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Ecosystem: the biological communities & their abiotic environment
Ecosystems are Characterized by:Energy flowMineral cycling
• Ecosystems are not self-contained (leaky!)
• Natural ecosystems are affected by human activities
The Biotic Community
Living organisms in an ecosystem are divided into two trophic levels:
Autotrophs: primary producersHeterotrophs: consumers (secondary P., Include:
HerbivoresCarnivoresOmnivoresDetritivoresDecomposers
Energy flowEnergy flow Mineral cyclingMineral cycling
Reflection & Absorption
Dec
om
po
sers
Oxidation (Respiration etc.)
Heat
Light
2°
Ca
rniv
ore
s
De
trit
us
Pri
mar
y P
rod
uce
rsP
ho
tos
yn
the
sis
1°
Co
ns
um
ers
(He
rbiv
ore
s)
Mader, 2001
• Gross Primary Productivity (GPP): the total energy captured from the sun by autotrophs
• Net Primary Productivity (NPP): GPP – Respiration = Energy passed on to herbivores
Secondary Production
The amount of chemical energy in consumers’ food converted to new biomass per unit time.
Trophic Efficiency and Ecological Pyramids
Trophic efficiency is the % of production transferred from one trophic level to the next.
Pyramids of production represent the multiplicative loss of energy from a food chain
Ecological Pyramids Energy & biomass pyramids are upright. As a rule, only 10% of energy or biomass are passed on to
the next level.
Energy Pyramid
Biomass Pyramids Represent the ecological consequence of low
trophic efficiencies. Most biomass pyramids narrow sharply from
primary producers to top-level carnivores because energy transfers are inefficient.
Numbers Pyramids
Show how the levels in the pyramids of biomass are proportional to the number of individuals present in each trophic level.