Stability and Change

**State what ecosystem stability means

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Stays balanced over time
Species survive, recycle nutrients, use energy well

**Give one example of a stable ecosystem

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Amazon rainforest – millions of years old and still functioning well

**State four things needed for ecosystem stability

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Energy supply, nutrient recycling, genetic diversity, stable climate

**Explain why nutrient recycling is important

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Dead stuff is broken down and reused
Without it, the system runs out of key materials

**Explain why sunlight is important in stable ecosystems

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Main energy source → powers photosynthesis

**State what happens if climate goes beyond tolerance

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Species may die or migrate

**Explain how genetic diversity helps ecosystems

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More variation = more chances of survival when conditions change

**Describe how the Amazon rainforest may reach a tipping point

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Too many trees removed → less transpiration → less rain → unstable system

**Explain why transpiration is important in rainforests

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Makes clouds, cools air, causes rainfall

**Calculate % forest lost

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(original - final area) ÷ original × 100

**Define mesocosm

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Mini model of an ecosystem in a container

**Explain why sealed mesocosms are better

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No matter goes in/out → better control of variables

**Give two things that must be included in a mesocosm

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Producers (like moss or algae)
Light source

**Explain what a control mesocosm is for

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Shows if changes came from 1 variable only

**State what a keystone species is

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One species that affects the whole ecosystem a lot

**Give one keystone species and what it does

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Sea otters eat urchins → protect kelp forests

**Explain what happens if a keystone species disappears

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Other species may collapse too → entire ecosystem destabilized

**Define sustainable harvesting

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Taking only what can grow back

**Give one sustainable method for black cherry trees

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Selective cutting → lets new trees grow

**Give one sustainable method for Alaska pollock fishing

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Avoiding bycatch & constant monitoring

**State one reason agriculture may be unsustainable

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Soil erosion removes top layer for growing

**Explain what leaching is

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Fertilizers washed into rivers → pollution

**State one problem with agrochemicals

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Can kill helpful or non-target species

**Explain why farming has a carbon footprint

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Uses fossil fuels for machines & fertilizer

**Define eutrophication

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Too many nutrients in water → algae bloom → oxygen loss

**Explain what BOD means in eutrophication

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Bacteria use up oxygen → fish die

**Define biomagnification

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Pollutants increase at each trophic level

**Give one example of a biomagnified toxin

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DDT – harms birds’ eggs

**Explain how mercury harms top predators

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Builds up in big fish → toxic to humans

**Differentiate macroplastic and microplastic

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*Macro

**State one effect of plastic on animals

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Turtles mistake bags for jellyfish → eat them

**Explain how science communication helped plastic action

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Public saw the effects → demanded change (like paper straws)

**Define rewilding

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Bringing back nature by restoring ecosystems

**Give one method of rewilding

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Reintroduce apex predators (e.g. wolves)

**Give one result of rewilding

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More plant diversity → more animals

**Give an example of rewilding success

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Hinewai Reserve (NZ) – former farmland returned to native forest

**Define ecological succession

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Slow change in species in a place over time

**Give two causes of succession

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Volcanic eruption (abiotic)
Organism dies & enriches soil (biotic)

**Define primary succession

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Starts on bare land (like new rock)

**List steps in primary succession

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Moss → small plants → shrubs → trees → climax community

**Explain what a pioneer species is

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First to grow in harsh conditions (e.g. moss, lichen)

**Define climax community

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Stable, final stage of succession

**Define secondary succession

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Starts on soil after damage (e.g. fire)

**Explain cyclical succession

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Ecosystem changes in a repeating cycle, not one climax

**Give one example of human-influenced succession

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*Grazing by sheep prevents trees from growi