1. 1
   A plant breeder wants to develop a variety of wheat that produces a higher yield of grain and is more resistant to a fungal disease that has damaged crops in recent years. She examines her existing wheat plants and identifies individuals that show either high yield or disease resistance.

   (a)

   What term describes the process the breeder uses, of repeatedly choosing and breeding together plants with the most desirable characteristics over many generations?

   [1 mark]

   • AGenetic modification
   • BSelective breeding
   • CCloning
   • DNatural selection

   (b)

   In this process, which plants does the breeder choose as parents for the next generation?

   [1 mark]

   • APlants showing the desired characteristics of high yield and disease resistance
   • BPlants chosen at random from the population
   • COnly the shortest plants in the population
   • DPlants that flower earliest, regardless of yield

   (c)

   Describe the steps the breeder would take, over several generations, to produce a wheat variety with both high yield and disease resistance.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A dairy farmer wants to increase the amount of milk produced by his herd of cows. Each year, he records the milk yield of each cow and identifies the bull whose daughters, when they become cows, consistently produce the highest milk yields.

   (a)

   Why does the farmer use artificial insemination from a single high-yielding bull across many cows, rather than allowing random mating?

   [1 mark]

   • AIt is cheaper than keeping any bulls at all
   • BIt increases genetic diversity in the herd
   • CIt guarantees all offspring will be female
   • DIt allows the desirable genes for high milk yield to be passed to a large number of offspring

   (b)

   Which of the following is most likely to result from many generations of this selective breeding programme?

   [1 mark]

   • AIncreased genetic variation within the herd
   • BNo change in the genetic make-up of the herd
   • CReduced genetic variation within the herd
   • DAn increase in the number of different alleles present

   (c)

   Explain why repeatedly breeding from the same high-yielding bull and its selected daughters could create a problem for the herd in the future.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A farmer keeps a flock of sheep and wants to improve the quality of the wool they produce. Over ten generations, he selects and breeds together only the sheep producing the finest, most valuable wool, keeping detailed breeding records each year.

   (a)

   Describe the process of selective breeding the farmer uses to improve wool quality in his flock over the ten generations.

   [3 marks]

   (b)

   Explain how, and why, this selective breeding programme changes the frequency of alleles for wool quality in the flock's gene pool over the ten generations, and describe one disadvantage that may result from this.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   Over many centuries, humans have selectively bred dogs from wild wolf ancestors, initially selecting for tameness and later for specific working abilities and physical characteristics, producing modern breeds ranging from tiny lapdogs to large working dogs.

   (a)

   Using the example of dog breeding, explain in detail how selective breeding over many generations can produce distinct breeds of dog that look very different from their wolf ancestor and from each other.

   [6 marks]

   (b)

   Discuss the advantages and disadvantages of selective breeding in domesticated animals such as dogs, referring to both the benefits to humans and the potential problems for the animals themselves.

   [6 marks]

   Total for question 4: 12 marks

End of questions