Biodiversity or biological diversity is defined as:
The variety of all living things, including plants, animals and micro-organisms, the genes they contain, and the ecosystems of which they form a part. It is not static, but is constantly changing. It is increased by genetic change and evolutionary processes and reduced by processes such as habitat degradation, population decline, and extinction.
(National Strategy for the Conservation of Australia’s Biological Diversity (DEST 1996))