Interactions in the Ecosystem

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Interactions in the Ecosystem

• Environmental Science
• Lesson Two

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2.1 Role of Living Things

• The organisms of most ecosystems gather food in
  three basic ways producer, consumer, and
  decomposer.
• Energy enters the ecosystem only at the level of
  producer.

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2.1 Role of Living ThingsProducers

• Producers are organisms that make their own food
  from inorganic molecules and energy.
• Plants are the most common producer.
• Almost all producers capture energy from the sun
  and use it to make food. (Photosynthesis).
• Plants are the most important producers in
  terrestrial (land) ecosystems.
• Protists and Bacteria are the most important
  producers in aquatic ecosystems.

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2.1 Role of Living ThingsConsumers

• Consumers are organisms that cannot make their
  own food.
• All animals are consumers, as are fungi and most
  Protists and bacteria.
• Herbivores eat only plants. (birds and insects)
• Carnivores eat only meat by capturing herbivores
  or other carnivores. (Lions)
• Omnivores eat plants and meat producers and
  consumers. (Humans)
• Scavengers usually do not hunt living prey, but
  instead feed on the bodies of dead organisms.
  (vultures/hyenas).

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2.1Role of Living ThingsDecomposers

• Bacteria and fungi that consume the bodies of
  dead organisms and other organic wastes are
  called decomposers.
• Decomposers are crucial to the ecosystem because
  they recycle nutrients from organisms back into
  the environment.
• Nutrients are returned to the soil, where plants
  can use them as raw materials for building new
  organic material.

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2.1 Role of Living ThingsTrophic Levels

• Scientists call the different feeding levels of
  organisms in an ecosystem trophic levels.
• A trophic level is a layer in the structure of
  feeding relationships in an ecosystem.

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2.1 Role of Living ThingsTrophic Levels

• Producers make up the first and largest trophic
  level in all ecosystems.
• Autotroph means self-nourished. Plants and
  other organisms that make their own food nourish
  themselves.
• Consumers form the second and higher trophic
  levels because they do not produce their own
  food.
• Heterotroph means other nourishes. These
  organisms get their food from other organisms.
• Most ecosystems have 3, 4, or 5 levels above
  autotrophs.

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1.2 Roles of Living Things - Assignment

1. In most ecosystems, the first trophic level
   contains more organisms than the second trophic
   level. Explain this pattern.
2. List the different groups of organisms in an
   ecosystem, and explain how each type gathers
   food.
3. How do autotrophs and heterotrophs differ?

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2.2 Ecosystem Structure Food Chains and Food Webs

• A series of different organisms that transfer
  food between the trophic levels of an ecosystem
  is call a food chain.
• All food chains begin with producers, which are
  usually plants in land ecosystems.

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2.2 Ecosystem StructureFood Chain

• Producer Primary Secondary
• Consumer Consumer

Decomposer
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2.2 Ecosystem StructureFood Chain

• Few ecosystems are simple enough to portray as
  single food chains.
• Most consumers feed on more than one type of
  food, and consumers feed on more than one trophic
  level.
• A food web is a network of food chains
  representing the feeding relationships among the
  organisms in an ecosystem.

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2.2 Ecosystem Structure -Food Web
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2.2 Ecosystem StructureDiversity and Stability

• The number of links in the food web varies from
  one ecosystem to another.
• Some ecologists think that a food web with more
  diversity is more stable than one with fewer
  species.
• A stable food web can better withstand the lost
  of one species than a simpler food web can. This
  stability helps an ecosystem affected by natural
  or human-caused disasters.

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2.2 Ecosystem StructureDiversity and Stability

• A deciduous forest is an example of a stable
  ecosystem that has a food web with many links. A
  small disturbance has little effect in a
  deciduous forest.
• A tundra food web, however, has fewer links. A
  small disturbance in the tundra can have
  longer-lasting effects.

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2.2 Ecosystem StructureBiological Magnification

• The increasing concentration of a pollutant in
  organisms at higher trophic levels in a food web
  is called biological magnification.
• Biological magnification shows how pollutants
  taken in by a few organisms can affect the whole
  food web.
• .

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Biological Magnification

• The pollutant DDT was actually passed through a
  food web. DDT is a pesticide, sprayed on crops
  to kill insects. DDT was washed from farmland
  into streams and rivers by rain. The producers
  took in small amounts of DDT. But as the
  producers were eaten by primary consumers, the
  DDT became concentrated in the bodies of the
  consumers. As the highest-level consumer, Bald
  Eagles had very high concentrations of DDT in
  their bodies. This caused problems in
  reproduction, and the population of bald eagles
  decreased. Bald Eagles are now on the Endangered
  Species List.

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Biological Magnification

• Dateline 1972
• The United States bans the pesticide DDT.
  In the early 1970s, fewer than 3,000 bald eagles
  remained in the lower 48 states.
• Since the banning of DDT, the bald eagle
  population has rebounded, growing to 12,000 in
  1991.
• Scientists think that the DDT ban and
  captive breeding programs have been responsible
  for the bald eagles success.

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2.2 Assignment

• Draw a diagram of a simple food chain containing
  grass, mice, snakes, and decomposing bacteria.
  What might happen to the population of grass,
  mice, and snakes if a cat entered the chain?
• (Cats feed on snakes and mice).
• Redraw the food chain as a food web, and include
  the cat.

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2.3 Energy in the Ecosystem

• Ecological Pyramids
• Ecologists represent the relative amounts of
  energy in an ecosystem in an ecological pyramid.
• An ecological pyramid is a diagram that shows the
  relative amounts of energy in different trophic
  levels in an ecosystem.
• The pyramid is divided into sections, each
  section representing one trophic level.

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2.3 Energy in the Ecosystem

• Ecological Pyramids

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2.3 Energy in the Ecosystem

• Tertiary Consumer .1
• Secondary Consumers 1
• Primary Consumers 10
• Producers 100
• Energy from the Sun

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2.3 Energy in the Ecosystem - Assignment

• 1. Humans are omnivores and can eat both
  producers and consumers. Some people think that
  humans should eat only producers, so that the
  worlds food supply will stretch further.
• ? What is the reasoning behind this opinion?
• 2. Read the article The Comeback of the Sea
  Otter, then answer the two questions under
  checkpoint.

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2.4 Cycles of Matter

• About 96 percent of your body is made up of just
  four elements oxygen, carbon, hydrogen, and
  nitrogen.
• Elements move within an ecosystem in cycles. The
  amount of matter that enters and leaves each
  cycle is relatively small. Matter cycles
  repeatedly move elements back and forth between
  organisms and the environment.

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2.4 Cycles of Matter

• The Water Cycle

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2.4 The Water Cycle

• Water moves between the ocean, the atmosphere,
  and the land.
• Water enters the atmosphere through the process
  of evaporation. (liquid to gas)
• Water evaporates from bodies of water and moist
  areas of land.
• Water can also enter the atmosphere through a
  process called transpiration. Transpiration is
  the evaporation of water for the leaves of
  plants. (Tropical Rain Forests).

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2.4 The Water Cycle

• Water the evaporates from Earths surface rises
  in columns of air warmed by sunlight. The water
  vapor cools as it rises and condenses into tiny
  droplets, forming clouds. A water molecule may
  remain in the atmosphere for about two weeks.
• Water then returns to Earth in the form of
  precipitation rain, snow, sleet, or hail.
• Water may return to Earth far from where it
  evaporated.

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2.4 Cycles of Matter The Carbon Cycle
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2.4 The Carbon Cycle

• Plants use CO2 and sunlight to make sugars and
  starches during photosynthesis. When these
  nutrients are consumed by the plant and any other
  organisms, CO2 and energy are released.
• Two other important sources of carbon are the
  ocean and rocks.
• The ocean holds a very large amount of CO2
  because it dissolves easily in water.
• Coal, oil, and limestone are formed from the
  bodies of dead organisms. Carbon is released CO2
  when we burn fossil fuels for energy.

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2.4 Cycles of Matter The Nitrogen Cycle
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2.4 Cycles of Matter - Nitrogen

• Organisms require nitrogen in order to make amino
  acids, the building blocks of proteins.
• Legumes are plants such as peanuts, beans, and
  clover that have colonies of nitrogen-fixing
  bacteria in nodules in their roots. But most
  ammonia is consumed by other bacteria. These
  bacteria produce compounds called nitrites and
  nitrates, compounds containing nitrogen and
  oxygen.
• Nitrate is the most common source of nitrogen for
  plants, and animals get the nitrogen they need
  from proteins in the food they consume.
• Decomposers return nitrogen to the soil in the
  form of ammonia, and the cycle starts again.

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Lab Activity

• Activity 2.4 Plants and the Water Cycle