Energy Flows in Ecosystems AP Env Sci

Why Green? Reminder: Photosynthesis “sets the table” for all energy flows that follow: Converts Low Potential Energy compounds to High Potential Energy compounds

Photosynthesis – Fate of Glucose Photosynthesis 6 CO H 2 0 C 6 H 12 O O 2 Respiration C 6 H 12 O O 2 6 CO H 2 0 Where’s the energy?

Photosynthesis – Fate of Glucose Not much value if all glucose is used for energy Where does the glucose go? –Making other organic molecules in plant –Broken down to release energy for plant activities –Storage as starch or oils Plants make new organic matter – primary producers.

Net Primary Productivity (NPP) Primary Productivity: –Gross Primary Productivity: total amount of photosynthetic activity –Net Primary Productivity: gross primary productivity minus energy the plants themselves consume. NPP is rate at which new organic matter is made available to consumers in ecosystem. –NPP Lab Coming Up!

Consumers and Cell Respiration Consumers break down complex organic compounds (from producers) into simpler compounds (ie. Glucose) Cells get energy from respiration – –High potential energy glucose to low potential energy CO2. –Reaction releases energy: 6 CO H energy C 6 H 12 O6 + 6 O 2

Respiration Note that Oxygen is released in photosynthesis but used in respiration. –Respiration is an oxidation reaction Conversion of chemical potential energy (glucose) to energy for the body is not 100% efficient –Result is body heat

The Fate of Food Of the food absorbed: 60-90% oxidized for energy Of the food absorbed: 10-40% converted to body tissue Production of body tissue: Secondary Production

Focus on Detritus Feeders and Decomposers Detritus is largely cellulose (“fiber”) –We cannot digest this, but other organisms can Most decomposers use O2 for cell respiration (like us) –Cellulose broken down into CO2, etc. –Fermentation: alternative where oxygen is limited

Fermentation Certain bacteria and yeast Chemical breakdown of glucose in absence of oxygen- –products include ethyl alcohol, methane, acetic acid Happens in anaerobic environments –Industrial fermentation –Lake sediment –Marshes, swamps –Animal gut –landfills

Cycle vs Flow Flow of Energy – starts with the Sun Cycling of Nutrients – producer, consumer, decomposer