Use of Biological Resources

What you'll learn

This topic examines how humans exploit living organisms and biological processes to produce food and other resources sustainably. You'll explore food production methods including crop cultivation, livestock farming, fish farming, and the industrial use of microorganisms. Understanding the balance between maximizing yields and environmental sustainability is essential for exam success.

Key terms and definitions

Selective breeding — the process of choosing organisms with desirable characteristics to breed together to produce offspring with improved traits

Monoculture — the cultivation of a single crop species over a large area

Biological control — the use of natural predators, parasites or diseases to control pest populations

Fermentation — the anaerobic breakdown of glucose by microorganisms, producing useful products such as ethanol or lactic acid

Mycoprotein — protein-rich food produced from the fungus Fusarium for human consumption

Eutrophication — the excessive enrichment of water bodies with nutrients, leading to algal blooms and oxygen depletion

Sustainable development — meeting present needs without compromising the ability of future generations to meet their own needs

Intraspecific variation — differences between individuals of the same species

Core concepts

Food production and crop yields

Maximizing crop yields requires optimizing growth conditions while managing costs and environmental impact. Farmers manipulate several factors:

Light availability

• Spacing plants appropriately to minimize shading
• Removing competing weeds that absorb light
• Using greenhouses to extend growing seasons in temperate climates

Nutrient supply

• Applying fertilizers containing nitrogen, phosphorus and potassium
• Organic fertilizers (manure, compost) improve soil structure but release nutrients slowly
• Inorganic/artificial fertilizers provide precise nutrient ratios but risk leaching into waterways

Water availability

• Irrigation systems deliver water to roots efficiently
• Drainage prevents waterlogging which restricts root respiration
• Mulching reduces water loss through evaporation

Pest and disease control

• Pesticides kill unwanted organisms but may harm beneficial species and accumulate in food chains
• Biological control uses natural predators (e.g., ladybirds eating aphids) without chemical residues
• Crop rotation prevents pathogen build-up in soil
• Growing pest-resistant varieties reduces chemical dependence

Temperature optimization

• Greenhouses trap heat, enabling crop production in cooler climates
• Controlled environments maintain optimal temperatures for enzyme activity and growth

The benefits of monoculture include specialized machinery use, uniform harvesting, and efficient pest management. However, disadvantages include increased disease spread, soil nutrient depletion, reduced biodiversity, and greater pest vulnerability.

Livestock production and management

Intensive animal farming maximizes protein production per unit area but raises welfare and environmental concerns.

Energy efficiency in food chains

• Only approximately 10% of energy transfers between trophic levels
• Feeding crops directly to humans is more energy-efficient than producing meat
• However, livestock can graze land unsuitable for crop cultivation

Intensive livestock farming methods

• Restricting movement reduces energy loss through respiration, increasing growth rates
• Maintaining warm, controlled environments minimizes energy expenditure on thermoregulation
• High-protein feed accelerates muscle development
• Antibiotics prevent disease in crowded conditions (though this contributes to antibiotic resistance)

Environmental impacts

• Methane production from cattle contributes to greenhouse gas emissions
• Slurry runoff causes eutrophication in water bodies
• Deforestation for pasture reduces carbon dioxide absorption
• High water consumption strains resources in drought-prone regions

Welfare considerations

• Confined spaces cause stress and restrict natural behaviors
• Ethical debates balance animal welfare against food production efficiency
• Free-range and organic farming systems offer alternatives with lower yields

Fish farming and sustainable fisheries

Aquaculture (fish farming) supplements declining wild fish stocks while creating environmental challenges.

Advantages of fish farming

• Controlled breeding increases predictable yields
• Selective feeding improves growth rates
• Protection from predators reduces losses
• Reduced pressure on wild populations

Disadvantages and environmental concerns

• High-density populations spread diseases and parasites
• Antibiotics and pesticides contaminate surrounding waters
• Escaped farmed fish compete with or interbreed with wild populations
• Uneaten feed and waste cause local eutrophication
• Carnivorous farmed fish require wild-caught fish for feed, transferring rather than solving overfishing

Sustainable fishing practices

• Setting catch quotas based on scientific stock assessments
• Implementing minimum net mesh sizes to allow juvenile fish to escape and reproduce
• Establishing protected breeding areas and seasonal fishing bans
• Reducing bycatch through selective fishing gear
• International cooperation to prevent illegal fishing

Selective breeding programmes

Selective breeding exploits intraspecific variation to develop organisms with enhanced characteristics.

The selective breeding process

1. Identify organisms displaying desirable traits (high yield, disease resistance, quality)
2. Select and breed individuals with the strongest expression of target characteristics
3. Select offspring showing the best combination of desired features
4. Repeat over multiple generations to establish consistent traits
5. Inbreed closely related individuals to maintain uniformity

Examples of selective breeding

• Cattle: increased milk yield, improved meat quality, docile temperament
• Wheat: shorter, stronger stems resist wind damage (lodging), higher grain production
• Disease-resistant crop varieties reducing pesticide requirements

Limitations and concerns

• Reduced genetic diversity increases vulnerability to new diseases or environmental changes
• Inbreeding can expose harmful recessive alleles, causing genetic disorders
• Time-intensive process requiring many generations
• Loss of other potentially valuable traits during selection

Microorganisms in food production

Microorganisms produce various foods through fermentation and other metabolic processes.

Bacterial fermentation — yogurt production

• Lactobacillus bacteria convert lactose (milk sugar) into lactic acid
• Lactic acid lowers pH, denaturing milk proteins to create thick texture
• Acidic conditions preserve the product by preventing harmful bacterial growth
• Process occurs at approximately 40°C for optimal bacterial enzyme activity

Fungal fermentation — bread production

• Yeast (Saccharomyces cerevisiae) respires anaerobically, producing ethanol and carbon dioxide
• Carbon dioxide bubbles become trapped in gluten, causing dough to rise
• Baking evaporates ethanol and denatures proteins, setting the structure
• Temperature control (warm, not hot) prevents enzyme denaturation

Mycoprotein production

• The fungus Fusarium venenatum is cultured in industrial fermenters
• Requires glucose (from maize starch), oxygen, nitrogen source, and minerals
• Continuous culture in controlled conditions produces biomass rapidly
• Harvested fungal protein provides meat-alternative high in protein and fiber, low in saturated fat
• Advantages: faster growth than livestock, lower environmental impact, uses waste materials

Industrial fermenter design features

• Sterile conditions prevent contamination by unwanted microorganisms
• Temperature control through water jackets maintains optimal enzyme activity
• pH monitoring and adjustment sustains metabolic efficiency
• Oxygen supply (for aerobic processes) via air pumps and stirring
• Nutrient supply continuously or in batches depending on product requirements

Environmental sustainability and conservation

Balancing resource use with environmental protection ensures long-term food security.

Eutrophication process

1. Fertilizers/sewage enter water bodies through runoff or leaching
2. Excessive nitrates and phosphates stimulate rapid algal growth
3. Dense algal blooms block light penetration to deeper water
4. Submerged plants cannot photosynthesize and die
5. Aerobic bacteria decompose dead organic matter, depleting oxygen
6. Aquatic animals suffocate as dissolved oxygen drops
7. Ecosystem collapse occurs with only anaerobic bacteria surviving

Strategies to reduce eutrophication

• Apply fertilizers precisely when crops actively grow
• Avoid application before heavy rainfall
• Create buffer zones with vegetation along waterways
• Treat sewage before discharge
• Use slow-release fertilizers reducing leaching

Sustainable resource management principles

• Maintain biodiversity to preserve ecosystem resilience
• Replenish resources at rates matching or exceeding consumption
• Minimize waste production and pollution
• Consider economic viability alongside environmental protection
• Educate stakeholders about long-term consequences of unsustainable practices

Conservation priorities

• Protecting habitats from agricultural expansion
• Maintaining hedgerows and field margins for wildlife corridors
• Reducing pesticide use to protect pollinator populations
• Preserving genetic diversity in crops and livestock for future breeding programmes

Worked examples

Example 1: Comparing food production efficiency

Question: Explain why producing beef protein is less energy-efficient than producing wheat protein. (4 marks)

Answer:

• Energy is lost between trophic levels / only approximately 10% transfers to the next level (1)
• Cattle use energy for respiration/movement/maintaining body temperature (1)
• This energy is lost as heat/not available in meat (1)
• Growing wheat for direct human consumption has fewer energy transfers/is shorter food chain (1)

Example 2: Fish farming sustainability

Question: A fish farm releases waste into a nearby lake, causing eutrophication. Describe how this process leads to oxygen depletion in the lake. (5 marks)

Answer:

• Nutrients/nitrates from waste increase in the water (1)
• Algae grow rapidly/algal bloom occurs (1)
• Light is blocked from reaching deeper water/plants below surface (1)
• Plants die/cannot photosynthesize (1)
• Bacteria decompose dead plant material (1)
• Bacteria use oxygen for aerobic respiration/oxygen is depleted (1) [Award any 5 marks]

Example 3: Selective breeding application

Question: A farmer wants to develop wheat plants that are resistant to a fungal disease. Outline the steps the farmer should take. (4 marks)

Answer:

• Identify/select wheat plants showing disease resistance (1)
• Breed these resistant plants together (1)
• Select offspring that show the best/strongest resistance (1)
• Repeat the process over several/many generations (1)

Common mistakes and how to avoid them

• Confusing selective breeding with genetic engineering — selective breeding uses natural reproduction between organisms of the same species; genetic modification transfers genes between different species using technology. Only describe traditional breeding techniques unless the question specifically mentions genetic modification.

• Stating that fertilizers directly cause algae death — fertilizers cause excessive algal growth; it's the subsequent blocking of light and bacterial decomposition that depletes oxygen. Describe the complete eutrophication sequence in the correct order.

• Claiming intensive farming is always wrong or always right — questions require balanced evaluation. Acknowledge both advantages (efficiency, lower costs, feeding populations) and disadvantages (welfare concerns, environmental damage, antibiotic resistance).

• Forgetting energy loss mechanisms in food chains — be specific about how energy is lost (respiration, heat, movement, excretion, not all biomass eaten) rather than just stating "energy is lost."

• Mixing up aerobic and anaerobic respiration in fermentation — yeast ferments anaerobically in bread-making (producing CO₂ and ethanol); mycoprotein production requires aerobic respiration. Check which process the question describes.

• Describing only chemical control methods — when asked about pest control, include biological control and other non-chemical alternatives. Examiners reward knowledge of sustainable practices.

Exam technique for "Use of Biological Resources"

• Command word precision — "Describe" requires stating what happens; "Explain" requires reasons/mechanisms. For "Suggest", apply knowledge to unfamiliar contexts, indicating your answer is reasoned but not definitive (e.g., "This may be because...").

• Mark allocation guides detail — a 4-mark question requires four distinct points. Use the mark allocation to judge answer length; one developed point per mark available. Lists of simple points are acceptable if they address the question.

• Use correct scientific terminology — replace vague language ("things," "stuff") with precise terms (eutrophication, intraspecific variation, selective breeding). This demonstrates understanding and earns credit in "quality of written communication" marks.

• Apply knowledge to data — questions often present graphs showing fertilizer application rates, fish stock changes, or crop yields. Quote specific values from the data, calculate differences, and link observations to biological principles for full marks.

Quick revision summary

Humans maximize food production by controlling environmental factors (light, water, nutrients, temperature, pests) while managing sustainability. Monoculture increases efficiency but reduces biodiversity. Intensive livestock farming improves yields through movement restriction and controlled feeding but raises welfare and environmental concerns. Fish farming supplements wild stocks but may cause pollution. Selective breeding develops desirable traits through repeated selection over generations. Microorganisms produce foods via fermentation (yogurt, bread) and fungal protein (mycoprotein). Eutrophication from fertilizer runoff causes oxygen depletion through algal blooms and decomposition. Sustainable practices balance production with long-term resource conservation.