Selective breedingIB MYP Biology: Mind map

Exam questions on Selective breeding

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.
   Explain why the average milk yield of the herd increases over many generations.2 marks
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.
   Calculate the percentage of plants showing rust in each variety.2 marks
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.
   State three differences between natural selection in gazelles and selective breeding in racing camels.3 marks