Food ProductionEdexcel IGCSE Biology: Flashcards

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How does a glasshouse increase crop yield?

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How does a glasshouse increase crop yield?: By raising temperature and CO2 concentration (and protecting from pests/weather), which increases the rate of photosynthesis.
Why can too high a glasshouse temperature reduce crop yield?: Because enzymes involved in processes like photosynthesis can be denatured above their optimum temperature.
How does fertiliser increase crop yield?: It adds mineral ions (e.g. nitrate) to the soil, supplying nutrients needed for growth.
Give one advantage and one disadvantage of using pesticides.: Advantage: fast-acting and effective. Disadvantage: can harm non-target species and accumulate in food chains.
Give one advantage and one disadvantage of biological control.: Advantage: no chemical residues/more sustainable. Disadvantage: slower acting, and the control organism could become a pest itself.
What does yeast produce during bread-making, and by what process?: Carbon dioxide (and ethanol), by anaerobic respiration of sugar.
Why does bread dough rise?: Carbon dioxide produced by anaerobic respiration of yeast gets trapped in the dough.
What bacterium is used to make yoghurt, and what does it produce?: Lactobacillus, which produces lactic acid from lactose.
How does lactic acid change milk into yoghurt?: It lowers the pH, causing milk proteins to coagulate (thicken).
List the conditions that must be controlled in an industrial fermenter.: Aseptic precautions, nutrients, optimum temperature and pH, oxygenation, and agitation.
Why are aseptic precautions needed in a fermenter?: To prevent contamination by unwanted micro-organisms, which could compete with or spoil the culture.
Why is agitation (stirring) needed in a fermenter?: To keep temperature, nutrients and oxygen evenly distributed and micro-organisms suspended.
Name three methods used to farm fish successfully.: Maintaining water quality, controlling predation, controlling disease, removing waste, controlling feeding, selective breeding (any three).