They might contain index fossils..
Answer:
Nitrogen is essential for all living things because it is a major part of amino acids, which are the building blocks of proteins and of nucleic acids such as DNA, which transfers genetic information to subsequent generations of organisms.
Take your shirt off, wave it round ya head like a helicopter
Microevolution - Allele frequency changes in a certain population over an amount of generations, it can also be simply described as "an evolutionary change in populations".
