Q.About how many species of organisms have been described and given scientific names so far?

The term 'biodiversity' was coined by Walter G. Rosen in 1986, popularising the concept of the variety and variability of life on Earth.

Biodiversity (biological diversity) refers to the variety of life forms — genetic diversity, species diversity, and ecosystem diversity — found within a given region or the planet as a whole. Walter Rosen first used the shortened term 'biodiversity' at the National Forum on BioDiversity held in Washington, D.C., in 1986, as a contraction of 'biological diversity'.

Edward O. Wilson, another notable ecologist, later popularised the term further, but the coining of the word itself is credited to Rosen. The other names listed (Aristotle, de Candolle, Tansley) are associated with different concepts — classification, phytogeography, and the ecosystem concept respectively — not with coining 'biodiversity'.

The term 'Biodiversity', short for biological diversity, was coined by Walter G. Rosen and later popularised by the biologist E. O. Wilson.

Biodiversity refers to the variety and variability of life forms found on Earth at all levels — genetic diversity within a species, species diversity among different organisms, and ecosystem diversity across habitats. While the underlying concept of variety of life had long been studied by taxonomists and ecologists, the specific contracted term 'Biodiversity' was coined by Walter G. Rosen in the mid-1980s (in the context of the 1986 National Forum on BioDiversity in Washington, D.C.), and the term was subsequently popularised in scientific and public use by the eminent biologist Edward O. Wilson. The other names listed are important historically for different reasons: Aristotle laid early foundations of classification/taxonomy in ancient Greece, A. P. de Candolle contributed to plant taxonomy and phytogeography, and A. G. Tansley coined the term 'ecosystem' (1935) — none of them coined 'biodiversity'.