1. Chapter 55 Ecosystems

2. Energy Flow
Energy flows through an ecosystem, while matter is recycled
Law of conservation of mass – matter cannot be created or destroyed
Two main processes occur in an ecosystem to transform energy and recycle matter:
Photosynthesis: H2O + CO2 + Light energy  Glucose + O2
Cell respiration: Glucose + O2  H2O + CO2 + Energy (ATP)

3. Relationships
Trophic levels - feeding relationships between organisms and an organisms position in that feeding relationship

4. Relationships Food chain – linear trophic level feeding pathway
Food webs - interconnected feeding relationship in a community

5. Primary producers – trophic level that supports all others; autotrophs
Convert light energy to chemical energy (glucose)
Primary consumers – herbivores that eat primary producers
Secondary consumers – carnivores that eat herbivores
Tertiary consumers – carnivores that eat other carnivores
Least amount of biomass
Decomposers/Detritivores – special consumers that derive nutrition from non-living organic matter
These organisms recycle the matter back to the soil for new primary producers to grow
Ex: fungi, earthworms, bacteria, slugs, dung flies

6. Prior Knowledge:
Know how to construct a food chain or web from a given list of organisms including correct direction of arrows connecting organisms
Know how to label the trophic levels. Organisms may be included in more than one trophic level.
Know the % energy transfer from one trophic level to the next and a reason why

7. Energy Flow NPP = GPP – Rs
Primary productivity: amount of energy from light converted to chemical energy (organic molecules) by autotrophs
Gross (GPP): total primary productivity energy in an ecosystem
Net (NPP): represents the energy in the producer that is available to consumers (stored chemical energy)
Gross primary productivity minus the energy used by the primary producer for respiration (Rs)
NPP = GPP – Rs

8. Different ecosystem’s contribution to the Earth’s NPP

9. Factors affecting Primary Production in Aquatic Ecosystems
Light limitation
Depth of light penetration (photic zone)
Increase in silt or sediment from deforestation up river

10. Factors affecting Primary Production in Aquatic Ecosystems
Nutrient limitation – the element that must be added for production to increase
Most often the limiting nutrient is nitrogen or phosphorous in marine ecosystems
Areas of upwelling of nutrients in the ocean correspond to growth of phytoplankton and high primary production
Nitrogen pollution can cause huge increases in algae in aquatic environments which can lead to eutrophication and a depletion of oxygen

11. Factors affecting Primary Production in Terrestrial Ecosystems
Temperature and moisture are the main factors controlling primary production
However just like in aquatic ecosystems, limiting nutrients such as nitrogen and phosphorous in the soil can affect primary production

12. Energy Flow
Biomass: primary productivity reflected as total dry mass of all organic material (g/m²)
Secondary productivity: amount of chemical energy in consumer’s food that is converted to new biomass
How much energy from food contributes to the organism’s growth
Most of the energy is lost as heat or released as waste for detritivores to breakdown

13. Trophic efficiency: % of energy transferred from one trophic level to the next (5-20%)
In other words, 90% of the energy available at one trophic level is NOT transferred to the next
Energy pyramid: loss of energy with each transfer in a food chain and is arranged in tiers
Biomass pyramid: each tier represents the total dry mass for that trophic level (can be inverted)
Numbers pyramid: each tier represents the number of individuals in that trophic level (can be inverted)
Energy Flow

16. Chemical Cycling
Biogeochemical cycles: the various nutrient circuits, which involve both abiotic and biotic components of an ecosystem
Water, Carbon, Nitrogen, Phosphorus

17. Water Cycle Biological Importance: Key Processes:
Essential for all organisms
Availability influences the rates of ecosystem processes such as primary productivity and decomposition
Key Processes:
Evaporation and transpiration from plants, condensation of water vapor, precipitation, run-off into surface and groundwater

18. Carbon Cycle Biological Importance: Key Processes:
Forms the framework of organic molecules essential for all life
Key Processes:
Photosynthesis removes CO2 from atmosphere, cellular respiration adds CO2, burning fossil fuels and wood adds CO2, volcanoes add CO2

19. Nitrogen Cycle Biological Importance: Key Processes:
Part of amino acids, proteins, and nucleic acids and is often a limiting plant nutrient
Key Processes:
Nitrogen fixation by certain bacteria in legume plant roots converts N2 gas to a form plants can use, lightning and volcanic activity fix nitrogen naturally, humans add fertilizer (nitrogen) to soil, other bacteria convert nitrogen again in the soil (nitrites and nitrates), denitrification by certain bacteria converts nitrate to N2 gas, human also release large amounts of nitrogen oxides into the atmosphere

20. Phosphorous Cycle Biological Importance: Key Processes:
Required for nucleic acids, phospholipids, and ATP as well as mineral component of bones and teeth
Key Processes:
Weathering of rocks adds PO4 to soil, gets into groundwater, P taken up by producers which are eaten by consumers, decomposition of biomass or excretion by consumers adds P back to soil or water

21. Human Impact
Biomagnification: trophic process in which retained substances become more concentrated at higher levels
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