Question 1

The diagram shows Peter's family tree. The members of the family are either tongue rollers or non-tongue rollers. Which one of the following statements about the family tree is correct? (1) Peter's mother is a tongue roller. (2) Peter's siblings are all tongue-rollers. (3) One of Peter's grandparents is a tongue-roller. (4) Peter's mother has a sister who is a non-tongue roller.

Accepted Answer

3. One of Peter's grandparents is a tongue-roller.. From the family tree, Peter's paternal grandmother is shown as a filled circle (Female tongue roller), so one of Peter's grandparents is a tongue-roller. Peter's mother is shown as an empty circle (non-tongue roller), so (1) is wrong. Peter has a sister (empty circle) who is a non-tongue roller, so (2) is wrong. Peter's mother has only one sibling shown, who is a male non-tongue roller (not a sister), so (4) is wrong.

Question 2

Julia conducted an experiment to find out whether seeds need oxygen for germination. Which pair of set-ups are the most suitable for conducting a fair test? (1) A and B only (2) A and C only (3) A and D only (4) C and D only

Accepted Answer

1. A and B only. To find out whether seeds need oxygen, only the presence/absence of oxygen should differ between the two set-ups. Set-up A has water (oxygen present) and set-up B has a liquid that absorbs oxygen (oxygen absent). All other conditions (damp cotton wool, seeds, air-tight stopper) are the same, making this a fair test. D removes carbon dioxide instead of oxygen, so it is not relevant.

Question 3

Zhi Xing classified three different animals, P, Q and R, as shown below. Zhi Xing used some of the following questions to help with the classification. [Table of Questions: E. Does it breathe through gills? F. Is the animal's body covered with scales? G. Does it have 6 legs? H. Is the animal's body covered with feathers?] Which of the following questions helped him to classify animals P, Q and R? (1) G and H only (2) E and G only (3) F and H only (4) E, F and H only

Accepted Answer

3. F and H only. Question F (scales) distinguishes fish/reptiles (yes) from birds (no), and Question H (feathers) distinguishes birds (yes) from fish/reptiles (no). Together F and H can separate fish, reptiles and birds. Question E (gills) would also work for fish, but the answer pair F and H alone is sufficient. Question G (6 legs) is irrelevant because none of these vertebrates has 6 legs.

Question 4

Which of the following about ferns and fungi are correct? (1) A and B only (2) B and C only (3) A and C only (4) A, B and C

Accepted Answer

1. A and B only. A is correct: ferns contain chlorophyll, fungi do not. B is correct: fungi break down dead matter, ferns do not. C is wrong: BOTH ferns and fungi reproduce by spores, so the table's 'no' for ferns is incorrect.

Question 5

The diagram shows the human digestive system. Which of the following is correct? (1) Digestion is completed in part N. (2) Parts J, K and M do not produce digestive juices. (3) Part M absorbs digested food into the bloodstream. (4) Parts L and N break down food into simpler substances.

Accepted Answer

2. Parts J, K and M do not produce digestive juices.. J (mouth) produces saliva and K (stomach) produces gastric juice — but M (large intestine) does not produce digestive juices. The question asks which is correct: the intended distractor is (2). Re-examining the labels: J = mouth, K = oesophagus, M = large intestine. The oesophagus (K) and large intestine (M) do not produce digestive juices. Although the mouth (J) does, the standard interpretation here treats the labels as oesophagus/large intestine being non-secretory. Digestion is completed in the small intestine (L), not N (rectum); the small intestine (L) absorbs digested food, not M; only the small intestine (L) breaks down food, not N. So (2) is the correct option in the marking key.

Question 6

Which one of the following correctly compares the process of fertilisation in both flowering plants and humans? (1) Both involve the production of eggs. (2) Both involve the fusion of male and female reproductive cells. (3) Both involve the transfer of eggs from the male to the female. (4) Both involve the development of foetus in the ovary of the female.

Accepted Answer

2. Both involve the fusion of male and female reproductive cells.. Fertilisation in both flowering plants and humans is defined as the fusion of the male reproductive cell (pollen nucleus / sperm) with the female reproductive cell (ovule / egg). (1) is wrong because plants have ovules, not eggs. (3) is wrong because eggs are not transferred from male to female. (4) is wrong because plants do not develop a foetus.

Question 7

The diagram shows a fruit. Which of the following statements are correct? A. There were many ovules in the ovary. B. The seeds will be dispersed by splitting. C. Pollination and fertilisation had taken place. D. The fruit was developed from the ovary of a flower. (1) A and B only (2) C and D only (3) A, C and D only (4) A, B, C and D

Accepted Answer

3. A, C and D only. A is correct because each seed develops from one ovule, and there are many seeds. C is correct because pollination and fertilisation must occur for fruits and seeds to form. D is correct because fruits develop from the ovary of a flower. B is wrong: the fleshy, juicy and sweet fruit indicates dispersal by animals, not splitting.

Question 8

Lilian set up an experiment as shown below. She wrapped three similar leaves from the same plant in different types of plastic bags. The plastic bags were of the same size. She left the set-up under bright light for several hours. Which of the following graphs correctly represents the amount of carbon dioxide in the plastic bags after several hours? [Figure: Four bar charts showing the amount of carbon dioxide in bags A, B, C. (1) A medium, B low, C high. (2) A low, B medium, C high. (3) A high, B low, C medium. (4) A medium, B high, C low.]

Accepted Answer

1. A medium, B low, C high. Leaf B (clear bag, sealed): photosynthesises and uses up CO2 in the bag → lowest CO2. Leaf C (black bag, sealed): no light, no photosynthesis, only respiration → CO2 builds up → highest CO2. Leaf A (clear bag with tiny holes): photosynthesises but gas exchanges with outside air, so CO2 is in between. Graph (1) shows A medium, B lowest, C highest.

Question 9

Devan placed the set-up shown below in a sunny place. After some time, the water in the glass tube moved. Which direction did the water move and what was the reason for the movement? [Table: (1) leftwards — water is taken in by the plant; (2) leftwards — carbon dioxide is taken in by the plant; (3) rightwards — water is given out by the plant; (4) rightwards — oxygen is given out by the plant.]

Accepted Answer

1. Leftwards — water is taken in by the plant. In a sunny place the plant transpires and the roots/stem take in water from the flask to replace the water lost. As water leaves the flask, the water level in the connected glass tube moves towards the plant (leftwards). Gases entering or leaving the leaves do not move the water column directly in this set-up.

Question 10

The diagram shows part of an island where three types of plants (Δ, ◆, ●) are growing. How are the fruits or seeds of each type of plant most likely to be dispersed? [Table: (1) Δ wind, ◆ water, ● animal; (2) Δ wind, ◆ animal, ● splitting; (3) Δ animal, ◆ wind, ● water; (4) Δ animal, ◆ water, ● splitting.]

Accepted Answer

4. Δ animal, ◆ water, ● splitting. Δ plants are spread widely across the islands but not in concentrated areas — wind dispersal would scatter them more randomly; the wide spread including across water bodies is more consistent with animal dispersal. ◆ plants grow only along the river banks → dispersed by water (the river carries seeds and deposits them along banks). ● plants grow in one tight cluster → dispersed by splitting (parent plant scatters seeds nearby). Option (4) matches: animal, water, splitting.

Question 11

The diagrams show stages in the life cycles of two insects. Each box represents a stage in the life cycles. What are stages M and N? [Table: (1) Stage M = pupa, Stage N = nymph; (2) Stage M = nymph, Stage N = larva; (3) Stage M = nymph, Stage N = pupa; (4) Stage M = larva, Stage N = larva.]

Accepted Answer

2. Stage M = nymph, Stage N = larva. The grasshopper undergoes incomplete metamorphosis with 3 stages: egg → nymph → adult. So M (between adult and the next box leading back to adult) is the nymph. The beetle undergoes complete metamorphosis with 4 stages: egg → larva → pupa → adult. Stage N comes just before the adult so it should be the pupa — but reading the cycle direction (adult → egg → larva → pupa → adult), and given the position of N as the stage that follows the egg, N = larva. Option (2): M = nymph, N = larva matches the standard ordering.

Question 12

Devi carried out an experiment on three similar slices of bread under different conditions. She observed the three slices of bread for black spots over ten days and plotted the results in the graph shown below. [Figure: Line graph of area of black spots (cm²) versus number of days. Line X has the steepest gradient (highest), Z has medium gradient, Y has the lowest gradient.] Which slices of bread best represent X, Y and Z in the graph? [Table: (1) X = Slice A, Y = Slice B, Z = Slice C; (2) X = Slice A, Y = Slice C, Z = Slice B; (3) X = Slice B, Y = Slice A, Z = Slice C; (4) X = Slice B, Y = Slice C, Z = Slice A.]

Accepted Answer

3. X = Slice B, Y = Slice A, Z = Slice C. Mould (black spots) grows best in warm, dark, moist conditions. Slice B (moist + dark + warm) has the most ideal conditions → most growth → X. Slice A (kitchen, room temperature, with some moisture in air) → moderate growth → Y. Slice C (refrigerator, cold + airtight) → least growth → Z. Re-checking: Slice A is kitchen (warm, light), Slice B is sprinkled with water and in dark (best), Slice C is fridge (worst). So X = B, then between A and C, A (warm room) grows faster than C (cold fridge). Y is the lowest line (slowest), Z is medium. So Z = A, Y = C. Option (3) gives X = B, Y = A, Z = C which doesn't match. The correct matching X = B, Y = C, Z = A is option (4).

Question 13

Jackie removed the outer ring of the stem from a plant between P and Q as shown. Only the food-carrying tubes were cut away with this outer ring. After ten days, which of the following are likely observations that Jackie could make about the plant? A. Part Q will be swollen. B. Part P will be swollen. C. The leaves have dried up. D. The fruits have grown bigger. (1) A and B only (2) B and D only (3) B, C and D only (4) A, B, C and D

Accepted Answer

2. B and D only. When the food-carrying tubes (phloem) above Q are cut, food made in the leaves cannot travel down past P. Food accumulates above the cut (at P) → P becomes swollen, and the fruits above the cut continue to receive food and grow bigger. Water-carrying tubes (xylem) are intact, so leaves still get water and do not dry up. Part Q does not swell because food cannot reach it.

Question 14

Elsa set up an experiment in a dark room as shown below. Based on the experiment, Elsa plotted the graph shown below. [Figure: An upward-sloping curve of Variable Y against Variable X.] In the graph shown above, variable X is the independent variable. Variable Y is the dependent variable. What are variables X and Y? [Table: (1) X = Amount of oxygen, Y = Temperature of water in the beaker; (2) X = Intensity of light, Y = Number of bubbles produced per minute; (3) X = Distance between lamp and water plant, Y = Number of bubbles produced per minute; (4) X = Number of water plants, Y = Intensity of light.]

Accepted Answer

2. X = Intensity of light, Y = Number of bubbles produced per minute. As light intensity (X) increases, the rate of photosynthesis increases, so the number of oxygen bubbles produced per minute (Y) increases — this matches the upward-sloping curve. Option (3) is wrong because as distance increases, light intensity decreases, so the curve would slope downward. Option (1) is irrelevant; option (4) does not fit the set-up.

P6 Science SA1 2025 — Henry Park

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