Bacteria. this word has been in the news and textbooks a lot lately. we know that some species of bacteria have evolved a resistance to antibiotics and are difficult if not impossible to kill. instead they are responsible for some potentially deadly illnesses and infections. we also know that recent biochemical discoveries have lead scientists down a path to completely change how life on earth is classified, starting with the bacteria. we have moved from a 5-kingdome system to a 3-domain, 6-kingdom system of classification. all bacteria are still known to be prokaryotes, but we know now that they differ biochemically. this phylogenic tree shows the changes in bacterial species from the ancestral species to the most current split in the modern classification system. this tree supports the theory that a) speciation results in biodiversity. b) natural selection favors the fittest. c) within a population, variation exists. d) extinction is the fate of the species that cannot adapt.

A

Explanation:I just took the test :)

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.