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U1 S2 L3 L4Energy Flow in Ecosystems
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What Affects the amount of Energy Reaching
Ecosystems?

• Albedo
• Other Environmental Factors

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The flow of energy from the sun
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The Albedo Effect
Albedo is a measure of the amount of light
reflected from an object. Albedo is normally
expressed as a decimal value representing the
percentage of light reflected. For example,
clouds have an average albedo about 0.27 so about
27 of the suns energy is normally reflected by
clouds back to space. On a clear day, more
light would be able to penetrate to the Earths
surface. What has a greater albedo effect, snow
covered glaciers or the canopy of the
rainforest? To stay warm in the winter what
color would you wear? Why?
Albedo affects the amount of energy from the sun
available for an ecosystem. The Higher the albedo
the less the energy available to an ecosystem!
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Sample Albedo Values
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Energy Budget

• Defined as the total Energy available to
  organisms in an ecosystem.
• What determines the energy budget?
• An ecosystem's energy budget depends on primary
  productivity
• Primary Productivity
• The total amount of food created by primary
  producers as a result of Photosynthesis.
• Photosynthesis
• 6CO2(g) 6H2O(l)
  C6H12O6(s) 6 O2(g)

Glucose or Food

• Only an estimated 1 of the light that does reach
  the primary producers is actually converted into
  chemical energy by photosynthesis.

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Examining Primary Productivity

• Gross Primary Productivity (GPP)
• Defined as the total amount of food created by
  plants in an area at any one time.
• Net Primary Productivity (NPP)
• Defined as the amount of food left to be passed
  on to the next trophic level after plants use
  some for their own purposes.
• NOTE NPP is ALWAYS less than GPP!!!

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Factors Affecting Primary Productivity

• The factors that affect productivity in the
  various terrestrial and aquatic ecosystems
  include
• light intensity,
• temperature,
• carbon dioxide availability,
• availability of nitrogen and phosphorus,
• latitude/altitude (terrestrial ecosystems) or
• depth (aquatic ecosystems)

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Food Chains

• One possible path for the flow of energy in an
  ecosystem.
• If the community has a great deal of
  biodiversity, there will be several organisms
  that can feed on more than one type of food
  resource, and as a result there would be several
  possible food chains.
• Each step in the food chain is called a trophic
  level.
• Corn ? Mouse ? Snake ? Hawk

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Food Webs

• All the possible Food Chains in an Ecosystem.

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Food Chains and Energy Flow

• What happens to energy as it flows along a food
  chain?
• Energy is lost!!!
• How?
• Cellular Respiration is used to convert sugar in
  foods into energy for organisms to use, but at
  the same time some energy is lost as heat!!
• Because energy is lost along the food chain,
  Pyramids of Energy, Biomass and Numbers are
  created.

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Pyramid of Energy

• The idea that each higher trophic level has less
  energy available to it.
• 10 rule only 10 of the energy of one trophic
  level gets transferred to the next trophic level
  (90 is lost as heat)!!

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Pyramid of Biomass

• A pyramid that represents the total biomass of
  organisms at each trophic level.
• Biomass -- The total dry weight of organisms in
  a trophic level.
• Why dry weight?
• Because amount of water varies in each ecosystem,
  so dry weight is used as a better measuring tool.
• Pyramid is similar in structure to a pyramid of
  Energy. 10 rule.
• There can be exceptions!!!!

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Pyramid of Numbers

• Pyramid that represents the total number of
  organisms that can be supported at each trophic
  level.
• There can be exceptions!!!

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Conditions Necessary for a Stable,
Self-sustaining or Sustainable Ecosystem

• Stability means that there is an ecological
  balance between the various organisms that make
  up the food web, and because of this balance the
  ecosystem is self-sustaining over long periods of
  time.
• To be stable there must be a balance between food
  production, food consumption, and decomposition
  of dead organisms and/or their wastes.

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Keystone Species

• A keystone species is one considered so important
  to the stability of the ecosystem, that if there
  was a decline in that species, the community
  would not be able to maintain its stability and
  may even collapse.
• For example
• sea otters in kelp forests keep sea urchins in
  check. Kelp roots are merely anchors, and not the
  vast nutrient gathering networks of land plants.
  Thus the urchins only need to eat the roots of
  the kelp, a tiny fraction of the plant's biomass,
  to remove it from the ecosystem.

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Another Example of a Keystone Species

• The beaver is another example of a keystone
  species.
• It transforms its territory from a stream to a
  pond or swamp

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• Niche vs habitat

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• Habitat
• the place were an organism lives.
• The habitat of an organism is part of its niche.
• The organism's habitat is its address - where it
  lives.
• Every organism has its own habitat.
• The habitat of slime molds is the damp floor of
  the forest.
• The organism's habitat is were the organism is
  best adapted to survive.
• a fish is adapted to life in water because it has
  gills to get oxygen.

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• A single area may satisfy the needs of many kinds
  of plants and animals. These organisms that
  associate together in a common habitat form
  communities.

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• For Example
• The Pine Marten prefers to live in undisturbed
  mature coniferous or mixed forest, with large
  evergreens and scattered birch and other hardwood
  trees.
• For denning and nesting sites, the martens uses
  hollow trees, stumps and logs.

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• Niche
• The role that a species plays within its
  ecosystem.
• In balanced ecosystems, each species occupies its
  own niche.
• The niche is like the organism's profession -
  what it does to survive.
• The function or position of an organism or
  population within an ecological community.
• The particular area within a habitat occupied by
  an organism.

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• Competition
• Organisms are forced to compete against their own
  species and also different species in order to
  survive.
• The stronger and more fit organisms have an
  advantage over those who are weaker, and they
  have a better chance of surviving.

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• Competition arises when organisms have
  requirements in common and they must compete to
  meet their own needs.
• The more needs organisms have in common, the more
  intense the competition.
• When the resources that are being competed for
  become scarce the competition becomes more
  intense, and eventually one of the species
  becomes eliminated.

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• Habitats have finite amounts of the resources
  needed by living organisms, such as food, water
  and space, and all organisms strive to reproduce
  themselves and increase their numbers.
• Sooner or later the demand for these resources is
  going to exceed supply, and organisms have to
  compete with each other to get them.

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• Plants typically compete with each other for
• light (for photosynthesis)
• water, and
• nutrients (minerals)
• Animals typically compete with each other for
• food
• water
• mates (so they can reproduce), and
• living space

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• Intra-specific competition
• Competition between the same species
• Many birds of the same species compete for the
  best nesting grounds.
• In cases when food or water is scarce, members of
  the same species will compete for food in order
  to survive.
• Bull moose competing for a mate

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• Inter-specific competition
• Competition between different species
• Different species often compete for space, food,
  or water.
• Fox and coyote compete for the rabbit