Selective breedingIB MYP Biology: Subtopic test

1. 1
   A dairy farmer in New Zealand wants her cows to produce more milk. Each year she chooses the cows with the highest milk yield and breeds them with bulls whose mothers also gave a lot of milk. She then repeats this with the best of their calves, generation after generation.

   (a)

   What name is given to the process the farmer is using?

   [1 mark]

   • ANatural selection
   • BSelective breeding
   • CGenetic engineering
   • DCloning

   (b)

   What should the farmer do with the calves in each generation?

   [1 mark]

   • ABreed from every calf at random
   • BBreed only from the calves with the lowest milk yield
   • CInsert a gene for milk production into each calf
   • DChoose the calves from the highest-yielding cows to breed from

   (c)

   Explain why the average milk yield of the herd increases over many generations.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   Plant breeders in Kazakhstan produced a new variety of wheat that is resistant to rust, a disease caused by a fungus. They did this by crossing wheat plants and choosing the least damaged offspring over several generations. To test the new variety, they grew 50 plants of the original variety and 50 plants of the new variety in the same field. Both groups were sown on the same day and sprayed with the same number of rust spores. After four weeks, 31 of the original plants and 4 of the new plants showed signs of rust.

   (a)

   Which is the independent variable in this test?

   [1 mark]

   • AWhether the wheat was the original or the new variety
   • BThe number of plants showing rust
   • CThe number of rust spores sprayed on the plants
   • DThe day on which the plants were sown

   (b)

   Why was it important to grow both varieties in the same field?

   [1 mark]

   • ASo that the new variety would grow taller
   • BSo that fewer rust spores were needed
   • CSo that soil and weather were the same and only the variety was different
   • DSo that the original wheat would also become resistant

   (c)

   Calculate the percentage of plants showing rust in each variety.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   Breeders of racing camels in the United Arab Emirates choose the fastest males and females as parents. A few champion males father large numbers of calves in many different herds, so many of the racing camels are now closely related. Wild gazelles in the same desert also run fast, because fast individuals are more likely to escape from predators.

   (a)

   State three differences between natural selection in gazelles and selective breeding in racing camels.

   [3 marks]

   (b)

   Explain the risks to the camel population of breeding from a small number of closely related animals.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A rice research institute in the Philippines wants to develop a new variety of rice. The variety most farmers grow gives a high yield but is badly damaged by a bacterial disease. A wild relative resists the disease but gives very little grain. The institute plans to use selective breeding. Farmers hope the new variety will cut their losses and reduce spending on pesticides. Some conservation scientists worry that if farmers grow only one or two varieties, the genetic variation of rice will fall.

   (a)

   Describe the steps the institute would follow to produce the new variety by selective breeding.

   [6 marks]

   (b)

   Discuss and evaluate the use of selective breeding to produce the new rice variety.

   [6 marks]

   Total for question 4: 12 marks

End of questions