Ecosystem Processes

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Ecosystem Processes
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Thinking Question

• While browsing through the drinks offered at a
  convenience store, you notice a new soft drink
  advertised as a low-calorie energy drink. Write
  out your definition of energy, and then decide
  if this drink label is accurate or a case of
  false advertising.

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Energy

• Energy is defined as the ability to do work.
• Energy is NOT a material. Energy is a phenomenon.
• Energy can be transformed (i.e. mechanical to
  heat) and transferred, but is not recycled.

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Energy flows

• Energy for most ecosystems on earth comes from
  the sun.
• Light energy is converted to chemical energy by
  producers to power their own metabolism.
• Energy is lost from the earth as heat.

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Nutrients

• Nutrient in an ecological sense refers to the
  inorganic materials taken in by producers and
  converted into organic molecules.
• Nutrients include carbon (as carbon dioxide),
  nitrogen, phosphorous, oxygen, and other building
  blocks of biological molecules.

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Nutrients Cycle

• Because nutrients ARE materials, they cycle in
  the earths ecosystems. Carbon from carbon
  dioxide may become carbon in a sugar made by a
  plant.
• Decomposers break down organic molecules and
  release inorganic nutrients to the ecosystem.

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Photosynthesis

• Energy is converted and nutrients are fixed by
  the process of photosynthesis.
• Producers use the suns energy to convert
  inorganic carbon dioxide into organic molecules,
  such as sugars.

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Net Productivity

• Net primary productivity is the energy that
  producers can make available to a community at
  any one time.
• Net productivity determines how much life an
  ecosystem supports.
• Productivity can be measured in calories (units
  of energy) or biomass (amount of organic
  material).

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Biomass (g/m2)
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Thinking question discussion

• So what about that low-calorie energy drink?

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Energy Flows
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Thinking Question

• One reason that some people become vegetarians is
  to reduce their impact on the environment. List
  as many positive ecological effects of
  vegetarianism as you can think of. Then list as
  many negative effects.

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Food Chain Concept

• Chemical energy is passed through the ecosystem
  as organisms consume other organisms.
• Organisms occupy one or more trophic levels
  (feeding levels) depending on what they are
  eating.

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Trophic Levels

• Producers Use light energy to manufacture
  organic molecules.
• Primary consumers eat producers
• Secondary consumers eat primary consumers
• Tertiary consumers eat secondary consumers.

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Food Webs

• A food web is a model of energy flow in a
  community.
• Arrows indicate the direction in which energy
  flows from one organism to the next. (Note that
  this is NOT a cycle.)
• A single organism will be involved in many food
  chains, and some will occupy several trophic
  levels.

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Death Eaters

• Decomposers Bacteria and fungi, which use
  external digestion to break organic matter down
  into inorganic substances.
• Detritivores Animals that feed on dead plant
  material.
• Scavengers Animals that feed on dead animal
  flesh.

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Energy Loss

• At each step in a food chain or food web, energy
  is lost as heat. Each organism takes in energy to
  meet its own needs, so most of the energy taken
  in is converted to motion and heat.
• 10 or less of the energy consumed will be
  available to the next consumer.

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Energy Pyramid

• Because 90 or more of consumed energy is used by
  the organism, and only a small amount can be
  passed on, the entire system is inefficient.
• The higher an organism is on the food chain, the
  greater amount of biomass is required to support
  that organism.

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Human Food Chain

• Humans are omnivores, capable of eating a wide
  variety of foods.
• We can create a human food chain by looking at
  our meat sources.

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Grass-fed Food Chain
A cow can convert grass, which we cannot eat,
into meat, which we can.
We obtain 8-10 of the energy that a pasture-fed
cow consumes.
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Industrial Food Chain
Corn, which could be fed to humans, is fed to
feedlot cattle. Because of overproduction, corn
is cheap.
Cheap burgers come at a high ecological cost. The
industrial food chain is about 1/3 as efficient
as the grass food chain.
A cows digestive system is not adapted to eating
corn. The cattle are often sick, and much of the
energy is wasted.
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Thinking question discussion

• What are possible positive and negative effects
  of going veggie?
• How can your everyday food choices have an impact
  on the environment?

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Nutrients Cycle
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Thinking Question

• Global climate change has everyones attention
  these days. One action that some people take in
  response is to plant trees. What does planting
  trees have to do with alleviating global climate
  change?

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Material Cycles

• Material cycling follows the law of conservation
  of matter.
• Elements used by living organisms are taken up
  and used by producers, used passed down the food
  chain by consumers, and are released back to the
  environment by decomposers.

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Nitrogen Cycle

• The earths atmosphere is 78 nitrogen, but in
  this form it cannot be used by producers.
• Nitrogen-fixing bacteria convert nitrogen gas
  into nitrogen compounds that plants can absorb
  and use in making amino acids to build proteins.

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Nitrogen Cycle
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Phosphorous Cycle

• Unlike other nutrients, phosphorous does not
  exist as an atmospheric gas.
• Rock phosphates dissolve in rain as rock
  weathers, carrying phosphates into streams and
  soil.
• Phosphates settle out on the bottoms of ponds,
  and may consolidate back into phosphate-rich rock.

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Phosphorous Cycle
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Water Cycle

• Weather patterns form part of the water cycle.
• Water remains chemically unchanged during the
  water cycle. It is evaporated as water vapor,
  condensed into rain clouds, and finally falls as
  precipitation.
• Water may collect in rocks as groundwater.

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Water Cycle
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Carbon Cycle

• Carbon forms the backbone of all organic
  molecules.
• Carbon from the atmosphere is fixed by
  producers, which manufacture organic molecules
  using the suns energy.
• Breakdown of these molecules releases carbon
  dioxide back to the atmosphere.

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Carbon Cycle
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Global Warming

• Global Warming better termed Global Climate
  Change has been strongly linked to levels of
  carbon dioxide in the atmosphere.
• While natural events add carbon dioxide to the
  atmosphere, humans activity also contributes to
  carbon levels.

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Fossil Fuels

• Fossil fuels are the remains of ancient swamps.
  Plants fixed carbon as carbon-rich organic
  compounds. Carbon compounds accumulated in swamps
  over hundreds of millions of years.
• In less than 200 years, humans have burned nearly
  half of the worlds fossil fuels.

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Greenhouse Effect
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Carbon and Temperature
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Future Trends?
The outcome depends on what happens to the west
Antarctic ice shelf.
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Current Effects
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Thinking question discussion

• What do trees have to do with global climate
  change?
• In what other ways can people reduce their carbon
  footprint?

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Big, scary question

• Is the typical American lifestyle ecologically
  sustainable?