This video lecture from Variety of Life (F.Sc. first year Biology) covers the concepts about why a virus needs a host cell to complete its life cycle?How viruses are host specific?How viruses survive inside the host cell and How viruses adapt themselves in unfavourable conditions. Find more e-learning material and educational video lectures in Urdu at maktab.pk. These videos are free to use for promotional and commercial purpose by keeping the credits to Maktab.