1. 1
   An agricultural scientist compares a hibiscus flower, which is large, brightly coloured and produces scented nectar, with a nearby barley plant, whose small, dull-coloured flowers hang loosely and release large amounts of powdery pollen into the wind.

   (a)

   Which feature of the hibiscus flower attracts insects for pollination?

   [1 mark]

   • ALarge, brightly coloured petals and scented nectar
   • BSmall, feathery stigmas hanging outside the flower
   • CLarge amounts of smooth, light pollen
   • DThe absence of petals

   (b)

   Which feature is typical of the barley plant's wind-pollinated flowers?

   [1 mark]

   • ABrightly coloured petals
   • BLarge, feathery stigmas that hang outside the flower to catch pollen
   • CSticky, scented nectar
   • DSmall amounts of large, heavy pollen grains

   (c)

   Explain two ways in which the barley's pollen is adapted for wind pollination, compared with the hibiscus's pollen.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A school science club germinates sunflower seeds in the dark, weighing the seed and the emerging seedling each day, and finds that the total dry mass decreases at first, before the first true leaves unfurl and turn green.

   (a)

   What is the main food store used by the germinating sunflower seed before it can photosynthesise?

   [1 mark]

   • AGlucose absorbed from the soil
   • BProtein absorbed from the soil
   • CStarch stored in the cotyledons
   • DChlorophyll stored in the seed coat

   (b)

   Why does the total dry mass of the seed and seedling decrease during the early stages of germination in the dark?

   [1 mark]

   • AWater is being lost by evaporation
   • BThe seedling is photosynthesising and losing oxygen
   • CThe seed coat is being shed
   • DStored food reserves are used in respiration, releasing carbon dioxide and losing mass

   (c)

   Explain why the dry mass of the seedling begins to increase again once the first leaves unfurl and turn green.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A couple undergoing fertility treatment are given hormone injections to stimulate the woman's ovaries before egg collection, and the fertilised embryos are screened to determine the sex chromosomes present before being implanted.

   (a)

   Explain the roles of FSH and LH in stimulating the maturation and release of an egg from the ovary.

   [3 marks]

   (b)

   Explain how the sex chromosomes present in the embryos are determined at fertilisation, and how the screening process could determine which embryos are male and which are female.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A genetic counsellor explains to a couple, who are both carriers of a recessive allele for cystic fibrosis, how a single mutation changes the protein produced by a gene, and works out the chance that their child will be affected by the condition.

   (a)

   Describe the stages of protein synthesis, transcription and translation, explaining how a mutation in the DNA base sequence could result in a faulty protein being made.

   [6 marks]

   (b)

   Using a genetic diagram, and the symbols F for the dominant normal allele and f for the recessive cystic fibrosis allele, explain the possible genotypes and phenotypes of the couple's children, and state the probability that a child will be affected by cystic fibrosis.

   [6 marks]

   Total for question 4: 12 marks

5. 5
   A plant nursery propagates a prize-winning rose bush by taking stem cuttings and growing them in rooting compost, and separately grows a spider plant that naturally produces small plantlets at the end of long runners.

   (a)

   What type of reproduction is occurring in both the rose cuttings and the spider plant's runners?

   [1 mark]

   • AAsexual reproduction
   • BSexual reproduction
   • CFertilisation
   • DPollination

   (b)

   Why are the new rose plants grown from cuttings genetically identical to the parent rose bush?

   [1 mark]

   • AThey are produced by meiosis, halving the chromosome number
   • BThey are produced by mitosis from the parent's cells, with no fusion of gametes
   • CThey result from the fusion of male and female gametes
   • DThey inherit half their genes from each parent

   (c)

   Give one advantage and one disadvantage of propagating the rose bush by taking cuttings rather than growing new plants from seed.

   [2 marks]

   Total for question 5: 4 marks

6. 6
   A farm vet notices that a common antibiotic, used for years to treat a bacterial infection in a cattle herd, is becoming less effective, and traces how resistance to the drug has spread through the herd's bacteria over several years.

   (a)

   What is the original source of the antibiotic resistance allele in the bacterial population?

   [1 mark]

   • AIt was created by the antibiotic itself
   • BIt only appears after several years of antibiotic use
   • CIt arose by random mutation before the antibiotic was ever used
   • DIt was passed from the cattle's DNA to the bacteria

   (b)

   Why does treating the herd with the antibiotic cause resistance to spread through the bacterial population?

   [1 mark]

   • AThe antibiotic directly changes the bacteria's DNA to make them resistant
   • BThe antibiotic makes all bacteria resistant equally
   • CThe antibiotic has no effect on which bacteria survive
   • DThe antibiotic kills the non-resistant bacteria, leaving resistant bacteria to survive and reproduce

   (c)

   Explain why using an antibiotic on the herd for many years increases the proportion of resistant bacteria, using the idea of natural selection.

   [2 marks]

   Total for question 6: 4 marks

7. 7
   A farmer monitors a pregnant ewe throughout gestation, and later compares the birth weights of all the lambs born on the farm that season, noting that birth weight varies even between lambs with very similar genetics.

   (a)

   Describe the role of the placenta in nourishing the developing lamb embryo.

   [3 marks]

   (b)

   Explain why the lambs' birth weights vary even between lambs with very similar genetics, and describe the difference between genetic variation and environmental variation.

   [4 marks]

   Total for question 7: 7 marks

8. 8
   A dairy farmer is surprised when one of his cows gives birth to genetically identical twin calves, formed when a single fertilised egg split into two separate embryos early in development, while another cow on the farm gives birth to a single calf from a separate mating with a different bull.

   (a)

   Explain how mitosis is involved in the development of the identical twin calves from a single fertilised egg, and why the two twin calves are genetically identical to each other.

   [6 marks]

   (b)

   Explain why the single calf, born from a separate mating, is not genetically identical to either of its parents or to the twin calves, referring to meiosis and random fertilisation.

   [6 marks]

   Total for question 8: 12 marks

End of questions