Primary 5 Science Semestral Assessment 2 (End of Year) Paper 1

TuitionGoWhere Exam Practice (AI) - Science Primary 5

SA2 Practice Paper - Answer Key Version 1 of 5

SECTION A: MULTIPLE CHOICE QUESTIONS (10 marks)

1. Answer: C [1]

Concept: Diversity refers to the variety of living things. Water changing from liquid to gas is a physical change in a non-living thing (water), not an example of biodiversity. Options A, B, and D all describe variations among living organisms.

Common mistake: Students may confuse "diversity" with any kind of difference, not realising it specifically refers to living organisms.

2. Answer: D [1]

Reasoning:

• Group X (eagle, bat, penguin): eagle and penguin are birds; bat is a mammal. All three are warm-blooded (maintain constant body temperature).
• Group Y (lizard, snake, crocodile): all are reptiles, which are cold-blooded.
• While eagle and penguin have feathers, bats have fur/hair, so A is incorrect.
• Bats don't have four legs (they have two wings + two legs), so B is incorrect.
• Penguins cannot fly, so C is incorrect.

3. Answer: B [1]

Reasoning:

• Box W (fish): lives in water, has scales, lays eggs in water
• Box X (frog): moist skin, lays eggs, undergoes metamorphosis ✓
• Box Y (pigeon): has feathers, warm-blooded, lays eggs with hard shell
• Box Z (mouse): has fur, live birth, warm-blooded

The key features "moist skin and lays eggs" identify an amphibian (frog = Box X).

4. Answer: B [1]

Fair test principles: Only ONE variable should differ between the two groups being compared.

• A: Spider has 8 legs, snail has 0 legs AND different movement methods (running vs crawling) — unfair, two variables
• B: Centipede and millipede — both are similar in length, both have many legs, only leg number differs ✓
• C: Butterfly vs fish — flying vs swimming, completely different environments
• D: Dog vs cat — both have 4 legs, but walking vs running is a behaviour difference, not a leg difference

5. Answer: A [1]

Insect characteristics: 6 legs, three body parts, usually with antennae.

• P: 6 legs, hard outer shell (exoskeleton) = INSECT ✓
• Q: 8 legs, hair = spider (arachnid)
• R: 4 legs, feathers = bird (vertebrate)
• S: 0 legs, moist skin = likely slug or snail (mollusc), or amphibian/worm

6. Answer: B [1]

Leaf venation patterns:

• Parallel venation: veins run side by side from base to tip (typical of monocots like grasses, palms, banana, corn)
• Net/reticulate venation: veins branch and form a network (typical of dicots like hibiscus, rose)

Expected visual: Leaf B shows straight veins running parallel to each other lengthwise without branching network.

7. Answer: C [1]

Working through the key:

1. "Has a shell" vs "No shell" → No shell → Go to 3
2. "Has legs" vs "No legs" → Has six legs → but wait, key says 6 legs!

Let me re-trace: From 3a "Has legs → Go to 4" From 4a "Has six legs → Water beetle" ✓ From 4b "Has more than six legs → Water spider"

Six legs matches 4a: Water beetle

8. Answer: C [1]

Fungi characteristics:

• NOT plants: cannot make their own food (no chlorophyll, no photosynthesis)
• NOT bacteria: fungi have nuclei and are much larger, different cell structure
• NOT animals: while both feed on other organisms, fungi do NOT ingest food — they absorb nutrients through their hyphae
• Fungi have their own kingdom because they are unique: heterotrophic (like animals) but non-motile, with cell walls (like plants), reproducing by spores

9. Answer: D [1]

Analysis:

• Rose, Hibiscus, Grass: all are flowering plants ✓
• Fern: non-flowering plant, reproduces by spores ✓
• Moss: non-flowering plant, reproduces by spores ✓
• Mushroom: NOT a plant at all — it is a FUNGUS

Mushrooms do not belong in either flowering or non-flowering plant categories. This is the incorrectly placed organism.

10. Answer: B [1]

Key characteristics given:

• 6 legs ✓ (insects have 6 legs; spiders have 8; crustaceans have 10+; millipedes have many)
• 2 antennae ✓ (insects have antennae; spiders don't)
• Hard outer covering (exoskeleton) ✓ (all arthropods, but 6 legs specifies insect)
• No wings (many insects are wingless, e.g., silverfish, some ants, or immature stages)

Brain tickler: Some insects like ants have wingless workers, and some adult insects like fleas are wingless. The key is 6 legs + 2 antennae + 3 body parts = insect.

SECTION B: STRUCTURED QUESTIONS (30 marks)

11. (a) [2]

Marking:

• X correctly identified for wind dispersal: 1 mark
• Z correctly identified with method (or W/Y with correct method): 1 mark

Note: X has feathery structures (like dandelion or cotton). Z has hooks/spines for animal dispersal. W (large, round) = self-propelled/explosion or animal eating. Y (hard coat, no special features) = self-dispersal or mechanical.

11. (b) [2]

Seed X is light and has feathery/hairy structures [1] that increase its surface area and allow it to be carried easily by wind over long distances [1]. This helps the seed to be dispersed far from the parent plant.

Concept: Wind-dispersed seeds need to be light and have structures that catch air (parachute/ wing-like adaptations).

11. (c) [1]

Any one valid reason:

• To reduce competition with the parent plant for sunlight, water, and nutrients [1]
• To colonise new areas suitable for growth [1]
• To prevent overcrowding which would lead to poor growth [1]

12. (a) [1]

Any one similarity:

• Both start from an egg [1]
• Both involve growth and development into an adult [1]
• Both involve changes in form as they develop [1]

12. (b) [2]

Difference: Organism A (frog) undergoes metamorphosis / has a larval stage (tadpole), while Organism B (bird) does not [1].

Survival advantage: The tadpole lives in water and feeds on algae/water plants, while the adult frog lives on land and eats insects. This means the tadpole and adult frog do not compete for the same food or habitat [1]. Having different life stages in different environments reduces competition and increases survival chances.

12. (c) [2]

Advantage of spores: Spores are very small and light, so they can be produced in large numbers and dispersed easily by wind/water to distant places [1]. Spores can also remain dormant for long periods until conditions are favourable for growth [1].

Disadvantage of spores: Unlike seeds, spores do not contain stored food (endosperm) for the young plant/organism to grow [1]. Spores also need to land in very moist conditions immediately to germinate, making survival less certain than seeds which can wait longer [1].

13. (a) [2]

Organism P (water lily) is a plant because:

1. It can make its own food / it carries out photosynthesis [1]
2. It cannot move from place to place / it is rooted in the pond [1]

Animals cannot make their own food and must feed on other organisms.

13. (b) [1]

R (frog) and T (eagle) [1]

Both have backbones / are vertebrates. (Either order accepted)

13. (c) [2]

Organism S (earthworm) has no legs [1], so it is difficult to use the "number of legs" criterion to classify it as vertebrate or invertebrate. Also, earthworms appear soft-bodied and might be mistaken for something else, but they are actually invertebrates (no backbone) [1]. Students might confuse it with small snakes (which are vertebrates) because of its elongated shape.

14. (a) [1]

Fungus ✓ [1]

14. (b) [1]

The area of mould increased rapidly / steadily [1] from Day 0 to Day 4 (from 0 cm² to 20 cm²). The growth was fastest between Day 2 and Day 3 / Day 3 and Day 4 [1 for any correct detail].

14. (c) [2]

Growth slowed because:

• The bread was running out of nutrients / food source was being used up [1]
• The mould had covered most of the available surface area / limited space for further growth [1]
• Competition for resources increased as the mould grew larger [1]
• Waste products may have accumulated and inhibited growth [1]

Any two valid points.

14. (d) [1]

Releasing spores into the air allows the bread mould to disperse to new food sources / new bread / new locations easily and quickly [1]. This ensures the mould can survive and reproduce even if the original bread is finished or dries out.

15. (a) [2]

Any two characteristics ALL living things share:

• Reproduce / produce young [1]
• Grow / increase in size [1]
• Need food / nutrition [1]
• Respire / breathe / release energy from food [1]
• Respond to stimuli / react to changes [1]
• Excrete / remove waste [1]

15. (b) [1]

Any one example:

• Bacteria in our intestines help digest food / produce vitamins [1]
• Bacteria are used to make yoghurt / cheese / other fermented foods [1]
• Bacteria help decompose dead matter and recycle nutrients in ecosystems [1]
• Some bacteria fix nitrogen in soil to help plants grow [1]

15. (c) [2]

16. (a) [1]

Insect [1]

16. (b) [1]

"Has six legs" / Characteristic used at Step 1a [1]

This is the first decision point in the key that separates this organism from those with more than six legs or no legs.

16. (c) [2]

A spider has two body parts (cephalothorax and abdomen) [1], but Jason's organism has three body parts (head, thorax, abdomen) [1]. Also, a spider has eight legs [1], but this organism has only six legs [1].

Either point fully explained scores 2 marks.

16. (d) [1]

The stinger helps bees defend themselves against predators / animals that might attack the hive [1]. This protects the bee colony and increases their chance of survival / allows them to protect their food stores and young.

SECTION C: FREE RESPONSE AND APPLICATION (20 marks)

17. (a) [1]

Parallel venation [1]

Monocot plants (e.g., grasses, lallang, banana, coconut, corn) have parallel-veined leaves.

17. (b) [2]

Working: $\text{Percentage} = \frac{35}{50} \times 100\%$ [1]

$= 70\%$ [1]

OR accept correct method with arithmetic error for 1 mark.

17. (c) [3]

This conclusion is not fully valid / only partially valid [1].

Reasons:

• The sample was taken from only one location (the school garden), which may not represent all plants in Singapore [1]
• The sample size of 50 leaves may be too small to make a general conclusion about all Singapore plants [1]
• Different habitats in Singapore (forests, parks, coastal areas) have different types of plants — some areas have more monocots / grasses [1]
• The investigation did not consider that season, time of year, or which part of the garden was sampled could affect results [1]

To improve: sample from multiple locations across Singapore, increase sample size, repeat the investigation.

Any two development points beyond the initial validity judgment.

18. (a) [2]

Mangrove trees and algae are called producers because they can make their own food [1] through photosynthesis [1]. They use sunlight, water, and carbon dioxide to produce glucose/food and oxygen. They do not need to eat other organisms.

18. (b) [2]

Any valid 4-organism food chain ending with eagle:

Example: Algae → Snail → Small fish → Heron → Eagle [2]

OR: Mangrove trees → Crabs → Larger fish → Eagle [2]

Marking: All organisms in correct order with arrows showing energy flow [1]; starts with producer and ends with eagle [1]. Deduct 1 if arrows point wrong way.

18. (c) (i) [2]

The population of small fish would decrease [1].

Explanation: Snails are a food source for small fish. With fewer snails, small fish have less food to eat [1], so some small fish may starve, die, or fail to reproduce successfully.

18. (c) (ii) [2]

Over a longer period, the population of larger fish would also decrease [1].

Explanation: Larger fish feed on small fish (and crabs). If small fish decrease due to lack of snails, larger fish would have less food available [1]. This shows the interdependence of organisms in a food web — a change in one population affects others through the food chain.

19. (a) [3]

Note: Container A has both plants AND a snail (animal), so "only plants" is technically none. However, if the question implies "contains plants," then A, B, D all apply.

Revised expected answers based on standard marking:

• Contains animals with backbones: B [1]
• Contains organisms that make their own food: A, B, D (any two correct = 1 mark, all three = 2 marks) [2]

19. (b) [3]

Snail (lays eggs):

• The snail produces many eggs that are laid in moist soil or on leaves [1]
• Advantage: Can produce many eggs at once [1], increasing chances that some will survive; eggs can survive dry conditions if protected; can be dispersed to new locations [any valid advantage = 1 mark]

Guppy (live birth):

• The guppy keeps eggs inside its body where they develop into young fish before being born [1]
• Advantage: The young are protected inside the mother / less likely to be eaten by predators; young are more developed when born, better survival chance [1]

19. (c) [2]

Mould should not be classified as a plant because:

1. It cannot make its own food / does not carry out photosynthesis [1] — it has no chlorophyll
2. It absorbs nutrients from the bread (dead/decaying matter) rather than making food from sunlight [1]
3. It does not have roots, stems, or leaves like true plants [1]

Any two valid points.

20. (a) [3]

X: Insect / Bee [1]
Y: Wind [1]
Z: Moth / Insect [1]

20. (b) [2]

Bright colours: attract bees/insects from a distance so they notice the flower [1]

Sweet scent: attracts bees/insects by smell, helping them locate the flower even when they are close but cannot see it clearly [1]

Both features work together to ensure pollination — when bees land to collect nectar, pollen sticks to their bodies and is transferred to the next flower.

20. (c) [2]

White colour: visible in dim moonlight / reflects what little light is available at night, making the flower noticeable to moths [1]

Strong sweet smell: moths have a good sense of smell and use this to find the flower in the dark when they cannot rely on sight [1]

Together, these are adaptations for night pollination when visual cues are less effective.

20. (d) [1]

Wind-pollinated flowers do not need nectar because wind does not need to be rewarded with food [1]. Nectar is produced to attract animal pollinators; since wind is not a living thing and does not "choose" which flowers to visit, there is no benefit in producing nectar. Wind-pollinated flowers instead produce large amounts of light, dry pollen to increase chances of successful transfer.

MARK SCHEME SUMMARY

END OF ANSWER KEY