Primary 4 Science Life Cycles Quiz

Primary 4 Science Quiz - Life Cycles

Answer Key

Section A: Multiple Choice Questions (10 marks)

1. B [1]

• Complete metamorphosis follows the sequence: egg → larva → pupa → adult.
• Common mistake: Students may confuse incomplete metamorphosis (egg → nymph → adult) with complete metamorphosis.

2. C [1]

• The caterpillar is the larval stage of a butterfly.
• Common mistake: Some students may select "pupa" because they associate the chrysalis with the caterpillar.

3. C [1]

• Grasshoppers undergo incomplete metamorphosis (egg → nymph → adult).
• Butterflies, mosquitoes, and beetles all undergo complete metamorphosis.

4. B [1]

• Incomplete metamorphosis does not have a pupal stage; the nymph gradually develops into the adult.
• Common mistake: Students may think incomplete metamorphosis has fewer stages overall, but the key difference is the absence of the pupal stage.

5. B [1]

• A tadpole is the larval stage of a frog.
• Common mistake: Students may confuse frogs with toads; both have tadpoles, but the question specifies the most common association at P4 level.

6. C [1]

• Grasshoppers undergo incomplete metamorphosis and do not have a pupal stage.
• The stages are egg → nymph → adult.

7. C [1]

• During the pupal stage, the insect is enclosed in a protective casing (e.g., chrysalis) and undergoes major body restructuring.
• Common mistake: Students may think the larval stage involves the most change because the caterpillar eats and grows a lot.

8. D [1]

• A nymph resembles a smaller version of the adult but usually lacks wings and reproductive organs.
• Common mistake: Students may confuse nymphs with larvae (caterpillars), which look very different from the adult.

9. D [1]

• Houseflies undergo complete metamorphosis and have a pupal stage.
• Cockroaches, grasshoppers, and dragonflies undergo incomplete metamorphosis (no pupal stage).

10. B [1]

• As a tadpole develops into a frog, it grows legs (first hind legs, then front legs), its tail shortens and is eventually absorbed, and it develops lungs for breathing air.
• Common mistake: Students may select "wings" or "feathers" if they confuse frogs with other animals.

Section B: Short Answer Questions (20 marks)

11. (a) Larva / Caterpillar [1]

• Stage B is the worm-like creature eating leaves, which is the larval stage.

(b) Pupa / Chrysalis [1]

• Stage C is the hard casing, which is the pupal stage.

(c) Complete metamorphosis [1]

• A butterfly has four distinct stages (egg, larva, pupa, adult), which is characteristic of complete metamorphosis.

12. Two differences between a nymph and a larva: [2 — 1 mark each]

1. A nymph looks similar to the adult (smaller version), while a larva looks very different from the adult.
2. A nymph does not go through a pupal stage, while a larva transforms into a pupa before becoming an adult.

• Accept any valid difference, e.g., nymphs may have wing buds while larvae do not; nymphs molt to grow while larvae also molt but undergo more dramatic change.

13. [2 — 1 mark for all three correct, 0 marks if any are wrong]

• The grasshopper life cycle is: egg → nymph → adult (incomplete metamorphosis).

14. [2 — 1 mark for all four in correct order, 0.5 marks if 2–3 are correct]

1. Egg
2. Larva
3. Pupa
4. Adult

• Mosquitoes undergo complete metamorphosis. Note: Mosquito larvae and pupae are aquatic.

15. [2 — accept any valid reason, 1 mark per valid point]

Sample answer:

• A frog's life cycle has three stages (egg → tadpole → adult) while a butterfly has four stages (egg → larva → pupa → adult).
• A frog does not have a pupal stage, but a butterfly does.
• A tadpole lives in water and breathes through gills, while a butterfly's stages are all land-based.
• A frog's young is called a tadpole, while a butterfly's young is called a caterpillar/larva.

16. (a) Insect P [1]

• Insect P has four stages including a pupal stage, which is characteristic of complete metamorphosis.

(b) Insect P has a pupal stage, which is only found in complete metamorphosis. Insect Q goes directly from nymph to adult without a pupal stage, so it undergoes incomplete metamorphosis. [1]

17. [2 — 1 mark per valid change]

Sample answer:

1. The tadpole develops legs (hind legs first, then front legs).
2. The tail becomes shorter and is eventually absorbed / disappears.

• Also accept: develops lungs for breathing air; gills disappear; body shape changes from fish-like to frog-like; eyes become more prominent.

18. [2]

The student is not correct. [1] A nymph is the young stage of insects that undergo incomplete metamorphosis (e.g., grasshopper), and it looks similar to the adult but smaller and without wings. A caterpillar is the larval stage of insects that undergo complete metamorphosis (e.g., butterfly), and it looks very different from the adult. [1]

• Award 1 mark for stating the student is incorrect, and 1 mark for a valid explanation.

Section C: Structured / Application Questions (10 marks)

19. (a) 3 [1]

• The cockroach life cycle has three stages: egg (egg case), nymph, and adult.

(b) Incomplete metamorphosis [1]

• The cockroach does not have a pupal stage.

(c) The diagram shows only three stages and there is no pupal stage. In complete metamorphosis, there must be four stages including a pupa. Since the cockroach goes directly from nymph to adult without forming a pupa, it undergoes incomplete metamorphosis. [2 — 1 mark for identifying no pupal stage, 1 mark for linking to incomplete metamorphosis]

(d) [2 — 1 mark for similarity, 1 mark for difference]

Similarity: The nymph looks similar in body shape to the adult / has the same body segments as the adult. [1]

Difference: The nymph does not have wings / is smaller than the adult / cannot reproduce. [1]

20. (a) Beetle [1]

• The beetle has four stages including a pupal stage, indicating complete metamorphosis.

(b) Dragonfly [1]

• The dragonfly has three stages (egg → nymph → adult) with no pupal stage, indicating incomplete metamorphosis.

(c) [2 — 1 mark for similarity, 1 mark for difference]

Similar: Both involve a change in body form as the animal develops from young to adult / both have a young stage that looks different from the adult. [1]

Different: The frog's life cycle has only three stages while insect complete metamorphosis has four stages / the frog does not have a pupal stage / the tadpole lives in water while insect nymphs and larvae usually live on land. [1]

• Accept any valid similarity and difference.