Biodiversity is the variety of life on earth and includes variation at all levels of biological organisation from genes to species to ecosystems.
The importance of biodiversity was one of the key subjects of the 1992 World Summit held in Rio de Janeiro, Brazil, which resulted in the Convention on Biological Diversity (CBD). It defines biodiversity as “the variability among living organisms from all sources including, terrestrial, marine and other aquatic ecosystems and the ecological complexes of which they are part; this includes diversity within species (genetic diversity), between species (species diversity),and of ecosystems (ecosystem diversity)”.
India, one of the 17 mega-diverse countries; due to its sheer size, range of topography, altitude and climate, India exhibits a rich variety of ecosystems such as forests, grasslands, deserts, wetlands, mangroves and coral reefs.
Forest ecosystem: India is home to evergreen forests in the NE and coastal areas; tropical deciduous forests in the Central India etc. Biodiversity here ranges from trees like timber to endangered animals as Asiatic Lion, Bengal Tiger etc.
Grassland ecosystem: They are widely scattered and are found in Indo-gangetic plain (TeraiDuar grasslands), Yamuna Brahmaputra floodplain; Shola grasslands of W.ghats etc. They are home to Chinkara, Asiatic Water Buffalo, black eagles and plants as ferns.
Desert ecosystem: It varies from arid to semi arid and also thorny and scrub types and is mostly found in North West India. Prominent flora include water conserving plants as cactus, babool. Camels, desert rats,snakes are major fauna components.
Wetlands: Ramsar Convention dots wetlands from Chilika in Orissa to Nalsarovar in Gujarat to Ropar in Punjab to name a few.
Sambharlake,Loktak are other wetlands of natural importance. They hold huge importance for carbon sequestration and during disasters.
Mangroves: Known for surviving in saline atmosphere they include Marshy lands of Kutch to Bhatirnaka of Orissa, Sunderbans of WB, those found in the coasts of Gujarat, TamilNadu(pichavaram) and Andaman.
Coral Reefs: They are found in Gulf of Kutch, Gulf of Mannar, Lakshdweep and Andaman and Nicobar Islands, are unique in themselves and are home to home to a number of aquatic species like Dugong.
Apart from the multiple uses of BD, they are an asset for the future generation as well. Thus, in order to preserve the rich biodiversity, achieve many national and international biodiversity goals such as the National Biodiversity Strategies and Action Plans and the Aichi Biodiversity Targets, as well as meet CBD objectives, biodiversity integration into developmental sectors is a prerequisite.
Note: Instead of listing like these when you are writing on the paper, you may just draw a diagram. So that answer fits within the word limit. You may then include various species and importance of BD. (There is no perfect answer, anything that suits your writing style and meets the demands of the question is fine.)