Ecosystems
Wednesday, April 27, 2022 8:39 AM
• Components of an Ecosystem
• Multiple communities of interacting organisms that live in a region
• Abiotic components
• How does energy enter an ecosystem?
• Through primary producers
○ Autotrophs: synthesize their own food from inorganic sources
§ E.g. Sunlight = Photosynthesis
§ Remember: not creating energy but transforming from solar energy
to chemical energy stored in sugars.
• Primary Productivity
• Gross primary productivity (GPP): the total amount of chemical energy
produced in a given area and time period.
• Primary producers use this chemical energy in two ways:
○ Cellular respiration to produce ATP to fuel metabolic processes
○ Growth and reproduction: energy invested in new tissue or offspring is
called net primary productivity (NPP)
• Total amount of chemical energy produced
• Growth and reproduction: NPP results in biomass, organic material that
consumers can eat (and from which they obtain energy).
○ NPP = GPP – R
○ NPP = Net Primary Productivity
○ GPP = Gross Primary Productivity
○ R = Respiration or “loss”
○ NPP results in biomass—the total amount of chemical energy that is
stored in organic material
• Trophic structure: food chains and food webs
• The total biomass produced per year is greatest at the lowest trophic level and
declines at higher levels
• Pyramid of Productivity
• Productivity declines at higher trophic levels
• In general, efficiency of biomass transfer between trophic levels is only about
10% (although this can vary dramatically)
• Biomagnification
Wednesday, April 27, 2022 8:39 AM
• Components of an Ecosystem
• Multiple communities of interacting organisms that live in a region
• Abiotic components
• How does energy enter an ecosystem?
• Through primary producers
○ Autotrophs: synthesize their own food from inorganic sources
§ E.g. Sunlight = Photosynthesis
§ Remember: not creating energy but transforming from solar energy
to chemical energy stored in sugars.
• Primary Productivity
• Gross primary productivity (GPP): the total amount of chemical energy
produced in a given area and time period.
• Primary producers use this chemical energy in two ways:
○ Cellular respiration to produce ATP to fuel metabolic processes
○ Growth and reproduction: energy invested in new tissue or offspring is
called net primary productivity (NPP)
• Total amount of chemical energy produced
• Growth and reproduction: NPP results in biomass, organic material that
consumers can eat (and from which they obtain energy).
○ NPP = GPP – R
○ NPP = Net Primary Productivity
○ GPP = Gross Primary Productivity
○ R = Respiration or “loss”
○ NPP results in biomass—the total amount of chemical energy that is
stored in organic material
• Trophic structure: food chains and food webs
• The total biomass produced per year is greatest at the lowest trophic level and
declines at higher levels
• Pyramid of Productivity
• Productivity declines at higher trophic levels
• In general, efficiency of biomass transfer between trophic levels is only about
10% (although this can vary dramatically)
• Biomagnification
