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Primary 6 PSLE Science Life Cycles Quiz
Free P6 PSLE Science Life Cycles quiz with questions, answers, and PSLE-focused practice for Singapore students preparing for school assessments.
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Questions
Primary 6 PSLE Science Quiz - Life Cycles
Name: _________________________________ Class: _______ Date: _______________
Score: _______ / 40 marks
Duration: 40 minutes
Instructions: Answer all questions. Write your answers in the spaces provided.
Section A: Multiple Choice (Questions 1–10, 1 mark each)
Choose the correct answer and write its letter in the bracket provided.
1. The life cycle of a butterfly is an example of ( )
A. complete metamorphosis
B. incomplete metamorphosis
C. direct development
D. no metamorphosis
Answer: ( )
2. Which of the following stages is NOT part of the life cycle of a flowering plant?
A. Seed
B. Seedling
C. Pupa
D. Young plant
Answer: ( )
3. During which stage of a frog's life cycle does it undergo the most dramatic change in body form?
A. Egg
B. Tadpole
C. Adult frog
D. The change from tadpole to adult frog
Answer: ( )
4. The diagram below shows a flowering plant's reproductive structure.
<image_placeholder> id: Q4-fig1 type: diagram linked_question: Q4 description: Cross-section of a flower showing reproductive parts labels: stigma, style, ovary, ovule, anther, filament, petal, sepal values: none must_show: labelled arrow pointing to ovary, clear distinction between male (stamen) and female (pistil) parts, pollen grains on anther </image_placeholder>
Which labelled part develops into the fruit after fertilisation?
A. Stigma
B. Ovary
C. Ovule
D. Anther
Answer: ( )
5. Which of the following correctly shows the sequence of a mosquito's life cycle?
A. Egg → Larva → Pupa → Adult
B. Egg → Pupa → Larva → Adult
C. Egg → Nymph → Adult
D. Egg → Larva → Nymph → Adult
Answer: ( )
6. A gardener wants to grow new plants that are genetically identical to a parent plant with desirable traits. Which method should she use?
A. Growing from seeds produced by sexual reproduction
B. Taking stem cuttings and planting them
C. Cross-pollinating with another plant
D. Genetic modification
Answer: ( )
7. The life cycle of a fern differs from that of a flowering plant because ferns:
A. do not produce seeds
B. have flowers but no fruits
C. reproduce only by spores found in cones
D. cannot perform photosynthesis
Answer: ( )
8. In the life cycle of a grasshopper, the nymph resembles the adult except that it:
A. has wings and can reproduce
B. lacks wings and is smaller in size
C. lives in water and has gills
D. has a completely different body shape
Answer: ( )
9. The graph below shows the survival rate of offspring in two different species. Species X produces many tiny eggs with no parental care. Species Y produces few large eggs with extensive parental care.
<image_placeholder> id: Q9-fig1 type: graph linked_question: Q9 description: Bar graph comparing survival rates of two species labels: Species X (many small eggs, no care), Species Y (few large eggs, with care), percentage survival rate values: Species X: 5% survival; Species Y: 85% survival; x-axis shows Species X and Species Y; y-axis shows survival rate (%), scale 0-100 must_show: clear bars with different colours/patterns, percentage labels on bars, title "Survival Rates of Different Reproductive Strategies" </image_placeholder>
Which statement best explains why both strategies can be successful?
A. Species X wastes less energy on reproduction
B. Species Y's offspring always survive disease better
C. Each strategy suits different environmental conditions and lifestyles
D. Species with more offspring always become more numerous
Answer: ( )
10. Which structure in a flowering plant contains the male gametes?
A. Ovule
B. Stigma
C. Pollen grain
D. Ovary
Answer: ( )
Section B: Short Answer (Questions 11–16, 2 marks each)
Write your answers in the spaces provided.
11. Explain two advantages of seed dispersal for flowering plants.
(2 marks)
12. The diagram below shows the life cycle of a bean plant.
<image_placeholder> id: Q12-fig1 type: diagram linked_question: Q12 description: Circular life cycle diagram of a bean plant showing four stages labels: A (seed), B (seedling with small leaves), C (young plant with flowers), D (flower with fruit developing), arrow back to A values: none must_show: circular arrangement with arrows showing progression, clear drawing of each stage, labels A-D, seeds inside fruit at stage D </image_placeholder>
(a) Name the process that must occur at stage C before stage D can develop.
(1 mark)
(b) Explain why seeds need to be dispersed away from the parent plant.
(1 mark)
13. The table below shows information about three different animals and their reproductive methods.
| Animal | Number of offspring per reproduction | Parental care | Development type |
|---|---|---|---|
| P (Frog) | 200–500 eggs | None | Metamorphosis |
| Q (Chicken) | 6–12 eggs | Some | Direct development |
| R (Rabbit) | 4–8 live young | Extensive | Direct development |
(a) Which animal is most likely to have the lowest survival rate of offspring to adulthood? Explain your answer.
(1 mark)
(b) Suggest one advantage and one disadvantage of the reproductive strategy used by animal R.
(1 mark)
14. Study the diagram of a human life cycle below.
<image_placeholder> id: Q14-fig1 type: diagram linked_question: Q14 description: Human life cycle showing stages from baby to elderly labels: baby, child, adolescent, adult, elderly; arrows between stages values: approximate ages: baby (0-2), child (2-12), adolescent (12-18), adult (18-65), elderly (65+) must_show: linear progression with arrows, stick figure or simplified human at each stage, age ranges labelled, reproductive capability indicated at adult stage </image_placeholder>
(a) At which stage does puberty typically occur?
(1 mark)
(b) Explain why the ability to reproduce is important for the continuation of a species.
(1 mark)
15. The photographs below show two different seed dispersal mechanisms.
<image_placeholder> id: Q15-fig1 type: diagram linked_question: Q15 description: Two side-by-side illustrations of seed dispersal mechanisms labels: Left: dandelion seed head with feathery pappus; Right: coconut fruit with thick fibrous husk, floating in water values: none must_show: dandelion with many small seeds attached to fluffy parachutes, coconut shown partially submerged with husk texture visible, arrows indicating dispersal direction (wind for dandelion, water current for coconut) </image_placeholder>
(a) Identify the method of seed dispersal shown by each plant.
| Plant | Method of seed dispersal |
|---|---|
| Dandelion | _______________________ |
| Coconut | _______________________ |
(1 mark)
(b) For each plant, explain one feature of its seed or fruit that suits its method of dispersal.
(1 mark)
16. The diagram below shows fertilisation in a flowering plant.
<image_placeholder> id: Q16-fig1 type: diagram linked_question: Q16 description: Diagram showing pollen tube growth in flower pistil labels: pollen grain on stigma, pollen tube growing through style, ovary containing ovules, male nucleus travelling down pollen tube, female nucleus in ovule values: none must_show: cross-section style, clear pollen tube path from stigma to ovule, double fertilisation showing one male nucleus fusing with female nucleus, labels for all key structures </image_placeholder>
Explain what happens after the male nucleus fuses with the female nucleus in the ovule, and what this structure eventually develops into.
(2 marks)
Section C: Structured and Application Questions (Questions 17–20, 3 marks each)
Answer all questions. Show your working and reasoning clearly.
17. A student set up an experiment to investigate conditions needed for seed germination. Four setups were used as shown below.
<image_placeholder> id: Q17-fig1 type: experimental_setup linked_question: Q17 description: Four identical test tubes with cotton wool and seeds, arranged in a row labels: Setup W: seeds + dry cotton wool + air (room temperature); Setup X: seeds + wet cotton wool + air (refrigerator, 4°C); Setup Y: seeds + wet cotton wool + air (room temperature); Setup Z: seeds + boiled water-covered cotton wool + no air (room temperature, oil layer on water) values: 5 seeds in each setup, tested for 7 days, room temperature = 25°C must_show: four clearly distinguished setups with labels W, X, Y, Z, cotton wool visible, seeds visible, oil layer on Z indicated, temperature differences indicated </image_placeholder>
(a) Which setup(s) will show germination after 7 days? Explain why.
(2 marks)
(b) What is the purpose of Setup W in this experiment?
(1 mark)
18. The diagram below shows the life cycle of a moth. Some stages are labelled.
<image_placeholder> id: Q18-fig1 type: diagram linked_question: Q18 description: Complete metamorphosis life cycle of a moth in circular arrangement labels: A (eggs on leaf), B (caterpillar/larva on leaf), C (pupa in cocoon on branch), D (adult moth) values: time for each stage: egg (4-10 days), larva (2-4 weeks), pupa (1-2 weeks), adult (1-2 weeks) must_show: circular arrows between stages, realistic drawings of each stage, cocoon/silk casing around pupa, eggs shown as cluster, time labels for each stage </image_placeholder>
(a) Identify the correct order of stages in the life cycle of this moth, using the letters provided.
(1 mark)
(b) Explain two differences between the life cycle of this moth and the life cycle of a grasshopper.
(2 marks)
19. Farmers growing apple trees want to produce large quantities of apples with consistent quality. They can use sexual reproduction (growing from seeds) or asexual reproduction (grafting branches onto rootstock).
(a) Explain why grafting would produce apple trees with more consistent fruit quality compared to growing from seeds.
(1 mark)
(b) Suggest one disadvantage of using grafting instead of growing from seeds for apple production.
(1 mark)
(c) Despite this disadvantage, explain why commercial apple farmers still prefer grafting for most of their production.
(1 mark)
20. The passage below describes changes in a forest ecosystem over 50 years.
In 1970, a large area of grassland was left undisturbed. Grasses and small flowering plants colonised the area. By 1985, shrubs and small trees had established themselves. By 2000, taller trees dominated and formed a dense canopy. The types of animals living there also changed over time. Initially, grasshoppers and butterflies were common. Later, birds that nested in shrubs appeared. Finally, squirrels and birds of prey that live in tall trees became established.
(a) What is the name of this gradual process of ecosystem change over time?
(1 mark)
(b) Explain why the types of animals changed as the plants changed during this process.
(1 mark)
(c) A farmer cleared the mature forest in 2020 to plant crops. Explain two ways this action could affect the organisms that had become established in the mature forest.
(1 mark)
END OF QUIZ
Check your answers before handing in your paper.
Answers
Primary 6 PSLE Science Quiz - Life Cycles: ANSWER KEY
Total Marks: 40
Section A: Multiple Choice (Questions 1–10, 1 mark each)
1. Answer: ( A )
Explanation: Complete metamorphosis involves four distinct stages: egg → larva (caterpillar) → pupa (chrysalis) → adult butterfly. The larva looks completely different from the adult and has different feeding habits. This is different from incomplete metamorphosis (like grasshoppers) where the young resemble small adults without wings.
Key concept: Complete metamorphosis = dramatic body change through pupa stage.
2. Answer: ( C )
Explanation: The life cycle of a flowering plant is: seed → seedling → young plant → mature plant (with flowers) → fruit and seeds. The pupa is a stage in the life cycle of insects with complete metamorphosis (butterflies, moths, beetles), not in plants.
Common mistake: Confusing animal and plant life cycles. Remember: plants don't have pupae!
3. Answer: ( D )
Explanation: While each stage involves growth, the metamorphosis from tadpole to adult frog is the most dramatic change. The tadpole lives in water, breathes with gills, has a tail, and eats plant matter. The adult frog lives on land and water, breathes with lungs and skin, has four legs, and eats insects. This complete body restructuring during metamorphosis is the most dramatic change.
Key concept: Metamorphosis = complete change in body form and lifestyle.
4. Answer: ( B )
Explanation: After fertilisation, the ovary swells and develops into the fruit. The ovules inside the ovary develop into seeds. The flower's other parts (petals, sepals, stamens, stigma, style) wither and fall away.
Teaching note: Remember this sequence: Ovary → Fruit; Ovule → Seed. The ovary is like a protective container that becomes the fruit wall.
5. Answer: ( A )
Explanation: Mosquitoes undergo complete metamorphosis: Egg → Larva (wriggler, lives in water) → Pupa (tumbler, also in water) → Adult (flying insect). The larva and pupa are aquatic, while the adult is terrestrial/aerial.
Key distinction: Complete metamorphosis always has a pupa stage; incomplete metamorphosis does not.
6. Answer: ( B )
Explanation: Stem cuttings are a form of asexual reproduction (vegetative propagation). The new plant grows from a part of the parent plant and has identical genetic material (same DNA). This produces a clone — genetically identical to the parent. Seeds from sexual reproduction combine genetic material from two parents, so offspring vary.
Key concept: Asexual reproduction = no genetic variation = identical offspring.
7. Answer: ( A )
Explanation: Ferns reproduce by spores, not seeds. They do not produce flowers, fruits, or cones. Spores develop in tiny cases (sporangia) on the underside of fronds. Ferns can perform photosynthesis (they are green plants); they just don't use seeds for reproduction.
Common mistake: Option C says "spores found in cones" — that's gymnosperms (conifers), not ferns. Ferns have sporangia, not cones.
8. Answer: ( B )
Explanation: Grasshoppers have incomplete metamorphosis (hemimetabolism): egg → nymph → adult. The nymph looks like a small adult but lacks fully developed wings and cannot reproduce yet. It goes through multiple moults, gradually developing wings and growing larger until it reaches adult form.
Key difference from complete metamorphosis: No pupa stage; gradual change, not dramatic transformation.
9. Answer: ( C )
Explanation: Both reproductive strategies are evolutionarily successful because they suit different niches:
- Many small eggs, no care (Species X): Good in unstable environments or where adult survival is uncertain. High quantity compensates for low survival.
- Few large eggs, with care (Species Y): Good in stable environments where investing heavily in each offspring pays off. High quality over quantity.
Neither is "better" absolutely — success depends on environment, predation pressure, resource availability, and parental survival.
Key concept: Reproductive strategies represent evolutionary trade-offs, not simple superiority.
10. Answer: ( C )
Explanation: The pollen grain contains the male gametes (male sex cells). When pollen lands on a compatible stigma, it germinates and grows a pollen tube down to the ovule for fertilisation. The ovule (A) contains the female gamete; stigma (B) receives pollen; ovary (D) protects ovules and becomes fruit.
Teaching tip: Remember: Pollen = male; Ovule = female.
Section B: Short Answer (Questions 11–16, 2 marks each)
11. Two advantages of seed dispersal: (2 marks)
Marking scheme — any two of:
| Point | Explanation |
|---|---|
| Reduces overcrowding/competition (1 mark) | Seeds that land away from parent plant have more space, light, water, and nutrients, reducing competition with parent and siblings |
| Colonises new habitats (1 mark) | Allows species to spread to new areas, increasing range and survival chances if original habitat becomes unsuitable |
| Reduces predation/disease buildup (1 mark) | Concentrated seedlings attract predators; dispersal spreads risk |
Sample answer:
- Seeds dispersed away from the parent plant reduce competition for light, water, and nutrients (1 mark)
- This allows the species to colonise new areas and increases survival chances (1 mark)
12. (a) Fertilisation / pollination and fertilisation (1 mark)
Note: Accept "pollination followed by fertilisation" or just "fertilisation." Pollination alone is not sufficient — fertilisation (fusion of male and female nuclei) must occur for fruits and seeds to develop.
(b) Why seeds need dispersal away from parent plant: (1 mark)
Key point: To reduce competition for resources (light, water, nutrients, space) with the parent plant, which would reduce survival of seedlings.
Sample answer: If seeds fall directly under the parent, they would compete with the parent for sunlight, water, and minerals, and most would not survive to grow into healthy plants.
13. (a) Animal P (Frog) — lowest survival rate (1 mark)
Reason: It produces the largest number of offspring but provides no parental care. With many eggs and no protection, most offspring will be eaten by predators or die from environmental conditions. This is a high-quantity, low-investment strategy with inherently low survival rates.
Note: Must state both high number AND no parental care to explain low survival.
(b) One advantage and one disadvantage of Animal R's strategy: (1 mark)
| Advantage (0.5 mark) | High survival rate of offspring due to extensive parental care and protection; offspring more likely to reach reproductive age |
| Disadvantage (0.5 mark) | High energy cost to parent; fewer offspring produced per reproduction; if parent dies, offspring vulnerable; slow population recovery if numbers drop |
Note: Any one valid advantage and one valid disadvantage accepted. Must identify which is which.
14. (a) Adolescent stage / teenage years / puberty (1 mark)
Accept: "Between child and adult" or approximate age range 12–18 years.
(b) Why reproduction is important for species continuation: (1 mark)
Key concept: Reproduction produces new individuals to replace aging/dead members, ensuring the species does not die out (extinction). It passes genetic information to the next generation.
Sample answer: Reproduction ensures that new individuals are produced to take the place of those that die, allowing the species to continue existing and preventing extinction.
15. (a) Methods of seed dispersal: (1 mark — both correct for 1 mark, no half marks)
| Plant | Method of seed dispersal |
|---|---|
| Dandelion | By wind |
| Coconut | By water |
(b) Features suited to dispersal method: (1 mark — one for each plant)
| Plant | Feature | How it suits method |
|---|---|---|
| Dandelion (0.5 mark) | Light seeds with feathery pappus/parachute | Increases surface area, catches wind, allows seeds to float far from parent |
| Coconut (0.5 mark) | Fibrous husk and waterproof shell / air spaces in husk | Provides buoyancy in water, protects embryo from salt water damage, allows long-distance travel by ocean currents |
16. Fertilisation and development: (2 marks)
Step-by-step answer:
| Step | What happens |
|---|---|
| 1 | The male nucleus fuses with the female nucleus in the ovule (0.5 mark) |
| 2 | This forms a zygote (fertilised egg cell) (0.5 mark) |
| 3 | The zygote divides repeatedly by mitosis to form an embryo (0.5 mark) |
| 4 | The embryo develops inside the seed, with stored food and protective seed coat; this structure is the seed which can grow into a new plant (0.5 mark) |
Teaching note: After fertilisation: zygote → embryo → seed. The ovule becomes the seed; the ovary becomes the fruit.
Section C: Structured and Application Questions (Questions 17–20, 3 marks each)
17. Seed germination experiment: (3 marks)
(a) Setup Y will show germination (1 mark)
Reason: Setup Y has all three necessary conditions for germination:
- Water — absorbed for metabolic processes and enzyme activation
- Air/oxygen — needed for aerobic respiration to release energy for growth
- Suitable temperature (room temperature, 25°C) — enzymes work best at moderate temperatures
(1 mark for correct identification, 1 mark for correct explanation of all three conditions)
Why others fail:
- W: No water — seeds remain dormant, metabolic reactions cannot start
- X: Too cold (4°C) — enzymes work too slowly, metabolic reactions halted
- Z: No oxygen — oil prevents air reaching seeds; seeds cannot respire aerobically to get energy
(b) Purpose of Setup W: (1 mark)
As a control. To show that seeds with air and suitable temperature but without water cannot germinate. This proves that water is necessary for germination by comparison with Setup Y.
18. Moth life cycle: (3 marks)
(a) Correct order: A → B → C → D (Egg → Larva → Pupa → Adult) (1 mark)
Must be in correct sequence. Accept written description if letters unclear.
(b) Two differences from grasshopper life cycle: (2 marks)
| Difference | Moth | Grasshopper |
|---|---|---|
| 1. Type of metamorphosis (1 mark) | Complete metamorphosis (dramatic change, pupa stage) | Incomplete metamorphosis (gradual change, no pupa) |
| 2. Larval form (1 mark) | Larva (caterpillar) looks completely different from adult — different body shape, feeding habits, habitat | Nymph looks like small adult — similar body shape, same food, same habitat |
| 3. Number of stages (alternative) | Four distinct stages | Three stages (egg, nymph, adult) |
| 4. Resting stage (alternative) | Has a pupa/cocoon stage where major restructuring occurs | No resting/pupa stage; active growth throughout |
Any two valid differences accepted, 1 mark each.
19. Apple tree reproduction strategies: (3 marks)
(a) Why grafting produces more consistent fruit quality: (1 mark)
Grafting is asexual reproduction/vegetative propagation. The new tree has identical genetic material/DNA to the parent plant (it is a clone). Therefore, it will produce fruit with the same characteristics (size, colour, taste, ripening time) as the parent with desirable traits.
Keywords: identical genes/DNA, clone, same desirable characteristics.
(b) One disadvantage of grafting: (1 mark)
- Lack of genetic variation — all trees are genetically identical, so if a new disease or pest appears that can attack one tree, all trees are equally vulnerable (no resistance variation)
- OR: Expensive and requires skill — needs trained workers, specific timing, correct rootstock selection
- OR: Dependent on existing rootstock — may have limited root characteristics (disease susceptibility, soil preference)
(c) Why commercial farmers still prefer grafting: (1 mark)
- Guaranteed quality and market requirements — consumers expect consistent apple size, colour, taste; grafting ensures this predictability
- Faster fruit production — grafted trees bear fruit in 2–3 years; seed-grown trees take 5–8 years or more
- Proven disease resistance of rootstock — can combine good fruit genes (scion) with strong root genes (rootstock)
Any valid economic or agricultural reason accepted.
20. Forest ecosystem changes: (3 marks)
(a) Ecological succession (1 mark)
Accept: "succession" or "secondary succession" (since it started from grassland, not bare rock).
(b) Why animal types changed with plant changes: (1 mark)
Animals are dependent on plants for food and habitat/shelter. As plant types changed:
- Grasses → grasshoppers/butterflies (herbivores feeding on grasses, nectar)
- Shrubs → shrub-nesting birds (nesting sites, berries/seeds)
- Tall trees → squirrels (tree-dwelling, nuts) and birds of prey (hunting from high perches, prey availability increased)
Key concept: Different animals have specific adaptations suited to particular plant structures and food sources.
(c) Two effects of forest clearing: (1 mark for any two valid points)
| Effect | Explanation |
|---|---|
| Loss of habitat/shelter | Trees destroyed, animals lose nesting sites and protection from predators/weather |
| Loss of food sources | Fruit, nuts, leaves, nectar gone; herbivores starve or migrate, followed by carnivores |
| Increased extinction risk | Species specialised for mature forest cannot survive in open farmland |
| Soil erosion | No tree roots to hold soil; streams polluted → affects aquatic organisms |
| Climate change | Less transpiration, local temperature/humidity changes |
Marking: Any two valid effects with brief explanation = 1 mark (0.5 each). Must be specific to "organisms established in mature forest."
END OF ANSWER KEY