Pollution and Conservation
BiologyΒ· 20.3, 20.4Β· 18 min read
1. Core: Types and Impacts of Pollutionβ β ββββ± 6 min
Pollution is the introduction of harmful substances into the environment by human activity, leading to negative impacts on living organisms and ecosystem health. The three core pollution types assessed are air pollution (greenhouse gases), water pollution (sewage, excess fertilisers), and plastic pollution.
Pollution
The addition of substances to the environment by human activity at a rate that causes harm to living organisms, as the substances cannot be broken down naturally fast enough to avoid damage.
Greenhouse gases (COβ from fossil fuel combustion, CHβ from cattle farming and landfill) trap heat in the Earth's atmosphere. The enhanced (human-caused) greenhouse effect leads to global warming, with consequences including melting polar ice caps, rising sea levels, more frequent extreme weather events, and disruption of food webs as species habitats change.
Untreated sewage causes oxygen depletion in water bodies, killing fish and aquatic invertebrates. Excess chemical fertiliser runoff from farmland also damages aquatic ecosystems. Plastic pollution harms wildlife via entanglement, ingestion of plastic fragments, and leaching of toxic chemicals into soil and water.
State three negative impacts of plastic pollution on terrestrial and aquatic ecosystems.
- 1
- Select syllabus-aligned impacts to guarantee marks:
- 2
First impact: Aquatic animals such as sea turtles and seabirds become entangled in plastic waste, leading to injury or death.
- 3
Second impact: Animals mistake small plastic fragments for food, causing internal blockages, poisoning, and starvation from reduced nutrient absorption.
- 4
Third impact: Plastic breaks down into microplastics that accumulate in food chains, eventually reaching top consumers including humans, with potential long-term health effects.
Exam tip:
Stick to syllabus-listed pollution impacts to gain full marks; off-syllabus examples (e.g. CFCs) will not be awarded marks unless provided in question context.
2. Core: Conservation Principles and Methodsβ β ββββ± 5 min
Conservation is the protection and sustainable management of natural resources and ecosystems to maintain biodiversity. Biodiversity is important because it supports ecosystem stability, provides food and medicine resources, and maintains natural services such as pollination and flood regulation.
Conservation
The process of protecting and maintaining ecosystems, species, and genetic diversity to ensure natural resources are available for future generations.
Key core conservation methods include: protected areas such as national parks and nature reserves, where harmful human activity is restricted to reduce habitat destruction
Captive breeding programmes for endangered species, followed by reintroduction into wild habitats when populations are stable
Sustainable harvesting of natural resources (e.g. selective logging, fishing quotas) to prevent overexploitation
Reduction, reuse and recycling of materials to reduce pollution and lower the rate of raw material extraction
Describe two ways that national parks help to conserve biodiversity.
- 1
- Link national park rules directly to measurable biodiversity benefits:
- 2
First method: National parks restrict destructive activities such as deforestation, mining, and unregulated tourism, preventing habitat destruction for native species and allowing populations to recover.
- 3
Second method: Many national parks run active monitoring programmes for endangered species, allowing rangers to address threats such as poaching or invasive species before they cause local extinctions.
3. Extended Only: Eutrophication and Greenhouse Effect Evaluationβ β β β βExtended onlyβ± 7 min
π« No Calculator
Extended learners must understand the detailed mechanism of eutrophication, explain the difference between natural and enhanced greenhouse effect, and evaluate the effectiveness of different pollution reduction strategies.
Eutrophication
The process by which excess nutrients enter aquatic ecosystems, leading to excessive algal growth, oxygen depletion, and death of aerobic aquatic organisms.
Excess nitrate/phosphate from fertiliser runoff or untreated sewage enters a river or lake
Nutrient surplus causes rapid algal growth (algal bloom) on the water surface
Algal bloom blocks sunlight from reaching submerged aquatic plants, which die as they cannot photosynthesise
Aerobic bacteria decompose dead plant matter, using up large amounts of dissolved oxygen in the water
Dissolved oxygen levels drop so low that fish and aquatic invertebrates die from oxygen starvation; anaerobic bacteria release toxic waste products into the water
Explain why excess fertiliser runoff from farmland leads to the death of fish in a nearby river.
- 1
- Follow the syllabus eutrophication sequence, linking each step to the next:
- 2
Step 1: Excess nitrate and phosphate ions from the fertiliser are washed into the river by rainwater runoff.
- 3
Step 2: High nutrient concentrations cause an algal bloom on the river surface, blocking sunlight from reaching submerged water plants.
- 4
Step 3: Submerged plants cannot photosynthesise, so they die.
- 5
Step 4: Decomposer bacteria feed on dead plant material, respiring aerobically and using up large amounts of dissolved oxygen in the river water.
- 6
Step 5: Dissolved oxygen concentrations fall below the level required for fish to survive, so the fish suffocate and die.
Exam tip:
Eutrophication questions require steps to be written in the correct sequence to gain full marks; if steps are out of order, you will lose marks even if all steps are included.
4. Extended Only: Evaluating Conservation Strategiesβ β β ββExtended onlyβ± 4 min
Extended candidates are expected to evaluate the advantages and disadvantages of different conservation methods, rather than just list them, for 3+ mark questions.
Comparison of two common conservation strategies:
Captive breeding programmes
Breeding endangered species in controlled zoo or sanctuary environments, then reintroducing them to wild habitats when populations are stable
+ Pros: Prevents extinction of critically endangered species with very small wild populations; Allows genetic monitoring to avoid inbreeding; Supports public education about conservation issues
β Cons: High cost to run programmes and monitor reintroduced populations; Captive-bred individuals may lack wild survival skills; Does not address root causes of population decline (e.g. habitat destruction) if unaddressed before reintroduction
Sustainable fishing quotas
Legal limits on the number and size of fish that can be caught from a specific area each year
+ Pros: Prevents overfishing of commercially valuable species, allowing populations to recover; Supports long-term livelihoods of fishing communities; Relatively easy to enforce via patrols and catch inspections
β Cons: Can cause short-term economic hardship for small fishing communities if quotas are set low; Illegal unreported fishing reduces effectiveness if enforcement is weak; May result in high levels of bycatch of non-target species if not designed carefully
Evaluate the use of reforestation (planting new trees) as a strategy to reduce atmospheric carbon dioxide levels.
- 1
- Include both advantages and disadvantages to demonstrate evaluation, as required for extended questions:
- 2
Advantage: Trees absorb COβ from the atmosphere during photosynthesis, locking it away in woody biomass for decades, directly reducing greenhouse gas concentrations.
- 3
Advantage: Reforestation also provides new habitats for native species, supporting biodiversity and reducing soil erosion.
- 4
Disadvantage: Newly planted trees take many years to reach maturity and maximum COβ absorption rate, so it is not a fast solution to rising emissions.
- 5
Disadvantage: Non-native tree species may outcompete native plants, reduce local biodiversity, or be vulnerable to disease leading to mass die-offs that release stored carbon back into the atmosphere.
5. Common Pitfalls
Wrong move:
Listing CFCs or nitrous oxide as greenhouse gases for core questions
Why:
The 0610 syllabus only requires core learners to name COβ and CHβ as main greenhouse gases; extra gases will not gain marks and waste time
Correct move:
Only reference COβ and CHβ unless a question explicitly mentions other gases in its context
Wrong move:
Mixing up the order of eutrophication steps (e.g. stating oxygen drops before decomposers act)
Why:
Eutrophication questions are sequential, so steps must be in the correct order to gain full marks
Correct move:
Use the N-A-S-D-O mnemonic to remember the correct sequence of eutrophication steps
Wrong move:
Stating that the greenhouse effect is always harmful
Why:
The natural greenhouse effect keeps the Earth warm enough to support life; only the enhanced (human-caused) greenhouse effect leads to harmful global warming
Correct move:
Distinguish between natural (beneficial) and enhanced (harmful) greenhouse effect when answering extended questions
Wrong move:
Only listing advantages for evaluation questions
Why:
Extended evaluation questions require balanced responses with both positives and negatives to gain full marks
Correct move:
Always include at least one advantage and one disadvantage when asked to evaluate a strategy
Wrong move:
Referencing off-syllabus climate change impacts (e.g. spread of tropical diseases)
Why:
Only impacts explicitly listed in the 0610 syllabus are awarded marks; off-syllabus points are ignored
Correct move:
Stick to listed impacts: melting ice, rising sea levels, extreme weather, food web disruption, habitat loss
6. Quick Reference Cheatsheet
Topic | Core Content | Extended Only Content |
|---|---|---|
Air Pollution | COβ (fossil fuels) and CHβ (cattle, landfill) as greenhouse gases; global warming impacts | Enhanced greenhouse effect mechanism; evaluate emission reduction strategies |
Water Pollution | Sewage and excess fertilisers harm aquatic ecosystems | Full sequence of eutrophication steps, explain each stage |
Plastic Pollution | 3 core impacts: entanglement, ingestion, toxic leaching | Evaluate effectiveness of plastic reduction strategies (bans, recycling, taxes) |
Conservation | List core methods: protected areas, captive breeding, sustainable harvesting, reduce/reuse/recycle | Evaluate pros and cons of all conservation methods, link to biodiversity benefits |
7. Frequently Asked
What greenhouse gases do I need to know for 0610?
You only need to name carbon dioxide (COβ) and methane (CHβ) as the main greenhouse gases for both core and extended papers. Do not reference CFCs or nitrous oxide unless explicitly provided in question context.
Is eutrophication assessed on the core paper?
No, eutrophication mechanisms and sequence are only examined in extended papers (2 and 4). Core learners only need to know that excess fertilisers and sewage harm aquatic ecosystems.
What counts as evaluation for extended questions?
Evaluation requires you to provide both advantages and disadvantages of a given strategy, plus a balanced conclusion if asked, to gain full marks.
Going deeper
What's Next
Now that you have mastered pollution and conservation content for CIE IGCSE Biology 0610, you are ready to move on to biotechnology content, the final section of Unit 15. You should also practice structured response questions from past papers 3 (core) and 4 (extended) to apply your knowledge, paying close attention to mark scheme keywords to maximise your score. Make sure to review the common pitfalls and use the cheatsheet for last-minute revision before your exam, as this topic appears frequently in both short and long answer questions. If you struggled with eutrophication, revisit the extended section sequence and practice writing the steps out in order to avoid mixing up stages.