ZAMBIA IS LOCATED in central Africa and is slightly larger than the state of Texas. It is completely landlocked, with the Zambezi River forming a natural boundary between Zambia and Zimbabwe to the south.
THE YENISEY AND ANGARA rivers form a dividing line between western and eastern Siberia. Like the other major rivers of the region, they flow from highlands in the south across the flat north Siberian plains to the Arctic Ocean.
BIOGEOGRAPHERS AND ecologists usually classify plants according to their water needs. Since the global distribution of water varies from dry to wet, plants also vary in their adaptation to the availability of water.