Soil is formed
from rocks and decaying plants and animals.
An average soil
sample is 45 percent minerals, 25 percent water,
25 percent air, and five percent organic matter.
mineral particles, such as sand, silt, and clay,
give soil its texture.
bacteria help break down organic matter in the
Plant roots and
lichens break up rocks which become
part of new soil.
Roots loosen the
soil, allowing oxygen to penetrate. This
benefits animals living in the soil.
Roots hold soil
together and help prevent erosion.
Five to 10 tons
of animal life can live in an acre of soil.
organic matter, recycle nutrients, and make the
surface soil richer.
Mice take seeds
and other plant materials into underground
burrows, where this material eventually decays
and becomes part of the soil.
Mice, moles, and
shrews dig burrows which help aerate the soil.