biome
savanna
desert
tundra
plankton
estuary
Littoral zone
Open-water zone
Deep-water zone
wetland
deciduous
temperate
conifers
canopy
steppes
evergreen trees
prairies
permafrost
Marine
Intertidal zone
Coral reef
Benthic zone
Sargasso Sea
pollution
Hazardous waste
overpopulation
Renewable resource
Exotic species
Biodiversity *
Non-renewable resource
deforestation
Point source pollution
Recycle
conservation
biodegradable
Endangered species
Alternative energy sources