Biology Year 11 · Module 2

Module 2 Quiz — Organisation of Living Things

Full module assessment covering all three inquiry questions and all 21 lessons. Questions are tagged by IQ so you know exactly which lessons to revisit if you struggle with a section.

30 questions20 MC + 10 short answer

Lessons coveredL01 – L21 (entire Module 2)

Suggested time45–55 minutes

IQ tagsIQ1IQ2IQ3

Section A — Multiple Choice

20 questions · 1 mark each

IQ11. Which best explains why cell specialisation is necessary in large multicellular organisms?

Specialised cells have larger SA:V ratios, improving diffusion efficiency

Specialised cells contain different DNA sequences coding for unique proteins

Specialised cells enable division of labour — different cell types perform specific functions more efficiently than unspecialised cells could, allowing the organism to function as a complex integrated system

Specialisation is only necessary in animals — plants maintain totipotent cells throughout life

IQ12. A red blood cell, a neuron, and a muscle cell all contain the same DNA. How do they have different structures and functions?

Different cell types retain only the chromosomes relevant to their function

All cells contain the same DNA, but different genes are expressed in different cell types during development — this is cell differentiation

Environmental conditions cause mutations in specific cells producing different structures

Specialised cells synthesise unique DNA sequences using reverse transcriptase after differentiation

IQ13. The correct hierarchical order from least to most complex is:

Organelle → cell → tissue → organ → organ system → organism

Cell → organelle → tissue → organ system → organ → organism

Organelle → cell → organ → tissue → organ system → organism

Cell → tissue → organelle → organ → organ system → organism

IQ24. Which correctly distinguishes the nutrient requirements of autotrophs from heterotrophs?

Autotrophs require organic carbon from food; heterotrophs require inorganic carbon from CO₂

Both require the same nutrients — the difference is only in energy source (light vs chemical)

Autotrophs require O₂ as both nutrient and energy source; heterotrophs require CO₂ for respiration

Autotrophs require inorganic inputs (CO₂, H₂O, minerals, light) to synthesise organic molecules; heterotrophs require pre-formed organic molecules (glucose, amino acids, fats) from their diet

IQ25. In bright daylight, a plant shows net CO₂ uptake and O₂ release. At night, the same plant shows CO₂ release and O₂ uptake. The most accurate explanation is:

Plants photosynthesise during the day and switch to respiration at night — they only do one process at a time

Daylight causes plants to reverse the direction of cellular respiration, producing O₂ instead of consuming it

Plants perform cellular respiration continuously. In daylight, photosynthesis rate exceeds respiration rate, giving net CO₂ uptake and O₂ release. At night, photosynthesis ceases; only respiration occurs, giving net CO₂ release and O₂ uptake

Daylight opens stomata (CO₂ in, O₂ out); darkness closes stomata, trapping CO₂ inside — purely mechanical

IQ26. Guard cells open stomata in response to light. The mechanism is:

Light directly increases turgor pressure in guard cells by providing energy for water entry

Light triggers active K⁺ accumulation into guard cells → lowers water potential → water enters by osmosis → guard cells inflate and bow outward, opening the pore

Light heats the leaf, causing guard cells to expand thermally and pull the pore open

Light provides energy for active pumping of water directly into guard cells, bypassing osmosis

IQ27. Which correctly describes the path of CO₂ from atmosphere to Calvin cycle in a leaf?

Atmosphere → stomata → epidermis cells → phloem → chloroplast stroma

Atmosphere → cuticle diffusion → palisade cell → mitochondria → chloroplast

Atmosphere → stomata → xylem vessels → mesophyll cells → chloroplast

Atmosphere → stomata (down CO₂ gradient) → leaf air spaces → dissolves in water film on mesophyll cell walls → diffuses through cell wall and membrane → chloroplast stroma (Calvin cycle)

IQ28. Which feature of the insect tracheal system is most analogous (convergently similar in function) to alveoli in mammalian lungs?

Tracheoles — finest branches of the tracheal system, providing large SA for gas exchange at low diffusion distances close to every cell

Spiracles — openings on the body surface, analogous to the nose and mouth

Tracheae — main air tubes running the length of the body, analogous to bronchi

Haemolymph — circulatory fluid, analogous to blood in mammals

IQ39. The Casparian strip forces water and minerals through endodermal cell cytoplasm rather than through cell walls. Why is this significant?

It speeds up water transport by eliminating the slower apoplast pathway

It prevents water evaporating through the root surface by sealing the endodermis

It allows the plant to selectively control which minerals enter the xylem — membrane transport proteins in endodermal cells accept specific ions while excluding others

It provides mechanical support to xylem vessels by surrounding them with a rigid endodermal layer

IQ310. Which correctly explains why xylem vessel elements are dead at functional maturity?

Dead cells cannot respire, so they do not compete with the plant for O₂ or glucose

Death removes cytoplasm (creating an unobstructed hollow lumen) and dissolves end walls (creating a continuous vessel). Living cytoplasm would obstruct water movement and impose osmotic resistance

Dead cells are more permeable to water than living cells, allowing water through vessel walls more easily

Dead cells require no ATP, reducing the plant's energy expenditure on water transport

IQ311. Which correctly describes the pressure-flow mechanism driving phloem transport from leaf to root?

Gravity pulls phloem sap downward — transport to shoot tips requires active pumping against gravity

Sucrose concentration is always highest in leaves — a permanent gradient always drives flow downward

Companion cells pump phloem sap directionally using ATP-powered pumps in sieve tube membranes

Active sucrose loading at the source raises turgor pressure there; unloading at the sink lowers turgor pressure; bulk flow moves from high to low turgor pressure toward the sink, regardless of its position relative to the source

IQ312. In a potometer experiment: still air = 1.3 mm/min; bright light = 2.0; fan wind = 2.4; 90% humidity = 0.4 mm/min. Which factor had the greatest single effect and why?

High humidity — reduced rate most dramatically (1.3 → 0.4 mm/min) because outside air approaching saturation nearly eliminates the water potential gradient between leaf air spaces and atmosphere, almost stopping diffusion through stomata

Fan wind — increased rate most because it chemically reacts with water vapour to drive faster evaporation

Bright light — produced the greatest increase by directly providing energy for leaf evaporation

Still air (baseline) — the control condition and by definition has the greatest effect

IQ313. Which correctly compares xylem vessels and arteries?

Both contain living cells with active regulatory functions; both operate under positive pressure

Xylem operates under positive pressure from root pressure; arteries operate under negative pressure from ventricular suction

Both have thick, reinforced walls resisting vessel deformation — but xylem walls resist collapse under tension (negative pressure) using lignin, while artery walls resist bursting under positive pressure using elastic fibres and smooth muscle

Xylem requires continuous ATP for water transport; arteries are passive conduits requiring no energy

IQ214. A student claims: "Van Helmont proved plant mass comes from water because the soil barely changed." The most significant error in this reasoning is:

He used only one plant — insufficient replication makes his conclusion unreliable

He could not account for CO₂ uptake from air (CO₂ was unknown in 1648) — the actual carbon source is atmospheric CO₂, not water. His data is valid; his conclusion exceeds what the data supports

"Proved" is inappropriate — science supports or refutes hypotheses but cannot prove them

He used distilled water which lacks minerals, invalidating the experiment

IQ315. Glucose rises to 12.8 units in the hepatic portal vein (post-meal) then falls to 4.6 units in the hepatic vein. Which correctly explains this?

The liver destroys excess glucose by converting it to CO₂ and water through respiration

Liver cells pump glucose out of the hepatic vein into surrounding tissue, diluting blood concentration

Glucose is converted to fat by liver adipocytes, permanently removing it from carbohydrate metabolism

The liver removes excess glucose and stores it as glycogen (glycogenesis), buffering blood glucose to near the set point (~4.5 units) before it enters the general circulation

IQ316. Which correctly lists evidence lines supporting cohesion-tension theory?

Bell jar mint experiment; paper chromatography; pressure probes in xylem

¹⁴CO₂ tracing; dendrometer measurements; microscopy of xylem vessels

Transpiration-controlled water uptake experiments; direct pressure probe measurements (negative pressures); acoustic detection of cavitation; dendrometer trunk diameter changes; D₂O isotope tracing at predicted flow rates

Potometer experiments only — all other evidence is theoretical

IQ317. Which correctly explains why phloem has no valves while veins require pocket valves?

Phloem operates under positive turgor pressure from osmosis at the source — bulk flow naturally proceeds from high to low turgor without backflow risk. Veins carry blood at very low positive pressure, often against gravity, so mechanical valves prevent backflow

Phloem is too narrow for valves to fit; veins are wide enough to accommodate them

Phloem sap is more viscous than blood, resisting backflow without valves

Both phloem and veins have valves — phloem sieve plates are functionally equivalent to vein pocket valves

IQ218. A xerophyte has stomata in deep crypts on the leaf underside. Which transpiration factor does this primarily reduce, and by what mechanism?

Temperature — crypts insulate stomata from direct sunlight

Light — crypts prevent light reaching guard cells, keeping stomata closed

Stomatal aperture — crypts physically narrow the stomatal pore

Boundary layer / humidity — still air accumulates in the crypt creating high humidity immediately outside the stomatal pore, reducing the water potential gradient between leaf interior and outside air

IQ319. Blood O₂ is high in the pulmonary vein (19 units) but falls to 12 in the vena cava. Which most accurately explains this?

O₂ is chemically destroyed by CO₂ produced during respiration — they react and both are consumed

As oxygenated blood passes through systemic capillaries, O₂ diffuses down its partial pressure gradient from blood into metabolically active tissue cells (where O₂ is continuously consumed by cellular respiration). By the time blood returns via the vena cava, tissues have extracted a significant fraction of O₂

Lower blood pressure on the right side of the heart forces O₂ out of haemoglobin into plasma, reducing measured O₂ levels

O₂ leaks through artery walls into surrounding tissue as blood travels from lungs to body

IQ320. A researcher feeds ¹⁴C-labelled CO₂ to a leaf. Six hours later, labelled sucrose appears in: developing fruit (above leaf), root tips (below), young shoot tips (above), but NOT in other mature leaves at the same level. Which best explains the distribution?

Sucrose moved downward via xylem to roots and upward via phloem to fruit — the two vascular tissues explain the bidirectional result

Mature leaves at the same level competed successfully, absorbing all labelled sucrose before it reached other tissues

Sucrose flows from the labelled leaf (source) via phloem to active sinks — growing fruit, root tips, and shoot tips all have high demand and low turgor pressure, driving phloem flow toward them. Other mature leaves are themselves sources, not sinks, so they neither receive nor require imported sucrose

Sucrose only moves upward in phloem due to transpiration pull — root tips received labelled sucrose through xylem backflow

Section B — Short Answer

10 questions · variable marks

IQ121. Explain why hierarchical organisation (cells → tissues → organs → organ systems) is functionally advantageous compared to an organism of only undifferentiated cells. 3 MARKS

IQ222. Compare gas exchange structures in fish gills and mammalian alveoli. Identify two structural similarities and one key functional difference. 4 MARKS

IQ223. Describe the role of enzymes in chemical digestion in the small intestine. Name two specific enzymes, their substrates, and products. Explain why enzyme specificity matters in this context. 4 MARKS

IQ324. Describe the cohesion-tension mechanism for water transport in xylem. Include: what creates the tension, what holds the water column together, and what drives water uptake at the roots. 5 MARKS

One mark each: tension origin · cohesion mechanism · tension transmission · root osmosis · integrating energy source statement.

IQ325. Trace the journey of a glucose molecule absorbed from the small intestine to its use in cellular respiration in a contracting bicep muscle cell. Name each vessel and organ it passes through. 4 MARKS

Must include: villus capillary → hepatic portal vein → liver → hepatic vein → vena cava → right heart → pulmonary circuit → left heart → aorta → systemic arteries → muscle capillary → muscle cell mitochondria.

IQ226. Choose two scientists from the history of photosynthesis (van Helmont, Priestley, Ingenhousz, de Saussure, Blackman, Calvin). For each: state what their experiment revealed, what it failed to explain, and how a subsequent scientist built on their work. 4 MARKS

IQ327. Compare how the composition of the transport medium changes in plant xylem sap and animal blood as each moves from its loading point to its delivery point. State one similarity and one difference. 3 MARKS

IQ328. Explain why the animal cardiovascular system requires a continuously pumping heart, while plant xylem transport requires no equivalent pump. 3 MARKS

IQ329. A secondary source states: "In young, well-watered plants, root pressure is the primary mechanism driving water from roots to leaves." Using your knowledge of cohesion-tension theory and its supporting evidence, evaluate this claim. 4 MARKS

Correct evaluation: claim is an oversimplification — incorrect as a general primary mechanism, especially for tall/transpiring plants. Must cite specific evidence lines.

IQ330. Extended response: "Multicellular organisms face the fundamental challenge of supplying every cell with materials for cellular respiration and removing waste." Using examples from both a plant and a mammal, describe how each organism meets this challenge through its gas exchange and transport systems. 7 MARKS

Marking: plant gas exchange + transport (2) · animal gas exchange + transport (2) · explicit comparison (1) · cellular-level delivery explanation (1) · quality of integration/conclusion (1).

Answers — Section A

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1. C — Division of labour. All cells have the same DNA (B wrong); specialisation occurs in plants too (D wrong).

2. B — Same DNA, different gene expression = cell differentiation. Different chromosomes (A) contradicts the fact all somatic cells are diploid with the full genome. Mutations (C) would change the DNA sequence itself.

3. A — Organelle → cell → tissue → organ → organ system → organism. Memorise this sequence — it's directly tested.

4. D — Autotrophs: inorganic inputs + light → organic molecules. Heterotrophs: consume pre-formed organic molecules. Both need O₂ for respiration (B ignores the different carbon sources).

5. C — Plants respire continuously. Photosynthesis only in light. Net gas exchange = PS rate minus respiration rate. The "only photosynthesise during day" idea (A) is the classic misconception.

6. B — K⁺ active uptake → lowers guard cell water potential → osmotic water entry → inflation → stomata open. This is the mechanism from L09.

7. D — CO₂ enters via stomata (not cuticle), dissolves in water film on cell walls, then diffuses to chloroplast stroma. Xylem (C) carries water and minerals, not CO₂.

8. A — Tracheoles are the exchange surface analogues — fine, close to cells, large collective SA. Spiracles are entry points (analogous to nostrils). Haemolymph is not used for gas transport in insects (the tracheal system delivers gases directly).

9. C — Casparian strip's primary function: selective mineral control. Forces membrane crossing → transport proteins control what enters xylem. Not speed (A) or evaporation prevention (B).

10. B — Two functional benefits: unobstructed lumen (cytoplasm removed) and continuous vessel (end walls dissolved). D is incidentally true but not the primary functional explanation.

11. D — Pressure-flow: source (high turgor) → sink (low turgor), driven by osmosis and active loading. Direction follows the gradient, not gravity (A) or a permanent concentration gradient (B).

12. A — High humidity produced the greatest change in absolute terms (from 1.3 to 0.4, a 69% reduction) by nearly eliminating the water potential gradient. Fan wind produced a +85% relative increase from baseline but smaller absolute change than humidity's reduction.

13. C — Both have thick walls resisting deformation, but opposite pressure signs require different structural solutions. Xylem: negative pressure → lignin prevents inward collapse. Artery: positive pressure → elastic fibres prevent outward burst. Neither requires ATP at the vessel (A wrong); xylem is under negative pressure (B wrong).

14. B — Van Helmont's data is valid. His conclusion fails because CO₂ was unknown — the actual carbon source in plant biomass is atmospheric CO₂, not water. The "proved" language error (C) is real but a philosophical point, not the most significant factual error about where plant mass comes from.

15. D — Liver performs glycogenesis (glucose → glycogen storage) when blood glucose is elevated, buffering it to near the set point. Glucose is stored, not destroyed (A). Fat conversion (C) happens but is not the primary explanation for the rapid post-meal glucose buffering seen in the data.

16. C — All five independent evidence lines correctly listed. ¹⁴CO₂ tracing (B) is the Calvin cycle experiment, not a cohesion-tension evidence line.

17. A — Phloem turgor from osmosis at source drives flow naturally toward lower-pressure sink — no reversal risk. Veins at low pressure against gravity need mechanical valves. Sieve plates (D) are perforated end walls for bulk flow, not functional valves.

18. D — Sunken stomata → still air accumulates in crypt → high humidity microenvironment outside stomatal pore → reduced water potential gradient → reduced transpiration. Temperature (A) and light effects (B) are not the primary mechanism of sunken stomata.

19. B — O₂ exits blood at systemic capillaries by diffusion as cells continuously consume it in cellular respiration, maintaining the gradient. O₂ and CO₂ do not chemically react in blood (A).

20. C — Source-sink polarity: the labelled leaf is a source; growing fruit, root tips, and shoot tips are active metabolic sinks. Other mature leaves are also sources — they don't import sucrose. Direction follows turgor gradient in phloem, not xylem (A).

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