A biome is the entirety of all the environmental conditions (temperature, humidity, pressure, topography etc.) found in a geographic area, that allow the survival of a particular biota, or set of organisms.

Classification of biomes

Lifezones Pengo.svg

The Holdridge classification of land biomes (1947).

Most biome classifications are more focused on land biomes, which are better understood than aquatic (and especially oceanic) ones.

The chart created in 1947 by the botanist Leslie Holdridge is based on three factors: biotemperature (the average of the monthly temperatures, where all the temperatures lower than freezing are brought to 0°C); precipitations (measured in mm per year) and the potential evapotranspiration ratio (the ratio between the amount of water lost through transpiration and precipitations).

<50 cm/y 50-100 cm/y 100-250 cm/y 250-350 cm/y
< -5 °C Tundra
-5 - 5°C Grassland Taiga (boreal forest)
5-20 °C Steppe Scrubland Deciduous for. Temp. rainforest
20-30 °C Desert Savannah Monsoon for. Tropic. rainforest

Whittaker's classification (1975) considers the yearly temperature average in °C and average precipitations in cm per year (see on the right).

Water biomes

Coastal biomes

Freshwater biomes

Lakes and swamps


Open sea

Cold sea

Temperate sea

Tropical sea

Deep sea

Land biomes


Temperate forest

  • Primary productivity:
  • Biomass production:
  • Example species:

Boreal forest


See main article: Rainforest





Arid biomes



Tundra and ice

Alien biomes


An organism in this biome would have to have balloons or sails to combat the problem of gaining or losing height. If the organism accidentally travels outside of its preferred elevation, the organism would be crushed under immense pressure or be ripped apart because of low air pressure.