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Energy Flow PAGES 366-369 Energy Flow in an Ecosystem Sun autotrophs heterotrophs producers consumers Producers/Autotrophs •Can make their own food through photosynthesis or chemosynthesis Productivity •Productivity: energy made by producers (after biological processes) available to consumers •Gross primary productivity (GPP): rate at which producers capture energy in organic compounds Productivity •Net primary productivity (NPP): the rate at which biomass accumulates (after some is used) •NPP= GPP – Cellular Respiration Productivity •Biomass: the amount of organic (living) material produced Consumers •Get energy by eating other organisms •There are 5 types Consumers •Herbivores: eat producers Consumers •Carnivores: eat other consumers Consumers •Omnivores: eat producers and consumers Consumers •Detritivores: feed on “garbage” or dead organic matter (ex. worms, millipedes, vultures) Consumers •Decomposer: break down dead organic matter into simpler molecules (fungi and bacteria) •Recycle nutrients back into ecosystem Food Chain •Food chain: a single pathway of feeding relationships in an ecosystem that traces the transfer of energy Food Web •Interconnected food chains •Arrows show transfer of energy Tropic Level •Trophic level: position in a series of energy transfers Energy flows through ecosystems sun secondary consumers (carnivores) primary consumers (herbivores) producers (plants) loss of energy loss of energy Trophic Levels •Only 10% of the total energy is passed onto the next trophic level (rule of 10%) ◦Energy lost to biological processes (digestion, growth and repair, running, walking etc.) ◦Energy lost as heat 90 % Energy Lost 90 % Energy Lost 90 % Energy Lost Large Carnivore • 3˚ Consumer • Ex: killer whale Small Carnivore • 2˚Consumer • Ex: sea otter Herbivore • 1˚ Consumer • Ex: sea urchin Producer • Ex: Kelp Question: Why is a pyramid used to display energy transfer and not a square? Approximately 90% loss of energy at each trophic level Keystone Species •Has disproportionately large effect on the ecosystem •Dictates community structure •Demonstrated by removal of keystone species from community • Ex. Sea stars, otters Sea star feeds on all bivalves. When the sea star is removed from the tide pools one bivalve (mussel) out competes the rest for resources and becomes the dominant species.