Chapter 4 Pyramids and Productivity. Three types of pyramids:. Pyramid of energy flow Pyramid of biomass Pyramid of numbers. Pyramid of Energy Flow. Illustrates the greater cumulative loss of usable energy as energy flows through the various trophic levels
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Inverted pyramid: Temperate forest (summer) – one large tree makes up primary producer level
Biomass Pyramids can also be upright or inverted, depending on the ecosystem – In Figure b for example, phytoplankton grow and reproduce quickly and the zooplankton eat phytoplankton so fast that there is never a lot of phytoplankton at any one time (small biomass)
Definition: the rate at which an ecosystem’s producers convert solar energy into chemical energy as biomass
NPP = (rate at which producers store chemical energy as biomass) – (rate at which producers use chemical energy stored as biomass)
In other words, total energy stored in photosynthesis minus energy used in respiration
Based on average NPP:
Based on total NPP:
Despite our addition of nutrients, agricultural land has a NPP of about 3200 kcal/m2/yr
Compare to estuaries at over 8800 kcal/m2/yr
How can we feed more people with the land we have?
Problem: Humans cannot survive on these foods and using them for food would disrupt the natural spawning grounds that provide us with other high-protein foods (e.g., shrimp)
Problem: Soil there is very poor, nutrients are tied up in plants, can’t support crops for long
Problem: Phytoplankton are so widely dispersed that it would take too much energy to collect them; it would also disrupt marine food webs
(humans waste 27% of the earth’s total NPP and 40% of the earth’s terrestrial ecosystems’ NPP)