Tophat

• In hiking up a mountain you are likely to pass through various community types as you proceed from the low-elevation lands to the summit. This change in community is called

  • zonation

  • A trophic cascade is an example of a(n) _____ effect

    • indirect

Reading: Chapter 19

• Primary productivity provides energy for the ecosystem

• Concepts

  • Primary productivity: the rate at which solar or chemical energy is captured and converted into chemical bonds by photosynthesis or chemosynthesis

  • Gross primary productivity (GPP): the rate at which energy is captured and assimilated by producers in a given area

  • Net primary productivity: the rate energy is assimilated by producers and converted into producer biomass in a given area

  • Standing crop: the biomass of producers present in a given area of an ecosystem at a particular moment in time

• GPP = NPP + Respiration

Why we measure primary productivity?

• Energy basis of the ecosystem

• Only a fraction of energy made by primary producers makes it to the top level

• Food pyramids inverted in aquatic ecosystems, tertiary consumers bigger than producers

Primary productivity provides energy for the ecosystem

• Measurements: gases

• 6 CO2 + gH20 = C6H12O6 + 6

• GPP = NPP + Respiration

• Measurements: harvesting

• Measurements: remote sensing

• The brown food web

  • some energy lost as heat every step

  • dead organic matter

  • detritus

• Secondary production

  • net secondary productivity: the rate of consumer biomass accumulation in a given area

• Drivers in terrestrial ecosystems

  • temperature

  • precipitation

  • Nitrogen and Phosphorus

    • all ecosystems

  • Silicon and iron

    • ocean

  • Solar radiation

  • ALL

The movement of energy depends on the efficiency of energy flow

• Trophic pyramids

• Efficiencies

  • proportions that help understand ecosystems

  • Conumption efficiency: the percentage of energy or biomass in a trophic level that is consumed by the next higher trophic level

  • Assimilation efficiency: the percentage of consumer energy that is assimilated

  • Net production efficiency: the percentage of assimilated energy that is used for growth and reproduction

  • Ecological efficiency: the percentage of net production from one trophic level, compared to the next lower tophic level

    • also known as food chain efficiency

  • Ecological efficiency and the number of trophic levels

• Residence times

  • the length of time that energy remains in a given trophic level

  • decomposition rates are higher in tropical ecosystems bc of temperature/humidity

• Stoichiometry: the study of the balance of nutrients in ecological interactions such as between a herbivore and a plant