Cryopresevation, in vitro fertilisation, micro-propagation / tissue culture, sperm bank / seed bank / gene bank.
Detailed Answer :
Four techniques where the principle of ex-situ conservation of bio-diversity has been employed are follows :
(i) Preservation of the gametes of threatened species (using cryopreservation technique) in viable and fertile condition for long periods.
(ii) In vitro fertilization of eggs.
(iii) Propagation of plants using tissue culture technique.
(iv) Keeping the seeds of different genetic strains that are commercially important plants for long period in seed bankers.