Question 1

The diagram below shows a tree habitat. Which of the following shows the correct number of communities and number of populations in this tree habitat?

Accepted Answer

(2) Number of communities: 1, Number of populations: 4. A community consists of all the different populations living and interacting in a particular place. In this tree habitat, all the organisms (bird, squirrel, grasshopper, tree) live and interact, forming a single community. A population refers to a group of individuals of the same species. In this habitat, there are four distinct types of organisms: trees, birds, squirrels, and grasshoppers. Thus, there are 4 populations. Therefore, the correct option is 1 community and 4 populations.

Question 2

Which of the following statements is true about the food made during photosynthesis?
(1) Excess food can only be stored in the roots.
(2) Excess food made through photosynthesis is stored as starch.
(3) Food is absorbed from the soil when the plant carries out photosynthesis.
(4) Food made in the leaves is only transported to all parts of the plant above the roots.

Accepted Answer

(2) Excess food made through photosynthesis is stored as starch.. Plants produce glucose during photosynthesis. Any excess glucose that is not immediately used is converted into starch for storage. Starch can be stored in various parts of the plant, including leaves, stems, and roots, not just roots. Food is produced by the plant through photosynthesis, not absorbed from the soil, and it is transported to all parts of the plant, including those below the roots.

Question 3

Which one of the following is correct?

Accepted Answer

(3) B and E | C | D | A. Let's analyze the roles of each organism from the food web:
- A: As arrows originate from A but none point to it, A is the Food Producer.
- B: B eats A (plant) and is eaten by C and D (animals). So, B is a primary consumer (herbivore) and prey.
- E: E eats A (plant) and is eaten by C (animal). So, E is a primary consumer (herbivore) and prey.
- C: C eats B and E (animals) and is not eaten by any other organism. So, C is a secondary consumer (carnivore) and a top predator.
- D: D eats B (animal) and is not eaten by any other organism. So, D is a secondary consumer (carnivore) and a top predator.

Matching these roles to the categories provided in the options:
- Food Producer: A (This is consistent with all options).
- Predator only: C (Eats animals and is not eaten).
- Prey only: B and E (They are primary consumers that are eaten by other animals. In some primary school contexts, their role as eaters of plants might not be termed 'predator', making 'prey only' plausible here).
- Prey and Predator: D (D eats animals but is not shown to be eaten by any other organism in the given food web. Therefore, D should ideally be classified as 'Predator only'. However, following the provided options, option (3) categorizes D as 'Prey and Predator', which implies it is both an animal eater and eaten by an animal, which is inconsistent with the diagram for D).

Given that this is a multiple-choice question and option (3) is indicated as the correct answer in the answer key, we select (3). The categorization for A, C, and B/E is plausible under common primary school simplifications, with D being the main inconsistency.

Question 4

Which of the following can be concluded from the above food web?
(1) B and D are plant-eaters.
(2) C is the only animal-eater.
(3) A is the only food producer.
(4) D is a plant-and-animal-eater.

Accepted Answer

(3) A is the only food producer.. Let's analyze each statement based on the food web:
- (1) B is a plant-eater (eats A), but D eats B (an animal), not A (plant). So, D is an animal-eater. This statement is incorrect.
- (2) C eats B and E (animals), so C is an animal-eater. However, D also eats B (an animal), so C is not the *only* animal-eater. This statement is incorrect.
- (3) Organism A has arrows pointing from it to other organisms (B and E), indicating it is consumed. There are no arrows pointing to A from other organisms, meaning it does not consume others. Therefore, A is the only food producer in this food web. This statement is correct.
- (4) D eats B (an animal). There is no arrow from A to D, indicating D does not eat plants. So, D is an animal-eater, not a plant-and-animal-eater (omnivore). This statement is incorrect.

Question 5

Gina carried out an experiment as shown below. How will the amount of oxygen in the water change after a few hours?

Accepted Answer

(2) increase | decrease. In setup X, the water plant is exposed to light. Plants perform photosynthesis in the presence of light, which produces oxygen. Thus, the amount of oxygen in the water in X will increase. In setup Y, the water plant is covered by a cardboard box, blocking out light. Without light, the plant cannot perform photosynthesis. However, the plant will still respire, consuming oxygen. Therefore, the amount of oxygen in the water in Y will decrease.

Question 6

The graph below shows the number of grasshoppers in a field community. What could have happened after point J that had caused the change in the number of grasshoppers?
(1) Fertilizer was added to the soil.
(2) More grass was planted in the field.
(3) Grasshoppers reproduce more quickly.
(4) More predators of grasshoppers were released into the field.

Accepted Answer

(4) More predators of grasshoppers were released into the field.. The graph shows a significant decrease in the number of grasshoppers after point J. Let's evaluate the options:
(1) Adding fertilizer or (2) planting more grass would increase the food source for grasshoppers, which would likely lead to an *increase* in their population.
(3) Grasshoppers reproducing more quickly would also lead to an *increase* in their population.
(4) Releasing more predators of grasshoppers (organisms that eat grasshoppers) would increase the mortality rate of grasshoppers, causing their population to *decrease*. This matches the trend shown in the graph after point J.

Question 7

The diagram below shows insect P on a tree branch. Insect P feeds only on the leaves of tree branches. They are often eaten by birds and reptiles but do not hide from its predators. How does keeping very still on a branch help insect P in its survival?
(1) It helps the insect to find food.
(2) It helps the insect to attract mates.
(3) It prevents the insect from falling off a tree branch.
(4) It prevents the insect from being detected by its predators.

Accepted Answer

(4) It prevents the insect from being detected by its predators.. Insect P is preyed upon by birds and reptiles. The diagram shows the insect blending in with the tree branch, suggesting camouflage. By keeping very still, the insect enhances its camouflage, making it much harder for predators to spot it. This reduces the chances of being eaten and increases its survival rate.

Question 8

Which of the following is an example of behavioural adaptation?
(1) Wolves hunt together in packs.
(2) Moles have claws to dig the soil.
(3) Jellyfish have venom to sting its prey.
(4) Ducks have webbed feet to paddle in the water.

Accepted Answer

(1) Wolves hunt together in packs.. A behavioural adaptation is an action or a way an animal acts that helps it survive or reproduce.
(1) Wolves hunting together in packs is a learned or innate action (behaviour) that improves their success in catching prey. This is a behavioural adaptation.
(2) Moles having claws is a structural adaptation (a physical feature of the body).
(3) Jellyfish having venom is a physiological adaptation (a chemical or internal body process).
(4) Ducks having webbed feet is a structural adaptation (a physical feature of the body).

Question 9

A population of W was introduced into a habitat. As a result, the population of X increased while the population of Y decreased. Which of the following food chains shows the correct food relationship between the organisms?
(1) Plant → X → Y → W
(2) Plant → X → W → Y
(3) Plant → W → Y → X
(4) Plant → Y → X → W

Accepted Answer

(1) Plant → X → Y → W. Let's analyze the effects of introducing W in each food chain based on the given observations: X increased, Y decreased.
(1) Plant → X → Y → W:
   - If W is introduced and eats Y, the population of Y will decrease (matches observation).
   - If Y (a predator of X) decreases, then X's predation pressure reduces, causing the population of X to increase (matches observation).
   - This food chain is consistent with both observations.
(2) Plant → X → W → Y:
   - If W is introduced and eats X, the population of X will decrease (contradicts observation 'X increased').
(3) Plant → W → Y → X:
   - If W is introduced and eats plants, W's population might increase. If Y eats W, then Y's population might increase (contradicts 'Y decreased').
(4) Plant → Y → X → W:
   - If W is introduced and eats X, the population of X will decrease (contradicts 'X increased').
Therefore, option (1) correctly shows the food relationship.

Question 10

The food web below shows the relationship between organisms J, K, L and M in a community. The jawbone of one of the organisms is shown below. Which organism in the food web above is likely to have such a jawbone?
(1) J
(2) K
(3) L
(4) M

Accepted Answer

(4) M. The jawbone shown has sharp, pointed teeth, which are characteristic of carnivores (meat-eaters) or omnivores (plant-and-meat-eaters) designed for tearing and consuming flesh.
Let's examine the feeding relationships in the food web:
- Plant → J: J eats plants, so J is a herbivore.
- Plant → L: L eats plants, so L is a herbivore.
- J → K: K eats J (an animal), so K is a carnivore.
- K → M: M eats K (an animal), so M is also a carnivore, and at a higher trophic level than K.
Both K and M are carnivores, but M is a secondary carnivore in this specific food chain (eating K, which eats J). Higher-level predators typically have more pronounced carnivorous features. Thus, M is the most likely candidate to possess such a jawbone.

Question 11

The graph below shows the mass of a butterfly during different stages of its life cycle. Which of the following best represents the butterfly at its pupal stage?
(1) A
(2) B
(3) C
(4) D

Accepted Answer

(3) C. The life cycle of a butterfly involves four stages: egg, larva (caterpillar), pupa, and adult.
- A represents the initial stage, likely the egg or early larva, with low mass.
- B represents the larval (caterpillar) stage, where the organism feeds heavily and grows rapidly, thus increasing significantly in mass.
- C represents the pupal stage. During this stage, the pupa does not feed, and its mass generally remains relatively constant or may slightly decrease as it uses stored energy for metamorphosis. The plateau in the graph at C best represents this period of stable mass.
- D represents the adult butterfly, which emerges from the pupa. Its mass might be similar or slightly different from the pupa, but the pupal stage is characterized by a stable mass after the larval growth.

Question 12

Diagrams 1 and 2 below show the reproductive systems of a flower and a female human respectively. Which two reproductive parts have a similar function?
(1) A and Q
(2) B and P
(3) C and P
(4) D and Q

Accepted Answer

(2) B and P. Let's identify the function of each labeled part:
- Diagram 1 (Flower):
    - A: Stigma (receives pollen).
    - B: Anther (produces pollen, containing male gametes).
    - C: Ovary (contains ovules, develops into fruit).
    - D: Ovule (contains female gamete, develops into seed).
- Diagram 2 (Female Human):
    - P: Ovary (produces eggs, female gametes).
    - Q: Uterus (site of embryo/fetus development).

Comparing functions:
- B (Anther) produces male gametes (pollen). P (Human Ovary) produces female gametes (eggs). Both B and P are involved in the production of gametes (reproductive cells), which is a similar fundamental function, albeit for different sexes and types of organisms.

Question 13

The diagram below shows how some of the systems in the human body work together. Which of the following systems are correctly identified?

Accepted Answer

(4) respiratory | digestive | circulatory. Let's identify the systems based on their inputs and outputs:
- System U takes in 'food', indicating it is the digestive system (responsible for processing food).
- System T takes in 'oxygen' and releases 'carbon dioxide', indicating it is the respiratory system (responsible for gas exchange).
- System V connects System U (digestive) and System T (respiratory) with two-way arrows, implying it transports substances between them and throughout the body. This is the function of the circulatory system (transporting digested nutrients, oxygen, and removing waste products).
Therefore, System T is respiratory, System U is digestive, and System V is circulatory.

Question 14

The diagram below shows a seed of a plant. Siti investigated how the length of hairs of a seed affects the time taken for the seed to reach the ground. The experiment was conducted in a room and the seeds were dropped from the same height. The results were shown below. What can be concluded from the results above?
(1) The seeds are dispersed by water.
(2) Seed B took a longer time to reach the ground than seed A.
(3) The seeds can be dispersed further if the average length of hair is decreased.
(4) As the average length of hairs increases, the time taken for the seed to reach the ground increases.

Accepted Answer

(4) As the average length of hairs increases, the time taken for the seed to reach the ground increases.. Let's analyze the data in the table:
- Seed A: 1.5 cm hair length, 4.8 s drop time.
- Seed B: 1.0 cm hair length, 4.0 s drop time.
- Seed C: 0.5 cm hair length, 2.6 s drop time.
Comparing the data, as the average length of hairs increases (from 0.5 cm to 1.5 cm), the time taken for the seed to reach the ground also increases (from 2.6 s to 4.8 s). This means longer hairs provide more air resistance, slowing the fall.
(1) The experiment tests falling in air, not water dispersal.
(2) Seed B (4.0 s) took a *shorter* time than seed A (4.8 s).
(3) If the average length of hair is decreased, the seed falls faster, which would result in *less* dispersal by wind, not further.
(4) This statement is a direct observation from the trend in the table: longer hairs (greater length) result in longer fall times (more time taken).

Question 15

Study the flow chart below. Based on the information above, which of the following correctly represents animals A, B and C?

Accepted Answer

(1) tiger | butterfly | grasshopper. Let's trace the flowchart for each animal type:
- **Animal A:** Does not lay eggs (viviparous).
- **Animal B:** Lays eggs, but does NOT have a 3-stage life cycle.
- **Animal C:** Lays eggs, AND has a 3-stage life cycle (e.g., egg, nymph, adult; or egg, larva, adult, but not egg, larva, pupa, adult).

Let's check option (1):
- **A: Tiger:** Tigers are mammals and give birth to live young, so they do not lay eggs. (Correct for A).
- **B: Butterfly:** Butterflies lay eggs, but they have a 4-stage life cycle (egg, larva, pupa, adult). Thus, they do NOT have a 3-stage life cycle. (Correct for B).
- **C: Grasshopper:** Grasshoppers lay eggs and have a 3-stage life cycle (egg, nymph, adult - incomplete metamorphosis). (Correct for C).

Option (1) fits all the criteria.

Question 16

The map below shows the location of the adult plants, A, B and C, and the distribution of their young plants. Which of the following shows the correct methods of seed dispersal for plants A, B and C?

Accepted Answer

(1) By Water: [Symbol for Plant A] | By Animal: [Symbol for Plant B] | By Wind: [Symbol for Plant C]. Let's analyze the dispersal patterns for each plant:
- **Adult Plant A (△) and Young Plant A (•):** Adult Plant A is located near a river. Its young plants are distributed downstream along the river, indicating dispersal by the 'Water Current'.
- **Adult Plant B (□) and Young Plant B (▲):** The young plants of B are generally clustered near the adult plant, but some are slightly further afield. This pattern is characteristic of animal dispersal, where animals might drop seeds after eating the fruit, or carry them on their fur and drop them nearby.
- **Adult Plant C (○) and Young Plant C (●):** The young plants of C are spread out downwind from the adult plant, in the direction of the 'Wind Direction' arrow. This indicates dispersal by 'Wind'.

Therefore, the correct methods are: Plant A by Water, Plant B by Animal, and Plant C by Wind.

Question 17

A microscope is used to view cell specimens. Which of the following materials is most suitable to make the objective lens that allows the specimens to be seen most clearly?

Accepted Answer

(4) H | 4500. To see specimens most clearly through a microscope's objective lens, the lens material must allow the maximum possible amount of light to pass through it. Comparing the 'Amount of light that passes through the material (units)' for each material:
- Material E: 0 units (opaque)
- Material F: 500 units
- Material G: 2000 units
- Material H: 4500 units
Material H allows the greatest amount of light to pass through (4500 units), making it the most suitable choice for an objective lens.

Question 18

Study the circuit diagram below. Which of the bulbs, if fused, would allow only one bulb to light up?

Accepted Answer

(3) Bulb C. Let's analyze the circuit:
- Bulb A is in series with the main circuit. If Bulb A fuses, the entire circuit breaks, and no bulbs will light up.
- After Bulb A, the circuit splits into two parallel branches. One branch contains Bulb B. The other branch contains Bulb C and Bulb D connected in series.
- If Bulb B fuses, the path through B is broken. However, current can still flow through the branch containing C and D. Since C and D are in series, both Bulb C and Bulb D would light up (2 bulbs).
- If Bulb C fuses, the series path containing C and D is broken, so neither C nor D will light up. However, current can still flow through the parallel branch containing Bulb B. So, only Bulb B would light up (1 bulb).
- If Bulb D fuses, similar to C, the series path containing C and D is broken. Current still flows through the branch containing Bulb B. So, only Bulb B would light up (1 bulb).
Therefore, if Bulb C or Bulb D fuses, only one bulb (Bulb B) would light up.

Question 19

Which of the forces, A, B, C or D, best represents frictional force?

Accepted Answer

(3) C. Let's trace the properties of frictional force through the flowchart:
1. **Can the force act from a distance?** Frictional force is a contact force; it requires direct contact between surfaces, so the answer is 'No'.
2. This leads to the question: **Does the force produce heat?** Frictional force always produces heat (e.g., rubbing hands together makes them warm). So, the answer is 'Yes'.
This path leads to C. Therefore, C best represents frictional force.

Question 20

Arthur threw a toy parachute from a height. Identify the force that caused the toy parachute to fall to the ground.

Accepted Answer

(1) A. The force that causes objects to fall to the ground is gravity. Let's trace the properties of gravity through the flowchart (from Q19 on page 15):
1. **Can the force act from a distance?** Yes, gravity acts at a distance.
2. This leads to the question: **Does the force only exert a pull on an object?** Yes, gravity always pulls objects downwards; it does not push.
This path leads to A. Therefore, A represents the gravitational force.

Question 21

The diagram below shows a plastic bottle with a capacity of 500 cm³. Which of the following can be stored completely in this bottle?
A: 600 cm³ of air
B: 350 cm³ of sand
C: 600 cm³ of water
(1) B only
(2) A and B only
(3) B and C only
(4) A, B and C

Accepted Answer

(2) A and B only. The bottle has a capacity of 500 cm³.
- A: 600 cm³ of air. Air is a gas, and gases expand to fill the entire volume of their container. So, 600 cm³ of air can be stored in the 500 cm³ bottle (it would simply occupy 500 cm³ of space). This can be stored completely.
- B: 350 cm³ of sand. Sand is a solid, which has a definite volume. Since 350 cm³ is less than the bottle's capacity of 500 cm³, it can be stored completely.
- C: 600 cm³ of water. Water is a liquid, which has a definite volume. Since 600 cm³ is greater than the bottle's capacity of 500 cm³, it cannot be stored completely; only 500 cm³ of water would fit.
Therefore, only A and B can be stored completely in the bottle.

Question 22

The diagram below shows a hair dryer that is switched on with hot air blowing out. Which of the following best shows the type(s) of energy that is present when the hair dryer is switched on?
(1) Heat energy only
(2) Heat energy and sound energy only
(3) Kinetic energy and sound energy only
(4) Heat energy, kinetic energy and sound energy

Accepted Answer

(4) Heat energy, kinetic energy and sound energy. When a hair dryer is switched on, electrical energy is converted into several forms of energy:
- **Heat energy:** The heating element in the hair dryer produces hot air.
- **Kinetic energy:** The fan inside moves, and the air is blown out, demonstrating kinetic energy.
- **Sound energy:** The motor and the movement of air produce noise, which is sound energy.
Therefore, all three types of energy (heat, kinetic, and sound energy) are present.

Question 23

A push was applied to move a wooden block as shown below. Which of the following correctly shows the directions of gravity and friction exerted on the wooden block when it is pushed?

Accepted Answer

(1) Gravity: [down arrow] | Friction: [left arrow]. Let's determine the direction of each force:
- **Gravity:** Gravity is a force that always pulls objects downwards, towards the center of the Earth. So, the gravity arrow should point vertically down.
- **Friction:** Friction is a force that opposes motion or attempted motion. Since the wooden block is being pushed to the right, the frictional force exerted by the surface on the block will act in the opposite direction, i.e., to the left.
Option (1) correctly shows gravity pointing down and friction pointing left.

Question 24

The diagram below shows a magnet brought near a steel block. What will happen to the steel block?
(1) It will move up.
(2) It will not move.
(3) It will move towards the magnet.
(4) It will move away from the magnet.

Accepted Answer

(3) It will move towards the magnet.. Steel is a ferromagnetic material, meaning it is attracted to magnets. When a magnet is brought near a steel block, the magnetic force of attraction will cause the steel block to move towards the magnet.

Question 25

The diagram below shows two blocks being hung at the same height from the ground. Which of the following correctly shows the energy possessed by both blocks and its amount in comparison with the other block?

Accepted Answer

(2) potential | same. The blocks are hung at a certain height above the ground and are stationary. Objects at a height possess gravitational potential energy (GPE). Since they are not moving, they do not possess kinetic energy. The formula for gravitational potential energy is GPE = mgh, where 'm' is mass, 'g' is the acceleration due to gravity, and 'h' is height.
Both blocks have the same mass (150g) and are hung at the same height from the ground. Since 'g' is constant, both blocks will possess the same amount of gravitational potential energy.

Question 26

Jack creates a shadow using the set-up as shown below. Which positions, S. T, U, V and W, should Jack place the torch, puppet and screen at to create the biggest shadow?

Accepted Answer

(2) S | T | W. To create the biggest shadow, the light source should be as close as possible to the object, and the screen should be as far as possible from the object.
- The torch (light source) should be at position S (farthest left, closest to where the puppet would be).
- The puppet (object) should be at position T (closest to the torch).
- The screen should be at position W (farthest right, farthest from the puppet).
Therefore, placing the torch at S, the puppet at T, and the screen at W will result in the biggest shadow.

Question 27

The diagram below shows a man walking along a path lined with special tiles. When the man steps on these tiles, electricity is generated and stored in a battery. This stored energy is used to light up street lamps at night. Which of the following best shows the correct conversion of energy?

Accepted Answer

(4) kinetic energy → electrical energy → potential energy → electrical energy → light energy. Let's trace the energy conversions:
1. **Man steps on tile:** The man's movement (walking) possesses kinetic energy.
2. **Electricity generated:** The special tiles convert this kinetic energy into electrical energy.
3. **Energy stored in battery:** The electrical energy is then stored in the battery as chemical potential energy (represented as 'potential energy' in the option).
4. **Street lamps light up:** The stored chemical potential energy is converted back into electrical energy, which flows to the street lamps. The lamps then convert this electrical energy into light energy (and also heat energy, though not specified in the final step of this option). 
Option (4) accurately represents this sequence of energy conversions.

Question 28

The diagram below shows a ball moving along the top of a hill towards X and then it rolled down from X to Y then to Z. The ball continued moving after Z. Which of the following graphs best represents the energy changes of the ball from position X to Z?

Accepted Answer

(1) [Graph 1]. Let's analyze the ball's energy changes from X to Z:
- **Position X:** The ball is at a high point on the slope and is already moving, so it possesses both high potential energy (PE) and some kinetic energy (KE).
- **From X to Y:** The ball rolls downhill from X to Y. Its height decreases, so its potential energy (PE) decreases. As it moves faster downhill, its kinetic energy (KE) increases.
- **Position Y:** This is the lowest point in the segment X-Z. The ball's PE is at its minimum for this segment, and its KE is at its maximum for this segment (due to conversion from PE).
- **From Y to Z:** The ball rolls up a slight incline from Y to Z. Its height increases (Z is higher than Y), so its potential energy (PE) increases. As it moves uphill, its kinetic energy (KE) decreases.

Now, let's examine the graphs:
- Graph (1) shows PE decreasing from X to Y and KE increasing. From Y to Z, PE increases and KE decreases. The KE at X is not zero. This matches the analysis.
- Graph (2) shows constant PE and KE from Y to Z, which is incorrect.
- Graph (3) shows KE starting at zero at X, which contradicts the statement that the ball was 'moving' towards X.
- Graph (4) shows constant PE and KE from X to Y, which is incorrect.

P6 Science SA1 2021 — Tao Nan

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P6 Science SA1 2021 — Tao Nan

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