Each vertical column of elements is called a what?

Why is the bottom layer of a trophic pyrimid the

According to the passage, which of these is true about gray water systems? a) gray water systems use plants that require less water. eliminate b) gray water systems require the use of less fossil fuels. c) gray water systems reduce the amount of fresh water used. d) gray water systems reduce the amount water used by shower heads.

What happens after sound waves create vibrations in the ear?