Question 1: Define selective breeding and explain its primary purpose in agriculture.

Answer: Selective breeding is the process of choosing organisms with desirable traits to reproduce, aiming to enhance those traits in future generations, primarily to improve crop yields, livestock quality, or disease resistance.

Question 2: Describe how selective breeding differs from natural selection.

Answer: Selective breeding is a human-directed process where specific traits are chosen to be passed on, whereas natural selection is driven by environmental pressures leading to survival of the fittest without human intervention.

Question 1: List three desirable traits that might be targeted in the selective breeding of cattle.

Answer: High milk production, disease resistance, fast growth rate.

Question 2: Identify two potential ethical concerns associated with selective breeding in animals.

Answer: Loss of genetic diversity and suffering due to breeding for extreme traits.

Question 3: In practical experiments, what variables must be controlled to ensure valid results when selecting for a specific trait?

Answer: Genetic background, environmental conditions, age, and health status of the organisms.

Question 1: A breed of sheep was selectively bred over five generations for increased wool yield. The average wool yield per sheep (in grams) was recorded as follows: Generation 1: 4,500g; Generation 2: 4,700g; Generation 3: 4,850g; Generation 4: 5,000g; Generation 5: 5,150g. Calculate the percentage increase in wool yield from generation 1 to generation 5.

Answer: Percentage increase = [(Final - Initial) / Initial] x 100 = [(5150 - 4500) / 4500] x 100 ≈ 14.44%

Question 2: Based on the data provided, describe the trend observed and suggest two factors that could have contributed to this trend.

Answer: The data shows a steady increase in wool yield across generations, indicating effective selection. Factors contributing could include consistent selection of high-yield sheep and genetic improvements accumulated over generations.

Question 3: In a breeding programme, if the goal is to increase wool yield while maintaining animal health, what considerations should be taken into account?

Answer: Breeders should monitor for signs of health problems, avoid selecting for extreme traits that may cause suffering, ensure genetic diversity is maintained, and balance productivity with animal welfare.

Question 1: Explain how selective breeding has been used to develop disease-resistant crops.

Answer: Scientists select plants that show resistance to specific diseases and breed them over generations, increasing the likelihood that future crops will inherit this resistance, thereby reducing crop losses.

Question 2: Discuss one advantage and one disadvantage of using genetic engineering versus traditional selective breeding.

Answer: Advantage: Genetic engineering allows for precise gene transfer and faster development of desired traits. Disadvantage: It may raise ethical concerns and potential environmental risks, unlike traditional methods which are more natural but slower.