1. Communities + physical processes interconnect to form ecosystems
Ecosystems are connected by:
1. energy flow between trophic levels; energy also released as heat energy into environment
Autotrophs = 10 producers
Primary productivity = amount of C fixed in an ecosystem by: CO2 + H20 + light --> (C6H1206) + O2
Heterotrophs
Consumers: herbivores, omnivores, carnivores
Decomposers
2. Nutrient and water cycling (Biogeochemical cycling)
1. water, 2. carbon, 3. nitrogen, 4. phosphorus
Humans have impacts on ecosystems

2. Energy flow (also refer to Fig. 20.3 & 20.7)
Only ~10 % transfers between levels.
Loss due to: Metabolism and waste

3. BioGeoChemical cycles = Nutrients cycle btwn biotic & abiotic forms
Definitions of: Reservoirs and fluxes, mineralization, fixation/assimilation
Flux rate dependent on ?
Major Biogeochemical cycles: Atmospheric cycles = carbon and nitrogen; Sedimentary = phosphorus; Hydrologic 9 9

4. Carbon
Reservoirs = ?
Transformations?

5. Fertilizer, atmospheric deposition
Nitrogen - why is N impt? - what is symbiotic N fixation? - cause and results of excess N?
Dead organisms
NH4+
ammonium
NO2-
nitrite
NO3-
nitrate
Organic matter
Decomposition
Mineralization
Plants
Assimilation
Fungi, bacteria, inverts
Fungi, bacteria N2
Nitrogen fixation
Rhizobium
Denitrification
Anaerobic
bacteria
Industrial inputs:
Fertilizer, atmospheric deposition

6. Phosphorus Pools? Transformations?
Cause and consequences of excess P in aquatic systems

7. PO4- is difficult to acquire
80 % of plants have mycorrhizal symbionts to help (fungi); other benefits (+H20) offset cost

8. Biotic factors increase nutrient retention – how?
Excessive disturbance decreases retention – why?

9. Human Impact 1
Reduced biodiversity, habitat loss, habitat fragmentation

10. Human Impact 2
Pollution: air, water, land
Reduction in ozone layer

11. Human Impact 3 - Excess N & P

12. Human Impact 4 - Accelerated release
of CO2