Food Production (Edexcel IGCSE Biology)

False.

Increasing temperature initially increases the rate of photosynthesis as enzyme activity rises, but beyond a certain temperature, enzymes denature, leading to a decrease in the rate of photosynthesis.

False.

Carbon dioxide concentration significantly influences the rate of photosynthesis, as it is one of the raw materials required for the process. Higher carbon dioxide levels can lead to faster rates of photosynthesis until another limiting factor comes into play.

A limiting factor in photosynthesis refers to the environmental factor, such as temperature, light intensity, or carbon dioxide concentration, that is in the shortest supply at a given time, restricting the overall rate of photosynthesis.

The rate of photosynthesis is positively correlated with carbon dioxide concentration, meaning that higher carbon dioxide levels generally lead to faster rates of photosynthesis until another factor becomes limiting.

False.

The rate of photosynthesis is influenced by multiple factors, including light intensity, temperature, and carbon dioxide concentration, with the factor that is in shortest supply at a given time acting as the limiting factor.

Light intensity directly influences the rate of photosynthesis, with higher light levels providing more energy for photosynthetic reactions to occur, leading to an increase in photosynthetic rate until another factor becomes limiting.

Food supply is increased through fertilisers because fertilisers replenish essential mineral ions in the soil e.g. nitrates, promoting healthier plant growth, and increasing crop yields.

False.

Fertilisers can be either organic (such as farmyard manure and compost) or chemical, providing essential nutrients like nitrogen, phosphorus, and potassium to crops to enhance growth and increase yields.

Organic fertilisers are derived from natural sources such as farmyard manure and compost, providing essential nutrients to plants while improving soil structure and fertility, thereby promoting sustainable and environmentally friendly agriculture.

Chemical fertilisers mainly provide nitrates, phosphates, and potassium to crop plants, essential for various biochemical processes like protein synthesis, DNA formation, and enzyme reactions, thus promoting healthy growth and higher yields.

True.

Lack of nitrates can lead to weak growth and yellowing of leaves in plants, this is because nitrates are used to build amino acids and proteins essential for growth.

Nitrates are required for amino acids and therefore building of proteins. Lack of nitrates can lead to weak growth and yellowing of leaves in plants.

Pests such as insects, weeds, and fungi can damage crops by consuming them, outcompeting them for resources like space, water, and nutrients, or infecting them with diseases, all of which can negatively impact crop growth and yield.

False.

Biological control involves using natural predators or introduced species to control pests, while chemical control involves the use of pesticides such as insecticides, herbicides, and fungicides to kill pests directly.

Pesticides, including insecticides, herbicides, and fungicides, are used in pest control to kill or control pests such as insects, weeds, and fungi, thereby reducing crop damage and ensuring higher yields in agricultural production.

Biological control refers to the use of natural predators or introduced species to control pest populations, promoting a balance in ecosystems by preying on pests and keeping their populations at lower, manageable levels without the need for chemical pesticides.

False.

Biological control does not completely eliminate pests but helps keep their populations at lower, manageable levels by introducing natural predators or species that prey on pests, thereby reducing crop damage and maintaining a sustainable balance in ecosystems.

Herbicides are pesticides used to kill or control plant pests such as weeds, which compete with crop plants for resources like space, water, and nutrients, thereby reducing competition and ensuring better crop growth and higher yields in agricultural fields.

Examples of biological control methods include the introduction of natural predators like ladybirds to control aphid populations, or the introduction of parasitic wasps to control whitefly infestations in crops, promoting natural pest management without chemical pesticides.

Biological control involves the use of natural predators or introduced species to control pests, promoting a sustainable balance in ecosystems, while chemical control relies on the use of pesticides to directly kill or control pests, often with potential environmental impacts.

Some examples of advantages of biological control include:

• Natural method - no pollution, bioaccumulation, biomagnification

• No resistance

• Can target certain specific species

• Long lasting

• Does not need to be reapplied

Some examples of disadvantages of biological control include:

• May eat other organisms instead of the pest

• Takes a longer period of time to be effective

• Cannot kill the entire population - some pests will always be present

• May not adapt to new environment or may move out of the area

• May become a pest itself

In bread making yeast produces enzymes that break down starch in flour, releasing sugars. These sugars are then used by yeast for anaerobic respiration, producing carbon dioxide that causes the dough to rise, resulting in the formation of bread during baking.

False.

Any ethanol produced by yeast during anaerobic respiration in bread making is evaporated during baking, ensuring that bread does not contain alcohol.

Yeast produces carbon dioxide during anaerobic respiration, which gets trapped in small air pockets in the dough, causing it to rise (increase in volume), ultimately resulting in the light and fluffy texture of bread after baking.

Yeast is killed by the high temperatures used during baking, preventing further respiration, while any ethanol produced as a waste product of anaerobic respiration is evaporated, ensuring that bread does not contain alcohol.

False.

Yeast can carry out anaerobic respiration, making it suitable for fermentation processes.

Fermentation is a metabolic process carried out by microorganisms like yeast, involving the breakdown of sugars into simpler compounds, often accompanied by the production of energy, ethanol, carbon dioxide, or other by-products under anaerobic conditions.

The effect of temperature on yeast fermentation can be investigated by measuring the rate of carbon dioxide production, which correlates with the rate of anaerobic respiration, at different temperatures using a water bath setup with yeast and sugar solution, observing the number of bubbles produced within a fixed time period.

Temperature affects the rate of yeast fermentation by influencing enzyme activity. Higher temperatures closer to the optimum temperature of yeast enzymes increase enzyme activity, leading to faster fermentation rates, while temperatures beyond the optimum can cause enzyme denaturation and decrease fermentation rates.

Adding oil to the yeast and sugar solution creates a barrier that prevents oxygen from entering the solution, thereby inhibiting aerobic respiration in the yeast and promoting anaerobic respiration, which is essential for observing the effect of temperature on yeast fermentation.

True.

Higher temperatures closer to the optimum temperature of yeast enzymes increase enzyme activity, facilitating faster fermentation rates due to increased rates of enzyme-controlled reactions involved in anaerobic respiration.

Limewater is used in the experiment to detect the production of carbon dioxide, which is a by-product of yeast fermentation. When carbon dioxide bubbles through limewater, it forms a cloudy precipitate of calcium carbonate, indicating the release of carbon dioxide during yeast fermentation.

If the temperature exceeds the optimum for yeast enzymes, enzyme denaturation occurs, leading to a decrease in enzyme activity and ultimately a slowdown or cessation of carbon dioxide production, as observed in the experiment investigating the effect of temperature on yeast fermentation.

Bacteria are useful in food production due to their capability to produce complex molecules, such as enzymes for milk fermentation, and their rapid reproduction, which accelerates the production of desired chemicals, enhancing efficiency in processes like yoghurt making.

Lactobacillus is the specific type of bacterium commonly used in yoghurt production, as it plays a crucial role in fermenting milk sugars (lactose) into lactic acid, thereby souring and thickening the milk to form yoghurt while also acting as a preservative due to the increased acidity.

True.

In yoghurt production, milk is pasteurised at temperatures between 85-95°C to eliminate unwanted bacteria that could interfere with the fermentation process, ensuring the growth of Lactobacillus bacteria and preventing contamination or spoilage of the yoghurt.

Fermentation in yoghurt production refers to the metabolic process carried out by Lactobacillus bacteria, where milk sugars (lactose) are converted into lactic acid, resulting in the souring and thickening of the milk to form yoghurt. Fermentation also helps preserve yoghurt by lowering pH and inhibiting harmful microorganisms.

The conversion of lactose into lactic acid by Lactobacillus bacteria will Lower the pH during yoghurt production .

Temperature control is critical in yoghurt production as it facilitates the optimum growth and activity of Lactobacillus bacteria.

False.

Lactobacillus bacteria convert lactose into lactic acid during yoghurt production through fermentation.

Sterilising equipment in yoghurt production is essential to eliminate unwanted bacteria, ensuring a clean environment for Lactobacillus bacteria to thrive during fermentation without competition or contamination, thereby maintaining the quality and safety of the yoghurt product.

Fermenters are containers used to grow (‘culture’) microorganisms like bacteria and fungi in large amounts.

They can then be used for:

• Brewing beer.

• Making yoghurt.

• Making mycoprotein.

• Producing genetically modified bacteria and moulds that produce antibiotics. (e.g. penicillin) or other medicines.

• Other valid examples.

The stirring paddles agitate the contents of the fermenter ensuring that microorganisms, nutrients, oxygen, temperature and pH are evenly distributed throughout.

The cooling jacket runs cold water around the outside of the fermenter. This helps to cool the contents to avoid overheating and to keep the temperature as close to optimum as possible. The microorganisms release heat energy as they carry out exothermic respiration so without the cooling jacket it would easily overheat.

The fermenter is cleaned using scorching hot steam. This is just water. No other chemicals are used. It is important to avoid using any harsh anti-microbial chemicals such as bleach because it could contaminate the product inside the fermenter and potentially kill the useful organisms inside the fermenter.

The microorganisms get their nutrients into the machine through pipes. The necessary biological molecules for the metabolism and reproduction of the organisms, such as glucose, are provided.

The temperature and pH are monitored through probes on the inside of the machine that connects to a computer where the readings can be viewed and adjustments made if the readings stray from the optimum.

Fish farming is the practice of raising large numbers of fish in confined freshwater or seawater enclosures for commercial purposes, primarily to provide food for human consumption.

Fish farming offers several advantages over wild-caught fish, such as:

• The ability to selectively breed fish for quality and fast growth.

• Protection against predators.

• Control over water quality to reduce pollutants like mercury.

• The ability to regulate feeding for rapid growth.

Fish farms employ various methods to ensure high yields including:

• Controlling and maintaining water quality.

• Managing intraspecific and interspecific predation.

• Preventing disease outbreaks.

• Removing waste products.

• Regulating the quality and frequency of feeding.

• Selective breeding techniques are utilised to produce fish with desirable traits.

Fish farming is regarded as a sustainable alternative to wild-caught fish due to its ability to produce large quantities of fish in a controlled environment, reducing pressure on wild fish populations.

Fish farms can ensure consistent production while mitigating environmental impacts such as overfishing and habitat destruction associated with traditional fishing methods.

True.

Fish farming provides the advantage of controlling various environmental factors such as water quality, feeding, and breeding conditions within the facility, allowing for optimal growth and health of farmed fish.

Fish farming helps address overfishing by providing an alternative source of fish protein that reduces the need for wild-caught fish. By raising fish in controlled environments, fish farms alleviate pressure on depleted wild fish populations, allowing them to recover and maintain ecological balance.

Fish farming contributes to water quality management by implementing measures to control and maintain optimal conditions within facilities. This includes monitoring and regulating factors such as oxygen levels, pH, temperature, and nutrient concentrations to create a healthy environment for fish growth.

Disease prevention in fish farming involves implementing strategies to minimise the risk of pathogens and infections among farmed fish. This includes strict biosecurity measures, regular health monitoring, vaccination programmes, and quarantine protocols to prevent the introduction and spread of diseases within aquaculture facilities.

Fish farming facilitates waste management by controlling and removing waste products generated by farmed fish, such as uneaten feed, faeces, and metabolic by-products. Techniques such as filtration systems help minimise environmental pollution and maintain water quality in facilities.