Primary 6 PSLE Science Life Cycles Quiz

Primary 6 PSLE Science Quiz - Life Cycles

Answer Key

Section A: Multiple Choice (Questions 1–10)

[1 mark each]

1. Answer: B

• The correct sequence for complete metamorphosis in a butterfly is: Egg → larva (caterpillar) → pupa (chrysalis) → adult.
• Common mistake: Students may confuse the order of larva and pupa.

2. Answer: C

• In the early tadpole stage, the organism breathes through gills. As it develops into a froglet, it begins to develop lungs.
• Common mistake: Selecting "B" (tadpole with legs only) — at that stage, the organism is transitioning and may still use gills but is developing lungs.

3. Answer: B

• Cockroaches undergo incomplete metamorphosis (egg → nymph → adult). Mosquitoes, butterflies, and beetles all undergo complete metamorphosis (with a pupa stage).

4. Answer: C

• Complete metamorphosis has four stages including a pupa stage. Incomplete metamorphosis has three stages (egg, nymph, adult) and does not have a pupa stage.

5. Answer: A

• Seeds represent the beginning of a new generation in the plant life cycle. They contain the embryo that will grow into a new plant.

6. Answer: C

• Pupation is a stage found in insect life cycles (e.g., butterflies, beetles), not in the life cycle of a flowering plant.

7. Answer: C

• During the pupa stage, the mosquito undergoes a major change in body structure (metamorphosis) inside a protective casing.

8. Answer: C

• A nymph in incomplete metamorphosis resembles a smaller version of the adult. It does not look very different (unlike a larva) and is not enclosed in a cocoon.

9. Answer: C

• When a caterpillar forms a hard casing around itself, it is entering the pupa stage (chrysalis). Inside the casing, it undergoes metamorphosis.

10. Answer: C

• Ladybirds undergo complete metamorphosis and have a pupa stage. Grasshoppers, dragonflies, and cockroaches undergo incomplete metamorphosis (no pupa stage).

Section B: Short-Answer Questions (Questions 11–17)

11. (a) [1 mark]

• Answer: Froglet stage
• The froglet is the stage at which the frog first develops lungs and begins to breathe air, while the tail is gradually absorbed.

11. (b) [1 mark]

• Accept any one of the following (or equivalent):
  • A tadpole breathes through gills, while an adult frog breathes through lungs (and skin).
  • A tadpole has a tail, while an adult frog does not.
  • A tadpole has no legs, while an adult frog has four legs.
  • A tadpole lives in water, while an adult frog can live on land and in water.

12. [2 marks — 1 mark per correct difference]

Accept any two of the following:

• Award 1 mark for each valid difference. Answers must compare the two organisms directly.

13. [1 mark]

• Answer: The plant flowers / Flowering stage
• The missing stage between the plant growing leaves and pollination is the flowering stage, where the plant produces flowers.

14. [2 marks]

• Award marks as follows:
  • 1 mark for stating that the pupa stage is when the organism undergoes a major change in body structure (metamorphosis).
  • 1 mark for explaining that the larva's body is broken down and reorganised into the adult form inside the pupa.

Model answer: During the pupa stage, the caterpillar's body undergoes a major change called metamorphosis. Inside the pupa, the larva's body tissues are broken down and reorganised into the body structure of an adult butterfly, including the development of wings, compound eyes, and other adult features.

15. (a) [2 marks — 1 mark per condition]

• Accept any two of the following:
  • Water / moisture
  • Warmth / suitable temperature
  • Air / oxygen

15. (b) [1 mark]

• Answer: A warm temperature provides the conditions needed for the enzymes inside the seed to work efficiently / Enzymes that help the seed germinate work best at a warm temperature.
• Common mistake: Students may say "warmth kills bacteria" — this is not the primary reason warmth aids germination.

16. [2 marks]

• Award marks as follows:
  • 1 mark for stating that the adult chicken lays eggs (completing the cycle).
  • 1 mark for explaining that this shows the life cycle repeats / the eggs hatch into chicks and the cycle continues.

Model answer: After the adult chicken stage, the adult chicken lays eggs. The eggs hatch into chicks, and the life cycle repeats. This shows that life cycles are continuous — each generation produces the next.

17. [1 mark]

• Accept any one of the following (or equivalent):
  • To increase the chances that some offspring will survive to adulthood.
  • Because many eggs/young will be eaten by predators / will not survive.
  • To ensure the continuation of the species.
• Common mistake: Saying "to have many babies" without linking to survival is too vague — award 0.

Section C: Structured / Long-Answer Questions (Questions 18–20)

18. (a) [1 mark]

• Answer: Complete metamorphosis

18. (b) [2 marks — 1 mark per change]

• Accept any two of the following (or equivalent):

  • The larva develops wings.
  • The larva develops hard wing cases (elytra).
  • The larva develops compound eyes.
  • The larva develops six legs (if not already present in larval form).
  • The body structure changes from a soft, worm-like form to a hard-bodied adult.
  • The size and shape of the body changes significantly.

• Award 1 mark per valid change described. Vague answers such as "it changes" without specifying what changes receive 0 marks.

19. (a) [2 marks]

• Award marks as follows:
  • 1 mark for stating that pollination is needed for fertilisation / for the male gamete to reach the female gamete (ovule).
  • 1 mark for linking fertilisation to fruit and seed formation / explaining that without pollination, fruits and seeds cannot form.

Model answer: Pollination is important because it allows the pollen grains (male reproductive cells) to be transferred to the stigma of the flower, enabling fertilisation of the ovules. Without pollisation, fertilisation cannot occur, and the flower will not be able to develop fruits and seeds.

19. (b) [1 mark]

• Accept any one of the following (or equivalent):

  • The farmer could carry out hand pollination / manually transfer pollen from one flower to another using a brush or cloth.
  • The farmer could plant more flowering plants to attract more insects.
  • The farmer could use wind-pollinated varieties (if applicable).

• Award 1 mark for a practical suggestion. "Use more insects" without explanation is too vague — award 0.

20. [2 marks]

• Award marks as follows:
  • 1 mark for explaining that both the butterfly and frog undergo metamorphosis — their young look very different from the adult and go through a major change in body structure during their life cycle.
  • 1 mark for explaining that the flowering plant does not undergo metamorphosis — the seedling resembles the adult plant and grows gradually without a dramatic change in body form.

Model answer: The butterfly and the frog are grouped together because both undergo metamorphosis — their young (larva/caterpillar and tadpole) look very different from the adult form, and they go through a major change in body structure during their life cycle. The flowering plant does not undergo metamorphosis because the seedling already resembles a smaller version of the adult plant and grows gradually in size without a dramatic change in body form.

• Common mistake: Students may simply restate the table without explaining the concept of metamorphosis. Award 1 mark only for partial answers.

Mark Summary

This quiz was generated using syllabus-aligned LLM-inferred templates. It complements but does not replicate past-year PSLE papers.