Environmental Science Ch. 3: How Ecosystems Work

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Environmental Science Ch. 3How Ecosystems Work
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Ch. 3-1 Energy Flow In Ecosystems

• Key Terms
• Cellular Respiration
• Consumer
• Decomposer
• Food Web
• Producer
• Trophic Level

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California Content Standards for Science
Addressed

• Life Science
• 6(d) Students know how water, carbon, and
  nitrogen cycle between abiotic resources and
  organic matter in the ecosystem and how oxygen
  cycles through photosynthesis and respiration.
• 6(e)Students know a vital part of an ecosystem is
  the stability of its producers and decomposers.
• 6(f)Students know at each link in a food web
  some energy is stored in newly made structures
  but much energy is dissipated into the
  environment as heat. This dissipation may be
  represented in an energy pyramid.

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Ch. 3 Section 1Why Do I Need To Know This?

• Because what you are depends upon what you eat .
  . . so we need to know what were eating and what
  that stuff is eating.
• Because we are removing major amounts of
  organisms from various levels in ecosystems and
  causing serious disruption to food webs and food
  chains.
• Because we can increase food production to feed
  more people without using toxic pesticides by
  understanding the importance of each and every
  trophic level in an ecosystem.

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Key Sections Ch. 3-1

• Energy Flow In Ecosystems
• Life Depends on the Sun
• An Exception in the Rule Deep-Ocean Ecosystems
• What Eats What
• Respiration Burning The Fuel
• Energy Transfers Food Chains, Food Webs, and
  Trophic Levels
• Food Chains and Food Webs
• Trophic Levels
• How Energy Loss Affects An Ecosystem

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Energy Flow In Ecosystems

• All organisms need energy in order to survive.
• To fully understand an organism and its
  ecosystem, we need to understand how it gets its
  energy and how the energy flows in the ecosystem.

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Life Depends on the Sun

• Almost all life depends either directly or
  indirectly for energy from the sun.
• Plants, algae and some bacteria can turn solar
  energy directly into energy through a process
  called photosynthesis. These organisms are
  called producers.
• When animals eat plants or other animals that ate
  plants, they are still getting their energy
  indirectly from the sun. These organisms are
  consumers.

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An Exception To the Rule Deep-Ocean Ecosystems

• There is one known exception to the rule about
  all life depending on the sun, and that is at the
  very bottom of the deep ocean.
• In 1977, scientists discovered that existed so
  deep that no sunlight could reach them.
• The scientists discovered that the plants and
  animals got their energy from volcanoes erupting
  underneath the ocean!
• They called this type of life chemosynthesis.

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What Eats What

• Consumers that only eat producers are called
  herbivores.
• Consumers that only eat other consumers are
  called carnivores.
• Consumers that eat both producers and other
  consumers are called omnivores.
• Consumers that get their nutrients by eating the
  dead remains of other organisms are called
  decomposers.

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Respiration Burning The Fuel

• Photosynthesis is the chemical reaction used by
  producers to make food.
• The chemical reaction is 6CO2 6 H20 Light
  Energy ? C6H12O6 6O2
• Respiration is the process that consumers use to
  produce energy from the food they eat.
• The chemical reaction is C6H12O6 6O2 ? 6CO2
• 6H20 Energy
• They are opposite reactions!

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Energy Transfers Food Chains, Food Webs, and
Trophic Levels

• Every time one organism eats another organism,
  energy is transferred in an ecosystem.
• Ecologists trace the transfer of energy in two
  ways
• Food Chains These show the direct line of how
  the energy is transferred from one organism to
  another.
• Food Webs These show the many feeding
  relationships between organisms in an ecosystem.

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Food Chains and Food Webs

• Food chains are especially useful in showing
  direct cause and effect relationships in an
  ecosystem.
• Food webs are useful in representing how an
  ecosystem truly works because most consumers
  usually eat more than one organism.

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Trophic Levels

• Each level of energy transfer in an ecosystem is
  known as a trophic level.
• As energy moves up each trophic level, about 90
  of the energy is lost, leaving only about 10 of
  the energy available for the next level.
• Therefore, the lowest trophic levels contain the
  largest population sizes and the highest trophic
  levels have the smallest population sizes.
• Energy is lost in each trophic level because all
  the life functions for the organisms at that
  level (such as growing, moving, reproducing,
  etc.).

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How Energy Loss Affects And Ecosystem

• When the amount of energy available at a lower
  level decreases, the amount of organisms that can
  be sustained at a higher trophic level also
  decreases and the number of trophic levels that
  can exist also decreases.
• Humans are at the top of all trophic levels.
• So, if we wipe out many lower tropic levels, we
  will reduce the number of people that can live on
  the planet and can wipe out many species that
  live at lower trophic levels.

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Ch. 3-2 The Cycling of Materials

• Key Terms
• Precipitation
• Water Cycle

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California Content Standards for Science
Addressed

• Life Science
• 6(d) Students know how water, carbon, and
  nitrogen cycle between abiotic resources and
  organic matter in the ecosystem and how oxygen
  cycles through photosynthesis and respiration.

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Ch. 3 Section 2Why Do I Need To Know This?

• Because every atom of every cell in your body has
  most likely been a part of another organism.
• Because every atom of every molecule of food that
  you eat or drink has probably been eaten, drunk,
  or used by another living organism.
• Because as long as the materials recycle, an
  ecosystem will stay in balance. When it no
  longer cycles from organism to organism, the
  ecosystem will collapse and die out.

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Key Sections Ch. 3-2

• The Cycling of Materials
• The Water Cycle
• The Carbon Cycle
• How Humans Are Affecting the Carbon Cycle
• The Nitrogen Cycle
• Closing the Nitrogen Cycle

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The Cycling of Materials

• In every ecosystem, all materials get recycled.
• All materials get recycled at various rates.
• Some are very fast, while others can take
  millions of years.
• Without the recycling of materials, all
  ecosystems would collapse when they ran out of
  limited resources.
• There are many cycles in nature, but 3 of the
  most important are
• The Water Cycle
• The Carbon Cycle
• The Nitrogen Cycle

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The Water Cycle

• Water is essential for all life.
• Although water changes form (from a solid to
  liquid to gas), the overall amount of water
  remains the same on the Earth.
• The 3 main steps to the water cycle are
• Evaporation
• Condensation
• Precipitation
• The overall force driving the water cycle is the
  energy from the sun.
• Water can be removed from the water cycle and
  stored underground as groundwater.

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The Water Cycle
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The Carbon Cycle

• Carbon is also essential for all life on Earth.
• Carbon is used to make up proteins, fats, and
  carbohydrates (all of which we need everyday).
• When consumers eat producers, they take in the
  carbon they need.
• During respiration, consumers give back carbon
  into the environment.
• Some carbon gets stored underground as the
  remains of plants and animals get buried. This
  carbon will go onto become fossil fuels.

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The Carbon Cycle
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How Humans Are Affecting The Carbon Cycle

• Fossil fuels, such as coal, oil and gasoline
  contain large amounts of carbon that has been
  stored underground.
• As humans burn fossil fuels, we are emitting
  large amounts of carbon dioxide into the
  ecosystem, which is having a major effect on the
  worlds atmosphere and climate.

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The Nitrogen Cycle

• Nitrogen is another essential element for life.
• Nitrogen is used to make proteins, which is
  necessary for life.
• Although 78 of the atmosphere is Nitrogen, only
  a special type of Nitrogen called Nitrates (NO3)
  can be used by most life forms on the planet.
• In order to get Nitrogen, most bacteria depend
  upon bacteria to fix the Nitrogen in the
  atmosphere to make it useable at Nitrates.
• The bacteria that fix the Nitrogen are called
  Nitrogen-fixing bacteria.

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Closing the Nitrogen Cycle

• Once Nitrogen enters into the ecosystem through
  the nitrogen fixing bacteria, it mostly stays
  there.
• Nitrogen in an ecosystem gets broken down by
  decomposers, such as fungi and bacteria.
• However, some Nitrogen is returned to the
  atmosphere by different bacteria.

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The Nitrogen Cycle
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Ch. 3-3 How Ecosystems Change

• Key Terms
• Climax Community
• Pioneers
• Succession

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California Content Standards for Science
Addressed

• Life Science
• 6(a) Students know biodiversity is the sum total
  of different kinds of organisms and is affected
  by alterations of habitats.
• 6(b) Students know how to analyze changes in an
  ecosystem resulting from changes in climate,
  human activity, introduction of nonnative
  species, or changes in population size.
• 6(e) Students know a vital part of an ecosystem
  is the stability of its producers and
  decomposers.

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Ch. 3 Section 3Why Do I Need To Know This?

• Because all ecosystems change over time.
• So that we can understand the role of each
  organism in its ecosystem to know how it is
  helping the ecosystem change.
• So that we can better respond to natural
  disasters and environmental problems by using
  succession to help fix the problem and restore a
  damaged ecosystem.

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Key Sections Ch. 3-3

• How Ecosystems Change
• Succession
• Secondary Succession
• Fire-Maintained Communities
• Primary Succession

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How Ecosystems Change

• All ecosystems change over time.
• Over time, areas will change from a rocky
  landscape to a very well developed and stable
  community.

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Succession

• Succession is the regular pattern of change in
  the species in a community.
• Succession happens because as one species enters
  into an ecosystem, it alters the ecosystem to
  suit it.
• As the species change the ecosystem, they make it
  more difficult for some organisms to live in the
  ecosystem and easier for others to live in it.
• Eventually, an ecosystem reaches a stable and
  final community. This is called a climax
  community.

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Secondary Succession

• Secondary succession occurs when a new community
  develops on the spot of a previously existing
  community.
• This typically happens after a major natural
  disaster (such as a fire) or after an area has
  been cleared for human use.
• Secondary succession happens rather rapidly
  (within about 150 years) because the soil and
  many of the necessary nutrients are already in
  place.
• During secondary succession, grasses and flowers
  recover first. Then, over time, shrubs and trees
  move in, and finally trees take over, crowding
  out the plants and shrubs.

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Secondary Succession
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Fire-Maintained Communities

• Many ecosystems depend upon natural fires to
  maintain themselves.
• Some species, pine trees, for example, require
  the heat from a fire to release their seeds.
• Many animals depend on natural fires to open up
  space for grasses and other producers to grow in
  order to feed upon them.
• Fire helps to eliminate new species to the
  ecosystem to help maintain the stability of that
  ecosystem.
• As a result, in some areas, firefighters allow
  naturally occurring fires to burn themselves out.

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Primary Succession

• Primary succession occurs on surfaces where no
  previous ecosystem existed.
• This is much slower process than secondary
  succession, typically taking thousands of years
  to happen.
• The first organisms to move into the new area are
  called pioneers. Bacteria and lichens are two
  common pioneers.
• The pioneers play an important role in succession
  because they turn raw material into useable
  resources for all species that follow them.