AI Generated Exam Paper
Primary 6 PSLE Science Practice Paper 4
Free P6 PSLE Science Practice Paper 4, Nemo3 AI version, with questions, answers, and PSLE-focused practice for Singapore students.
These static practice materials are generated from the site's syllabus and paper-generation workflow, with source and model context shown so students and parents can evaluate the material before use.
Questions
TuitionGoWhere Practice Paper - Science Primary 6 PSLE
TuitionGoWhere Practice Paper (AI)
Subject: Science
Level: Primary 6 PSLE
Paper: Practice Paper 4 (Diversity Theme Focus)
Duration: 1 hour 45 minutes
Total Marks: 100
Name: ________________________
Class: ________________________
Date: ________________________
INSTRUCTIONS TO CANDIDATES
- Do not open this booklet until you are told to do so.
- Follow all instructions carefully.
- Answer all questions.
- The number of marks is given in brackets [ ] at the end of each question or part question.
- The total marks for this paper is 100.
- For Section A, shade your answers on the Optical Answer Sheet (OAS) provided.
- For Section B, write your answers in the spaces provided in this booklet.
SECTION A (56 marks)
For each question from 1 to 28, four options are given. One of them is the correct answer. Make your choice (1, 2, 3 or 4) and shade the correct oval on the Optical Answer Sheet.
Question 1 [2 marks]
Which of the following groups of organisms are all classified as fungi?
(1) Yeast, mushroom, moss
(2) Mould, yeast, mushroom
(3) Bacteria, mould, yeast
(4) Fern, moss, mushroom
Question 2 [2 marks]
Study the classification chart below.
Generated diagram for Q1.
Which of the following headings best represent Group X and Group Y?
| Group X | Group Y | |
|---|---|---|
| (1) | Microorganisms | Non-microorganisms |
| (2) | Single-celled organisms | Multi-celled organisms |
| (3) | Bacteria and Protists | Fungi |
| (4) | Decomposers | Producers |
Question 3 [2 marks]
Four students made the following statements about bacteria:
- Ali: All bacteria are harmful to humans.
- Bala: Bacteria can only be seen under a microscope.
- Cindy: Bacteria reproduce by binary fission.
- Devi: Bacteria have a nucleus.
Which two students made correct statements?
(1) Ali and Bala
(2) Bala and Cindy
(3) Cindy and Devi
(4) Ali and Devi
Question 4 [2 marks]
The diagram below shows a plant cell and an animal cell.
Generated diagram for Q4.
Which of the following statements about the two cells is correct?
(1) Only the plant cell has a cell membrane.
(2) Only the animal cell has cytoplasm.
(3) Both cells have a nucleus.
(4) Both cells have chloroplasts.
Question 5 [2 marks]
Which of the following organisms is classified as a vertebrate?
(1) Earthworm
(2) Grasshopper
(3) Frog
(4) Snail
Question 6 [2 marks]
Study the flowchart below.
Generated diagram for Q6.
Animal X has a backbone, has hair, and gives birth to live young. Which group does Animal X belong to?
(1) Bird
(2) Mammal
(3) Reptile
(4) Fish
Question 7 [2 marks]
Which of the following is a characteristic of all flowering plants?
(1) They reproduce by spores.
(2) They produce seeds enclosed in fruits.
(3) They are non-vascular plants.
(4) They do not have true roots.
Question 8 [2 marks]
The diagram below shows a cross-section of a flower.
Generated diagram for Q8.
Which part develops into a fruit after fertilisation?
(1) Ovary
(2) Ovule
(3) Stigma
(4) Anther
Question 9 [2 marks]
Which of the following shows the correct order of the life cycle of a flowering plant?
(1) Seed → Seedling → Adult plant → Flower → Fruit → Seed
(2) Seed → Flower → Seedling → Adult plant → Fruit → Seed
(3) Seed → Adult plant → Seedling → Flower → Fruit → Seed
(4) Seed → Seedling → Flower → Adult plant → Fruit → Seed
Question 10 [2 marks]
Study the table below.
| Organism | Method of Reproduction |
|---|---|
| Bacteria | Binary fission |
| Yeast | Budding |
| Mould | Spore formation |
| Fern | Spore formation |
| Moss | Spore formation |
Which of the following statements is correct?
(1) Only fungi reproduce by spores.
(2) Bacteria and yeast are both fungi.
(3) Ferns and mosses reproduce by spores.
(4) All microorganisms reproduce by binary fission.
Question 11 [2 marks]
The diagram below shows three types of microorganisms viewed under a microscope.
Generated diagram for Q11.
Which of the following correctly identifies the microorganisms?
| View A | View B | View C | |
|---|---|---|---|
| (1) | Bacteria | Yeast | Mould |
| (2) | Yeast | Mould | Bacteria |
| (3) | Mould | Bacteria | Yeast |
| (4) | Bacteria | Mould | Yeast |
Question 12 [2 marks]
Which of the following groups contains only invertebrates?
(1) Snake, lizard, crocodile
(2) Butterfly, spider, earthworm
(3) Frog, toad, salamander
(4) Shark, dolphin, whale
Question 13 [2 marks]
The diagram below shows a food web in a garden ecosystem.
Image pending generation: diagram for Q13.
How many food chains in the food web have exactly four organisms (including the producer)?
(1) 2
(2) 3
(3) 4
(4) 5
Question 14 [2 marks]
Which of the following adaptations helps a plant survive in a dry environment?
(1) Large, broad leaves
(2) Thick, waxy cuticle
(3) Shallow root system
(4) Brightly coloured flowers
Question 15 [2 marks]
Study the classification table below.
| Group | Characteristics | Examples |
|---|---|---|
| A | Have scales, lay eggs, cold-blooded | Snake, Lizard |
| B | Have feathers, lay eggs, warm-blooded | Eagle, Sparrow |
| C | Have hair/fur, give birth to live young, warm-blooded | Human, Whale |
| D | Have moist skin, lay eggs in water, cold-blooded | Frog, Toad |
Which group represents amphibians?
(1) Group A
(2) Group B
(3) Group C
(4) Group D
Question 16 [2 marks]
The diagram below shows a cell.
Generated diagram for Q16.
Based on the diagram, which of the following processes can this cell carry out?
(1) Photosynthesis only
(2) Respiration only
(3) Both photosynthesis and respiration
(4) Neither photosynthesis nor respiration
Question 17 [2 marks]
Which of the following statements about microorganisms is correct?
(1) All microorganisms cause diseases.
(2) Viruses are larger than bacteria.
(3) Some microorganisms are useful to humans.
(4) Microorganisms can only live in water.
Question 18 [2 marks]
The diagram below shows the life cycle of a mosquito.
Generated diagram for Q18.
At which stage does the mosquito live in water and breathe through a siphon tube?
(1) Egg
(2) Larva
(3) Pupa
(4) Adult
Question 19 [2 marks]
Which of the following is NOT a characteristic of fungi?
(1) They reproduce by spores.
(2) They feed on dead or decaying matter.
(3) They make their own food through photosynthesis.
(4) They can be unicellular or multicellular.
Question 20 [2 marks]
Study the diagram below.
Generated diagram for Q20.
A plant produces seeds but does not produce flowers. Which group does it belong to?
(1) Flowering plant
(2) Non-flowering plant (cone-bearing)
(3) Fern
(4) Moss
Question 21 [2 marks]
The table below shows the characteristics of four organisms.
| Organism | Nucleus | Cell Wall | Chloroplasts | Mode of Nutrition |
|---|---|---|---|---|
| W | Yes | Yes (cellulose) | Yes | Autotrophic |
| X | Yes | Yes (chitin) | No | Saprotrophic |
| Y | No | Yes (peptidoglycan) | No | Heterotrophic |
| Z | Yes | No | No | Heterotrophic |
Which organism is a bacterium?
(1) W
(2) X
(3) Y
(4) Z
Question 22 [2 marks]
Which of the following shows the correct classification hierarchy from broadest to most specific?
(1) Kingdom → Phylum → Class → Order → Family → Genus → Species
(2) Species → Genus → Family → Order → Class → Phylum → Kingdom
(3) Kingdom → Class → Phylum → Order → Family → Genus → Species
(4) Phylum → Kingdom → Class → Order → Family → Genus → Species
Question 23 [2 marks]
The diagram below shows a food chain.
Generated diagram for Q23.
What percentage of energy is transferred from the small fish to the large fish?
(1) 1%
(2) 10%
(3) 50%
(4) 90%
Question 24 [2 marks]
Which of the following organisms is a decomposer?
(1) Earthworm
(2) Mushroom
(3) Caterpillar
(4) Eagle
Question 25 [2 marks]
Study the diagram below.
Generated diagram for Q25.
In which layer of the leaf are most chloroplasts found?
(1) Upper epidermis
(2) Palisade mesophyll
(3) Spongy mesophyll
(4) Lower epidermis
Question 26 [2 marks]
Which of the following statements about viruses is correct?
(1) Viruses are cells.
(2) Viruses can reproduce on their own.
(3) Viruses are smaller than bacteria.
(4) Viruses have a nucleus.
Question 27 [2 marks]
The diagram below shows a pyramid of numbers.
Generated diagram for Q27.
What does the pyramid of numbers show about this ecosystem?
(1) There are more producers than primary consumers.
(2) There are more secondary consumers than primary consumers.
(3) The number of organisms increases at each trophic level.
(4) The hawk has the largest population.
Question 28 [2 marks]
Which of the following is an example of a structural adaptation?
(1) A bird migrating south for winter
(2) A bear hibernating in winter
(3) A cactus having spines instead of leaves
(4) A dog panting to cool down
SECTION B (44 marks)
Write your answers in the spaces provided.
Question 29 [3 marks]
The diagram below shows two cells, Cell A and Cell B.
Image pending generation: diagram for Q29.
(a) Identify Cell A and Cell B. [1]
Cell A: ________________________
Cell B: ________________________
(b) State one function of the chloroplasts in Cell B. [1]
(c) Explain why Cell A does not have a cell wall. [1]
Question 30 [4 marks]
The flowchart below shows the classification of five organisms: Bacterium, Amoeba, Mushroom, Fern, and Bird.
Generated diagram for Q30.
(a) Based on the flowchart, state two characteristics of a bacterium. [2]
(b) The fern and the bird are both living things. State one similarity and one difference between them. [2]
Similarity: ____________________________________________________________________
Difference: ____________________________________________________________________
Question 31 [3 marks]
The diagram below shows the life cycle of a flowering plant.
Generated diagram for Q31.
(a) Name the process that occurs between pollination and fruit formation. [1]
(b) Explain why seed dispersal is important for the survival of the plant species. [2]
Question 32 [4 marks]
Study the food web below.
Generated diagram for Q32.
(a) Write down a food chain with four organisms from the food web. [1]
(b) If all the zooplankton are removed from the food web, explain what will happen to the population of small fish. [2]
(c) State the role of decomposers in this food web. [1]
Question 33 [3 marks]
The table below shows the characteristics of four vertebrates.
| Animal | Body Covering | Reproduction | Body Temperature |
|---|---|---|---|
| P | Scales | Lay eggs | Cold-blooded |
| Q | Feathers | Lay eggs | Warm-blooded |
| R | Hair/Fur | Live birth | Warm-blooded |
| S | Moist skin | Lay eggs in water | Cold-blooded |
(a) Which animal (P, Q, R, or S) is a mammal? [1]
(b) Animal P and Animal S are both cold-blooded. State one difference in their body coverings. [1]
(c) Animal Q lays eggs but is warm-blooded. Name the group Animal Q belongs to. [1]
Question 34 [4 marks]
The diagram below shows an experiment set-up to investigate the conditions needed for germination.
Generated experimental_setup for Q34.
(a) Which tube(s) serve as the control set-up? Explain your answer. [2]
(b) In which tube(s) will the seeds germinate? Explain why the other tubes do not allow germination. [2]
Question 35 [3 marks]
The diagram below shows a microorganism viewed under a microscope.
Generated diagram for Q35.
(a) Identify the microorganism. [1]
(b) Name the structure labelled X (pseudopodium) and state its function. [1]
(c) Is this microorganism a plant or an animal? Explain your answer. [1]
Question 36 [4 marks]
Study the dichotomous key below.
Generated diagram for Q36.
(a) Using the key, identify the invertebrate that has 6 legs and wings. [1]
(b) An invertebrate has a segmented body and no legs. What is it? [1]
(c) State two differences between a spider and an insect. [2]
Question 37 [3 marks]
The diagram below shows a pyramid of energy.
Generated diagram for Q37.
(a) Calculate the percentage of energy transferred from producers to primary consumers. [1]
(b) Explain why the amount of energy decreases at each trophic level. [2]
Question 38 [4 marks]
The diagram below shows a plant growing in a desert environment.
Generated diagram for Q38.
(a) Name the adaptation labelled X (spines) and explain how it helps the plant survive in the desert. [2]
(b) The plant has a shallow but extensive root system. Explain how this adaptation helps the plant absorb water. [2]
Question 39 [3 marks]
The table below shows the number of species in different groups of organisms.
| Group | Number of Species |
|---|---|
| Insects | 1,000,000 |
| Plants | 390,000 |
| Fungi | 144,000 |
| Vertebrates | 65,000 |
| Bacteria | 10,000 (known) |
(a) Which group has the greatest number of species? [1]
(b) Calculate how many times more insect species there are compared to vertebrate species. [1]
(c) Suggest one reason why the number of known bacteria species is much lower than the actual number. [1]
Question 40 [4 marks]
The diagram below shows the human digestive system.
Generated diagram for Q40.
(a) In which organ does most absorption of digested food take place? [1]
(b) State the function of the liver in digestion. [1]
(c) Explain why the small intestine has a highly folded inner surface with villi. [2]
Question 41 [3 marks]
Study the classification chart below.
Image pending generation: diagram for Q41.
(a) A student classifies a whale as a fish because it lives in water and has fins. Explain why this classification is incorrect. [2]
(b) State one characteristic that all vertebrates share. [1]
Question 42 [4 marks]
The diagram below shows a pond ecosystem.
Generated diagram for Q42.
(a) Construct a food chain with four organisms from this pond ecosystem. [1]
(b) The kingfisher is a top predator. Explain what would happen to the frog population if all kingfishers were removed from the ecosystem. [2]
(c) State one way humans can have a positive impact on this pond ecosystem. [1]
Question 43 [3 marks]
The diagram below shows a seed germinating.
Generated diagram for Q43.
(a) Name the part labelled X (radicle) and state its function. [1]
(b) The cotyledons shrink as the seedling grows. Explain why. [2]
Question 44 [4 marks]
The diagram below shows three types of microorganisms and their uses.
Generated diagram for Q44.
(a) Name the process carried out by yeast in baking and brewing. [1]
(b) Explain how bacteria help in the process of decomposition. [2]
(c) State one harmful effect of microorganisms on humans. [1]
END OF PAPER
Answers
TuitionGoWhere Practice Paper - Science Primary 6 PSLE (Answer Key)
Subject: Science
Level: Primary 6 PSLE
Paper: Practice Paper 4 (Diversity Theme Focus)
Total Marks: 100
SECTION A (56 marks)
Question 1 [2 marks]
Answer: (2) Mould, yeast, mushroom
Explanation: Fungi include moulds, yeasts, and mushrooms. Moss is a non-flowering plant (bryophyte), not a fungus. Bacteria are prokaryotes, not fungi. Ferns are vascular plants.
Question 2 [2 marks]
Answer: (3) Bacteria and Protists | Fungi
Explanation: Group X contains Bacteria (prokaryotes), Amoeba and Paramecium (protists) — all are microorganisms but from different kingdoms. Group Y contains Mushroom, Yeast, Mould — all are fungi. Option (1) is incorrect because both groups are microorganisms. Option (2) is incorrect because yeast is unicellular. Option (4) is incorrect because fungi are decomposers, not producers.
Question 3 [2 marks]
Answer: (2) Bala and Cindy
Explanation:
- Ali is incorrect: Not all bacteria are harmful; many are beneficial (e.g., gut bacteria, decomposers, yogurt production).
- Bala is correct: Bacteria are microscopic and can only be seen under a microscope.
- Cindy is correct: Bacteria reproduce asexually by binary
<stage5_exam_answers_md>
TuitionGoWhere Practice Paper - Science Primary 6 PSLE (Answer Key)
Subject: Science
Level: Primary 6 PSLE
Paper: Practice Paper 4 (Diversity Theme Focus)
Total Marks: 100
SECTION A (56 marks)
| Question | Answer | Explanation |
|---|---|---|
| 1 | (2) | Mould, yeast, and mushroom are all fungi. Moss is a non-flowering plant. Bacteria are prokaryotes. Fern is a non-flowering plant. |
| 2 | (3) | Group X contains Bacteria (prokaryotes) and Protists (Amoeba, Paramecium). Group Y contains Mushroom, Yeast, Mould — all fungi. |
| 3 | (2) | Bala: Bacteria are microscopic. Cindy: Bacteria reproduce by binary fission. Ali is wrong (some bacteria are beneficial). Devi is wrong (bacteria lack a nucleus). |
| 4 | (3) | Both plant and animal cells have a nucleus. Plant cells have cell walls and chloroplasts; animal cells do not. Both have cell membranes and cytoplasm. |
| 5 | (3) | Frog is a vertebrate (amphibian). Earthworm (annelid), grasshopper (insect), snail (mollusc) are invertebrates. |
| 6 | (2) | Backbone → Vertebrate → Hair/fur → Mammal. Mammals give birth to live young (except monotremes). |
| 7 | (2) | Flowering plants (angiosperms) produce seeds enclosed in fruits. They reproduce by seeds, not spores. They are vascular and have true roots. |
| 8 | (1) | The ovary develops into the fruit after fertilisation. The ovule develops into the seed. |
| 9 | (1) | Correct sequence: Seed → Seedling → Adult plant → Flower → Fruit → Seed. |
| 10 | (3) | Ferns and mosses are non-flowering plants that reproduce by spores. Bacteria reproduce by binary fission; yeast by budding; mould by spores. |
| 11 | (1) | View A: Rod-shaped bacteria. View B: Yeast budding. View C: Mould with hyphae and sporangia. |
| 12 | (2) | Butterfly (insect), spider (arachnid), earthworm (annelid) are all invertebrates. Others contain vertebrates. |
| 13 | (3) | Four-organism chains (producer + 3 consumers): Grass→Grasshopper→Frog→Hawk; Grass→Grasshopper→Snake→Hawk; Grass→Rabbit→Snake→Hawk; Grass→Mouse→Snake→Owl. (4 chains) |
| 14 | (2) | Thick, waxy cuticle reduces water loss. Large leaves increase transpiration. Shallow roots access less water. Bright flowers attract pollinators. |
| 15 | (4) | Amphibians have moist skin, lay eggs in water, are cold-blooded. Group A: Reptiles. Group B: Birds. Group C: Mammals. |
| 16 | (3) | The cell has chloroplasts (photosynthesis) and mitochondria (implied, though not shown) for respiration. All living cells respire. |
| 17 | (3) | Many microorganisms are useful (e.g., yeast in baking, bacteria in yoghurt, decomposers). Not all cause disease. Viruses are smaller than bacteria. Microorganisms live in diverse habitats. |
| 18 | (2) | Larva (wriggler) lives in water and breathes through a siphon tube at the posterior end. Pupa also lives in water but breathes through trumpets. |
| 19 | (3) | Fungi are heterotrophs (saprotrophs); they do not photosynthesise. They reproduce by spores, feed on decaying matter, and can be unicellular (yeast) or multicellular (mould, mushroom). |
| 20 | (2) | Seeds but no flowers → Non-flowering plant (cone-bearing), i.e., gymnosperms (conifers). Ferns and mosses do not produce seeds. |
| 21 | (3) | Bacteria (Y): No nucleus (prokaryote), cell wall of peptidoglycan, no chloroplasts, heterotrophic. W = Plant. X = Fungus (chitin cell wall, saprotrophic). Z = Animal (no cell wall). |
| 22 | (1) | Standard taxonomic hierarchy: Kingdom → Phylum → Class → Order → Family → Genus → Species. |
| 23 | (2) | Energy transfer = (10 J / 100 J) × 100% = 10%. Each level shows ~10% transfer. |
| 24 | (2) | Mushroom (fungus) is a decomposer. Earthworm is a detritivore. Caterpillar is a herbivore. Eagle is a carnivore. |
| 25 | (2) | Palisade mesophyll cells are densely packed with chloroplasts for maximum light absorption. |
| 26 | (3) | Viruses are non-cellular, smaller than bacteria, cannot reproduce independently, and lack a nucleus. |
| 27 | (1) | Pyramid shows 10,000 grass (producers) > 100 grasshoppers (primary consumers) > 10 frogs (secondary) > 1 hawk (tertiary). Producers outnumber primary consumers. |
| 28 | (3) | Structural adaptation: physical feature (cactus spines reduce water loss). Others are behavioural adaptations. |
SECTION B (44 marks)
Question 29 [3 marks]
(a) Cell A: Animal cell
Cell B: Plant cell
(b) Chloroplasts contain chlorophyll to trap light energy for photosynthesis (to make food/glucose).
(c) Cell wall (or chloroplasts or large central vacuole) — any one structure present in Cell B but not Cell A.
Question 30 [3 marks]
(a) Bacterium / Bacteria (accept: prokaryote)
(b) No nucleus (genetic material in cytoplasm) and cell wall made of peptidoglycan (not cellulose or chitin).
(c) Binary fission — the cell divides into two identical daughter cells.
Question 31 [4 marks]
(a) Fungi (or Mould / Yeast)
(b) Saprotrophic nutrition — they secrete enzymes onto dead/decaying matter to break it down externally, then absorb the digested nutrients.
(c) Decomposers break down dead organisms and waste, recycling nutrients (mineral salts) back into the environment for plants to reuse.
(d) Yeast — used in bread-making (fermentation produces CO₂ to make dough rise) or beer/wine production.
Question 32 [3 marks]
(a) Vertebrates — they have a backbone.
(b) Group P: Mammals (have hair/fur, produce milk).
Group Q: Birds (have feathers, lay eggs).
(c) Bat — it has hair/fur and gives birth to live young (mammal), but it can fly (unlike most mammals).
Question 33 [4 marks]
(a) Ovule
(b) Anther — produces pollen grains (male gametes).
(c) Pollination — transfer of pollen from anther to stigma.
(d) Fruit — protects the seeds and aids in seed dispersal (by wind, water, animals, or splitting).
Question 34 [4 marks]
(a) Fern — reproduces by spores (on underside of fronds), has vascular tissue, no seeds/flowers.
(b) Moss — non-vascular, reproduces by spores, no true roots/stems/leaves.
(c) Similarity: Both reproduce by spores (not seeds).
Difference: Ferns have vascular tissue (xylem and phloem); mosses do not have vascular tissue.
Question 35 [4 marks]
(a) Producer — makes its own food through photosynthesis.
(b) Grass → Grasshopper → Frog → Snake → Hawk (or any valid 5-organism chain from the web).
(c) Energy decreases at each trophic level (only ~10% transferred; rest lost as heat, waste, uneaten parts).
(d) Population of grasshoppers increases (less predation by frogs) → grass population decreases (more herbivory).
Question 36 [3 marks]
(a) Structural adaptation — thick, fleshy stem stores water.
(b) Behavioural adaptation — active at night (nocturnal) to avoid daytime heat and reduce water loss.
(c) Spines (modified leaves) — reduce surface area to minimise water loss through transpiration; also deter herbivores.
Question 37 [4 marks]
(a) X: Xylem — transports water and mineral salts from roots to leaves.
Y: Phloem — transports food (sugar) from leaves to all parts of the plant.
(b) Xylem: Dead cells, hollow tubes, thick lignified walls (no cytoplasm/nucleus).
Phloem: Living cells (sieve tubes + companion cells), transport sugars bidirectionally.
(c) Transpiration pull — evaporation of water from stomata creates suction, pulling water up through xylem (cohesion-tension theory).
Question 38 [4 marks]
(a) Decreases — energy is lost as heat (respiration), waste (faeces/urine), and uneaten parts at each transfer.
(b) 100 J — 10% of 1000 J (primary consumer level).
(c) Pyramid of energy — always upright because energy decreases at each level; pyramid of numbers can be inverted (e.g., one tree → many insects).
(d) Shorter food chains — more energy reaches top consumers; less energy lost in transfers.
Question 39 [3 marks]
(a) Virus — non-cellular, protein coat (capsid) enclosing genetic material (DNA/RNA).
(b) Viruses cannot reproduce on their own — they must infect a living host cell and hijack its machinery to replicate.
(c) Vaccination — introduces weakened/dead virus to stimulate antibody production without causing disease.
Question 40 [4 marks]
(a) Insect — 3 body parts (head, thorax, abdomen), 6 legs, 1 pair of antennae, usually 2 pairs of wings.
(b) Arachnid — 2 body parts (cephalothorax, abdomen), 8 legs, no antennae, no wings.
(c) Complete metamorphosis: Egg → Larva → Pupa → Adult (e.g., butterfly, mosquito).
Incomplete metamorphosis: Egg → Nymph → Adult (e.g., grasshopper, cockroach). Nymph resembles small adult.
(d) Mosquito — larvae and pupae live in stagnant water; removing breeding sites breaks the life cycle.
Question 41 [4 marks]
(a) Camouflage — colour/pattern matches surroundings to avoid detection by predators or prey.
(b) Mimicry — harmless species mimics appearance of harmful species (e.g., viceroy butterfly mimics monarch) to deter predators.
(c) Polar bear: Thick fur + fat layer (insulation), white fur (camouflage), padded feet (insulation + grip on ice).
Cactus: Spines (reduce water loss), thick waxy cuticle, fleshy stem (water storage), deep/extensive roots.
(d) Adaptations are inherited traits that enhance survival and reproduction in a specific environment; they arise through natural selection over generations.
Question 42 [4 marks]
(a) Bacteria and Fungi (mould, yeast) — break down dead organic matter.
(b) Carbon cycle: Decomposers release CO₂ through respiration, returning carbon to atmosphere for photosynthesis.
Nitrogen cycle: Decomposers convert organic nitrogen → ammonia (ammonification) → nitrites/nitrates (nitrification) for plant uptake.
(c) Nutrients accumulate in dead matter → soil becomes infertile → plants cannot grow → food chains collapse.
(d) Composting — using decomposers to recycle kitchen/garden waste into nutrient-rich humus for soil fertility.
END OF ANSWER KEY
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