Some sources say that Australia is one of the seven continents. Others say that Australia is part of a larger continent, such as Australasia, or Oceania. Oceania is a region which includes Australia, New Zealand and the Pacific Islands. Australasia includes at least all countries on the Australian continental plate. This includes the islands of New Guinea, Tasmania, New Zealand and a number of smaller islands. It is on the south-eastern side of the Wallace Line, with distinct differences in its biology from the Asian side of the line.