Pearson Edexcel GCSE (9-1) Biology revision notes
Natural selection and genetic modification Revision Notes
Review revision notes for Natural selection and genetic modification in Edexcel Biology.
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Natural selection and genetic modification
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Agricultural Solutions for a Growing Population Revision Notes
Fertilisers: Benefits and Limitations
Fertilisers supply essential mineral ions (nitrates, phosphates, potassium) to the soil, which are vital for plant growth and development. This leads to increased crop yields, allowing more food to be produced from the same area of land. Benefits include higher food production and more efficient land use. However, overuse of fertilisers can cause eutrophication: excess nutrients leach into waterways, promoting rapid algal growth. This blocks sunlight from submerged plants, which then die. Decomposers break down dead plants, consuming large amounts of oxygen, leading to the death of other aquatic organisms like fish.
Biological Control: Benefits and Limitations
Biological control uses natural enemies (predators, parasites, or pathogens) to reduce pest populations, offering an alternative to chemical pesticides. Benefits include reduced chemical pollution, less harm to beneficial insects and other non-target species, and the prevention of pesticide resistance in pests. Limitations involve the potential for the introduced control agent to become an invasive species or disrupt the local ecosystem. It can also be a slower and less predictable method compared to chemical pest control, and may not achieve complete eradication of the pest, requiring careful management.
Meeting Food Demands
As the global population grows, so does the demand for food. Agricultural solutions like optimised fertiliser use and biological control are crucial for sustainable intensification. These methods aim to maximise crop output while managing environmental impacts. Understanding the benefits and limitations of each approach is key to developing integrated pest and nutrient management strategies that are both productive and ecologically sound.
Genetic Engineering and Selective Breeding in Modern Applications Revision Notes
Genetic Engineering: Benefits and Risks
Genetic engineering (GE) is a process that alters the genetic material of an organism. Benefits in agriculture include increased crop yields, enhanced nutritional value (e.g., 'golden rice' with more vitamin A), and resistance to pests, diseases, or harsh environmental conditions like drought. In medicine, GE allows for the production of insulin, growth hormones, and vaccines, and holds promise for gene therapy to treat genetic disorders. Risks pose ethical concerns regarding altering natural organisms, potential unforeseen consequences on ecosystems (e.g., spread of modified genes to wild populations), and 'designer babies'. Practical concerns include the cost of development, intellectual property issues, and potential allergic reactions to new proteins.
Selective Breeding: Benefits and Risks
Selective breeding (also known as artificial selection) involves choosing organisms with desired phenotypic traits to reproduce, aiming to enhance those traits in offspring. Benefits in agriculture include developing crops with higher yields, better flavour, or specific disease resistance. It has also led to domestic animals with desired characteristics such as increased milk production in cows or faster growth rates in livestock. In medicine, selective breeding doesn't directly apply to human treatment but has been used to create animal models for research. Risks include reduced genetic diversity, which can make populations more vulnerable to new diseases or environmental changes. It can also lead to unintended undesirable traits and welfare issues, such as specific breed health problems in dogs or high-yielding chickens with fragile bones.
Practical and Ethical Implications
Both genetic engineering and selective breeding have practical and ethical implications. Practical implications involve the cost, technical expertise required, timeframes, and market acceptance. For example, genetically modified (GM) crops face regulatory hurdles and public skepticism in some regions. Ethical implications revolve around 'playing God', animal welfare, food safety, and potential socio-economic impacts. The long-term effects of consuming GM foods are still debated, and there are concerns about corporate control over seed supplies. Balancing increased productivity and medical advancements with these considerations is crucial for their responsible application.
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