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

TuitionGoWhere Practice Paper - Science Primary 5 (Answer Key)

Topic Focus: Diversity (Adaptations, Classification, Interactions)
Version: 4 of 5

Section A (28 marks)

1. (3)

• Reasoning: Mammals are characterized by having hair or fur and giving birth to live young (with few exceptions like the platypus, but at P5 level, giving birth is the key discriminator against birds/reptiles/fish). Animal R has hair/fur and gives birth.
• Common Mistake: Choosing P (scales/eggs) which is a reptile or fish.

2. (2)

• Reasoning: Group X has 6 legs. Insects have 6 legs. An ant is an insect.
  • Spider: 8 legs (Arachnid).
  • Earthworm: No legs (Annelid).
  • Centipede: Many legs (Myriapod).
• Concept: Classification of invertebrates based on leg count.

3. (2)

• Reasoning: In desert plants (xerophytes), thick fleshy stems are adapted to store water. Spines reduce surface area to minimize water loss and protect against herbivores.
• Concept: Adaptation to dry environments.

4. (2)

• Reasoning: The diagram shows a perching foot (anisodactyl arrangement: 3 toes forward, 1 back) with sharp claws for gripping. This is typical of birds that sit on branches.
  • Swimming feet are webbed.
  • Scratching feet have strong, thick toes (like chickens).
  • Wading feet have long toes to distribute weight on mud.
• Concept: Structural adaptation for locomotion/perching.

5. (3)

• Reasoning: Fungi are not plants; they cannot photosynthesize (no chlorophyll). They are saprophytes, obtaining nutrients by secreting enzymes to break down dead organic matter externally and then absorbing it.
• Common Mistake: Thinking fungi are plants because they don't move.

6. (3)

• Reasoning: Photosynthesis requires light to produce chlorophyll (green pigment) and food. Without light, Plant B cannot make chlorophyll, leading to pale (etiolated) and weak growth. Plant A has light, so it remains green and healthy.
• Concept: Conditions for photosynthesis and plant health.

7. (1)

• Reasoning: The graph shows a classic predator-prey cycle. The prey (beetles) population increases, providing more food for predators (birds), so the bird population increases. As birds eat more beetles, the beetle population drops, leading to a subsequent drop in the bird population due to lack of food.
• Concept: Interdependence in ecosystems.

8. (1)

• Reasoning:
  • Bacteria, Virus, and Fungi (like yeast/mold) are microorganisms (mostly microscopic, though some fungi are visible, their basic unit is microscopic). Note: At P5, Fungi like mushrooms are often treated separately, but Yeast/Mold are microorganisms. However, looking at the options:
  • (2) Moss is a plant.
  • (3) Mushroom is a macro-fungus (visible), but Virus/Bacteria are micro. Wait, let's look closer. Standard P5 classification: Microorganisms include Bacteria, Fungi (Yeast/Mold), Protozoa, Algae (some), Viruses.
  • Let's re-evaluate Option 1 vs 3. Option 1 has "Fungi". Option 3 has "Mushroom". Mushrooms are fungi. But usually, "Microorganisms" refers to those needing a microscope. Yeast is a microorganism. Mushroom is not.
  • Let's look at Option 1 again: Bacteria, Virus, Fungi. Some fungi are microscopic (yeast).
  • Let's look at Option 4: Fern is a plant.
  • Let's look at Option 2: Moss is a plant.
  • Between 1 and 3: Option 1 is the best fit if we consider "Fungi" to include microscopic forms like yeast/mold which are standard examples of microorganisms in P5. Option 3 lists "Mushroom" which is clearly visible. Therefore, (1) is the intended answer as it lists groups that contain microorganisms, whereas Mushroom is a specific macroscopic fruiting body. Correction: In many P5 contexts, "Fungi" is a kingdom, but "Microorganisms" is a functional group. Bacteria and Viruses are definitely micro. Yeast (a fungus) is a micro. So (1) is correct.

9. (2)

• Reasoning: Selecting specific individuals with desirable traits to breed is selective breeding (artificial selection). Natural selection happens without human intervention.
• Concept: Human impact on diversity/breeding.

10. (2)

• Reasoning: If caterpillars (food for birds) decrease, birds will have less food. Their population will decrease due to starvation or reduced reproduction.
• Concept: Food chain dynamics.

11. (2)

• Reasoning: Desert plants need to maximize water absorption when it rarely rains. Shallow, widespread roots catch surface rain quickly.
  • (1) Broad leaves increase water loss.
  • (3) Thin skin increases water loss.
  • (4) Large SA:Vol ratio increases water loss.
• Concept: Adaptation for water conservation and absorption.

12. (1)

• Reasoning: Follow the key:
  • Edge jagged? Yes -> Leaf P.
  • The key stops at Leaf P for jagged edges. The vein type is irrelevant once Leaf P is identified.
• Concept: Using a dichotomous key.

13. (3)

• Reasoning: Decomposers break down dead organisms and waste, releasing nutrients (minerals) back into the soil for plants to use. This recycles nutrients.
• Concept: Role of decomposers.

14. (3)

• Reasoning: Variation provides a range of traits. In a changing environment, some traits may be advantageous, allowing those individuals to survive and reproduce (natural selection).
• Concept: Importance of variation.

Section B (28 marks)

15. (a) Animal A: Bird [1] Animal C: Mammal [1] * Note: Birds have feathers and lay eggs. Mammals have hair and give birth/feed milk.

(b) They breathe using lungs. OR They have dry, scaly skin. OR They are cold-blooded (body temperature varies). [1] * Note: Any valid reptile characteristic not already listed (scales/eggs/temp variation is in table, so "breathes with lungs" is a safe addition, or "cold-blooded" is implied by "varies with environment" but explicitly stating it is good). The table says "Varies with environment", so stating "Cold-blooded" is a valid interpretation/name for that trait. Better answer: They breathe with lungs.

(c) To ensure their body enzymes work efficiently. [1] Enzymes control chemical reactions in the body (like digestion/respiration) and work best at a specific temperature. [1] * Teaching Note: Mammals are endotherms. Maintaining constant temperature ensures metabolic processes remain stable regardless of external weather.

16. (a) Anther [1] * Note: The anther produces pollen.

(b) Pollination is the transfer of pollen grains from the anther to the stigma. [2] * Marking: 1 mark for "from anther", 1 mark for "to stigma". Must mention both parts.

(c) Fruit [1] * Note: The ovary becomes the fruit; the ovules inside become the seeds.

17. (a) Surface area of the leaf (or Size of the leaf). [1]

(b) To prevent water loss from the cut surfaces. [1] * Reasoning: This ensures that any change in mass is due to water loss from the leaf surface (transpiration) only, making it a fair test.

(c) Leaf: X [1] Explanation: Leaf X has the largest surface area. [1] More stomata are present on a larger surface area, leading to a higher rate of transpiration (water loss). [1] * Teaching Note: Transpiration occurs mainly through stomata on the leaf surface. More surface area = more stomata = more water loss.

18. (a) Algae [1]

(b) The population of Herons will decrease. [1] Because Small Fish are a food source for Herons. With fewer Small Fish, Herons have less food. [1] * Note: Even though Herons also eat Large Fish, the direct loss of one food source impacts the total available energy/food supply.

(c) Energy is lost at each trophic level (as heat/waste/movement). [1] Therefore, less energy is available to support organisms at higher trophic levels, resulting in fewer individuals. [1] * Teaching Note: This is the "Pyramid of Numbers/Energy" concept. Only ~10% of energy is passed on.

19. (a) It provides camouflage. [1] This helps the Polar Bear hide from its prey (or predators, though they are apex) while hunting in the snow. [1] * Note: The question asks how it helps survive. Camouflage aids hunting success.

(b) The large surface area of the paws distributes the bear's weight over a larger area. [1] This reduces the pressure on the snow, preventing the bear from sinking. [1] * Concept: Pressure = Force / Area. Larger area = Lower pressure.

(c) Teeth type: Canines (or Sharp teeth). [1] Reason: To tear flesh/meat. [1] * Note: Carnivores need sharp canines for killing and tearing.

20. (a) Type: Fungus [1] Reason: It has cell walls, reproduces by spores, and obtains nutrients by absorbing decaying matter (cannot make its own food). [1] * Note: Plants make their own food. Animals do not have cell walls. Fungi fit all criteria.

(b) It cannot perform photosynthesis because there is no sunlight in the cave. [1] * Alternative: It does not have chlorophyll.

(c) It acts as a decomposer, breaking down dead matter and recycling nutrients in the cave ecosystem. [1]