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Chapter 5: How Ecosystems Work
Ecology Chapter 5: How Ecosystems Work
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Section 1: Energy Flow in Ecosystems
Life ultimately depends on the sun! Energy enters ecosystems as radiant energy from the sun. Photosynthesis 6H20 + 6CO2 + sunlight C6H12O6 + 6O2 Cellular Respiration C6H12O6 + 6 O2 6H2O + 6CO2 + ATP Energy exits ecosystems as heat
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Matter Cycles & Energy Flow
Biosphere Carbon cycle Phosphorus cycle Nitrogen cycle Water cycle Oxygen Cycle Figure 3.7 Natural capital: life on the earth depends on the flow of energy (wavy arrows) from the sun through the biosphere and back into space, the cycling of crucial elements (solid arrows around ovals), and gravity, which keeps atmospheric gases from escaping into space and helps recycle nutrients through air, water, soil, and organisms. This simplified model depicts only a few of the many cycling elements. Heat in the environment Heat Heat Heat
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Producers/Autotrophs
Use light energy to make their own food through photosynthesis
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Consumers/Heterotrophs
Cannot make their own food. Instead, they get energy by feeding on other organisms
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Types of Consumer Herbivore—gets energy by eating producers
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Omnivore Gets energy by eating producers and consumers
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Carnivore Gets energy by eating consumers
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Decomposer Get energy by breaking down dead organisms
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Energy Transfer Energy is transferred from one organism to another through feeding relationships Food Chains/Webs Purpose – shows how energy & nutrients move from one organism to another through the ecosystem Show energy flow through feeding relationships Direction: grass cow human
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Trophic Levels Each step in a food chain is a trophic level
How many trophic levels are in this food chain?
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Energy Loss Energy is lost as its transferred from one trophic level to the next Energy Pyramids show energy loss
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10% Rule Only 10% of the energy in a given trophic level is passed to the trophic level above it
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Consequences of Energy Loss
What happens to population size as one moves from lower trophic levels to higher trophic levels?
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Section 3: How Ecosystems Change
Ecological Succession The gradual process of change in the make-up of a community The final stable community is called the climax community Our climax community is an oak hickory forest The type of climax community differs depending on where you are in the world
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Saguaro national park Tucson
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Grassland Montana
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Primary Succession Primary succession begins on bare rock or sand
The first organisms are pioneer species Key idea: succession begins without soil
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Pioneer Organisms Examples include lichens, mosses and dune grass
As these organisms break apart rock, die and decompose soil begins to form. This process changes the conditions of the environment making it suitable for new organisms
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As new organisms move into the area the conditions continue to change making the area suitable for an even greater variety of organisms This process continues until a climax community is achieved
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Secondary Succession When a community undergoes a disturbance and succession occurs again it is called secondary succession Examples of disturbances include: fire, storms, farming, foresting A disturbance doesn’t remove the soil Key idea: succession begins with soil already in place.
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Old Field Succession Secondary succession that occurs after a farm is abandoned
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