Home / iGCSE Biology (0610)-18.3 Selection – iGCSE Style Questions Paper 4

iGCSE Biology (0610)-18.3 Selection – iGCSE Style Questions Paper 4

IGCSE Biology (0610) Practice Questions Paper 4 - All Chapters
Question

Characteristics of plants are controlled by genes. Alleles are alternative forms of a gene.
(a) Explain how new alleles are formed.

(b) The number of hours of daylight affects when plants produce flowers. This ensures that flowers are produced at an appropriate time of year for each species. This response to the number of hours of daylight is controlled by genes.
(i) Wheat is a crop plant. A farmer wants to produce a type of wheat that flowers when there are fewer hours of daylight. Describe how the farmer could selectively breed this type of wheat.

(ii) Wheat is grown from seeds. State two conditions needed for the germination of seeds.

(iii) Different types of wheat have also evolved through natural selection. Explain how natural selection differs from artificial selection.

(c) Scientists can selectively breed for increased pest resistance in wheat. Explain the benefits of growing wheat with increased pest resistance.

▶️ Answer/Explanation
Solution

Ans

(a) New alleles are formed through mutations, which are changes in the DNA base sequence. These can occur spontaneously or be induced by mutagens like radiation or chemicals.

(b)(i) The farmer could selectively breed wheat by:

  1. Selecting plants that flower under shorter daylight conditions.
  2. Crossing these plants to produce offspring.
  3. Repeating the process over generations to stabilize the trait.

(b)(ii) Seed germination requires:

  • Water (for metabolic reactions)
  • Oxygen (for respiration)
  • Suitable temperature (for enzyme activity)

(b)(iii) Natural selection differs from artificial selection:

  • Natural selection is driven by environmental pressures, favoring traits that enhance survival and reproduction.
  • Artificial selection is human-directed, targeting specific desirable traits (e.g., early flowering).

(c) Benefits of pest-resistant wheat:

  • Reduces pesticide use, minimizing environmental pollution.
  • Improves crop yield and quality by reducing pest damage.
  • Protects non-target species (e.g., pollinators) and farm workers’ health.

Question

Fig. 4.1 shows a wild pig and a Saddleback pig. The drawings are to the same scale.

(a) The Saddleback pig has been produced from the wild pig by artificial selection (selective breeding). Suggest two useful characteristics, visible in Fig. 4.1, which the farmers selected when breeding the Saddleback pig.
1 ………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………..
2 ……………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………

(b) Explain how the Saddleback pig could have been produced by artificial selection.
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(c) There are different varieties of sheep. Some of these varieties have white wool and some have brown wool. The allele for white wool colour, N, is dominant to the allele for brown wool colour, n. A genetic diagram for the result of crossing a white-coloured sheep with a brown-coloured sheep is shown in Fig. 4.2. Complete the genetic diagram to show how wool colour is inherited in this cross.

Answer/Explanation

Ans:

(a) (selected for) greater volume/ larger animal/ higher yield of meat;
       smaller/ absent tusks;

(b) wild pigs allowed to breed;
      bigger pigs / pigs with small tusks selected (from offspring);
      repeat above procedure;
      for many generations;
     ‘saddleback’ type pigs interbreed/ not allowed to breed with wild pigs;

(c) parental genotype                             Nn× (nn);
      gametes                                           N + n × n + n;
      offspring genotype                                    Nn         nn           Nn          nn;
      offspring phenotype                          white        brown     white    (brown);

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