LEARNING OBJECTIVES
What you will be able to do
- evaluate food production
- explain habitat destruction
- describe pollution and eutrophication
- explain sustainable conservation
AT A GLANCE
INTRODUCTION · THE BIG IDEA
How food production, habitat change, pollution and conservation alter biodiversity.
Human activity can increase food supply and economic output while also changing habitats, nutrient cycles and biodiversity. Most decisions therefore involve trade-offs.
Strong evaluations trace a specific action through its biological consequences and distinguish short-term yield from long-term sustainability.
SECTION 01
Food supply
Machinery, fertilisers, insecticides, herbicides and selective breeding increase yield or efficiency but may create environmental and welfare costs.
DETAILED EXPLANATION
- Intensive livestock increases output in limited space, but raises disease, waste and welfare concerns.
SECTION 02
Habitat destruction
Biodiversity is the number of species in an area. Housing, farming, extraction and pollution destroy habitats and alter food webs.
DETAILED EXPLANATION
- Less root binding and interception increase erosion and flooding.
- Less photosynthesis and burning raise carbon dioxide.
- Introduced species may outcompete or prey on native species.
SECTION 03
Pollution and eutrophication
Sewage and fertiliser add mineral ions. Persistent plastics entangle or are eaten by animals. Carbon dioxide and methane enhance greenhouse warming and climate change.
SECTION 04
Conservation
A sustainable resource is replaced as rapidly as removed. Conservation maintains biodiversity, ecosystem functions and resources.
DETAILED EXPLANATION
- Fish: closed seasons, reserves, quotas, mesh controls and monitoring.
- Species: habitat protection, captive breeding, artificial insemination, IVF and seed banks.
- Small populations lose genetic variation and become more vulnerable.
STEP-BY-STEP EXAM EXAMPLE
Explaining eutrophication as a sequence
- Nitrate-rich runoff enters water and promotes rapid algal growth.
- The algal bloom blocks light, so submerged plants die.
- Decomposers feed on dead material and respire aerobically.
- Dissolved oxygen falls, causing aquatic animals to die.
Answer: Nutrient enrichment indirectly causes oxygen depletion through growth, death and decomposition.
QUICK CHAPTER SUMMARY
The ideas to carry forward
- Food methods have trade-offs.
- Habitat loss reduces biodiversity.
- Eutrophication removes dissolved oxygen.
- Greenhouse gases alter climate.
- Sustainable management balances removal and replacement.
QUICK REVISION CHECKLIST
Can you do each of these without your notes?
- evaluate food production
- explain habitat destruction
- describe pollution and eutrophication
- explain sustainable conservation