Sustainable resource — replaced as fast as it is removed
A sustainable resource is one produced (replaced) as rapidly as it is removed from the environment, so that it does not run out. The syllabus names two: forests (replanted at the rate they are felled) and fish stocks (allowed to breed back to the level caught). Think of it as a balance — removal rate against replacement rate. If removal exceeds replacement the resource declines toward exhaustion; that is overharvesting, the opposite of sustainable use.
Endangered and extinct — six named causes
Endangered = the population has fallen so far the species is at serious risk of extinction (no living members left). Six named causes: climate change (conditions shift faster than a species can adapt); habitat destruction (loss of the environment it depends on); hunting (for food, products or sport); overharvesting (removal faster than reproduction replaces); pollution; introduced species (non-natives that outcompete or infect natives).
Conservation methods — four Core, then Extended add-ons
Core, any endangered species: monitoring and protecting species/habitats; education; captive breeding; seed banks (stored cool and dry, preserving genetic diversity). (Extended) Forests: education, protected areas, quotas on timber volume, replanting. (Extended) Fish stocks: education, closed seasons, protected areas, controlled net type/mesh size, quotas, monitoring. (Extended) Captive breeding: AI and IVF raise success where natural mating is impractical.
Drawn from real examiner reports.
Sustainable use ≠ never using it
A forest that is never felled at all is not being "used sustainably" — it simply is not being harvested. Sustainability describes an ongoing harvest-and-replace cycle: replanting matches the felling rate, or fish are allowed to breed back to the same stock level before the next catch. Answers that ban all use miss what the syllabus means by sustainable management.
"Looked after" is not the definition
Writing that a sustainable resource is one that is "looked after" or "not overused" misses the two-part balance the mark scheme requires. Both halves must appear: the removal rate AND the replacement rate. Full-credit form is "a resource produced or replaced as rapidly as it is removed, so it does not run out". One element alone will not score the definition mark.
Small population ≠ just fewer animals
Candidates say a shrinking population is risky because "there are not many left", and stop. The creditable chain is: population falls, so fewer breeding individuals carry fewer different alleles (reduced genetic variation), so less variation remains for natural selection to act on if a new disease or climate shift hits — the species cannot adapt, and extinction risk rises.
Flagged w22 P42/43 Q4a iii; s23 P33 Q8d ii — reduced genetic variation in small populations rarely mentioned
Fines and burning earn no credit
For reducing waste pressure on resources, the valid mark-scheme answers are recycling, reusing and biodegradable alternatives. Suggesting that people be fined, or that the waste be burned, is not credited — burning a non-biodegradable material also releases harmful gases. Recycling scores because it cuts the rate at which new raw material must be extracted.
Flagged w22 P32 Q3b — recycling/reusing/biodegradable valid; fines and burning not credited
Quotas ≠ closed seasons
A quota limits HOW MUCH may be caught — a maximum total mass or number of fish, or a maximum area of timber felled. A closed season limits WHEN fishing may happen, banning it during the breeding period so more fish survive to spawn. They answer different threats and can be applied together, so do not offer one as a definition of the other.
Captive breeding ≠ genetic modification
Captive breeding, including AI and IVF, breeds existing individuals of the same species under controlled conditions — no gene is altered. Altering genes directly is genetic engineering, which belongs to Topic 21, not to conservation. Describing a captive breeding programme as "changing the animals' genes to make them survive better" is wrong biology and scores nothing.
Match the method to the threat
Read off the threat the question names, then pick the method that counters it: overharvesting to quotas, closed seasons or mesh size; habitat loss to protected areas; a small population to captive breeding (AI/IVF) or seed banks. Any memorised term will not do.
Name the mechanism, not the label
"Better nets are used" scores nothing. Say what the method does: "a larger mesh size lets young, undersized fish escape the net, so they reach breeding age and replace the stock." On four-mark method questions the label usually carries one mark and the mechanism the other.
Four reasons, four separate marks
Name the specific reason: maintaining or increasing biodiversity; reducing extinction; protecting vulnerable ecosystems; maintaining ecosystem functions (nutrient cycling; resource provision — food, drugs, fuel, genes). "To help the environment" is one vague point, not four.
On data questions, compare removed with replaced
For a table of felled against replanted area, judge each year on its own row rather than on whether the numbers look large. Equal means sustainable; removal above replacement does not. Quote both figures — the comparison earns the mark.
Sustainable resource: a resource that is produced (replaced) as rapidly as it is removed from the environment, so that it does not run out. Named examples: forests, fish stocks.
Endangered species: a species whose population has declined to the point where it is at serious risk of extinction.
Six causes of endangerment/extinction: climate change, habitat destruction, hunting, overharvesting, pollution, introduced species.
Core conservation methods (any endangered species):
| Method | What it involves |
|---|---|
| Monitoring and protecting | surveying population size/habitat condition; legally protecting habitats/reserves |
| Education | raising public awareness of causes and of how to reduce harm |
| Captive breeding programmes | breeding endangered animals in a controlled environment (e.g. a zoo) |
| Seed banks | storing seeds from many plant species in cool, dry, controlled conditions to preserve genetic diversity |
(Extended) Forest-specific methods: education, protected areas, quotas (limits on timber volume cut), replanting.
(Extended) Fish-stock-specific methods: education, closed seasons, protected areas, controlled net types/mesh size, quotas, monitoring.
(Extended) Reasons for conservation programmes (statement 7): (a) maintaining or increasing biodiversity, (b) reducing extinction, (c) protecting vulnerable ecosystems, (d) maintaining ecosystem functions -- limited to nutrient cycling and resource provision (food, drugs, fuel, genes).
(Extended) AI and IVF in captive breeding: artificial insemination (AI) uses collected sperm to fertilise a female without natural mating; in vitro fertilisation (IVF) combines eggs and sperm outside the body, and the resulting embryo is implanted. Both help when natural mating between suitable individuals is difficult, e.g. animals kept far apart, or very few breeding individuals remain.
(Extended) Risk of a shrinking population (statement 9): a smaller population contains fewer alleles (less genetic variation). Less genetic variation means less raw material for natural selection to act on, so the population is less able to adapt to future change (e.g. new disease, changing climate) -- increasing extinction risk. (Genetic drift is not required by name.)
Role of recycling: recycling reduces the rate at which new raw material must be extracted from the environment, helping a resource stay within its sustainable (replace remove) balance; it is one practical contribution to sustainable development -- meeting current human needs without compromising the ability of future generations/ecosystems to meet theirs.
Define a sustainable resource.
(a) Define the term sustainable resource. [2]
(b) State TWO named examples of resources that can be conserved and managed sustainably. [2]
