Transcript Chapter 3

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
-- 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
2. 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.
2.
3.
4.
5.
Similar to C4 pathway
Utilizes PEP and rubisco
Both steps occur in mesophyll cell
Obtain CO2 at night
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.
b.
c.
d.
e.
Leaching of soluble compounds
Detritivores fragment it
Bacteria and fungi break it down further
Consuming of bacteria and fungi
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