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