Ch.20&21- Energy Flow Flashcards
Earth is an Open system for Energy
- Energy arrives from the sun
- Energy leaves by radiating into space
Earth is a Closed system for matter
-Chemicals are converted, but are not gained or lost
Primary prodcution
-all energy in an ecosystem comes from primary production (autotrophs)
Gross primary production (GPP)
total amount of carbon fixed by autotrophs in a n ecosystem
-controlled by climate, nutrients, and autorophes biomass
Net Primary production (NPP)
NPP= GPP-carbon lost to respiration
-plants need ~ 1/2 carbon fixed to support biosynthesis and cellular maintenance
Actual evapotranspiration
AET= the total amount of water that evaporates and transpires off a landscapre (mL water/year)
Trophic dynamics
-energy must be transferred from autotrophs to higher trophic levels
~in trophic pyramids, the amount of biomass or energy= size in the layer of pyramid
~size of layer determined by:
-amount of NPP
-Ecological efficiency
Ecological efficiency
The percentage of energy at one trophic level transferred to another
Consumption efficiency
-Proportion of available biomass that is ingested
-higher trophic levels=higher consumption efficiency
Ex: zebra eats grass, lion eats zebra
Assimilation efficiency
-proportion of ingested food that is absorbed by digestive trac (determined by food quality)
-Higher food quality as you move up trophic levels
Ex: assimilation efficiency:
herbivores= 20-50%, carnivores =80%
Production efficiency
-Proportion of assimilated biomass used to produce new consumer biomass
Energy lost between trophic levels
- 2nd law of thermodynamic: energy is lost during transfer due to an increase in entropy(disorder)
- 90% lost at each transfer
Trends in Biomass
-Most PP in aquatic systems takes place in phytoplankton
~compared to plants, a greater portion is digestible
-Primary producers are quickly consumed in aquatic systems
-although they differ in biomass, they do NOT differ in energy trends
NPP is limited by climatic factors
- correlated with temp and precipitation
- range of conditions for photosynthesis
NPP can be limited by nutrients
- Nitrogen, phosphorus, calcium, potassium
- more nutrients = more NPP
Patterns of NPP in water
~NPP primarily limited by nutrient and light availability in aquatic systems
-phosphorous and nitrogen are the major limiting nutrients
~highest rates in oceans are in zones of upwelling
Global NPP patterns
-highest rates on land are in tropics
~due to growing season, light, and precipitation
Nutrients
elements that are required for the development,maintenance, and reproduction of organisms
~diff. from energy in that they aren’t lost in transfer (not a one-way trip)
Nutrients in organisms
-five elements make up 93-97% of biomass of plants, animals, fungi, and bacteria: Carbon, Oxygen, Hydrogen, Nitrogen, Phosphorus.
~limiting nutrients are Nitrogen and phosphorus
Agriculture and N-and P- cycling
Harber-Bosch process
agriculture has dramatically increased N and P inputs to terrestrial plants communities
Eutrophication
the transformation of an ecosystem from low nutrient levels to high nutrient levels
- Usually caused by humans
- Produced bottom-up changes in communities
Decomposition
The breakdown of organic matter accompanied by release of CO2
