food production

• The increasing human population requires an increased food yield.
• By adding in a gene, any pest species which feed on the crop would die so crop yield is increased
• GM Crops could be used to reduce the use of pesticides
• To increase food yield, humans use fertilisers and pesticides.
• Fertilisers are added to soil to provide chemicals like nitrates to increase crop yield.
• Nitrates dissolved in soil are absorbed into plants through their roots, used to make amino acids which are joined together to form proteins in the plant.
• Plant proteins allow plants to grow and so increase crop yield.
• Animals eat plants (or eat animals which eat plants) to gain amino acids for making proteins, a process called protein synthesis.
• Fertilisers are not always beneficial as they can leach into fresh water, adding in extra, unwanted nitrates.
• Fertilisers can leach into fresh water which adds in extra, unwanted nitrates.
• Algal populations increase because they have lots of nutrients, causing an algal bloom to form.
• Algal blooms stop light from reaching the plants below.
• Algal blooms kill the plants as they cannot photosynthesise.
• Algal blooms also die as they have run out of nutrients.
• Bacteria use the dead algae and plants as food, causing them to increase in number.
• Fertilisers leaching into fresh water can cause the bacteria to use up most of the oxygen, reducing the oxygen available for other organisms.
• With no oxygen available, the animals in the fresh water die.
• An experiment can be carried out to show the effect of fertiliser on biodiversity.
• Genetically modified crops can be used to reduce the use of fertilisers.
• Genetically modified crops can have increased yield, grow in soil with low nitrates, be herbicide-resistant so crop does not die when sprayed to kill weeds, kill pest species if crop is eaten, and increase nutrition e.g. golden rice.
• Pesticides are chemicals that are sprayed onto crops to kill pest species that feed on crops, reducing the crop yield.
• Pesticides that are sprayed onto crops can build up (bioaccumulate) in the bodies of organisms over time, increasing to lethal levels as the pesticide is passed along the food chain.
• DDT is a pesticide that was used to control populations of mosquito in the 1940s.
• Alternatives to using pesticides include biological controls and using GM crops.
• Biological control uses natural predators of a pest species as a way to keep their population size low, for example, a ladybird is a natural predator of the aphid.
• Biological controls might not survive in a new environment, might bring new diseases into the new environment, and might become a pest species.