scientist can learn how the rat has evolved based on where they live. it also helps find what the common ancestor was and all the common traits they have, for example rats in Norway may be used to the cold. and the rats in africa need to adapt to the heat and the constant threat of them being eaten.
It certainly is possible that the North American population has to carry different mutations than a population of Norway rats in Africa. Genetic mutation is a random event, and the alleles resulting from mutation may rise in frequency and be fixed within the population if they provide a benefit to the fitness of the individuals with that allele. One random mutation could occur in the North American population and not be found in the African population because the occurrence of this mutation is random. It is also possible that the two populations carry the same mutations. This would be the case if the mutation occurred either if the mutation occurred in a common ancestor, or if the mutation occurred prior to the 2 populations becoming allopatric. By studying the genomes of each population scientists will be able to determine when certain mutations occurred. Mutations found in one population and not the other occurred more recently, while mutations found in both populations occurred further back in evolutionary time, and may have originated in a common ancestor.
They saw how smoking effected the body since smoking was pushed as something good for a long time, a lot of people started smoking and after a few years doctors finally saw a difference between a smokers body and a non smokers body
The very primitive organism is the oldest because, over time, organisms gradually evolved into more complex organisms. First came the primitive organism, then it evolved into the more complex one, or the younger fossil.
