Is a PCI-E 2.0 x16 Graphics card compatible with a PCI-E 1.0 slot?

Please help me in this situation as I really don't know how to determine if a motherboard supports v2.0 PCI-E. In case the heading is not clear enough, let me rephrase it by asking is a PCI-E 2.0 x16 graphics card gonna work in a PCI-E 1.0 x16 slot? Thanks