Having one or more extra sets of chromosomes is known as polyploidy. In humans, it is virtually impossible to survive to adulthood as a polyploidy. Such a condition is more common among plants (in fact, this is a common method by which new plant species arise) and some groups of fish and amphibians; for example, some salamanders, frogs, and leeches are polyploids. But note: polyploids that arise within a species are different from those that arise due to the hybridization of two distinct species; the former are known as autopolyploids and the latter are referred to as allopolyploids.