Ecosystems as open systems at Higher Level: The same ideas as SL, with Singapore's mangroves and forest and the Belize Barrier Reef.
Practise this as you read
- Name the energy and matter that cross an ecosystem's boundary.
- Outline how losing one ecosystem harms its neighbour.
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A community and its surroundings: An ecosystem is a community and the physical environment with which it interacts.
The points to remember
- An ecosystem is a community plus the physical environment it interacts with.
- Living parts are biotic; non-living parts (soil, water, air, light, temperature) are abiotic.
- Name a local ecosystem precisely: 'deciduous woodland', 'freshwater pond', 'salt marsh'.
- Not enough: a broad group ('terrestrial', 'freshwater ecosystem') or just 'forest'.
- Not an ecosystem: a biome ('taiga biome') is a much larger, worldwide group.
- Ecosystems come in any size: a pond, a wood, a whole reef.
Remember it as: Community + surroundings = ecosystem. Name it exactly, never just 'forest'.
Precise enough
- Temperate deciduous woodland
- Freshwater pond
- Salt marsh
Too broad
- Forest
- Terrestrial ecosystem
- Taiga biome
Real example: Singapore holds a mangrove wetland at Sungei Buloh and tropical rainforest at Bukit Timah, only a few kilometres apart.
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Open and closed systems were met in 1.2.5. Every real ecosystem is open.
The points to remember: open systems
- Ecosystems are open systems: both energy and matter cross their boundary.
- Energy enters as sunlight and leaves as heat.
- Matter enters and leaves: water, nutrients and soil, gases, and living things.
- Living things cross too: seeds blown in, animals migrating or wandering out.
- We draw the boundary, so what counts as an input depends on where we draw it.
Remember it as: Sunlight in, heat out. Water, nutrients, gases and living things in and out.
Real example: at Sungei Buloh, the tide floods the mangroves twice a day, and shorebirds from Siberia arrive to feed each year from about September to March.
Neighbours share their flows: Along warm coasts, mangroves, seagrass and coral reefs sit side by side and pass matter and energy between them.
The points to remember: when one ecosystem is lost
- Open ecosystems are linked, so losing one affects its neighbours.
- Less protection from storm waves and currents for the ecosystem behind it.
- Fewer nursery and breeding grounds for species that move between them.
- Less organic matter and nutrients passed on to the neighbour.
- Cloudier water without filtering or trapping, so less light for photosynthesis.
- Species move in, raising competition; fewer grazing fish can even mean more seagrass.
- Fewer tourists, so less money to protect the neighbouring ecosystem.
Say what happens to the neighbour: 'Biodiversity is lost' or 'the water is cloudier' alone is not enough: say how it harms the neighbouring ecosystem.
Real example: on the Belize Barrier Reef, mangrove cays and seagrass beds shelter young reef fish, so clearing mangroves for building also harms the reef.
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How this comes up: Paper 1 [1]: identify an ecosystem from a map. Paper 1 [2]: outline how losing one ecosystem affects its neighbour.
Figure 1 shows how mangroves, seagrass and a coral reef are linked along a tropical coast. Boat anchors and dredging have destroyed much of the seagrass.
With reference to Figure 1, outline how loss of the seagrass meadow could impact the mangrove forest.
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