Secondary 2 Science Life Sciences Quiz

Secondary 2 Science Quiz - Life Sciences

Answer Key

Section A: Multiple Choice Questions

1. C. Mitochondrion [2]
Marking note: Award 2 marks for C only. No partial credit.

2. B. To carry oxygen from the lungs to body tissues [2]
Marking note: Award 2 marks for B only. Common mistake — students confuse red blood cells with white blood cells (option A).

3. C. Small intestine [2]
Marking note: Award 2 marks for C only.

4. D. Aorta [2]
Marking note: Award 2 marks for D only. Common mistake — students select pulmonary artery (C), which carries deoxygenated blood to the lungs, not oxygenated blood to the body.

5. C. Carbon dioxide [2]
Marking note: Award 2 marks for C only.

Section B: Short Answer Questions

6. Carbon dioxide + Water →(sunlight, chlorophyll)→ Glucose + Oxygen [2]
Marking note: Award 1 mark for correct reactants (carbon dioxide and water). Award 1 mark for correct products (glucose and oxygen). Award full marks if the equation is written as a word equation with correct direction. Do NOT require "sunlight" and "chlorophyll" for full marks, but accept them if included. Common mistake — students reverse the equation (write respiration instead of photosynthesis).

7. [2]
Award 1 mark for each correct difference, up to a maximum of 2. Acceptable answers include:

• Arteries have thicker walls than veins.
• Arteries carry blood away from the heart; veins carry blood towards the heart.
• Arteries carry oxygenated blood (except pulmonary artery); veins carry deoxygenated blood (except pulmonary vein).
• Arteries have no valves; veins have valves to prevent backflow.
• Arteries have a smaller lumen; veins have a larger lumen.

Marking note: Answers must compare arteries and veins directly. Award 0 marks if only one vessel type is described without comparison.

8. [2]

• The villi increase the surface area of the small intestine. [1]
• This increases the rate of absorption of digested food / nutrients into the bloodstream. [1]

Marking note: Both points required for full marks. Award 1 mark if student states "increases surface area" without linking to absorption. Common mistake — students state that villi "absorb food" without explaining the surface area adaptation.

9. (a) Transpiration [1]
Marking note: Accept "transpiration" only. Do NOT accept "evaporation" or "respiration."

(b) Any one of the following: [1]

• Increase in temperature
• Increase in wind speed / air movement
• Decrease in humidity
• Increase in light intensity

Marking note: Award 1 mark for any valid factor. Do NOT accept "more water" or "rain" as these are not factors that increase the rate of transpiration.

10. [2]
Award 1 mark for each correct function, up to a maximum of 2. Acceptable answers include:

• Support / maintains body shape
• Protection of internal organs (e.g., skull protects brain, ribs protect heart and lungs)
• Movement / provides framework for muscle attachment
• Production of blood cells (in bone marrow)
• Storage of minerals (e.g., calcium)

11. (a) To kill the leaf cells / stop all chemical reactions (including enzyme activity) [1]
Marking note: Accept any answer that conveys stopping cell activity or killing the leaf. Do NOT accept "to soften the leaf" alone.

(b) To dissolve the chlorophyll / remove the green pigment from the leaf [1]
Marking note: Award 1 mark for stating that ethanol removes chlorophyll. Common mistake — students state ethanol is used to "cook the leaf" without mentioning chlorophyll removal.

12. [3]
Blood flows from the right ventricle → pulmonary artery → lungs (gas exchange occurs) → pulmonary vein → left atrium. [3]

Marking note: Award marks as follows:

• 1 mark: Right ventricle identified as the starting chamber.
• 1 mark: Correct sequence of blood vessels (pulmonary artery to lungs, then pulmonary vein).
• 1 mark: Left atrium identified as the destination chamber.
• Common mistake — students write "right atrium" instead of "right ventricle" as the starting point. Award 0 for the starting chamber in that case but credit the rest if correct.

13. [2]

• The left ventricle pumps blood to the entire body / all parts of the body. [1]
• This requires greater pressure, so the muscular wall is thicker to generate a stronger force of contraction. [1]

Marking note: Award 1 mark for identifying that the left ventricle pumps blood to the body. Award 1 mark for linking the thicker wall to generating greater pressure. Common mistake — students state "the left side has more blood" without explaining the pressure requirement.

14. [3]
(a) Plasma: Transport of dissolved substances (e.g., nutrients, hormones, carbon dioxide, urea) around the body. [1]
Marking note: Award 1 mark for stating transport function. Accept specific examples.

(b) White blood cells: Defence against disease / fight infections / engulf pathogens / produce antibodies. [1]
Marking note: Award 1 mark for any valid immune/defence function.

(c) Platelets: Blood clotting / prevent excessive bleeding at wound sites. [1]
Marking note: Award 1 mark for clotting function. Accept "help blood to clot."

15. (a) Starch [1]
Marking note: Award 1 mark for "starch" only.

(b) Any one of the following: [1]

• Rice
• Bread
• Potato
• Pasta
• Noodles

Marking note: Award 1 mark for any valid starch-rich food.

Section C: Structured / Data-Based Questions

16. (a) X (Palisade mesophyll layer) [1]
This layer contains the most chloroplasts because it is positioned near the upper surface of the leaf where it receives the most sunlight for photosynthesis. [1]

Marking note: Award 1 mark for identifying X. Award 1 mark for the explanation linking chloroplasts to sunlight exposure. Accept "palisade layer" if the student does not use the letter X.

(b) The palisade mesophyll cells are: [2]

• Packed with chloroplasts to maximise light absorption for photosynthesis. [1]
• Elongated and closely packed / arranged vertically to allow maximum exposure to light. [1]

Marking note: Award 1 mark for each valid adaptation point. Common mistake — students state "it has chloroplasts" without explaining WHY this is an adaptation.

(c) Stomata allow gas exchange / allow carbon dioxide to enter the leaf and oxygen to leave the leaf / allow water vapour to leave the leaf (transpiration). [1]
Marking note: Award 1 mark for any valid function. Accept "gas exchange" as a standalone answer.

17. (a) The concentration of oxygen in the blood increases (from 60 to 100 units) as blood passes through the lungs. [1]
Marking note: Award 1 mark for stating the increase. Accept "oxygen concentration increases" or "oxygen level rises."

(b) [2]

• Carbon dioxide diffuses out of the blood into the alveoli / air sacs of the lungs. [1]
• This occurs because the concentration of carbon dioxide is higher in the blood than in the alveoli, so it moves down the concentration gradient. [1]

Marking note: Award 1 mark for stating that CO₂ moves out of the blood. Award 1 mark for explaining the concentration gradient. Common mistake — students state "CO₂ is breathed out" without explaining diffusion.

(c) Diffusion [1]
Marking note: Award 1 mark for "diffusion" only. Do NOT accept "osmosis" or "active transport."

18. (a) Q (Stomach) [1]
Marking note: Award 1 mark for Q or "stomach." Protein digestion begins in the stomach where pepsin breaks down proteins.

(b) [2]

• The small intestine has a large surface area due to the presence of villi and microvilli. [1]
• This large surface area allows for rapid / efficient absorption of digested nutrients into the bloodstream. [1]

Marking note: Award 1 mark for mentioning villi/microvilli increasing surface area. Award 1 mark for linking this to efficient absorption. Common mistake — students state "the small intestine is long" without mentioning villi.

(c) [2]

• Water is absorbed from the undigested food material into the blood. [1]
• The remaining solid waste (faeces) is stored and later egested / eliminated through the anus. [1]

Marking note: Award 1 mark for water absorption. Award 1 mark for faeces being egested/eliminated. Common mistake — students confuse "egestion" with "excretion."

19. (a) As the distance from the lamp increases, the number of oxygen bubbles per minute decreases / the rate of photosynthesis decreases. [2]
Marking note: Award 2 marks for a clear description of the inverse relationship. Award 1 mark if the student only states "it decreases" without mentioning the relationship with distance.

(b) [2]

• Light intensity decreases as the distance from the lamp increases. [1]
• Since light is needed for photosynthesis, a lower light intensity results in a lower rate of photosynthesis. [1]

Marking note: Award 1 mark for identifying light intensity as the factor. Award 1 mark for linking light intensity to the rate of photosynthesis.

(c) Any one of the following: [1]

• The bubbles may not all be the same size, so counting bubbles may not accurately measure the volume of oxygen produced.
• Some oxygen may dissolve in the water and not form visible bubbles.
• The plant may not produce bubbles at a constant rate over time.

Marking note: Award 1 mark for any valid limitation.

20. (a) [2]

• Blood passes through the heart twice during one complete circuit around the body. [1]
• There are two circuits: the pulmonary circuit (heart → lungs → heart) and the systemic circuit (heart → body → heart). [1]

Marking note: Award 1 mark for stating blood passes through the heart twice. Award 1 mark for identifying the two circuits.

(b) [2]

• The double circulatory system allows blood to be pumped at higher pressure in the systemic circuit. [1]
• This ensures oxygenated blood is delivered quickly and efficiently to all body tissues / maintains a high rate of oxygen delivery to meet the body's needs. [1]

Marking note: Award 1 mark for mentioning higher pressure. Award 1 mark for linking this to efficient oxygen delivery. Common mistake — students state "blood goes faster" without explaining pressure.

(c) Oxygenated [1]
Marking note: Award 1 mark for "oxygenated." The pulmonary vein carries oxygenated blood from the lungs to the left atrium of the heart.

Total: 40 marks