OxfordAQA IGCSE Biology: Organisation — Practice Questions

These are original questions written for Marlbridge, in the style and at the standard of the examination. They are not reproduced past-paper questions — examination boards hold copyright in their own papers. Use these alongside the official past papers available free from your board.

Related: Organisation revision notes

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Section A

1. Define a tissue and an organ, giving an example of each. [4]

2. Name two sub-cellular structures found in a plant cell but not in an animal cell. [2]

3. State the difference between diffusion and active transport. [2]

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Section B

4. A student places three identical potato chips into sugar solutions of different concentration and records the change in mass after 30 minutes.

Sugar solution / mol dm⁻³	Change in mass / %
0.0	+8
0.2	+3
0.4	−2
0.6	−7
0.8	−11

(a) Name the process responsible for the changes in mass. [1]

(b) Explain why the chip in 0.0 mol dm⁻³ solution gained mass. [3]

(c) Explain why the chip in 0.8 mol dm⁻³ solution lost mass. [3]

(d) Estimate the concentration at which there would be no change in mass, and name this condition. [2]

5. Root hair cells absorb mineral ions from the soil even when the ions are in lower concentration in the soil than inside the cell.

(a) Name the process involved. [1]

(b) Explain why this process requires energy from respiration, and state where in the cell most of that energy is released. [3]

6. The stomach is an example of an organ.

(a) Name the three types of tissue found in the stomach, and state the function of each. [3]

(b) Explain the difference between a tissue and an organ, using the stomach to illustrate your answer. [3]

7. Explain three ways in which the small intestine is adapted as an efficient exchange surface. [6]

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Section C

8. A leaf is an organ made of several plant tissues.

(a) Name the plant tissue that carries out most photosynthesis in a leaf, and explain why its position in the leaf suits this function. [2]

(b) Name the plant tissue with air spaces that aid gas diffusion. [1]

(c) State one similarity and one difference between the functions of xylem and phloem. [3]

9. A bacterial cell and a plant cell both have a cell wall, but a bacterial cell has no nucleus.

(a) State where the genetic material is found in a bacterial cell instead. [2]

(b) Compare a bacterial (prokaryotic) cell with a plant (eukaryotic) cell, describing two further differences. [4]

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Answers

1. Tissue — a group of similar cells working together for a shared function [1], e.g. muscular tissue [1]. Organ — a group of different tissues working together [1], e.g. the stomach [1].

2. Any two: chloroplasts, cell wall, permanent vacuole [1] [1].

3. Diffusion is the net movement of particles from a higher to a lower concentration and needs no energy from respiration [1]. Active transport moves particles against a concentration gradient (low to high) and requires energy from respiration [1].

4. (a) Osmosis [1].

(b) The sugar solution outside the chip was more dilute than the cell contents [1], so there was a higher concentration of water outside the cell than inside [1]. Water moved into the cells by osmosis, across the partially permeable cell membrane, increasing the mass [1].

(c) The sugar solution outside the chip was more concentrated than the cell contents [1], so there was a lower concentration of water outside the cell than inside [1]. Water moved out of the cells by osmosis, decreasing the mass [1].

(d) Approximately 0.3 mol dm⁻³ (accept a value between 0.2 and 0.4 read from the trend) [1]; this is the concentration at which the solution is isotonic with the cell contents, so there is no net movement of water [1].

5. (a) Active transport [1].

(b) The ions move against a concentration gradient (from a lower to a higher concentration), which diffusion cannot do, so energy is needed to move them [1]. This energy comes from respiration [1], most of which is released in the mitochondria [1].

6. (a) Muscular tissue — contracts to move the stomach’s contents [1]; glandular tissue — produces digestive juices [1]; epithelial tissue — covers the inside and outside of the stomach [1].

(b) A tissue is a group of cells with similar structure and function (e.g. the stomach’s muscular tissue, made only of muscle cells) [1]; an organ is made of several different tissues working together (e.g. the stomach itself, made of muscular, glandular and epithelial tissue) [1], so the stomach is an organ built from its component tissues [1].

7. Any three, each with the adaptation [1] and its reason [1]: It is long, giving a large surface area over its length. It is folded, and covered in villi and microvilli, further increasing surface area. It has a thin, one-cell-thick wall, giving a short diffusion path. It has a rich blood supply, maintaining a steep concentration gradient.

8. (a) Palisade mesophyll [1]; it is positioned near the top of the leaf, close to the light source, so it absorbs the most light for photosynthesis [1].

(b) Spongy mesophyll [1].

(c) Similarity: both transport substances around the plant [1]. Difference: xylem transports water and mineral ions from roots to leaves (one direction) [1], while phloem transports dissolved sugars from the leaves to the rest of the plant, in either direction depending on need (translocation) [1].

9. (a) In circular structures called plasmids (and loose in the cytoplasm), not enclosed in a nucleus [2].

(b) Any two: a bacterial cell has no mitochondria (a plant cell does) [1]; a bacterial cell has no chloroplasts even though some bacteria photosynthesise differently [1]; a bacterial cell is generally much smaller than a plant cell [1]; a bacterial cell has no permanent vacuole of the kind found in plant cells [1].

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Where marks are usually lost

• Naming osmosis as “diffusion of water” without stating the direction (dilute to concentrated) or the partially permeable membrane.
• Confusing diffusion, osmosis and active transport, or forgetting that only active transport needs energy from respiration.
• Describing a tissue and an organ without giving a named example of each.
• Naming an exchange-surface adaptation without saying what it increases or shortens (surface area, diffusion distance).
• Stating that a bacterial cell has a nucleus, or that a plant cell lacks mitochondria.
• Giving palisade mesophyll’s function without linking its position in the leaf to the amount of light it receives.