1. Ecosystems & Energy
Chapter 55

2. YOU MUST KNOW
How energy flows through the ecosystem by understanding the terms that relate to food chains & food webs
The difference between gross primary productivity and net primary productivity
The carbon and nitrogen biogeochemical cycles
How biogeochemical cycles impact individual organisms and/or populations and ecosystems

3. Ecosystem ecology
A. Involves energy flow and chemical cycling
B. Governed by physical laws
1. 1st Law of Thermodynamics – energy cannot be created or destroyed but only transferred and transformed
2. 2nd Law – When energy is transformed/transferred, entropy (disorder) increases

4. 1. Primary producers – autotrophs, support all other organisms
Nutrient cycling
1. Primary producers – autotrophs, support all other organisms
Diet of berries, fish, and insects

5. 2. Heterotrophs – eat other organisms
Nutrient cycling
2. Heterotrophs – eat other organisms
a. Herbivores – eat primary producers, primary consumers
b. Carnivores – those that eat herbivores are secondary consumers, and those that eat other carnivores are tertiary consumers
Diet of berries, fish, and insects
*** Often feed at more than one trophic level***

6. 3. Detritovores/decomposers – feed on nonliving organic material,
3. Detritovores/decomposers – feed on nonliving organic material, convert organic material to inorganic for use by autotrophs
Diet of berries, fish, and insects

7. Primary production – the amount of light energy converted to chemical energy by autotrophs in an ecosystem
A. Gross primary production (GPP) – total primary production
B. Net primary production (NPP) – GPP minus the energy used by the primary producers for “autotrophic respiration” (Ra)
NPP = GPP – Ra

8. Limiting factors affecting primary production
1. Availability of light & nutrients (primarily nitrogen & phosphorus)
2. Evapotranspiration – combination of water lost by transpiration in plants and evaporation

9. Energy transfer between trophic levels A. Only about 10% efficient
Ecological pyramids – can display energy, biomass, of population sizes
Pyramid can never be inverted

10. Biogeochemical cycles – nutrient cycles that contain both biotic and abiotic components
A. Carbon cycle

11. B. Nitrogen Cycle
Nitrification – ammonium (NH4+) is oxidized to nitrite (NO2-) and then nitrate (NO3-) by bacteria
Most of Earth’s nitrogen is in the form of N2, unusable by plants (can use nitrates and ammonium)
Denitrification – bacteria releases nitrogen to the atmosphere
Nitrogen fixation – conversion of N2 to forms plants can use by bacteris

12. Restoration Ecology
A. Return degraded ecosystems to their natural state
B. Bioremediation – use of organisms (usually prokaryotes, fungi, or plants) to detoxify polluted ecosystems (from mining, oil drilling, radioactivity, etc.)
C. Bioaugmentation – introduction of desirable species such as nitrogen fixers to add essential nutrients