A certain species of blowfly attacks sheep, laying eggs in damp, soiled wool around the breech (rear) and shoulders. The hatching larvae feed on the sheep's skin and tissue, causing severe distress, infection, and reduced wool and meat yield. To minimize blowfly strike, farmers aim to breed sheep with completely wool-free skin on both their breech and shoulders.
Suggest why blowflies are attracted to these areas on sheep.
Farmers cross different breeds of sheep to obtain offspring with desired phenotypic characteristics. The features of three sheep breeds are shown below:
| Breed of sheep | Bare-skin characteristic |
|---|---|
| Wiltshire Horn | wool-free skin on the breech |
| Dorper | wool-free skin on the shoulders |
| Suffolk | wool-free skin on the abdomen |
Describe how farmers could use selective breeding to develop sheep with wool-free skin on both their breech and their shoulders.
Describe two differences between selective breeding (artificial selection) and natural selection.
Farmers sometimes use chemical organophosphate dips or synthetic pyrethroid sprays to control blowfly infestations. Give two ecological or biological disadvantages of using these chemical treatments.
