Answer to Question 1
The biofuels used for transportation are ethanol from corn and biodiesel from used vegetable oil. The production costs to make ethanol are almost twice as great as gasoline.
In 20052006, 4.3 billion gallons of ethanol for fuel, the equivalent of 100 million barrels of oil, were used in the United States. Some 14 of the nation's corn crop is dedicated to this use; an ethanol factory also produces corn oil and livestock feed. Ethanol plants under construction will increase the production capacity to 6.3 billion gallons. A production tax credit of 51 cents a gallon helps ethanol compete with gasoline.
Currently, ethanol represents about 1.6 of U.S. gasoline consumption. This could rise to 13 if the country's entire corn crop were devoted to ethanol productionan impossible assumption, given the importance of corn for animal feed and export. With some 75 million acres devoted to corn harvest in the United States, there is little suitable farmland for significant expansion.
Answer to Question 2
The ability of an ecosystem to return to normal functioning after a disturbance is resilience. Resilience mechanisms are the processes of replenishment of nutrients, dispersion by surrounding plants and animals, rapid regrowth of plant cover and succession to a forest. Resilience can fail when soil is lost through deforestation, overgrazing, and other devastating factors.
Water Potential, Solute Potential, and Pressure Potential
An Action Potential
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Resting Membrane Potential: Voltage Difference