Biodiversity is not easily defined. Try What is Biodiversity? and Defining The 'B' Word for approaches with differing emphases. Below is a definition adapted from the World Resources Institute, World Conservation Union, and United Nations Environment Programme in Global Biodiversity Strategy 1992.

"Biodiversity is the totality of genes, species, and ecosystems in a region... Biodiversity can be divided into three hierarchical categories -- genes, species, and ecosystems -- that describe quite different aspects of living systems and that scientists measure in different ways.

Genetic diversity refers to the variation of genes within species. This covers distinct populations of the same species (such as the thousands of traditional rice varieties in India) or genetic variation within a populations (high among Indian rhinos, and very low among cheetahs) ...

Species diversity refers to the variety of species within a region. Such diversity can be measured in many ways, and scientists have not settled on a single best method. The number of species in a region -- its species richness -- is one often- used measure, but a more precise measurement, taxonomic diversity, also considers the relationship of species to each other. For example, an island with two species of birds and one species of lizard has a greater taxonomic diversity than an island with three species of birds but no lizards ...

Ecosystem diversity is harder to measure than species or genetic diversity because the boundaries of communities -- associations of species -- and ecosystems are elusive. Nevertheless, as long as a consistent set of criteria is used to define communities and ecosystems, their numbers and distribution can be measured ..."

Resources related to biodiversity or conservation as an issue or a topic of debate belong primarily in the relevant subcategory of Society/Issues/Environment.

Related: (very comprehensive guide) Where should I submit my website about animals? Or, where will I find the animal topic I am looking for?