What are the four most important materials needed by living organisms?

• water, carbon, oxygen, nitrogen
• water, food, oxygen, carbon
• water, carbon, nitrogen, phosphorous
• water, carbon, food, phosphorous

An underground layer of rocks or sand that can hold groundwater.

• watershed
• levee
• aquifer
• erosion

An area or ridge of land that separates waters flowing to different rivers, basins, or seas.

• watershed
• levee
• aquifer
• erosion

How much of the Earth's water is stored in the oceans?

• 50%
• 67%
• 97%
• 85%

This is essential to living organisms, it is found in nucleic acid and amino acids.

• Nitrogen
• Carbon
• Water
• Phosphorous

This is part of nucleic acids, ATP, and helps form animals' bones and teeth.

• Nitrogen
• Carbon
• Water
• Phosphorous

The conversion of ammonium to nitrate is called what?

• nitrification
• renitrification
• denitrification
• unnitrification

The conversion of nitrate to nitrogen gas is called what?

• nitrification
• renitrification
• denitrification
• unnitrification

What is it called when water vapor cools and changes into a liquid?

• condensation
• respiration
• precipitation
• evaporation

Where would you find most of the Earth's phosphorous?

• In the atmosphere
• Underwater
• on the Earth's surface
• Underground