Food Production

Since the development of agriculture, a rising human population has rapidly increased the demand for food. In order to maximise yields, organisms are grown within carefully controlled conditions inside greenhouses, fermenters or fish farms.

Factors affecting food security

Food security is having enough food to feed a population. It is estimated that 800 million people around the world face daily hunger and a lack of access to adequate food. Food security in some countries is threatened due to the following biological factors:

1. Increasing birth rate

2. Changing diets in developed countries means limited food resources are transported to other countries around the world

3. New pests and pathogens that damage crops / livestock

4. Weather changes e.g. droughts mean there is not enough water to grow crops

5. Cost of agricultural inputs

6. Conflicts / war which affect the availability of food or water

Farming techniques

• Limiting movement and keeping animals indoors means less energy is wasted on movement and maintaining body temperature

• More energy can be invested in growth (production of biomass)

• Some animals are also fed high protein foods to increase growth.

• These practices cause the animals to grow bigger and more quickly, meaning that more food is available to a growing human population.

• However, these farming techniques can be cruel to animals and reduce their quality of life.

Crop production

Farmers can use greenhouses to increase the yield of crops produced by carefully controlling the conditions inside. Inside greenhouses, the temperature, lighting, carbon dioxide concentration and water content of soil can be regulated to maximise the amount of photosynthesis.

Polythene tunnels also increase yield by protecting crops from the wind, rain and extreme temperatures.

Fertilisers are chemicals which are added to soil to make it more fertile. The chemicals contain nitrogen, phosphorous and potassium which dissolve in the water in the soil and are absorbed by the roots of the plant to help the plant to grow. In order to feed a growing population, the use of fertilisers has increased to maximise crop yields. This has had negative impacts on the environment as fertilisers can be washed away by rainwater from farmland and enter nearby streams and rivers, resulting in eutrophication.

Pesticides can also be used to increase crop yield by killing animals and plants that eat or compete with the crops. Insecticides kill insects, such as slugs which feed on plants, whereas herbicides kill weeds which grow nearby and compete with plants for resources. There are a number of disadvantages to the use of pesticides:

• unintentional killing of other plants and animals

• pests may develop resistance to the pesticide

• can be toxic to humans if accidentally consumed

Biological control involves the introduction of a predator species in order to reduce the number of pests. For example, the release of parasitic wasps are used to control the numbers of aphids. The wasp lays its eggs inside the body of the aphid, causing the aphid to die as the new wasp hatches from the its body. This mechanism of pest control will not eliminate the pest completely, but should ensure the population size doesn’t get out of control.

There are plenty of instances when biological control has not gone according to plan. In the 1930’s two suitcases full of cane toads made their way to Queensland, Australia with the hope that they would reduce the population of cane beetles which were eating and destroying sugar cane plants. Unfortunately the toads didn’t have much of an appetite for the cane beetle, choosing to eat other animals and reproducing so successfully that they now number over 1.5 billion. Cane toads are poisonous and have disrupted populations of native species, becoming a bigger pest than the ones they were supposed to control.

Using yeast for food production

Yeast respire anaerobically in the process of fermentation to convert glucose into ethanol and carbon dioxide.

Humans have exploited this reaction for the production of alcoholic drinks (beer and wine) and for bread making. Yeast are added to dough so that the carbon dioxide produced during fermentation causes the bread to rise, producing a light, fluffy loaf of bread. Ethanol is also produced but this evaporates from the bread as it is baked.

Using bacteria for food production

Lactobacillus are a type of bacteria used to make yoghurt. Lactose in milk is digested by the bacteria into lactic acid (lactate). The lactic acid reduces the pH of the yoghurt which denatures milk proteins and gives yoghurt a thicker texture and helps to preserve the yoghurt (as microorganisms don’t survive well in acidic conditions).

Industrial fermenters

Bacteria and fungi, such as Lactobacillus and yeast, can be grown on a large scale inside industrial fermenters. The fermenters are made from stainless steel (which does not corrode) and are sterilised using hot steam to remove any contaminating microorganisms which may kill or compete the bacteria or fungi. The air inlet provides a supply of oxygen to allow the microorganisms to respire aerobically and paddles to distribute the nutrients and oxygen evenly. The temperature can be carefully controlled using a thermostat and a water jacket. pH is also kept constant using a pH sensor which ensures than the pH is at an optimum value for enzymes within bacteria and fungi to function efficiently.

Fish farming

Catching fish in the wild is unsustainable and can have a negative impact on our environment. Such large numbers of fish have been caught in the past that their populations have dwindled, impacting the rest of the food chain. For example, cod are at risk from overfishing and their population size has become so depleted that they may never recover. In addition, modern fishing techniques such as dredging and bottom-trawling can damage coral reefs and impact the sea-floor habitat.

A much more sustainable way of producing fish is by fish farming, where fish are grown in freshwater tanks and enclosures. As the fish are living closer together than they would be in the wild, the farmer needs to ensure that fish of different ages and species are kept in separate tanks to reduce intraspecific and interspecific competition.

The farmer also carries out the following steps to ensure the maximum growth of fish:

• Regular cleaning of water - this reduces disease (by removing pathogens) and prevents the build up of waste which could lead to eutrophication and reduced oxygen levels

• Use of antibiotics and separating fish to avoid crowded conditions - this prevents the spread of disease

• Fencing and scarecrows - to prevent predation of fish

• Frequent feeding with small food pellets - feeding the fish a small quantity of food more often prevents the accumulation of excess food in the water and allows the fish to grow rapidly

• Selective breeding - this technique can produce fish which grow much more quickly than fish in the wild

• Genetic modification - fish can be genetically modified for disease resistance. Using less energy to fight an infection means more energy can be used for growth.

Fish farming is not only more sustainable than wild fishing but it gives the farmers more control of the species and age of fish that they want to catch. Wild fishing often results in catching unwanted fish or young fish which are often dead or injured when they are thrown back to sea. Fish farming is also much quicker and the fish are easier to catch than catching fish in the ocean. The disadvantages to fish farming are that the fish tend to be closely related, which facilitates the spread of disease as they are equally susceptible to the same diseases. This can be overcome through the use of antibiotics and regularly cleaning the water which can be expensive and time-consuming.