Chapter 54: Ecosystems

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Chapter 54 Ecosystems
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Ecosystem

• All the organisms and abiotic factors in a
  community.

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Ecosystem Studies

• 1. Energy Flow the movement of energy through
  trophic levels.
• 2. Chemical Cycling the movement of matter from
  one part of the ecosystem to another.

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Trophic Levels

• Division of an ecosystem based on the source of
  nutrition (energy).
• 1. Primary Producers
• 2. Primary Consumers
• 3. Secondary Consumers
• 4. Detritivores

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Primary Producers

• Usually plants, capture energy and store it in
  chemical bonds.
• Are the source of the energy available to an
  ecosystem.

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Consumers

• Primary Consumers
• Organisms that feed on the producers.
• Ex Herbivores
• Secondary Consumers
• Organisms that feed on the Primary Consumers.
• Ex Carnivores
• Comment
• There may be several layers of Secondary
  Consumers in an ecosystem.

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Detritivores

• Get their energy from the organic waste produced
  by all levels.
• Ex bacteria and fungi

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Food Chain

• Linear pathway of who eats who in an ecosystem.

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Food Webs

• Network showing all the feeding relationships in
  an ecosystem.

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Primary Productivity

• The rate at which light energy is captured by
  autotrophs or primary producers.
• NPP GPP - Rs
• NPP Net Primary Productivity
• GPP Gross Primary Productivity
• Rs Respiration

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Available Energy

• Daily - 1022 joules of solar radiation.
• 1 - captured by Ps.
• About 170 billion tons of organic matter is
  created each year.

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Primary Producers

• 50 - 90 of GPP is lost to Rs by the primary
  producers.
• NPP 10 - 50
• Animals - use only NPP, which limits the food
  webs.

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Limiting Factors

• Material or nutrient that is not present in
  sufficient quantity for the primary producers.
• Ex N, P, K, Mg Light, CO2

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Energy Transfers

• Not 100 efficient.
• Why?
• Second law of thermodynamics.
• Waste.
• Materials that cant be digested etc.
• Averages 10 with each Trophic Level change.

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Question ?

• Why do most ecosystems have only 3 - 4 trophic
  levels?
• There isnt enough energy passed up through the
  food web to support more levels.

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Implications

• There has to be fewer high level consumers in a
  food web.
• The higher level consumers usually need a large
  geographical area.

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Question

• Which would support more humans per area?
• Eating meat?
• Eating plants?

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Pyramids

• Graphical representation of relationships in
  ecosystems.
• Ex
• 1. Productivity
• 2. Biomass
• 3. Numbers

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Chemical Cycling

• Matter is recycled through ecosystems.
• Ex Biogeochemical Cycles
• Matter Reservoirs
• 1. Organic Materials
• 2. Inorganic Materials
• Available ?? Unavailable

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Representative Cycles

• Water
• Carbon
• Nitrogen
• Know one or more of these cycles for an essay
  question.

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Energy vs Matter

• Energy - flows through ecosystems and is mostly
  lost as heat.
• Matter - cycles in ecosystems.
• Question?
• What is Man's influence on Ecosystems ?
• Humans have had many negative impacts.

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Hubbard Brook
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Biological Magnification

• The concentration of toxins in successive levels
  of a food web.
• Ex DDT Heavy metals (Hg, Cd Pb)

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Causes

• Not broken down by digestion/decomposition.
• Lipophilic.
• Concentrates and effects the upper levels of the
  food web.

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Greenhouse Effects

• The trapping of heat by the Earth's atmosphere.
  (CO2, H2O etc.).
• Carbon Dioxide Levels
• Prior 1850 - 274 ppm 1958 - 316 ppm
  1992 - 351 ppm
• Point the levels of CO2 are rising. The cause is
  probably due to humans.

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Greenhouse Effects

• Causes
• Industrialization.
• Burning of fossil fuels.
• Loss of forests.
• Results
• Earth will heat up.
• Ice caps melt and sea levels will rise.
• Climate shifts.
• Increased Ps (?)

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Acid Rain

• Caused by air pollution.
• Lowers the pH of rainfall.
• Is seriously damaging many ecosystems.

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Exotic Species

• When transplanted species are too successful and
  upset the ecosystem in new areas.
• Ex Starlings Fire Ants Carp

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Habitat Destruction

• Worst problem threatening most species today.

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Comment

• Man has a major impact on the Biosphere.
• Man needs to learn how to work with the Biosphere.

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Summary

• Know the tropic levels of ecosystems.
• Know an example of a food chain and a food web.
• Know how energy moves through an ecosystem.

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Summary

• Know how matter moves through an ecosystem.
• Know one or more examples of matter cycling.
• Be able to discuss in detail a human impact
  problem on ecosystems.