages and a segmented body, which this organism lacks.

Marking: Award 1 mark for any valid distinguishing feature.

Section C — Structured / Free-Response Questions (40 marks)

17. [10 marks]

(a) [3]

Plants: Fern, Moss, Rose bush, Mushroom (Note: Mushroom is a fungus, but if the student lists it under plants, deduct 1 mark and note the error. Accept the answer as "Fern, Moss, Rose bush" for 2 marks if mushroom is excluded.)

Full credit answer:

• Plants: Fern, Moss, Rose bush
• Fungi: Mushroom
• Animals: Grasshopper, Earthworm, Crab, Frog, Fish, Eagle

Marking: 1 mark for correctly listing all three plants, 1 mark for correctly listing all six animals, 1 mark for correctly identifying mushroom as a fungus (or not including it under plants).

If student lists mushroom under plants: award 2/3 (deduct 1 mark).

(b) [3]

Vertebrates: Frog, Fish, Eagle Invertebrates: Grasshopper, Earthworm, Crab

Marking: 1 mark for each correctly classified vertebrate group (frog, fish, eagle = 3 organisms, 1 mark for all correct), 1 mark for each correctly classified invertebrate group (grasshopper, earthworm, crab = 3 organisms, 1 mark for all correct), 1 mark for overall accuracy.

Alternative marking: 1 mark for vertebrates list (all 3 correct), 1 mark for invertebrates list (all 3 correct), 1 mark for no errors.

(c) [4]

• Reason 1: Mushrooms do not have chlorophyll and cannot carry out photosynthesis to make their own food. Plants have chlorophyll and can photosynthesise.
• Reason 2: Mushrooms do not have roots, stems, or leaves, which are structures found in plants. Instead, they have a network of thread-like structures called hyphae.
• (Accept also: Mushrooms reproduce by spores but do not have the complex structures of plants; mushrooms obtain nutrients by decomposing dead organic matter, whereas plants make their own food.)

Marking: 2 marks per valid reason. Award 1 mark if the reason is partially correct or lacks clarity.

18. [10 marks]

(a) [2] (i) C (Lizard) — has a backbone (Go to 2), does not have feathers (Go to 3), has dry scales → C. (ii) E (Jellyfish) — no backbone (Go to 4), no jointed legs → E.

Marking: 1 mark each for correct letter and name.

(b) [2] Any two of the following:

1. Amphibians have moist, permeable skin that can absorb water and oxygen.
2. Amphibians undergo metamorphosis (e.g., tadpole → frog).
3. Amphibians lay their eggs in water or moist environments.
4. Amphibians are ectothermic (cold-blooded) — their body temperature changes with the environment.
5. Young amphibians (tadpoles) breathe through gills; adults breathe through lungs and skin.

Marking: 1 mark per valid characteristic.

(c) [3] The student's claim is incorrect because classification is based on multiple shared characteristics, not just one feature. While both the beetle and lizard have legs, they differ in fundamental ways:

• The beetle is an invertebrate (no backbone) with an exoskeleton and jointed legs, placing it in the arthropod group.
• The lizard is a vertebrate (has a backbone) with dry scales and lungs, placing it in the reptile group.
• Grouping organisms requires considering body covering, presence of backbone, method of reproduction, and other structural features, not just the presence of legs.

Marking: 1 mark for stating that classification requires multiple characteristics, 1 mark for identifying key differences (backbone vs. no backbone), 1 mark for clear explanation of why the grouping is wrong.

(d) [3] Accept any valid dichotomous key. Example:

1a. Organism has a backbone ........................ Go to 2
1b. Organism has no backbone ........................ Go to 3

2a. Organism has feathers ........................... Sparrow
2b. Organism has scales and fins .................... Shark

3a. Organism has jointed legs ....................... Butterfly
3b. Organism does not have jointed legs ............. Earthworm

Marking: 1 mark for correct first-level split (backbone vs. no backbone), 1 mark for correct second-level splits within each branch, 1 mark for all four organisms correctly identified at the end of the key.

Alternative valid keys are acceptable (e.g., starting with habitat, body covering, etc.) as long as they correctly classify all four organisms.

19. [10 marks]

(a) [1] Mangrove (34 animal species, the highest among the three habitats).

(b) [3] Although both habitats have the same total number of species (46), the composition of species is different:

• The mangrove has more animal species (34) but fewer plant species (12).
• The garden has more plant species (28) but fewer animal species (18).
• This means the types of organisms and the balance between plants and animals differ between the two habitats. Biodiversity includes not just the total number of species but also the variety of different types of organisms present.
• The mangrove and garden support different communities of organisms adapted to different environmental conditions.

Marking: 1 mark for identifying the difference in composition, 1 mark for explaining that biodiversity includes variety of types (not just total number), 1 mark for clear comparison.

(c) [2]

1. The habitat would be destroyed, leading to the loss of all organisms (plants and animals) that depend on the pond for survival.
2. The number of species in the area would decrease, reducing biodiversity. Organisms such as fish, frogs, and aquatic plants would lose their home and may die or migrate.

Marking: 1 mark per valid effect. Accept equivalent answers (e.g., "organisms would lose their habitat," "food chains would be disrupted," "water plants would die").

(d) [2] Any two of the following:

1. Plant a variety of flowering plants to attract more insects (e.g., butterflies, bees) and birds.
2. Create a small pond or water feature to attract aquatic organisms and amphibians.
3. Avoid using pesticides that could harm insects and other small organisms.
4. Add compost or mulch to encourage decomposers (e.g., earthworms, fungi) to thrive.
5. Plant native species that are well-adapted to the local environment and support local wildlife.

Marking: 1 mark per valid suggestion.

(e) [2] Maintaining biodiversity is important because:

• A greater variety of species means a more stable ecosystem. If one species is affected (e.g., by disease), other species can fill its role, and the ecosystem continues to function.
• Different species are interconnected through food chains and food webs. The loss of one species can affect many others that depend on it for food or other ecological roles.
• Biodiversity ensures that nutrient cycles and energy flow continue efficiently, supporting the survival of all organisms in the ecosystem.

Marking: 1 mark for mentioning stability/resilience, 1 mark for explaining interconnectedness (food chains/webs or nutrient cycles).

20. [10 marks]

(a) [2] The pitcher plant is a flowering plant. It produces flowers for reproduction (even though the passage focuses on its modified leaves, pitcher plants do produce flowers). It also carries out photosynthesis, which is a characteristic of plants.

Marking: 1 mark for identifying it as a flowering plant, 1 mark for a valid reason (produces flowers / photosynthesises / has chlorophyll / has roots, stems, and leaves).

Note: Some students may argue "non-flowering" if they focus only on the passage. Award 1 mark for the identification and 1 mark for any reasonable justification. The scientifically correct answer is that pitcher plants ARE flowering plants (they belong to the order Ericales or Nepenthales depending on classification).

(b) [2]

1. The pitcher plant has modified leaves that form a deep, liquid-filled cavity (the pitcher) to trap insects.
2. The rim of the pitcher is slippery, causing insects to fall in and be unable to escape.
3. The plant produces nectar and bright colours to attract insects to the pitcher.
4. The liquid inside the pitcher contains digestive enzymes that break down the insect's body so the plant can absorb the nutrients.

Marking: 1 mark per valid adaptation (any two).

(c) [2]

1. Sunlight (light energy)
2. Carbon dioxide (from the air)
3. Water (from the soil)
4. Chlorophyll (in the leaves — accept as it is needed for the process)

Marking: 1 mark per valid requirement (any two from the above).

(d) [2] The statement is not accurate because:

• The pitcher plant is not a carnivore in the way animals are. It is a plant that carries out photosynthesis to make its own food (glucose).
• It only absorbs nutrients from insects to supplement the nutrients it cannot obtain from the poor soil — it still produces its own food through photosynthesis.
• A true carnivore is an animal that eats other animals as its primary source of energy and nutrition. The pitcher plant's primary energy source is sunlight, not insects.

Marking: 1 mark for explaining that the plant still photosynthesises, 1 mark for distinguishing between supplementing nutrients vs. being a true carnivore.

(e) [1] Commensalism — one organism benefits (mosquito larvae get shelter and food) while the other is neither helped nor harmed (pitcher plant).

(f) Venus flytrap / sundew / bladderwort / cobra lily (any valid example of a carnivorous or unusual nutrient-obtaining plant).

Marking: 1 mark for any valid example.

END OF ANSWER KEY

Mark Summary:

Note: Section B totals 30 marks and Section C totals 50 marks, giving a grand total of 100 marks. Individual question marks are indicated in brackets throughout.