Home / iGCSE / Coordinated Sciences / B17.2 Selection Paper 4

CIE iGCSE Co-Ordinated Science B17.2 Selection Exam Style Questions Paper 4

CIE iGCSE Co-Ordinated Science Paper 4 - All Chapters

Question

(a) Variation occurs in all organisms.
There are two types of variation, continuous variation and discontinuous variation.
Complete Table 4.1 by placing a tick (✓) in each row to show if the description is about continuous or discontinuous variation.
(b) Antibiotics are used to treat people with bacterial infections.
Some strains of bacteria have become resistant to antibiotics.
Describe how strains of antibiotic-resistant bacteria develop by natural selection.
(c) (i) Many bacteria are decomposers in food chains.
Describe what is meant by a decomposer.
(ii) Energy in food chains is lost through processes such as excretion of urea.
State two other ways that energy is lost between one trophic level and the next.

Most-appropriate topic codes (Cambridge IGCSE Co-ordinated Sciences 0654):

• Topic B17.1 — Variation (Part (a))
• Topic B17.2 — Selection / Natural selection (Part (b))
• Topic B18.2 — Food chains and food webs / Decomposers (Part (c)(i))
• Topic B18.2 — Energy transfer between trophic levels (Part (c)(ii))

▶️ Answer/Explanation

(a) Table 4.1 completed:

Discontinuous variation has a limited number of phenotypes with no intermediates (like blood groups); continuous variation shows a range between extremes (like height).

(b) Some bacteria mutate and become resistant to antibiotics. These resistant bacteria survive and reproduce, passing on their alleles for resistance to offspring, increasing the frequency of resistance in the population.
Antibiotics act as a selective pressure, killing non-resistant bacteria. The resistant ones survive and multiply, so the resistant trait becomes more common over generations.

(c)(i) A decomposer is an organism that gets its energy from dead or waste organic material.
Decomposers like bacteria and fungi break down dead organisms and waste, recycling nutrients back into the ecosystem.

(c)(ii) 1. Egestion (faeces / indigestible material) ; 2. Respiration (heat loss).
Energy is lost as heat during respiration, and in uneaten or indigestible parts like bones and teeth. Other losses include movement and excretion.

Question

A farmer planted some seeds.
(a) Explain why the farmer digs the soil to ensure there are air spaces in the soil before the seeds are planted.
(b) The seeds grow and some of the tips are removed.
Fig. 10.1 shows the shoots after a few days.
(i) State the name of the tropic response shown by shoot A in Fig. 10.1.
(ii) Explain why shoot B does not grow towards the light in Fig. 10.1.
(c) State the name of the type of selection the farmer could use to improve the quality of crop plants.
(d) The shoots eventually flower.
Fig. 10.2 is a drawing of one of the flowers.
(i) Label the part in Fig. 10.2 that protects the developing flower. Use a label line and the correct name.
(ii) Describe one visible feature that shows the flower in Fig. 10.2 is insect-pollinated.
(e) Explain the effect of a magnesium deficiency in the soil on the colour of the plant leaves.

Most-appropriate topic codes (Cambridge IGCSE Co-ordinated Sciences 0654, 2025–2027 syllabus):

• Topic B6.1 — Photosynthesis (Parts (a), (e))
• Topic B13.1 — Coordination and response (Part (b))
• Topic B17.2 — Selection (Part (c))
• Topic B15.3 — Sexual reproduction in plants (Part (d))

▶️ Answer/Explanation

(a) Provides oxygen for germination

Air spaces in the soil allow oxygen to reach the seed.
This oxygen is required for aerobic respiration during germination, releasing the energy needed for growth.

(b)(i) Phototropism

Shoot A bends towards the light source, which is the definition of a positive phototropic response.

(b)(ii) No auxin reaches the growing region

Auxin (the growth hormone) is produced in the tip of the shoot.
Since the tip of shoot B has been removed, no auxin is made, so no unequal cell elongation is stimulated and the shoot does not bend towards the light.

(c) Artificial selection

Artificial selection is the process where a farmer deliberately breeds plants with desirable characteristics to improve crop quality.

(d)(i) Sepal

The outermost part that encloses and protects the flower bud before it opens is the sepal.

(d)(ii) Large, brightly coloured petals (or anther/stigma positioned inside the flower)

Insect-pollinated flowers typically have large, conspicuous petals to attract insects.
The reproductive parts (anther and stigma) are usually located inside the flower so insects brush against them.

(e) Less chlorophyll is made, causing yellow leaves

Magnesium is needed to synthesise chlorophyll.
A deficiency means less (or no) chlorophyll can be made.
This results in the leaves appearing yellow rather than green.

More CIE iGCSE Co-Ordinated Science Paper 4 Questions..
Scroll to Top