1.3: Biomes

biomes: main ecological zones

• biome: an ecological system that covers a large area
  • terrestrial (land-based) biomes on earth
  • eg. deciduous forest, tundra
  • aquatic biomes
  • eg. marine, freshwater
• the climate (precipitation and temperature) determine if a region is a desert or rainforest

example: tundras

• biome with cold temperatures, low precipitation

characteristics of the tundra

• permafrost: a layer of the ground that is “permanently” frozen (below 32 degrees F)
• found in Alaska, Canada, Russia, Scandinavia
• currently thawing
• consequences: release of greenhouse gasses, crumbling infrastructure, risk of diseases

trophic levels in the tundra

• heterotrophs release the energy that they consume through cellular respiration
• all organisms (autotrophs and heterotrophs) can be eaten by decomposers (eg. worms, fungi)

matter and energy in the ecosystem

• matter is recycled within an ecosystem
• energy is not recycled within an ecosystem → it follows a one-way flow
• this is explained by the second law of thermodynamics
• generally, about 90% of energy is lost from one trophic level to another
• note that this energy lost to the ecosystem, not the universe as a whole

ecological pyramids

• pyramid of energy: a representation of amount of energy present at each trophic level of a food web

energy can easily be converted in biomass

• biomass: the total mass of living material
  • measured in units of mass, eg. kg or g

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