Soil is a mixture of minerals, organic matter, water and air. The minerals come from bits of broken-down rock. Organic matter is material that is alive or used to be alive. It includes leaves, twigs, bugs and many microscopic, or tiny, organisms like bacteria and fungi. In fact, there are more microorganisms in a handful of soil than there are people on the planet. Soil is needed for life to exist on Earth. It contains many nutrients that help plants grow. Then the plants provide nutrients that help animals grow. Which of these is not a natural part of soil?

Cells in the nervous system have a potential difference of 70 mv across the cell membrane separating the interior of the cell from the extracellular fluid. this potential difference is maintained by ion pumps that move charged ions across the membrane. is this an emf? select the correct answer and explanation. 1)no. the ion pumps cannot separate charges; thus, they cannot create a potential difference. 2)yes. the ion pumps cannot separate charges, but they still can create a potential difference. 3)yes. the ion pumps can actively separate charge; thus, they can create a potential difference. 4)no. the ion pumps can separate charges, but they cannot create a potential difference.