Key processes of exchange Chapter 6 Key processes of exchange

Ecological concepts I. Assimilation II. Respiration III. Decomposition

Assimilation A. Carbon—most common nutrient, essential for maintaining all life processes. --Source of carbon for plants—CO2 --Plants take inorganic carbon and transform into organic forms --Primary consumers derive energy from sunlight. --Assimilation through photosynthesis

Photosynthesis B. Transforms carbon + other nutrients into organic forms --CO2 --H2O --Chlorophyll --Solar energy

Photosynthesis 6CO2 + 12H20  C6H12O6 + 6O2 + 6H2O For every CO2 used —one O2 produced For every 6 CO2 + 6 H20 used —one sugar molecule produced

C. Enzyme = a chemical that speeds up a chemical reaction without being used up in the reaction. Rubisco = ribulose biphosphate carboxylase-oxygenase

Atmospheric chemistry 78% Nitrogen 21% Oxygen 1% Argon 0.003% CO2

CO2 uptake D. CO2 enters via stomata --moves through cells via diffusion --driven by a concentration gradient --inward movement CO2 transformed into simple sugars --decreasing concentration of CO2

E. Stomata 2 functions of stomata -- H2O loss -- CO2 uptake -- H2O loss --transpiration --diffusion gradient

F. C3 pathway 1. Initial transformation of CO2 into 3 carbon molecules 2. Utilizes rubisco 3. Transformation occurs entirely in one cell –mesophyll cell 4. Most common form of photosynthesis

Aquatic plants 1. Floating leaf aquatic plants --stomata located on surface Submerged aquatic plants --stomata absent --CO2 and HCO3 enter via direct diffusion

G. C4 pathway 1. CO2 diffuses into mesophyll cell—photosynthesis occurs here utilizing PEP—Fixes carbon into 4-carbon acids 2. Bundle sheath cells receive products of photosynthesis—rubisco present here

Advantages/disadvantages of C4 photosynthesis --more effective use of CO2 --CO2 in bundle sheath cell can be 6 times greater than outside air --increased water-use efficiency --more carbon fixed --higher energy expenditure--PEP

H. CAM pathway 1. Similar to C4 pathway 2. Utilizes PEP and rubisco 3. Both steps occur in mesophyll cell 4. Obtain CO2 at night 5. Stomata closed during day 6. Highest E usage of all pathways

II. Respiration A. All life forms require ATP B. Energy comes from breakdown of sugars and carbohydrates C. Chemical reaction is called oxygenation D. Not a reversal of photosynthesis

III. Decomposition A. Breakdown of organic matter by consumers (secondary producers) B. Detrivores feed on larger dead organic matter C. Consumers assimilate organic matter— may become food/energy for other consumers D. Primary Producers assimilate inorganic nutrients to produce organic matter— become food/energy for consumers

Process of decomposition a. Leaching of soluble compounds b. Detritivores fragment it c. Bacteria and fungi break it down further d. Consuming of bacteria and fungi e. Excretion of organic and inorganic compounds

Final outcome a. True decomposers are microbes b. Accomplished because detrivores break organic material into smaller pieces c. Final decomposition is the return of CO2 originally fixed by photosynthesis back into the atmosphere d. Return of elements back into the soil and water—only to be used again