The scientists can easily distinguish between the two species of bacteria when studying and amplifying the same DNA region in both by looking at their nucleotide base sequences. The nucleotide sequence for most of the bacteria are known by the scientists today. The knowledge of these sequences can help differentiate between two species while amplifying the same regions of DNA. The sequences can be entered in the database already present to find out the bacterial species the sequence belongs to.
The inner core is solid because it is made of very dense, or heavy, materials - like iron and nickel. Even though it is very hot, these materials don't "melt" very easily, so they stay solid.
