See also: Organic, Archaean, Aerobic, Complex Ocean, Simple Land, Complex Land, Extensive

The build up of oxygen (or similar high-energy molecule, such as chlorine on some worlds) enables the evolution of far more complex life forms. The start of this classification sees the arrival of large amounts of sponges, algae and plankton, and by the end complex life forms such as jellyfish, crustaceans and others have arrived.

• Low Oxygen
• High Carbon Dioxide
• OrganicToxins
• Standard
• Tainted

The ecosystem is beginning to fill out now, with complex organic life forms. Very little has evolved hard shells, so jellies and simple plants are about all that is available. The Metazoan classification covers a wide range of evolutionary periods, so whilst some worlds may have little more than algae, others may have more complex forms of resource available.

• Sponges - Basic animals (sort of).
• Metazoa - Basic multi-celled animals other than sponges, includes plankton.
• Ediacaran - Complex organisms centimetres in size.
• Kelp - Large water plants
• Jellies - Large amoebic animals with no hard parts