How do ecosystems work? Part 1!

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How do ecosystems work? Part 1!
Chapter 41
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Overview Pathways of energy and nutrients

• Materials cycle
• Note complete cycles for purple arrows.
• Energy flows one way!
• Energy (red) arrows in direction of energy flow
• Note heat loss at each step.

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Energy flow through communities

• Energy enters communities through photosynthesis
• Carbon dioxide, water and suns energy used
  directly for photosynthesis
• Inorganic mineral nutrients needed to build other
  molecules (proteins, lipids, carbohydrates)

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Energy flow through communities

• Trophic levels
• Autotrophs
• Which Domains/Kingdoms include at least some
  autotrophs?
• Heterotrophs or consumers
• Primary consumers herbivores consume primary
  producers
• Secondary consumers and higher carnivores
  consume other consumers
• Detritus feeders and decomposers
• Consume dead organic matter
• Convert organic molecules back to inorganic ones
  so primary producers can use them (bacteria
  mostly do this step.)
• What if there were no decomposers?

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Energy flow through communities

• Terrestrial food chain and trophic levels
• What is missing here?

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Energy flow through communities

• Marine food chain and trophic levels
• What is missing here?

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Energy flow through communities

• Trophic levels (cont.)
• Many consumers cannot be strictly categorized
• Omnivores Feed as both herbivores and carnivores
• Many carnivores feed at multiple levels
• Example Leopard seal in Antarctic marine food
  web

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Antarctic marine food web (simplified)
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Energy flow through communities

• Energy transfer is inefficient
• On average, only 10 of energy gets transferred
  from one trophic level to the next (red arrows)
• Most of the rest is lost as heat (yellow arrows)
• Some converted to unusable form (i.e.
  indigestible for the consumer, such as cellulose
  for us.)

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Energy pyramid shows inefficiency of energy
transfer
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Biomagnification Unlike energy, toxins become
concentrated up the food web

• Top predators are most affected by toxins
• At the peak of DDT use, predatory birds contained
  DDT concentrations up to 1 million times the
  concentration in water.

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Cycling of nutrients Carbon

• CO2 sinks
• Primary producers (via photosynthesis)
• Terrestrial
• Marine (gt50)
• Ocean water
• Ocean sediments
• Carbonification
• Fossil fuels formed from phytoplankton (oil and
  gas) and plants (coal, peat)

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Cycling of nutrients Carbon

• CO2 sources
• Respiration All organisms
• Decomposition
• Fires
• Natural
• For agriculture
• Burning of fossil fuels
• Use 1 million times as fast as it is formed!

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In sum, decrease of CO2 sinks and increase of CO2
sources

• Increase in global CO2 correlates with global
  warming

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Highest temperature increases are along the
Antarctic Peninsula