The Flow of Energy: Primary Production and Higher Trophic Levels

Take home messages:

1.  Time affects everything; always consider time. 

2.  Ecological efficiency will get us in the end. 

Main Terms:

Autotrophs vs. Heterotrophs; Primary producers vs. Consumers

Photosynthesis vs. Chemosynthesis


Gross Primary Production (GPP) vs. Net Primary Production (NPP)

Net Ecosystem Production (NEP)

Turnover rate

Trophic levels

Assimilation, ingestion, and excretion

Secondary production

Homeotherm vs. poikilotherms

Assimilation efficiency vs. net production efficiency vs. ecological efficiency

Pyramids of biomass, energy, and numbers

Main Concepts:

·        What is primary production and how is it measured? How efficient is the process of photosynthesis?

·        Why does so little of the sun’s radiation actually reach earth’s surface?

·        How are standing crop, primary production, and turnover time related?

·        Understand the difference between GPP and NPP.

·        Do the most productive systems per unit area always contribute the most to global NPP?  Why or why not?

·        What limits or controls primary production at the scale of the globe?  At different local or regional scales?

·        What is the fate of NPP?; What can you conclude about the fate of NPP in our world?

·        What are the “rules” for energy transfer in trophic levels.

·        Understand the principles behind calculating assimilation, net production, and ecological efficiency.

·        What are the relationships among these different efficiencies, and what do each of them actually mean?

·        Understand how pyramids of biomass, energy, and numbers are constructed, and the typical shapes of these pyramids. 

·        Know or be able to calculate the relative residence time of energy for various ecosystems; what does the residence time mean or indicate in this example?

·        Have a general understanding of how much energy humans consume; the notes present two scenarios estimating human appropriation of the world’s NPP (focus on how the highest, and most realistic, estimate is calculated and what terms go into the calculation).