World biomes — A/L Biology

What must I remember about World biomes?

• A biome is a vast, macro-scale terrestrial or aquatic ecological region characterized by distinct climactic patterns, soil types, and dominant plant and animal growth forms.
• Tropical Rain Forests: Characterized by year-round high temperatures (>25°C), abundant annual rainfall (>2000 mm), nutrient-poor leached soils (oxisols), multi-layered vertical canopy stratification, and the highest terrestrial biodiversity on Earth.
• Temperate Deciduous Forests and Grasslands: Temperate forests feature four distinct seasons, moderate precipitation, and broad-leaved deciduous trees shedding leaves in winter; Temperate grasslands (prairies, steppes) feature cold winters, hot summers, fertile mollisol soils, and dominant perennial grasses maintained by periodic fires and herbivory.
• Taiga (Boreal Coniferous Forest): Largest terrestrial biome, marked by long, severe freezing winters, short cool summers, acidic podzolic soils, and evergreen needle-leaved gymnosperms (spruce, pine, fir) with conical shapes shedding snow load.
• Tundra and Deserts: Tundra features extreme polar cold, low precipitation, and permanent subsoil Permafrost preventing deep root penetration; Deserts feature extreme aridity (<250 mm annual rainfall), extreme diurnal temperature fluctuations, and xerophytic adaptations (CAM photosynthesis, succulent stems, reduced spines).

Test yourself (1 minute)

1. Climatic drivers of biomes (Whittaker's diagram)

   Mean annual temperature and mean annual precipitation are the two primary climactic determinants establishing global biome distribution.

2. Permafrost ecological constraint

   Continuously frozen subsoil in Arctic tundra restricts root growth to shallow active layers and prevents water drainage, creating boggy bogs in brief summers.

3. Nutrient paradox of tropical rainforests

   Despite colossal aboveground biomass, rainforest soils are notoriously nutrient-poor and acidic because high humidity and heat promote immediate microbial decomposition and instant root reabsorption, leaving zero humus reserves.

Practise World biomes questions today

Source: NIE G.C.E. (A/L) Biology Syllabus & Resource Book, Unit 6

What should I study first?

What comes next?

Next in the syllabus

Where does World biomes fit in the syllabus?

Year 2 · Term 2