a) Primary productivity is influenced by some physical options as  Light intensity light-weight length Temperature Soil pH convenience of nutrients carbonic acid gas levels While different options influencing NPP is that the presence of biomass per unit space over a given period by plants throughout chemical change is outlined as primary productivity it's expressed in term of weight (g ) or energy (Kcal m ). Productivity will be categorized into gross primary productivity (GPP) and web primary productivity (NPP).  GPP is that the production rate of organic matter at the time of chemical change. Primary productivity is directly proportional to the quantity of greenhouse emission, daylight, and water and is reciprocally proportional to metastasis losses. It will be expressed as NPP = GPP - metastasis losses (R) b) Consumption of oxygen is the elementary step for decomposition that is directly associated with the quantity of oxygen within the atmosphere. Chemical nature of detritus and environmental condition regulates consumption of oxygen.  The rate of decomposition decreases if detritus is richly supported by polymer or polyose meantime its rate will increase if detritus is equipped nitrogen and sugar.