Water is considered a resource.
oil, coal, and natural gas are considered resources.
energy is able to be replaced within the ecosystem for human use.
a farmer who wants to produce the best crop yield will use
when a pollutant increases in concentration at higher levels of the trophic level, can harm organisms at the highest levels.

renewable

nonrenewable

Renewable  

topsoil

magnification

Water pollution can come from many sources. Point-source pollution comes from large farms, factories, septic systems, sanitation systems, and landfills. Nonpoint pollution sources include cities, abandoned mining sites, and animal waste.

Greenhouse gases absorb energy from the sun. The gases hold onto this heat and trap it in the atmosphere instead of allowing it to be reflected into space. The increased temperature from the gases in the atmosphere is a major factor in climate change.

Explanation:

the answer that best describes the relative refractory period in the neuron is the resting membrane potential is restored, but concentrations of sodium and potassium are not restored to their original state.

the refractory period is the time during which another stimulus given to the neuron will not lead to a second potential. thus, because na+ channels are inactivated during this time, additional depolarizing stimuli do not lead to new action potentials.  

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try using substitution:

x + y - 6 = x - y. (i'm not giving you the exact answer). since 0 = x - y, then sub 0 in the equation with x - y. combine your like terms, and then use inverse operations, and you'll have your answer.

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