Natural selection and genetic modification study guide

The emergence of antibiotic-resistant bacteria provides a clear, observable example of natural selection, a key mechanism of Charles Darwin's theory of evolution. Within any large bacterial population, there's natural genetic variation, meaning some individual bacteria may possess mutations that confer a degree of resistance to certain antibiotics. When an antibiotic is introduced, it acts as a selective pressure, killing off the non-resistant bacteria. The resistant individuals survive, reproduce, and pass on their resistance genes to their offspring. Over generations, the proportion of resistant bacteria in the population increases, leading to a strain that is largely unaffected by the antibiotic. This demonstrates 'survival of the fittest' at a microbial level, where beneficial traits (antibiotic resistance) become more common in the population due to environmental challenges.

A growing human population continually increases the demand for food. Agricultural practices need to intensify and become more efficient to meet this demand. Two key solutions are the use of fertilisers and biological control. Fertilisers, containing essential mineral ions like nitrates, phosphates, and potassium, enhance crop yields by providing nutrients for plant growth. This directly boosts the amount of food produced per unit area. However, excessive use can lead to environmental issues such as eutrophication of water bodies, where algal blooms deplete oxygen and harm aquatic life. Biological control involves using natural predators, parasites, or pathogens to manage pests, reducing the need for chemical pesticides. This method is generally more environmentally friendly, as it avoids chemical pollution and reduces harm to non-target species. Its limitations include the potential for the control agent to become a pest itself if not carefully chosen, and it can be slower-acting and less predictable than chemical methods. Both strategies aim to increase food production but come with distinct benefits and environmental trade-offs.