Elephants are not the most abundant species in African grasslands, yet they influence community structure. The grasslands contain scattered woody plants, but they are kept in check by the uprooting activities of the elephants. Take away the elephants, and the grasslands are converted to forests or to shrublands. The newly growing forests support fewer species than the previous grasslands. Which of the following statements describes why elephants are the keystone species in this scenario?

According to researchers, the first increase in atmospheric oxygen can be explained primarily by

What do sleep deprivation studies suggest about the  main reason we need to sleep?

Primarily, Atlantic hurricanes develop and move __________ as a result of air convergence along the __________.

When sea level rises and floods a glacially carved valley, the area is called a(n)

A practical voltage source has an internal series resistance RS. The practical voltage source is connected to a load resistor RL. Assume VS = {VS} V , RS = {RS} kΩ A maximum power transfer, from source to load, happens when RL = __________ kΩ (The unit of the answer is . Do NOT type the unit when you type your answer)

Kelp (large brown algae) grows along the western coast of North America because of the __________ nutrient-rich waters provided by __________.

Assume IS= {IS} mA , R1= {R1} kΩ , R2= {R2} kΩ , R3= {R3} kΩ For Thevenin’s equivalent circuit between points A and B (as seen by RL), the value of VTH is VTH = __________ V (The unit of the answer is . Do NOT type the unit when you type your answer)

The phlebotomist can help reduce the customers stress by which of the following:

Which of the following is MOST dangerous to swimmers?