The red-cockaded woodpecker is a keystone species in pine forests of the southeastern United States. Red-cockaded woodpeckers feed on insects and nest in cavities that they bore into pine trees. Many other species of animals use these cavities
for roosting and nesting after they are abandoned by the woodpeckers.
If the population of red-cockaded woodpeckers suddenly decreased in a certain forest, which of the following would most likely
occur in the ecosystem over time?
ОА.
an increase in number for populations that are predators of woodpecken
ОВ.
a decrease in the number of pine tree cavities available for other species to nest in
OC. an increase in the number of species that live in pine tree cavities
D
a decrease in competition between other species that nest in pine tree cavities

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.

many other transport proteins, often called pumps, move materials against a concentration gradient. active transport drives molecules across a membrane from a region of lower concentration to a region of higher concentration. this process, shown in figure 5.1, uses transport proteins powered by chemi- cal energy.