Biological resources
50 exam-style questions with answers for 3.5 Biological resources in AQA A-level Environmental Science (spec 7447). Practise with flashcards, a topic quiz, a random quiz across the course, 5 crosswords, Five Degrees, Associations, or read every question and answer below. Not official AQA material.
All 50 questions and answers
Question 1
Define ‘maximum sustainable yield’ (MSY). [1 mark]
Answer:The largest catch that can be taken each year without reducing the population’s ability to replace itself.Question 2
Explain how a larger net mesh size reduces by-catch. [2 marks]
Answer:Gaps are bigger, so small fish and juveniles escape. They survive to breed and the population can recover.Question 3
Give one advantage and one disadvantage of monoculture. [2 marks]
Answer:Advantage: one management plan for planting, nutrients and harvest. Disadvantage: pests and disease spread rapidly, so the whole crop is at risk.Question 4
Define the term ‘food conversion ratio’. [1 mark]
Answer:The mass of food needed to produce a given mass of animal biomass.Question 5
Explain why extensive farming has a higher energy ratio than intensive farming. [2 marks]
Answer:Extensive systems have low inputs of fertiliser, machinery and fuel for a lower but still worthwhile yield.Question 6
Describe two cultural pest control methods. [2 marks]
Answer:Any two from: crop rotation, barrier crops, companion crops, predator habitats such as beetle banks.Question 7
Describe the sterile male technique. [2 marks]
Answer:Sterilised males are released to mate with females, which then lay infertile eggs, reducing the pest population.Question 8
Explain why neonicotinoids harm bees. [2 marks]
Answer:They are systemic so reach pollen and nectar, they are neurotoxic and persistent, and they can act synergistically with fungicides.Question 9
State two environmental impacts of intensive aquaculture. [2 marks]
Answer:Organic waste causing deoxygenation, escapes affecting wild gene pools, habitat loss, and pesticide use.Question 10
Describe how catch data may show overfishing. [2 marks]
Answer:Catch per unit effort falls, and mean fish size and age decrease.Question 11
Explain why k-selected species are vulnerable to overexploitation. [2 marks]
Answer:They mature late and breed slowly, so populations recover slowly.Question 12
Describe how no-take zones increase catches. [2 marks]
Answer:Breeding populations are protected and spill over to repopulate fished areas.Question 13
Explain the effect of deforestation on soil. [3 marks]
Answer:Less leaf litter reduces organic matter, there is no root binding, and exposed soil is eroded by rain and wind.Question 14
State two sustainable forest management methods. [2 marks]
Answer:Any two from: mixed species plantations, indigenous species, mixed age structure, selective logging.Question 15
Explain why productivity is highest in upwelling areas. [2 marks]
Answer:Currents bring nutrients from the seabed to the surface where there is light.Question 16
Define the term ‘integrated pest control’. [1 mark]
Answer:Using pesticides only when non-chemical methods do not work.Question 17
Explain why crop rotation helps sustainability. [2 marks]
Answer:Different crops break pest life cycles and use different nutrients, and legumes fix nitrogen.Question 18
Describe how legumes improve soil fertility. [2 marks]
Answer:Root nodule bacteria fix nitrogen into nitrates.Question 19
Describe selective breeding. [2 marks]
Answer:Individuals with desirable traits are bred over generations to improve yield or resistance.Question 20
Define the term ‘transgenics’. [1 mark]
Answer:The transfer of genetic material from one species to another.Question 21
State two advantages of GM crops. [2 marks]
Answer:Pest resistance reducing pesticide use, drought tolerance, higher yield, improved nutrition such as Golden rice.Question 22
State two disadvantages of GM crops. [2 marks]
Answer:Gene transfer to wild plants, toxins passing along food chains, the cost of buying seed again, public opposition.Question 23
Define the term ‘energy ratio’. [1 mark]
Answer:The energy in the food produced divided by the energy input.Question 24
Explain why intensive systems have lower energy ratios. [2 marks]
Answer:They need large energy subsidies for machinery, fertiliser, pesticides and processing.Question 25
Describe how drip irrigation is more sustainable. [2 marks]
Answer:Water is delivered directly to roots, reducing evaporation and over-abstraction.Question 26
Explain how overgrazing damages soil. [2 marks]
Answer:Vegetation is removed and soil compacted, increasing runoff and erosion.Question 27
Describe how demersal trawling damages habitats. [2 marks]
Answer:Nets dragged along the seabed destroy corals and seagrass and stir up sediment.Question 28
Explain how a Turtle Excluder Device (TED) works. [2 marks]
Answer:A spring-loaded hatch in the net lets turtles escape.Question 29
Explain why a minimum catch size helps populations recover. [2 marks]
Answer:Fish grow and breed before they can be caught.Question 30
State one habitat impact of shrimp farming. [1 mark]
Answer:Mangrove forest is cleared to build ponds.Question 31
Define the term ‘productivity’ in agriculture. [1 mark]
Answer:The yield per unit area of land.Question 32
Explain the law of diminishing returns in agriculture. [2 marks]
Answer:Each extra unit of input (eg fertiliser) increases yield (1); but by less than the previous unit, so eventually extra inputs are not worthwhile (1).Question 33
Define the term ‘energy subsidy’ and give an example. [2 marks]
Answer:Energy inputs needed to increase food output (1); eg machinery fuel, fertiliser and pesticide manufacture, transport, processing (1).Question 34
State three ecosystem services provided by forests. [3 marks]
Answer:Any three: carbon storage/atmospheric regulation; regulating the hydrological cycle; soil conservation; habitat and wildlife refuge; climate regulation; recreation.Question 35
Explain how deforestation affects the local hydrological cycle. [3 marks]
Answer:Less interception and transpiration (1); more rainwater reaches the ground and infiltration falls so surface runoff increases (1); greater risk of flooding and less rainfall downwind (1).Question 36
Explain why single-species plantations have low biodiversity. [2 marks]
Answer:Fewer niches, food sources and types of habitat (1); same age and close planting gives uniform light and little ground flora, so few species can live there (1).Question 37
Explain how F1 hybrids give uniform crops. [3 marks]
Answer:F1 hybrids are bred from two true-breeding homozygous varieties (1); so all offspring inherit the same predictable characteristics (1); giving uniform growth rate, ripening and harvest time, making management easier (1).Question 38
Describe how embryo transfer is used in livestock breeding. [3 marks]
Answer:Eggs are taken from a female with desirable traits and fertilised (1); embryos are implanted into surrogate females (1); one female can produce many offspring, and embryos can be frozen (1).Question 39
Explain the risks of using antibiotics as growth promoters. [2 marks]
Answer:Continuous low-level use selects for antibiotic-resistant bacteria (1); resistant pathogens may spread to humans so infections become harder to treat (1).Question 40
Explain how irrigation can cause soil salinisation. [3 marks]
Answer:Irrigation water contains dissolved salts (1); in hot dry conditions water evaporates, leaving salts in the soil surface (1); high salinity causes osmotic dehydration, killing plants and reducing yields (1).Question 41
Explain the disadvantages of high stocking density. [3 marks]
Answer:Faster spread of disease and pests (1); competition and stress, injuries and trampling/soil compaction (1); high inputs of food and nutrients and more waste produced (1).Question 42
Distinguish between demersal and pelagic fishing. [2 marks]
Answer:Demersal fishing targets species living near the seabed such as cod and plaice (1); pelagic fishing targets species in mid-water or near the surface such as herring and tuna (1).Question 43
Explain why purse seining has high catch selectivity. [2 marks]
Answer:Shoals of a single species can be located and encircled (1); so by-catch is low, except for predators following the shoal such as dolphins (1).Question 44
Describe how catch per unit effort (CPUE) is used to monitor fish stocks. [2 marks]
Answer:Calculated from the landed catch and the fishing effort (gear size and time spent fishing) (1); a decline in CPUE suggests that the stock is falling, even if total catch is unchanged (1).Question 45
Explain what ghost fishing is and how it can be reduced. [2 marks]
Answer:Lost or abandoned fishing gear continues to catch and kill marine life (1); reduced by biodegradable rope, escape holes and radio-tracked equipment (1).Question 46
Compare the productivity of open oceans and coastal areas. [3 marks]
Answer:Open oceans have lowest productivity because nutrients sink to the seabed when organisms die (1); coastal areas have medium to high productivity as rivers and wind bring nutrients from land (1); light penetrates the photic zone in both, so nutrients are the main limiting factor (1).Question 47
Explain how fishmeal for aquaculture can put pressure on wild fish stocks. [2 marks]
Answer:Carnivorous farmed fish are fed on wild-caught fish such as sandeels (1); overfishing these fish reduces food for wild predators including seabirds such as puffins (1).Question 48
Describe how Integrated Multi-Trophic Aquaculture (IMTA) reduces pollution. [2 marks]
Answer:Different species are farmed together (1); molluscs and seaweeds absorb and filter organic waste and nutrients released by fish (1).Question 49
Explain how terracing reduces soil erosion on slopes. [2 marks]
Answer:Creates flat steps that slow the flow of water down the slope (1); increases infiltration and reduces runoff so less soil is washed away (1).Question 50
Explain how windbreaks improve crop productivity. [2 marks]
Answer:Hedges or trees reduce wind velocity, so less soil erosion and drying (1); less physical damage to crops such as lodging of cereals (1).