Answer to Question 1Most rural and many suburban homes in the United States use septic systems to treat their wastewater. In a septic
system, the wastewater and suspended solids flow away from the house into a septic tank. In the septic tank, organic
matter is decomposed partially by organisms such as bacteria and fungi. The decomposed material either settles
to the bottom of the tank as sludge, close to the surface of the tank as oil or grease, or is liquefied and mixed with
the water. The liquid effluent flows from the tank to an absorption field. Once it reaches the absorption field, the
effluent flows into field lines, which are porous. The effluent passes out of the field lines into the surrounding soil
where it is attenuated further by microorganisms, dilution, and adsorption to soil particles
Answer to Question 2The mechanical and chemical processes used to prepare water for human consumption consist of three stages. In
the first stage, larger pieces of solid materials that are floating or suspended in the water are filtered out. In the
second stage, smaller particles are coagulated into larger clumps that can be allowed to settle out in the form of
sedimentation. During both the first and second stages, biological decomposition of organic contaminants takes
place and most of the resulting decomposed materials are either filtered or settled out. During the third stage,
chemical treatment of the water is used to remove most of the remaining impurities.
The dynamic nature of the endomembrane system
Some of the pathways of the auditory system that lead from one ear to the cortex.
The Renin-Angiotensin System
Elimination, System of Linear Equations
Complement System
Pathway by which the nervous system controls skeletal muscle contraction