LECTURE 26 CH 23
PATHWAYS OF ELEMENTS IN THE ECOSYSTEM
Answers to ASSIGNMENT from Tuesday Lecture
Use: U of I’s Nutrition Analysis Tool 2.0: http:www.nat.illinois.edu/mainnat.html
1) ideal calories for height, weight, body build, physical activity _______
2) calories consumed from plants _______
from animals _______ 3) % from animals ___________
total calories _______
4) amount of ecologically equivalent calories consumed relative to a vegetarian
total calories = ______
plant calories = ______ = ecological equivalent plant calories
animal calories = ______; (_____ x 10) = ______= ecological equivalent animal calories
total ecologically equivalent calories = ________
My diet/vegetarian diet = _______/______ = _____ X more ecologically equivalent calories
than vegetarian
e.g. total calories = 2100; plant calories = 1449 = ecological equivalent plant calories
animal calories = 651; (651 x 10) = 6510 = ecological equivalent animal calories
total ecologically equivalent calories = 7959
My diet/vegetarian diet = 7959/2100 = 3.8 X more ecologically equivalent calories
than vegetarian
MAJOR CONCEPTS
1. Energy transformation and element cycling are intimately linked.
2. A model of ecosystems includes linked compartments (pools):
air; organisms; soil/rock; water
3. Nutrients move from source compartments to sink compartments;
the rate of movement = flux
4. The water cycle is physical, not chemical.
5. The carbon cycle is closely tied to the flux of energy through the biosphere.
6. Nitrogen exists in many oxidized and reduced forms in its cycling.
7. The phosphorous cycle involves little change in chemistry; a very large pool
in rock; P is ‘lost’ to inactive sediments in oceans/lakes; its cycle is geological
in time scale.
8. Sulfur exists in many oxidized and reduced forms in its cycling.
9. C, N, and S cycles differ greatly under aerobic vs. anaerobic conditions.
10. Microorganisms assume significant and diverse roles in N, P, S cycles.
I. Elements and their uses in organisms
CHO: organic compounds and water
N, P, S: proteins, amino acids
Ca, P: bones, exoskeleton, cell membranes
Fe, Mg: pigments, enzymes (e.g. hemoglobin, chlorophyll
K, Na: ionic balance, neural transmission
II. Matter cycles/is reused; energy flows; not reused 483-4
Energy transformations and element cycling are intimately linked 23.1, 23.2
III. Features of ecosystems
Size; boundaries
Temporal scale
IV. General model of ecosystems 484-5 23.3
Linked compartments (boxes) (pools) (air; organisms; soil/rock; water)
Rate of movement between compartments (arrows) (fluxes)
Sinks: boxes with input/output increasing
Sources: boxes with input/output decreasing
Residence time varies among pools and cycles
V. Water cycle 486-7 23.4
Physical model, not chemical
Balance of fluxes
VI. Carbon cycle 487-490 23.5
A. Tied to energy flux; solar-powered
B. Processes 23.6
Assimilation; dissimilation; redox reactions 483-4
Photosynthesis, respiration, methanogenesis
Exchange of CO2 between air and oceans
Sedimentation of carbonates 23.7
C. Human alterations: fossil fuel burning; tropical deforestation as new fluxes 482
The “missing sink”: sources>sinks
Elevated CO2 experiments: Are plants limited by [Co2]? 492-3 Fig. 2, 3
Can plants sequester more carbon? Does increased CO2 act as fertilizer?
D. Geological time scale changes in cycle 490-1 23.9, 23.10
E. Variation in flux and pools among biomes
VII. Nitrogen cycle 493-6 23.11
Many oxidized/reduced forms
Importance of microbes
Nitrogen fixation 23.12
Nitrification
Denitrification
VIII. Phosphorus cycle 497-8 23.14
Little change in chemistry; form = (PO4-3)
Large lithosphere pool; no atmospheric pool
Lost to inactive sediments in oceans/lakes
Cycle is geological in time scale
Importance of mycorrhizae in phosphorus uptake
IX. Sulfur cycle 500-1 23.17
Many oxidized/reduced forms
Importance of microbes
X. Microorganisms assume diverse roles in element cycles 501-2
Summary: 1-12, 14, 16-17