Primary 4 Science Semestral Assessment 2 (End of Year) Paper 5

TuitionGoWhere Practice Paper - Science Primary 4

SA2 Answer Key — Version 5 of 5

Total Marks: 50

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

1. Answer: C) A potted plant

• Reasoning: A potted plant is a living thing as it can grow, reproduce, and carry out life processes. A plastic bottle, wooden chair, and glass marble are non-living things.
• Common mistake: Students may choose B (wooden chair) because wood comes from trees, but the chair itself is no longer alive.

2. Answer: B) They can grow.

• Reasoning: All living things share characteristics including growth, the need for food/water/air, reproduction, response to stimuli, and excretion. Not all living things can fly, are green, or live on land.

3. Answer: B) Ocean

• Reasoning: Fish are aquatic animals that breathe through gills and need water to survive. The ocean is a water habitat suitable for fish.

4. Answer: B) A wooden table

• Reasoning: Wood comes from trees, which are living things. A wooden table was once part of a living tree. A rock, river, and cloud were never part of a living thing.

5. Answer: B) A polar bear with thick fur and a layer of fat

• Reasoning: Thick fur and a layer of fat (blubber) insulate the polar bear against the extreme cold of the Arctic. Camels are adapted to hot deserts, frogs to moist environments, and parrots to tropical forests.

6. Answer: B) Living things need food, water, air, and can reproduce, while non-living things do not.

• Reasoning: This is the fundamental distinction. Living things carry out life processes (nutrition, respiration, excretion, growth, reproduction, movement, sensitivity). Non-living things do not.

7. Answer: C) Plants

• Reasoning: Plants make their own food through photosynthesis using sunlight, water, and carbon dioxide. Animals and fungi cannot make their own food.

8. Answer: C) Frog

• Reasoning: A butterfly, eagle, and spider are all animals with features of the arthropod or bird groups that have wings or are insects/arachnids. A frog is an amphibian — it does not have wings and belongs to a different classification group. (Accept: C — Frog, as it is the only amphibian/non-insect/non-bird in the list.)

9. Answer: C) A pond with water, plants, and small organisms

• Reasoning: A habitat is the natural home or environment of an organism. A pond with its water, plants, and organisms is a complete habitat. A wing, fin, or bark are body parts, not habitats.

10. Answer: C) A whale

• Reasoning: Whales are mammals — they breathe air through lungs, give birth to live young, and feed their young with milk. A lizard is a reptile, a shark is a fish, and a chicken is a bird.

Section B: Short Answer Questions (10 × 2 marks = 20 marks)

11. State two characteristics that all living things share.

• Answer: Any two of the following (1 mark each):
  • They can grow.
  • They need food and water.
  • They need air (oxygen/carbon dioxide).
  • They can reproduce.
  • They can respond to changes in their surroundings.
  • They carry out excretion (remove waste).
  • They can move (in some way).
• Marking note: Accept any valid life characteristic. Do not accept "they can die" alone without context.

12. Classify each item as Living (L) or Non-living (NL).

• Marking note: 0.5 mark per correct answer. Mushrooms are living (fungi) — a common misconception is that they are non-living because they are not animals or plants.

13. Give two ways in which a cactus is adapted to survive in a hot, dry desert.

• Answer: Any two of the following (1 mark each):
  • It has a thick, waxy stem to store water.
  • It has spines instead of leaves to reduce water loss through transpiration.
  • It has shallow but widespread roots to absorb water quickly when it rains.
  • Its green stem can make food (photosynthesis) since leaves are reduced.
• Common mistake: Students may say "it has sharp thorns to protect itself from animals" — this is partially correct but the primary adaptation is for reducing water loss.

14. A polar bear has thick, white fur. Explain two ways this adaptation helps it survive in the Arctic.

• Answer: (1 mark each)
  • The thick fur traps a layer of air close to the skin, providing insulation to keep the bear warm in freezing temperatures.
  • The white colour of the fur acts as camouflage against the snow and ice, helping the bear hide from prey (or blend into its environment).
• Marking note: Students must link the feature to the survival benefit. Simply stating "it is white" without explaining camouflage is insufficient for full marks.

15. Complete the table with the correct habitat for each organism.

• Marking note: 0.5 mark per correct answer. Accept any reasonable description of the habitat.

16. Explain why a fish cannot survive on land for a long period of time.

• Answer: (2 marks)
  • Fish breathe through gills, which extract oxygen dissolved in water. On land, the gills cannot extract oxygen from the air, so the fish cannot breathe and will suffocate.
  • (Accept also: Fish are adapted to water — their body shape, fins, and lack of limbs make it difficult to move or support themselves on land; their skin may dry out without water.)
• Marking note: Award 1 mark for mentioning gills/water breathing, and 1 mark for a second valid reason or elaboration.

17. List the living things and explain how you know.

• Answer:
  • Living things: Ladybird, worm (1 mark)
  • Explanation: They are living things because they can grow, move, feed, reproduce, and respond to changes in their surroundings. The stone and plastic bag do not carry out any life processes. (1 mark)
• Common mistake: Students may include the plastic bag because it "moves" in the wind — clarify that movement caused by an external force is not the same as living things moving on their own.

18. What is the difference between complete and incomplete metamorphosis? Give one example of each.

• Answer:
  • Complete metamorphosis has four stages: egg → larva → pupa → adult. The young (larva) looks very different from the adult. (Example: butterfly, mosquito, beetle) — 1 mark
  • Incomplete metamorphosis has three stages: egg → nymph → adult. There is no pupal stage. The nymph looks similar to the adult but is smaller and may lack wings. (Example: grasshopper, cockroach, dragonfly) — 1 mark
• Common mistake: Students may say incomplete metamorphosis has only two stages. Clarify that it has three (egg, nymph, adult) — the pupal stage is what is missing.

19. State two ways in which animals can be grouped or classified.

• Answer: Any two of the following (1 mark each):
  • By their body covering (fur, feathers, scales, exoskeleton).
  • By their habitat (land, water, air).
  • By how they move (walk, swim, fly, crawl).
  • By how they reproduce (lay eggs, give birth to live young).
  • By whether they are vertebrates or invertebrates.
  • By what they eat (herbivore, carnivore, omnivore).
• Marking note: Accept any valid classification criterion.

20. Explain how the changes from tadpole to adult frog help it survive.

• Answer: (2 marks)
  • The tadpole develops legs, which allow the frog to move on land (jump, walk) and also swim more effectively. (1 mark)
  • The tadpole loses its tail, which is no longer needed as the frog's legs take over movement. The frog can now live both in water and on land (amphibious lifestyle), giving it access to more food sources and habitats. (1 mark)
• Marking note: Award 1 mark for each valid explanation linking the change to survival. Accept answers relating to the development of lungs for breathing air.

Section C: Structured / Application Questions (2 × 5 marks = 10 marks)

21. (5 marks)

(a) (1 mark) Which habitat has more types of organisms observed? Explain.

• Answer: Both habitats have the same number of organisms observed — five each. (1 mark)
• Accept: If a student argues one habitat has more, they must justify it. But based on the table, both have 5 organisms listed.

(b) (2 marks) Describe one adaptation for one organism from each habitat.

• Answer: (1 mark each — any valid adaptation)
  • Pond example — Fish: Has gills to breathe underwater / has fins and a streamlined body to swim efficiently in water / has a lateral line to detect movement in water.
  • Pond example — Frog: Has webbed feet to swim in water / has moist skin that can absorb oxygen in water / has strong hind legs to jump and swim.
  • Pond example — Dragonfly: Has wings to fly and catch prey near the water / has large compound eyes to spot prey and predators.
  • Pond example — Water lily: Has broad, flat leaves that float on the water surface to get sunlight / has long stems to reach from the bottom of the pond to the surface.
  • Field example — Grasshopper: Has strong hind legs to jump away from predators / has green colour for camouflage in grass.
  • Field example — Butterfly: Has wings to fly and reach flowers for nectar / has a proboscis to suck nectar from flowers.
  • Field example — Earthworm: Has a thin, moist body that can move through soil / has no legs but uses tiny bristles (setae) to grip the soil.
  • Field example — Ant: Has six legs for walking and carrying food / lives in colonies for protection and cooperation.
  • Field example — Mushroom: Has spores for reproduction that are carried by wind / grows in damp, shaded areas to avoid drying out.
• Marking note: Award 1 mark per organism if the adaptation is correctly described and linked to survival in that habitat.

(c) (2 marks) Explain two reasons why the frog depends on the pond habitat.

• Answer: (1 mark each)
  • Frogs need water for reproduction — they lay their eggs in water, and the eggs need water to develop and hatch into tadpoles.
  • Frogs have moist skin that needs to stay wet; without water, their skin would dry out and they would not be able to breathe through it properly.
  • (Accept also: Frogs' tadpoles live entirely in water and breathe through gills; without water, the tadpoles would die.)
  • (Accept also: Frogs hunt for insects and other small organisms near the water for food.)
• Marking note: Award 1 mark per valid reason. Answers must link the pond to the frog's survival needs.

22. (5 marks)

(a) (1 mark) Classify each organism.

• Marking note: 0.25 mark per correct answer. Organism W has feathers and can fly → bird. Organism X has scales, gills, lives in water → fish. Organism Y has fur, gives birth to live young, feeds milk → mammal. Organism Z has six legs and exoskeleton → insect.

(b) (2 marks) Name the four stages of complete metamorphosis in order.

• Answer: Egg → Larva → Pupa → Adult (0.5 mark per stage in correct order)
• Common mistake: Students may write "caterpillar" instead of "larva" or "chrysalis" instead of "pupa" — accept these as they are specific examples of larva and pupa stages for butterflies.

(c) (2 marks) Explain why Organism Y is a mammal and not a bird. Give two reasons.

• Answer: (1 mark each)
  • Organism Y has fur/hair, whereas birds have feathers.
  • Organism Y gives birth to live young and feeds its young with milk, whereas birds lay eggs and do not produce milk.
  • (Accept also: Organism Y does not have wings or the ability to fly like most birds.)
• Marking note: Award 1 mark per valid distinguishing feature. The answer must contrast mammal characteristics with bird characteristics.

END OF ANSWER KEY

Marking Summary: