lecture 36 — trophic structure
the importance of energy
all organisms need energy
get it from the sun, chemicals or each other
in most ecosystems, energy comes from sun, converted into organic molecules by
primary producers in photosynthesis
total amount of energy generated by autotrophs in an ecosystem = Gross Primary
Production (GPP)
but autotrophs use up energy themselves
so a more important measurement is NPP
Net Primary Production (NPP) = how much energy is available to other organisms
NPP = GPP — respiration by autotrophs
NPP is roughly half of GPP
NPP varies dramatically across earth (see ppt for map)
tropical rainforest is the highest
virtually nothing in sahara and the poles
there are big chunks of the ocean where not much NPP
greatest in equatorial regions, with high rainfall
limitations on NPP
the rate of NPP is usually constrianed by one of the following:
energy (e.g. temperature, light penetration of aquatic ecosystems, etc.)
lecture 36 — trophic structure 1
the importance of energy
all organisms need energy
get it from the sun, chemicals or each other
in most ecosystems, energy comes from sun, converted into organic molecules by
primary producers in photosynthesis
total amount of energy generated by autotrophs in an ecosystem = Gross Primary
Production (GPP)
but autotrophs use up energy themselves
so a more important measurement is NPP
Net Primary Production (NPP) = how much energy is available to other organisms
NPP = GPP — respiration by autotrophs
NPP is roughly half of GPP
NPP varies dramatically across earth (see ppt for map)
tropical rainforest is the highest
virtually nothing in sahara and the poles
there are big chunks of the ocean where not much NPP
greatest in equatorial regions, with high rainfall
limitations on NPP
the rate of NPP is usually constrianed by one of the following:
energy (e.g. temperature, light penetration of aquatic ecosystems, etc.)
lecture 36 — trophic structure 1
