Biosphere

• Biodiversity and conservation: the web of life
  
• The British National Space Centre's Learning Zone
  
• The atmosphere, by NASA
  
• The atmosphere, by Learner.org
  
• What is the hydrosphere?
  
• Ecology, by the Free Dictionary
  
• Ecology, by Encarta
  
• Backyard ecology
  
• Energy flow in ecosystems
  
• Ecosystems, biomes and habitats
  
• Major biomes of the world
  
• Major Biomes of the World, by Fact Monster
  
• The world's biomes, by the University of California
  
• Nutrient cycles
  
• Decomposition, by the Offwell Woodland & Wildlife Trust