Key Terms: Biomes (AQA A Level Geography): Revision Note

Nature of biomes - key terms

Altitude – Increasing height above sea level leads to lower temperatures, reduced vegetation growth, and decreased biodiversity.

Biome – A large, naturally occurring ecosystem defined by its climate, vegetation, and animal life (e.g. tropical rainforest, tundra).

Climate – The long-term pattern of temperature and precipitation, which determines the type and distribution of biomes.

Continentality – Describes how inland areas experience greater temperature extremes than coastal areas due to the absence of moderating oceans.

Latitude – The distance from the equator; affects temperature and sunlight levels, influencing the distribution of biomes.

Limiting factors – Environmental conditions, such as rainfall or temperature, that restrict the growth and distribution of plants and animals.

Ocean currents – Large-scale flows of seawater that influence regional climate and biome distribution by transferring heat.

Relief – The shape and height of the land; steep slopes limit soil formation and plant growth.

Tropical rainforest biome - key terms

Canopy – The dense upper layer of the rainforest formed by the tops of trees, where most photosynthesis and biodiversity occur.

Emergent layer – The highest layer of the rainforest, made up of tall trees that receive the most sunlight.

Epiphytes – Plants that grow harmlessly on other plants (e.g. orchids), obtaining nutrients from rain and air.

Humus – Organic material formed from decomposed plant and animal matter, crucial for retaining nutrients in rainforest soil.

Latosols – Deep, red tropical soils low in nutrients due to intense weathering and leaching.

Leaching – The removal of nutrients from the soil by heavy rainfall, common in rainforest environments.

Net Primary Productivity (NPP) – A measure of how much energy is stored by plants through photosynthesis after respiration; very high in rainforests.

Nutrient cycling – The rapid movement of nutrients through biomass, litter, and soil, accelerated by warm and wet conditions.

Shrub layer – The lowest layer in the rainforest, where only 5% of light reaches, supporting shade-tolerant plants.

Tropical rainforest – A biome found near the equator, characterised by high temperatures, heavy rainfall, and exceptional biodiversity.

Under-canopy – The layer beneath the canopy, consisting of smaller trees and lianas competing for limited light.

Human activity and rainforests - key terms

Agriculture – A leading cause of deforestation, especially through slash-and-burn farming and monoculture plantations like palm oil or soy.

Carbon emissions – Deforestation releases stored carbon dioxide, contributing to global warming.

Deforestation – The large-scale removal of forest, often for farming, logging, or infrastructure development, causing environmental damage.

Debt-for-nature swap – An agreement where a nation’s debt is reduced in exchange for commitments to protect natural ecosystems.

Ecotourism – Environmentally responsible travel aimed at conserving ecosystems and benefiting local communities.

Hydroelectric power (HEP) – Large dams built in rainforest regions for energy production, often flooding habitats and displacing people.

Logging – The commercial harvesting of trees, which often leads to habitat loss, erosion, and ecosystem degradation.

REDD programme – A global initiative (Reducing Emissions from Deforestation and Forest Degradation) that supports sustainable forest management.

Selective logging – The cutting of specific valuable trees, which can still lead to ecosystem disruption and increased vulnerability to erosion.

Settlement growth – Expansion of human habitation into rainforest areas, driven by population pressure and land needs.

Sustainability – Managing rainforest resources in a way that meets present needs without harming future ecological balance.

TNC involvement – Transnational corporations play a major role in deforestation through resource extraction and agricultural investment.

Savanna grassland biome - key terms

Acacia tree – A drought-tolerant tree with adaptations like deep roots, thorns, and a flat canopy to survive savanna conditions.

Baobab tree – Known as the “Tree of Life,” it stores water in its trunk and provides food, shelter, and shade in savannas.

Climatic savanna – Naturally occurring grassland maintained by seasonal drought and wildfires.

Derived savanna – Grassland formed by human activity, such as deforestation or grazing, often replacing former forest.

Edaphic savanna – Savanna shaped by soil conditions rather than climate, found on poor or shallow soils.

Grass tuft – Clumps of drought-resistant grass adapted to dry, fire-prone savanna environments.

Savanna – A tropical grassland biome characterised by seasonal rainfall, scattered trees, and grazing animals.

Seasonality – Savannas experience distinct wet and dry seasons, which influence plant growth and animal migrations.

Whistling thorn – A tree with a symbiotic relationship with ants, providing mutual protection and nutrition.

Human activity and savanna grasslands - key terms

Bushmeat trade – The hunting of wild animals for meat, which poses a threat to biodiversity and species survival.

Desertification – The degradation of land into desert, often caused by overgrazing, deforestation, and poor land management.

Game reserves – Protected areas that limit human activity and help conserve savanna biodiversity.

Land fragmentation – Breaking up of continuous savanna ecosystems due to roads, farming, and settlements, reducing connectivity for wildlife.

Overgrazing – Excessive grazing by livestock that depletes vegetation, exposes soil, and accelerates erosion.

Poaching – Illegal hunting of animals, especially for ivory and horn, which threatens species survival and ecosystem balance.

Population pressure – Increasing human populations in savanna areas lead to higher demand for land, food, and water.

Soil erosion – The wearing away of topsoil due to overgrazing, agriculture, and deforestation, reducing land productivity.

Sustainable tourism – Responsible travel practices that aim to minimise impact on the environment and support local conservation efforts.

Trophy hunting – The targeted killing of animals for sport, which can disrupt savanna ecosystems and skew population structures.

Water abstraction – The removal of water from natural sources for agriculture or domestic use, often reducing availability for native species.