Answer to Question 1
Roots can break apart fractures in rock by growing deeper and searching for water. Burrowing animals mix up rock matter and soil and bring fresher material to the surface, where it can be broken down more readily by chemical and physical processes.
Answer to Question 2
Carbonic acid is formed in nature by falling rain dissolving carbon dioxide out of the atmosphere. Groundwater also dissolves carbon dioxide from decaying organic matter. The weathering of potassium feldspar involves a chemical reaction in which the hydrogen ions (H+) in the carbonic acid replace the potassium ions (K+) in the feldspar structure. Once removed, the potassium is available as a nutrient for plants or becomes the soluble salt potassium bicarbonate, which may be incorporated into other minerals or carried to the ocean by groundwater and streams. The remaining elements in feldspar reorganize to form clay minerals. Additionally, the chemical reaction removes some silica from the feldspar structure via dissolution, which is eventually precipitated out as chert.
In most ecosystems, sunlight provides the ultimate source of energy to power all biological activity
Extent of agricultural activity across the planet (data from Foley et al. 2005).
Participation of water in biological reactions
Summary of Cytokine Activity
Peer group activity of adolescents
Dog Temperament Activity