Biotest, is a new and powerful system to measure environmental stress in organisms, which has been developed and refined using Australian species. It works like this: any organism, whether plant or animal, under stress from, say, heavy metal pollution begins to lose homeostasis - the ability to maintain its physical development at an optimal level. A decline in homeostatic efficiency may result in changes to the organism's biochemical functions, chromosomes, physical appearance or ability to defend itself against infection and parasites; in short, it may lose fitness. These homeostatic changes provide the foundation for what promises to be a reliable, cheap and universal method of environmental assessment.