Lesson 4: Ecosystems

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Lesson 4 Ecosystems

• Big Question
• What Is Necessary to Sustain Life on Earth?

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Lesson Goals

• After reading Chapter 4 and hearing/reading this
  lesson, you should be able to explain
• why the ecosystem is the basic system that
  supports life and enables it to persist
• what food chains, food webs, and trophic levels
  are
• how energy enters ecosystems and determines
  biological productivity
• what a community-level effect is
• what ecosystem management involves and
• how conservation and management of the
  environment might be improved through ecosystem
  management.

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How Populations Change OverTime and Interact
with Each Other

• How and why does the abundance of a species
  change even without human influence?
• Interactions include competition, symbiosis, and
  predation/parasitism
• Would nature remain in balance if we didnt
  interfere?
• Long term study of wolves and moose of Isle
  Royale National Park, Michigan

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• The populations of wolves and moose change over
  time, even without human interference.

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American Chestnut Blight

• For more information, see "Chestnut Blight" and
  the Wikipedia article on Chestnut Blight.

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Professions and Places TheEcological Niche and
the Habitat

• What is a habitat, and what is a niche?
• Where a species lives is its habitat
• What it does for a living (its profession) is its
  ecological niche
• Will a change in land use affect a species
  niche?
• A species habitat may be damaged to the point
  where its niche requirements are no longer
  available

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Measuring Niches

• Can species share a niche?
• Two flatworm species some streams have just one
  of the species, others have both
• Temperature is key

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How Species Coexist

• Flour Beetle Experiments
• In a uniform environment, one species always wins

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Two Examples of Symbiosis

• Elk-ruminant bacteria to digest cellulose
• Red alder Frankia to fix Nitrogen from air

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The Community Effect Sea Otter
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The Effect of Sea Otters on the Community
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The Ecosystem Sustaining Lifeon Earth

• The oldest fossils are more than 3.5 billion
  years old
• Ecosystems are crucial to sustaining life
• An ecosystem is comprised of the individuals of
  various species and their nonliving environment.

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A Simple Ecosystem Yellowstone Hot Spring
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A Food Web
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Food Webs

• Some food webs appear simple and neat.

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Food Web of the Harp Seal

• In reality, many food webs are complex because
  most creatures feed on several trophic levels.

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Ecosystem Energy Flow

• Energy is the ability to do work, and to move
  matter through an ecosystem.

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Life and the Laws of Thermodynamics

• The law of conservation of energy energy is
  neither created nor destroyed but merely changed
  from one form to another
• Why cant the same energy continually cycle
  through an ecosystem?

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The Law of Entropy

• The law of entropy energy always changes from a
  more useful, more highly organized form to a less
  useful, disorganized form
• Whenever useful work is done, heat is released to
  the environment and that energy can never be
  recycled
• The net flow of energy through an ecosystem is a
  one-way flow

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Producing New Organic Matter

• Primary production Some organisms make their own
  organic matter from a source of energy and
  inorganic compounds
• Autotrophs include green plants, algae, some
  bacteria
• Secondary production Other organisms cannot make
  their own organic compounds from inorganic ones
  and must feed on other living things
• Heterotrophs all animals, fungi, most bacteria

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Respiration

• Living things use energy from organic matter
  through respiration
• Organic compound are combined with oxygen to
  release energy and produce carbon dioxide and
  water
• Involves organic chemicals called enzymes

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Gross and Net Production

• Autotroph production involves
• producing organic matter within the body--gross
  production
• using some of this new organic matter as a fuel
  in respiration and
• storing some of the newly produced organic matter
  for future use--net production.
• Most primary production takes place through
  photosynthesis.

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Practical Implication I Human Domination of
Ecosystems

• Human domination is not yet a global catastrophe,
  although serious environmental degradation has
  resulted.
• Earths ecological and biological resources have
  been and will continue to be greatly modified by
  human use of the environment
• An important human-induced alteration of Earths
  ecosystems is land modification
• We can act to cause less damage.

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Practical Implication IIEcosystem Management

• Ecosystems can be natural or artificial or a
  combination of both.
• The ecosystem concept is central to management of
  natural resources.
• We must focus on their ecosystem and make sure
  that it continues to function.

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Chapter 4 Ecosystems

• Question? E-mail your TA. eschelp_at_u.washington.edu