In a cladogram (a type of phylogenetic tree), clades are groups of related organisms. In the past, phylogenetic lists built clades using the idea of parsimony, that the pattern that uses the fewest evolutionary changes is the most likely to be correct. Today, with the use of computers and DNA sequences, the explanation that is thought to be the best is .

one with the fewest number of genetic differences in the nucleotide sequence.

Explanation:

A cladogram is a diagram capable of showing the relationships among different species and/or group of organisms. In a cladogram, the root indicates the common ancestor, while internal nodes represent the common ancestors of each group. In consequence, this diagram can be used to establish evolutionary relationships in which the start branch points represent common ancestors shared by the organisms found in the 'branches'. Nonetheless, the length of the branches in the cladogram does not represent evolutionary distances among groups. In recent years, cladograms based on DNA sequencing data have been combined with morphological data to establish evolutionary relationships among species.

americans began to notice growing differences between the northern and southern sections of the country. there were more people living in cities in the north, which made it more urban. more people lived on farms in the south, which made it more rural. while many people were farmers in the northern states, there were now other ways to make a living, such as working in mechanical cotton gins factories manufacturing cloth, tools and other goods. people in the north supported high tariffs on goods imported from europe because the extra cost encouraged people to “buy american” instead. in the southern states, planters did not like tariffs because they sold most of their production to europe and bought their tools from there as well. southerners believed the protective tariff was something that only northern factory owners keep their profits high. so the southern politicians came up with an idea. they would opt out. they would simply ignore the protective tariff. it was ‘null and void’ in south carolina. the state would not collect the taxes on goods imported into south carolina, no matter what the president said they had to do. this decision led to the nullification crisis.