Describe an ecosystem as a unit containing the community of organisms and their environment, interacting together

Describe a community as all of the populations of different species in an ecosystem

Describe a population as a group of organisms of one species, living in the same area, at the same time

State the roles of microorganisms in the nitrogen cycle, limited to: decomposition, nitrification, nitrogen fixation and denitrification (generic names of individual bacteria, e.g. Rhizobium, are not required)

Describe the nitrogen cycle with reference to: • decomposition of plant and animal protein to ammonium ions • nitrification • nitrogen fixation by lightning and bacteria • absorption of nitrate ions by plants • production of amino acids and proteins • feeding and digestion of proteins • deamination • denitrification

Describe the carbon cycle, limited to: photosynthesis, respiration, feeding, decomposition, formation of fossil fuels and combustion

Explain, in terms of energy loss, why food chains usually have fewer than five trophic levels

Explain why the transfer of energy from one trophic level to another is often not efficient

Discuss the advantages of using a pyramid of energy rather than pyramids of numbers or biomass to represent a food chain

Draw, describe and interpret pyramids of energy