The soil layers and the living organisms
The soil is composed of three layers, They are the top soil layers, the lower soil layers and the rocky layers, The soil horizon is the layer that parallel to the soil crust and its physical characteristics differ from the layers above and beneath each soil type.
The top soil layers
The top soil layers contain the roots of the plants, the leaves of the plants, the humus, the small pieces of the rocks may be found, the organisms as the earthworms, the ants, the spiders and the insects, So, a lot of the creatures exist in the top layers.
The roots are very important to the soil as they help the soil to be cohesive, they provide the soil with the nutrients as they are converted into the humus after death, and they prevent the soil erosion from happening quickly.
The leaves of the plants are the parts of the plants exist in the top soil layers, and when these parts fall in the soil, they decay forming the humus.
The ants and other insects are the organisms existing in the top soil layers, they dig the tunnels in the soil to make the nests and lay the eggs, and when these organisms die, their bodies decay forming the humus.
The earthworms and some spiders are the organisms existing in the top soil layers, and the soil is very important to them. It is considered the shelter for the earthworms and some spiders because they make their home underground by digging the tunnels.
The earthworms and some spiders are very important to the plants as they help in the growth of the plant roots, as the tunnels that are formed by them allow the air, the water and the nutrients to pass easily through the soil, then to the plant roots.
The lower soil layers
The lower soil layers lie beneath the top soil layers, and the do not have much humus.
The rocky layers
The upper layers of the rocky layers contain pieces of the rocks, but their lower layers contain the solid rocks.