WAEC - Biology (2009 - No. 2)
Viruses are economically important because they?
do not have cell structures
can only reproduce inside living cells.
cause diseases in plants and animals
exist as crystals outside living cells
Explication
Plant viruses are of considerable economic importance because many of them infect crop and ornamental plants.
Numerous plant viruses are rodlike and can be extracted readily from plant tissue and crystallized.
Animal viruses of economic importance: Genetic variation, persistence, and prospects for their control.