When stressed (usually by warming), corals expel their symbiotic zooxanthellae (algae that provide colour and food), turning white. They can recover if stress eases, but die if it persists. Learn it step by step →
Ecosystems is a core part of A-Level Geography. Revise the key concepts and common mistakes below, then lock them in with the free games.
Habitat FragmentationBreaking up of ecosystems into isolated patches by roads, farms; reduces species viability; e.g. Atlantic rainforest 12% remaining.
Rewilding KneppSussex estate restored from intensive farming since 2001; reintroduced large herbivores; turtle dove, nightingale, purple emperor returned.
Global heat budgetThe balance between incoming shortwave solar radiation and outgoing longwave radiation; a surplus at low latitudes and deficit at the poles drives circulation.
Global atmospheric circulationThe Hadley, Ferrel and Polar cells redistribute heat from the equator towards the poles, creating belts of high and low pressure.
What your exam board covers
Where Ecosystems sits in each exam board's specification. Tap a board to see what it lists.
Questions where students often pick the tempting wrong answer — make sure you know the right one:
What is coral bleaching?✗ Coral bleaching is when coral is killed by sunlight bleaching its colour.✓ When stressed (usually by warming), corals expel their symbiotic zooxanthellae (algae that provide colour and food), turning white. They can recover if stress eases, but die if it persists.
What is the ITCZ and why does it bring rain?✗ The ITCZ is a fixed band of permanent storms at the equator.✓ The Intertropical Convergence Zone is where trade winds from both hemispheres converge near the equator, forcing air to rise, cool and produce heavy convectional rainfall.
Practise Ecosystems — free games
Test yourself with these quick revision games for this topic:
