The Living World — AQA GCSE Geography

This unit looks at ecosystems and two global biomes: tropical rainforests and hot deserts (or cold environments).

Ecosystems

An ecosystem is a community of plants and animals interacting with each other and the non-living (abiotic) environment. Key terms: producer, consumer, decomposer, food chain, food web, nutrient cycling. A small-scale UK ecosystem (e.g. a freshwater pond) shows how a change to one component affects the whole system. Global ecosystems (biomes) — such as tropical rainforest, hot desert, tundra and deciduous forest — are distributed in broad bands related to climate.

Tropical rainforests

Rainforests have a hot, wet climate all year. They have distinctive characteristics: layered structure (emergents, canopy, under-canopy, shrub layer), high biodiversity, and rapid nutrient cycling. Plants and animals show adaptations (e.g. drip-tip leaves, buttress roots, lianas, camouflage). Rainforests have high biodiversity that is interdependent and fragile.

Deforestation is caused by logging, farming (cattle ranching, soy), mineral extraction, energy development, road building and settlement. Impacts include economic gains but also soil erosion, loss of biodiversity and contribution to climate change. Rainforests should be managed sustainably through selective logging, replanting, conservation, education, ecotourism, international agreements and reducing debt. A case study of a tropical rainforest is required.

Hot deserts (or cold environments)

Hot deserts have an extreme climate (very hot days, cold nights, very low rainfall). Plants and animals are adapted to the lack of water and heat (e.g. cacti with spines and water storage, nocturnal animals). Biodiversity is lower than the rainforest. Deserts offer development opportunities (mineral extraction, energy, farming, tourism) but face challenges (extreme temperatures, water supply, inaccessibility). Desertification (the spread of desert-like conditions) is caused by climate change and human activities (over-grazing, over-cultivation, removal of fuel wood); it can be reduced by water/soil management, tree planting and appropriate technology.

Exam tips

• Learn the key ecosystem vocabulary and how components are interdependent.
• Use named case studies for the rainforest and the hot desert (or cold environment).
• Explain plant/animal adaptations clearly.
• Distinguish causes, impacts and management of deforestation and desertification.