Biodiversity is the term popularised by the sociobiologist Edward Wilson to describe the combined diversity at all the levels of biological organization. It is related to all living plants, animals, and microbes found in their natural habitats. There are more than 20,000 species of ants, 3,00,000 species of beetles, 28,000 species of fishes and nearly 20,000 species of orchids. The biodiversity is measured at three levels; genetic diversity, species diversity and ecological diversity.
So, the correct answer is 'Living plants, animals and microbes found in their natural habitats'.