Ecosystems

1
Ecosystems

• Starr/Taggarts
• Biology
• The Unity and Diversity of Life, 9e
• Chapter 49

2
Key Concepts

• An ecosystem is an association of organisms and
  their environment
• Every ecosystem has inputs and outputs of both
  energy and nutrients
• Energy flows in only one direction through an
  ecosystem
• Autotrophs are primary producer organisms for the
  ecosystem

3
Key Concepts

• The food web extends from producers through
  consumers, decomposers, and detritivores
• Water, carbon, nitrogen, and phosphorus have
  biogeochemical cycles that are global in scale
• Each substance moves through a hydrologic,
  atmospheric, or sedimentary cycle

4
The Nature of Ecosystems

• Primary producers
• Consumers
• Decomposers
• Detritivores

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fruits
insects
rodents, rabbits
birds
fruits
rodents, rabbits
insects
birds
fruits
rodents, rabbits
insects
birds
fruits
insects
rodents, rabbits
birds
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Structure of Ecosystems

• Trophic Levels
• 1st - Primary producers
• Autotrophs
• 2nd - Primary consumers
• Herbivores, Decomposers, Detritivores
• 3rd - Secondary consumers
• Primary carnivores
• 4th - Tertiary consumers
• Secondary carnivores and parasites

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MARSH HAWK
UPLAND SANDPIPER
GARTER SNAKE
CUTWORM
PLANTS
8
MARSH HAWK
CROW
HIGHER TROPHIC LEVELS Complex array of
carnivores, omnivores and other consumers. Many
feed at more than one trophic level continually,
seasonally, or when an oppportunity presents
itself
UPLAND SANDPIPER
GARTER SNAKE
FROG
WEASEL
BADGER
COYOTE
SPIDER
SECOND TROPHIC LEVEL Primary consumers (e.g.,
herbivores)
CLAY-COLORED SPARROW
EARTHWORMS, INSECTS (E.G., GRASSHOPPPERS,
CUTWORMS)
GROUND SQUIRREL
POCKET GOPHER
PRAIRIE VOLE
FIRST TROPHIC LEVEL Primary producers
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Food Webs

• Network of crossing, interlinked food chains
  involving primary producers, consumers, and
  decomposers

10
Major Pathways of Energy Flow

• Primary source
• Grazing food webs
• Photosynthetic organisms to herbivores
• Detrital food webs
• Photosynthetic organisms to detritivores and
  decomposers

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Food Webs
12
Ecological Pyramids
Decomposers
Top carnivores
Primary carnivores
Herbivores
Primary Producers
13
Energy Flow

• Energy loss with each trophic level

14
Biogeochemical Cycles
15
Hydrologic Cycle

• Rain and snow returns water to land
• Ocean currents and winds
• Evaporation
• Watershed

16
ATMOSPERE
precipitation onto land 111,000
wind driven water vapor 40,000
evaporation from land plants (evapotranspiration)
71,000
evaporation from ocean 425,000
precipitation into ocean 385,000
surface and groudwater flow 40,000
LAND
OCEAN
17
Experimental Watershed

• Deforested area had greater calcium loss than
  undisturbed area

18
Carbon Cycle

• Aerobic respiration ------gt CO2
• Fossil fuel burning
• Volcanic eruptions
• Atmosphere, soils, plant biomass
• Largest holding stations for Carbon
• CO2 - fixation
• Photosynthetic autotrophs

19
Greenhouse Gases and a Warmer Planet

• Greenhouse effect
• CO2, Ozone, Methane, Nitrous oxide, CFCs

20
Global Warming

• Atmospheric CO2
• Glaciation and Interglacial Periods

21
Greenhouse Gases
Fossil Fuel burning Deforestation
22
Nitrogen Cycle

• N2 gases converted to usable forms
• Bacteria Volcanic action Lightning

23
Human Intervention in the Nitrogen Cycle

• Decline of spruce forests
• Nutrient imbalances

24
Sedimentary Cycle

• Phosphorus Cycle
• From land to sediments at bottom of the sea then
  back to land
• Earths Crust
• Largest reservoir of phosphorus

25
Eutrophication

• Activities that increase the concentration of
  dissolved nutrients
• Nutrient enrichment of any aquatic ecosystem
• Most minerals enter sedimentary cycles
• Fertilizers use phosphates
• Dense algae blooms

26
Ecosystem Modeling

• Prediction of unforeseen effects of disturbance
• Computer programs and models
• Case Study
• DDT - mosquito control
• Biological magnification
• Higher trophic organisms have higher
  concentrations

27
In Conclusion

• An ecosystem is an array of producers, consumers,
  detritivores and decomposers and their
  environment
• There is a one-way flow of energy into and out
  from an ecosystem and cycling of materials
• Primary producers are mainly photoautotrophs

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In Conclusion

• The rate at which primary producers capture and
  store energy is the primary productivity
• Energy fixed by photosynthesizers passes through
  grazing food webs and detrital food webs
• Food webs lose energy due to metabolic activities
  of organisms in ecosystems

29
In Conclusion

• The availability of water and nutrients
  contribute to primary productivity
• Various cycles occur which move substances like
  ions, water, and nutrients from the atmosphere to
  land, animals, and back to the atmosphere
• Fossil fuel burning and deforestation contribute
  to increases in global warming

30
In Conclusion

• Nitrogen availability is a limiting factor for
  the total net primary productivity of land
  ecosystems
• Phosphorus and other minerals enter sedimentary
  cycles
• Disturbances of an ecosystem can have unexpected
  effects
• Computer modeling helps identify ecosystem
  relationships and can incorporate them into
  models
• developed by M. Roig