Mention those red list categories which together are reffered to as threatened species.

Explanation

IUNC is International Union of Conservation of Nature and Natural Resource which is now called World Conservation Union (WCU). It has beadquaters at Merges, Switzerland. It maintains a red data book or red list which is a catalogue of taxa facing risk os extinaction red data book or red list was initiated in 1963. the 200 red list has made assessment of 18,000 spesies out of which 11096 species (5485 animals and 5611 plants ) are on the threatened list worldwide. the number of threatened species has now gone up to 15,500 (iunc,2004). the purpose of preparation of red list is to (i) provide awareness to the degree of threat to biodiversity, (ii) provide global index about already decline of biodiversity,(iii) identification and documentation of species at high risk of extinction,(iv) preparing conservation priorities and help in conservation action. red list has eight categories os species.
(i) Extinct,(ii) Extinct in the wild,(iii) Critically Endangered, (iv) Vuincrable,(v) Lower risk, (vi) Data deficient ,(vii) Not Evaluated.