Use of Biological Resources

• The knowledge about limiting factors and how they affect the rate of photosynthesis can be used by farmers to improve crop yields.
• Growing crops outside does not allow farmers to control any of these factors.
• Glasshouses and polythene tunnels provide an enclosed environment in which farmers can, to some extent, control the climate inside and increase their crop yields.
• In a glasshouse, several conditions can be manipulated to increase the rate of photosynthesis, including artificial heating, artificial lighting, increasing carbon dioxide content of the air inside, regular watering, and controlling pests and diseases.
• Farmers need to balance the extra cost of providing heating, lighting and carbon dioxide against the increased income.
• In tropical countries where temperatures are much hotter, glasshouses may still be used to control other conditions however they may need to be ventilated to release hot air and avoid temperatures rising too high, which could cause the denaturation of the enzymes controlling the photosynthesis reaction.
• Polythene tunnels, also known as polytunnels, are large plastic tunnels that cover crops.
• Polytunnels can protect crops grown outside from the effects of the weather, including excessive wind, rain and extreme temperatures.
• Polytunnels increase the temperature slightly inside the tunnel.
• Polytunnels can prevent the entry of pests that can damage plants or diseases that can kill plants.
• Fish farms can protect against predators.
• An industrial fermenter used to produce large quantities of microorganisms is shown in the image below.
• Fish farming is a method of raising large numbers of fish in a small space to provide food (protein) for humans.
• The benefits of fish farming include the ability to selectively breed fish to ensure high quality, fast-growing fish.
• Fish farms can control water quality as many wild-caught fish have significant levels of pollutants such as mercury in their flesh.
• Within fish farms, large numbers of fish are kept in freshwater or seawater enclosures and are carefully monitored and controlled in many different ways to ensure high yields (fast growth of healthy fish).
• The methods used in fish farms to ensure high yield include the control of water quality, the control of intraspecific predation, the control of interspecific predation, the control of disease, the control (and removal) of waste products, the control of the quality and frequency of feeding, and the use of selective breeding.
• The advantage of using a fermenter is that conditions can be carefully controlled to produce large quantities of exactly the right type of microorganism.
• In an industrial fermenter, conditions can be controlled to produce large quantities of exactly the right type of microorganism.
• Fermenters are containers used to grow (‘culture’) microorganisms like bacteria and fungi in large amounts.
• Fish farms can control feeding to ensure rapid growth.
• These can then be used for brewing beer, making yoghurt and mycoprotein and other processes not involving food, like producing genetically modified bacteria and moulds that produce antibiotics (e.g. penicillin).
• However, as the reaction is controlled by enzymes, this trend only continues up to a certain temperature beyond which the enzymes begin to denature and the rate of reaction decreases.
• Pesticides kill unwanted insects and weed species, meaning that there is less damage done to crop plants by insects, as well as reducing competition from other plant species, which increases yields.
• The more light a plant receives, the faster the rate of photosynthesis.
• This trend will continue until some other factor required for photosynthesis prevents the rate from increasing further because it is now in short supply.
• Fertilisers increase the amount of key nutrients in the soil for crop plants, meaning that they can grow larger and are more healthy, which increases yields.
• Carbon dioxide is one of the raw materials required for photosynthesis, meaning the more carbon dioxide that is present, the faster the reaction can occur.
• Plants require a range of mineral ions in order to grow well.
• Modern technology has increased food supply substantially in two key ways: Fertilisers and Pesticides.
• There are three main factors that limit the rate of photosynthesis: Temperature, Light intensity, and Carbon dioxide concentration.
• Most often plants do not have unlimited supplies of these things, so their rate of photosynthesis is limited by whatever factor is the lowest at that time, known as the limiting factor.
• As temperature increases the rate of photosynthesis increases as the reaction is controlled by enzymes.
• As crop plants take up these mineral ions from the soil, the mineral ions need to be replaced if crops are grown repeatedly in the same field.
• If a plant is given unlimited light, carbon dioxide and water and is at a warm temperature, the only thing limiting the rate at which it can photosynthesise is its own ability to absorb these materials and make them react.
• Fermentation is economically important in the manufacture of bread (where the production of carbon dioxide makes dough rise) and alcoholic drinks (as ethanol is a type of alcohol).
• Anaerobic respiration in yeast cells is called fermentation.
• Change the temperature of the water bath and repeat the experiment to investigate the effect of temperature on yeast fermentation.
• To investigate the effect of temperature on yeast fermentation, mix yeast with sugar solution in a boiling tube.
• The carbon dioxide produced by the anaerobic respiration of glucose is what makes bread dough rise.