Chapter 17 Ecosystems

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Chapter 17Ecosystems
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Levels of Organization

• Ecologists recognize a hierarchy of organization
  in the environment biosphere, ecosystem,
  community, population, and organism.

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Levels of Organization
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Levels of Organization, continued

• The Biosphere
• The broadest, most inclusive level of
  organization is the biosphere, the volume of
  Earth and its atmosphere that supports life.

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Levels of Organization, continued

• Ecosystems
• The biosphere is composed of smaller units called
  ecosystems.

- An ecosystem includes all of the organisms and
the nonliving environment found in a
particular place.
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Levels of Organization, continued

• A community is all the interacting organisms
  living in an area.

- Below the community level of organization is
the population level, where the focus is on the
individual organisms of a single species.
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Habitat the place where a particular
population of species lives

• Biotic and Abiotic Factors
• Both biotic, or living, factors and abiotic, or
  nonliving, factors influence organisms.

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• Biodiversity
• -the number of species living within an
  ecosystem
• - a larger number of different species in an
  area means that there is greater biodiversity

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Boundaries

• Physical boundaries between ecosystems is not
  easily defined

Is the ecosystem a whole forest, or the single
rotting log . it often depends on what is being
studied.
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Ecosystems Change

• Over time ecosystems naturally change in a
  process called succession
• (Fields becoming forests, ponds fill up,etc.)

Types Primary succession occurs when no plants
have grown before Pioneer species the
first organisms to appear
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Secondary Succession occurs when there has been
previous growth (fires, floods, earthquakes,
etc._)
See Glacier Bay example page 363
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How Energy Moves in Ecosystems

• Everything that living things do requires energy.
• The flow of energy controls the types of
  organisms that live in an ecosystem

Most life depends on photosynthetic organisms
which get their energy from the sun and produce
food (organic compounds)
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• Producers
• -organism which capture energy
• (plants, some bacteria, and algae)

Consumers - organisms that consume plants or
other organisms to obtain energy necessary to live
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• Trophic Level
• a group of organisms that have the same source of
  energy
• a specific level in a food chain

Energy moves from one trophic level to another
...
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Energy Flow

• Food Chains and Food Webs
• A single pathway of energy transfer is a food
  chain
• A network showing all paths of energy transfer is
  a food web

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The lowest trophic level of any ecosystem are the
producers which take energy from the sun and
build energy-rich carbohydrates
Primary consumers are next
Herbivores animals that eat plants or other
producers (must be able to break down a plants
molecules
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The lowest trophic level of any ecosystem are the
producers which take energy from the sun and
build energy-rich carbohydrates
Primary consumers are next
Herbivores animals that eat plants or other
producers (must be able to break down a plants
molecules
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• Carnivores - animals that eat herbivores
  (meat)

Omnivores organisms that eat both plants and
animals
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• Detritivores
• organisms that obtain their energy from the
  organic wastes and dead bodies
• Decomposers
• cause decay which releases nutrients back into
  the soil

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Energy Loss in ecosystems

• When energy transfers from one organism to
  another a portion of it is lost (movement,
  breathing, almost 50 as heat)

In fact, only 10 of energy is available to the
next level
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• Energy Pyramids
• - the greatest biomass is at the bottom because
  it supports all organisms above it.

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• Trophic levels are limited
• Due to potential energy loss
• To determine the amount of energy present at
  trophic levels, ecologists measure the biomass
  (dry weight of tissue and other organic matter
  found in an ecosystem.

- each higher trophic level contains only 10 of
the biomass found in the level below it
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17-3 Ecosystems Cycle Materials

• Materials cycle between living and nonliving
  things
• Water, minerals, carbon, etc.
• Biogeochemical cycles pathways that form when a
  substance enters a living organism, stays, then
  returns to a nonliving environment

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• Water Cycle
• - Precipitation rain, snow, sleet, hail
• - Transpiration
• Loss of water (evaporation) through leaves

- Evaporation from liquid to water vapor
in the air
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• - Percolation when water filters through the
  soil to become ground water
• - Runoff
• When precipitation travels to lakes and streams

- Water Vapor the gas form of water, when it
condenses, clouds form
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Carbon Cycle
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• Carbon Cycle
• Photosynthesis
• Requires carbon dioxide
• Cell respiration
• Uses carbon dioxide
• Combustion
• Burning of fossil fuels returns Carbon dioxide
• Erosion
• Erosion of limestone allows carbon dioxide to
  become available

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• Nitrogen Cycle
• Living organisms cannot use Nitrogen directly
  from the atmosphere
• Nitrogen needed for proteins
• Plants and bacteria work together to make
  Nitrogen available

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• Nitrogen Fixation
• - the process of combining nitrogen with
  hydrogen to form ammonia
• - carried out primarily by bacteria
• the ammonia is converted to nitrates in the soil
  that plants can absorb into their systems to help
  them build proteins and nucleic acids