1. 1
   A biology class is told that sexual reproduction involves the fusion of the nuclei of two gametes to form a zygote, producing offspring that are genetically different from each other, unlike offspring produced by asexual reproduction.

   (a)

   A biology class is told that offspring produced by sexual reproduction, unlike offspring produced asexually, are genetically different from one another and from their parents. What process, involving two gametes, produces this genetic variation?

   [1 mark]

   • AFertilisation, the fusion of the nuclei of two gametes
   • BMitosis, the division of a single body cell
   • COsmosis, the movement of water across a membrane
   • DDiffusion, the net movement of particles down a concentration gradient

   (b)

   Gametes, such as sperm and egg cells, contain half the number of chromosomes found in a normal body cell. What term describes the nucleus of a gamete?

   [1 mark]

   • ADiploid
   • BHaploid
   • CHomozygous
   • DHeterozygous

   (c)

   Describe fertilisation, and state whether the resulting zygote is haploid or diploid.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   Scientists studying a wild rabbit population compare the genetic variation seen among offspring produced by sexual reproduction with the genetic identity that would result if the same parent reproduced asexually, in order to understand the population's ability to survive environmental change.

   (a)

   Two rabbits, from the same wild population, are compared. One is bred from parents that reproduced sexually, and the other is a hypothetical clone produced asexually from a single parent. Which rabbit is expected to show more variation in its characteristics compared to other members of the population?

   [1 mark]

   • ANeither, because both types of reproduction always produce identical variation
   • BThe asexually produced clone, because asexual reproduction always increases variation
   • CThe sexually produced rabbit, because sexual reproduction combines genetic material from two parents
   • DThe asexually produced clone, because mutation only occurs during asexual reproduction

   (b)

   The scientists conclude that greater genetic variation in a population produced by sexual reproduction is generally an advantage in the wild. Which of the following best explains why?

   [1 mark]

   • AGreater variation removes the need for gametes to fuse
   • BGreater variation guarantees that every individual will survive any environmental change
   • CGreater variation means every individual reproduces more quickly
   • DGreater variation increases the chance that some individuals are suited to survive a change in the environment

   (c)

   Discuss one advantage and one disadvantage of sexual reproduction for a population of wild rabbits, compared with asexual reproduction.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A dairy farmer is deciding between two breeding strategies for their cattle herd: sexual reproduction between selected bulls and cows with desirable traits, or asexual cloning of a single cow known to produce an exceptionally high milk yield.

   (a)

   A dairy farmer compares two breeding strategies for cattle: sexual reproduction between selected bulls and cows, and asexual cloning of a single high-milk-yield cow. Discuss the advantages and disadvantages of sexual reproduction for the farmer's herd.

   [3 marks]

   (b)

   Explain why the farmer might choose to clone (reproduce asexually from) the single high-milk-yield cow rather than breed her sexually with a bull, and describe one risk of relying on this asexual approach for the whole herd.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A conservation charity managing a small, endangered animal population is debating whether to clone the remaining individuals to quickly boost numbers, or to encourage sexual reproduction between as many different individuals as possible, and is also concerned about the risk of inbreeding within such a small population.

   (a)

   A conservation charity is managing a small, endangered population of animals in a breeding programme. Some scientists suggest cloning the few remaining individuals to quickly increase the population size, while others argue that encouraging sexual reproduction between as many different individuals as possible, even though it is slower, is a better long-term strategy. Evaluate both approaches, explaining the biological reasoning behind each.

   [6 marks]

   (b)

   The charity is also concerned that, because the surviving population is so small, encouraging sexual reproduction between closely related individuals could lead to inbreeding. Explain what is meant by inbreeding in this context, and explain why reduced genetic variation resulting from inbreeding could still pose a risk to the population even though sexual reproduction, rather than cloning, is being used.

   [6 marks]

   Total for question 4: 12 marks

End of questions