Ecosystems and interactions
An ecosystem is the living and non-living parts of an area together, and each organism is named by the role it plays.
A worked example
Counting 15 clover plants in a 5 m by 5 m square gives 15 / 25 = 0.6 plants per square metre, so a 2 000 m2 field holds roughly 1 200.
The mistake people actually make
Decomposers are not just another kind of consumer. They break dead material down and return the nutrients to the soil. When scaling a sample up, work from the sample's area, not the length of one side.