topic 2

• system - set of things interconnected that produce their own pattern of behavoir
• parts of a system: element, interconnection, function
• basic functions that operates at all levels: energetics, development, evolution, diversity, integration, regulation
• stock: foundation of system
• stocks take time to change = flows take time to flow
• feedback loops: creates behavoir that persist over time
• stabilizing loops: balancing feedback loops; goal seeking; stability seeking
• negative feed back loop: reduce exessive responses, keep variables within normal range
• reinforcing feedback loops: enhances whatever direction of change is imposed on it
• positive feedback loop: intensifies the response until a threshold is met
• energy flow - ability to do work
• forms of energy: mechanical, radiant, sound, chemical, heat, energetic, nuclear
• 1st law: law of conversion of energy - energy cant be destroyed or created only converted from one to another
• 2nd law: law of increasing energy - entropy tends to increase overtime; as more energy is used more of it is converted to heat
• energy flows from a higher to lower level
• production: rate of formation of new material by autotrophs
• calories/m2/year - energy
• grams/m2/year = dry organic matter
• gross primary production: total amount of CO2 lost from metabolic activity
• net primary production: net amount of primary production after the costs of respiration by plants, heterotrophs, and decomposers are all included
• NPP = GPP - R
• net ecosystem production: net amount of primary production after the costs of plant respirations are included
• NEP = GPP - (Rp + Rd + Rn)
• factors affecting rates of productivity: sunlight, temperature, precipitation, nutrient availability