What is a biome? — A large-scale ecosystem characterized by a dominant type of vegetation and the climate that supports it. Biomes are primarily determined by temperature and precipitation. Examples: desert, rainforest, tundra.

What is the tropical rainforest biome and where is it found? — Found within 5–10° of the equator (ITCZ zone). High rainfall (>2000mm/year), consistently high temperatures (~27°C). Amazon Basin (South America), Congo Basin (Africa), Southeast Asia.

What are key features of tropical rainforest structure? — 4 layers: Emergent (tallest trees >40m), Canopy (dense leaf cover ~30m), Understory (shade-adapted shrubs), Forest floor (dark, nutrient-poor, rapid decomposition). High biodiversity — ~50% of all species.

What is nutrient cycling in tropical rainforests? — Nutrients are held in the biomass (plants), not the soil. When leaves fall, rapid decomposition by fungi and bacteria releases nutrients instantly reabsorbed by tree roots. If trees are removed, nutrients are lost — explaining poor soils after deforestation.

What is the savanna (tropical grassland) biome? — Found 5–20° north and south of the equator, between rainforest and desert. Distinct wet and dry seasons. Tall grasses with scattered drought-adapted trees (acacia, baobab). Home to African megafauna.

What is a hot desert biome and where is it found? — Found at ~30° north and south (subtropical high pressure zones). Rainfall < 250mm/year. Extreme temperature range (hot days, cold nights). Examples: Sahara (Africa), Arabian, Sonoran (USA), Australian Outback.

What adaptations do plants have in hot deserts? — Cacti: Store water in fleshy stems. Long lateral roots absorb surface rainwater. Spines reduce water loss and deter animals. Succulents: CAM photosynthesis (open stomata only at night). Deep taproots. Waxy coatings.

What is a cold desert and give an example? — Cold deserts have very low rainfall AND cold winters. Example: Gobi Desert (China/Mongolia) — freezing winters, hot summers. Antarctic Desert — Earth's largest desert (precipitation < 50mm/year of snow).

What is the temperate deciduous forest biome? — Found at 40–60°N (Western Europe, eastern USA, eastern Asia). Four distinct seasons. Moderate rainfall year-round. Trees shed leaves in winter (oak, beech, ash, maple) to conserve water and energy.

What is the boreal forest (taiga) biome? — The world's largest land biome, found at 50–70°N across Russia, Canada, and Scandinavia. Long, cold winters; short summers. Dominated by coniferous trees (pine, fir, spruce) — needle-shaped leaves reduce water loss and snow accumulation.

What is the tundra biome? — Found at 60–75°N (Arctic regions) and at high altitudes. Permafrost prevents deep root growth. Very low rainfall, extreme cold. Vegetation: mosses, lichens, sedges, dwarf shrubs. Short growing season (6–10 weeks).

What is permafrost? — Permanently frozen ground (soil or rock) below 0°C for at least two consecutive years. Found in tundra and some boreal regions. As it thaws due to climate change, it releases methane — a powerful greenhouse gas.

What is the Mediterranean climate biome? — Found at 30–45° latitude on the west coasts of continents. Hot, dry summers and mild, wet winters. Vegetation: drought-resistant shrubs (chaparral/maquis). Example locations: Mediterranean coast, California, South Africa (Cape), SW Australia.

What is the ITCZ and how does it drive equatorial rainfall? — The Intertropical Convergence Zone is where the trade winds from both hemispheres meet near the equator. Intense solar heating causes hot air to rise, creating low pressure, heavy rainfall, and tropical rainforest climate.

What is the albedo effect? — The proportion of sunlight reflected by a surface. High albedo: Ice, snow, clouds (reflect ~80–90% of sunlight). Low albedo: Forests, oceans (absorb more). As ice melts, albedo decreases → more heat absorbed → more warming (positive feedback).

What is the greenhouse effect? — Solar radiation passes through the atmosphere to warm Earth's surface. Earth radiates infrared radiation (heat), which is absorbed by greenhouse gases (CO₂, CH₄, H₂O vapor, N₂O) and re-emitted back to Earth, keeping it warm.

What are the main greenhouse gases and their sources? — CO₂: Fossil fuels, deforestation. CH₄ (methane): Livestock, rice paddies, landfills, natural gas leaks. N₂O: Agriculture (fertilizers). Water vapor: Evaporation. CFCs: Refrigerants (also deplete ozone).

What is the El Niño Southern Oscillation (ENSO)? — A periodic climate pattern in the Pacific Ocean. El Niño: Warmer-than-normal sea surface temperatures in eastern Pacific → droughts in Australia/SE Asia, heavy rain in Peru/Ecuador. La Niña: Opposite effects. Occurs every 2–7 years.

What are the climate zones by latitude? — 0–10°: Tropical (hot, wet). 10–30°: Subtropical (hot, dry — deserts). 30–60°: Temperate (four seasons). 60–75°: Subarctic/Boreal. 75–90°: Polar (cold, dry). Also: Equatorial, Mediterranean, Monsoon, Continental by ocean distance and wind patterns.

What is deforestation and its impacts? — Removal of forests, primarily for agriculture, logging, and urban expansion. Impacts: loss of biodiversity, increased CO₂, soil erosion, disruption of water cycle, desertification, loss of indigenous communities. Amazon has lost ~20% of its original extent.

What is desertification? — The process by which fertile land becomes desert due to drought, deforestation, and unsustainable land use. Particularly affects the Sahel region (south of the Sahara). Results in food insecurity and forced migration.

What are the threats to tropical rainforests? — Deforestation for cattle ranching (Brazil), palm oil plantations (SE Asia), logging, mining, and dam construction. Rate: ~4.7 million hectares lost per year. Consequences: Loss of biodiversity, carbon release, disrupted rainfall patterns.

What is coral bleaching and what causes it? — When sea temperatures rise, corals expel their symbiotic algae (zooxanthellae), turning white. Without algae, corals lose their food source and die. Caused by climate change and ocean warming. The Great Barrier Reef has experienced mass bleaching events.

What is the water cycle (hydrological cycle)? — The continuous movement of water through evaporation (ocean/land → atmosphere), condensation (clouds form), precipitation (rain/snow), surface runoff, infiltration, and transpiration (plants). Rivers return water to the ocean.

What is biome shifting? — As temperatures rise due to climate change, climatic zones are moving poleward and to higher altitudes. Species must migrate, adapt, or face extinction. Tundra biome is shrinking as boreal forest advances northward.