Ecosystems: What Are They and How Do They Work?

1
Chapter 3

• Ecosystems What Are They and How Do They Work?

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THE NATURE OF ECOLOGY

• Ecology - study of how organisms interact with
  one another and with their nonliving environment.

Figure 3-2
3
Important Ecological Terms

• Organism
• Cell
• Eukaryote
• Prokaryote
• Species
• Asexual Reproduction
• Sexual Reproduction

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Organisms and Species

• Organisms
• Populations
• Communities
• Ecosystems
• Biomes
• Biosphere

Figure 3-3
5
Other animals 281,000
Known species 1,412,000
Insects 751,000
Fungi 69,000
Prokaryotes 4,800
Plants 248,400
Protists 57,700
Fig. 3-3, p. 52
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Populations

• Genetic diversity provides basis for survival
  in harsh conditions possibilities for evolution
  

Figure 3-5
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Oceanic Crust
Continental Crust
Atmosphere
Vegetation and animals
Biosphere
Lithosphere
Soil
Upper mantle
Crust
Asthenosphere
Rock
Lower mantle
Core
Mantle
Crust (soil and rock)
Biosphere (living and dead organisms)
Hydrosphere (water)
Lithosphere (crust, top of upper mantle)
Atmospherre (ai)
Fig. 3-6, p. 54
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Earths Life-Support Systems

• Atmosphere
• Contains troposphere (inner layer - 11 miles
  above sea level - weather) stratosphere (ozone
  layer).
• Hydrosphere
• All the earths water liquid, ice, water vapor
• Lithosphere
• The earths crust and upper mantle.

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What Sustains Life on Earth?

• 1) Solar energy
• 2) Cycling of matter
• 3) Gravity

Figure 3-7
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What Happens to Solar Energy Reaching the Earth?

• 1) Warms the atmosphere
• 2) Evaporates and recycles water
• 3) Generates winds and supports plant growth.

Figure 3-8
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ECOSYSTEM COMPONENTS

• Biomes (terrestrial aquatic)
• Climate vs. weather
• Range of tolerance

Figure 3-9
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Nonliving and Living Components of Ecosystems

• Abiotic vs. biotic components
• Ecotones (edge effect)

Figure 3-10
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Factors That Limit Population Growth

• Law of tolerance
• Limiting factors

Figure 3-11
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Factors That Limit Population Growth

• The physical conditions of the environment can
  limit the distribution of a species.

Figure 3-12
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Biotic components of ecosystems

• Producers
• Consumers
• Decomposers
• Herbivores (prim. Consumer)
• Carnivores (primary, secondary, tertiary)
• Omnivore
• Detritivore
• Scavenger

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Producers Basic Source of All Food

• Chemosynthesis
• Organisms such as deep ocean bacteria draw energy
  from hydrothermal vents and produce carbohydrates
  from hydrogen sulfide (H2S) gas
• Photosynthesis

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Photosynthesis A Closer Look

• Chlorophyll molecules in the chloroplasts of
  plant cells absorb solar energy.
• Complex series of chemical reactions converts
  carbon dioxide and water to sugars and oxygen.

Figure 3-A
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Decomposers and Detritivores

• Decomposers Recycle nutrients in ecosystems.
• Detritivores Insects or other scavengers that
  feed on wastes or dead bodies.

Figure 3-13
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Aerobic and Anaerobic Respiration Getting Energy
for Survival

• Aerobic Respiration
• The opposite of photosynthesis

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Aerobic and Anaerobic Respiration Getting Energy
for Survival

• Anaerobic respiration or fermentation
• In the absence of oxygen.
• The end products vary based on the chemical
  reaction
• Methane gas
• Ethyl alcohol
• Acetic acid
• Hydrogen sulfide

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BIODIVERSITY
Figure 3-15
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Biodiversity Loss and Species Extinction
Remember HIPPO

• H for habitat destruction and degradation
• I for invasive species
• P for pollution
• P for human population growth
• O for overexploitation

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Why Should We Care About Biodiversity?

• Biodiversity provides us with
• 1) Natural Resources (food water, wood, energy,
  and medicines)
• 2) Natural Services (air and water purification,
  soil fertility, waste disposal, pest control)
• 3) Aesthetic pleasure

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ENERGY FLOW IN ECOSYSTEMS

• Food chains
• Food webs

Figure 3-17
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Food Webs

• Trophic levels are interconnected within a more
  complicated food web.

Figure 3-18
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Energy Flow in an Ecosystem Losing Energy in
Food Chains and Webs

• 2nd law of thermodynamics - there is a decrease
  in the amount of energy available to each
  succeeding organism in a food chain or web.
• 10 Rule
• Rarely have more than 4-5 trophic levels

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Energy Flow in an Ecosystem Losing Energy in
Food Chains and Webs

• Ecological efficiency percentage of useable
  energy transferred as biomass from one trophic
  level to the next.

Figure 3-19
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Productivity of Producers The Rate Is Crucial

• Gross primary production (GPP)
• Rate at which an ecosystems producers convert
  solar energy into chemical energy as biomass.

Figure 3-20
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Net Primary Production (NPP)

• NPP GPP R
• Rate at which producers use photosynthesis to
  store energy minus the rate at which they use
  some of this energy through respiration (R).

Figure 3-21
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• What are natures three most productive and three
  least productive systems?

Figure 3-22
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MATTER CYCLING IN ECOSYSTEMS

• Nutrient Cycles Global Recycling
• Biogeochemical cycles move substances through
  air, water, soil, rock and living organisms.
• 1) Hydrologic cycle (water)
• 2) Atmospheric cycles (C, N)
• 3) Sedimentary cycles (P, S)

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The Water Cycle
Figure 3-26
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Effects of Human Activities on Water Cycle

• We alter the water cycle by
• 1) Withdrawing large amounts of freshwater.
• 2) Clearing vegetation and eroding soils.
• 3) Polluting surface and underground water.
• 4) Contributing to climate change.

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The Carbon CyclePart of Natures Thermostat
Figure 3-27
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Effects of Human Activities on Carbon Cycle

• We alter the carbon cycle by adding excess CO2 to
  the atmosphere through
• 1) Burning fossil fuels.
• 2) Clearing vegetation faster than it is
  replaced.

Figure 3-28
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The Nitrogen Cycle Bacteria in Action
Figure 3-29
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The Nitrogen Cycle

• Nitrogen fixation occurs through atmospheric
  electrical discharges or nitrogen-fixing bacteria
  which
• Convert (fix) atmospheric Nitrogen to ammonia
  (NH3) that is converted to ammonium ions (NH4)
  that can be used by plants

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The Nitrogen Cycle

• Ammonia not used by plants may go through
  nitrification soil bacteria convert NH3 and
  NH4 to nitrite ions (poisonous to plants) and
  then to nitrate ions (can be used by plants)

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Other processes of Nitrogen Cycle

• Ammonification specialized decomposer bacteria
  convert nitrogen-rich organic compounds into
  simpler compounds such as NH3 and water-soluble
  salts containing NH4
• Denitrification Nitrogen leaves the soil as
  specialized bacteria convert NH4 and NH3 back
  into nitrite and nitrate ions, then into N2 gas
  and N2O (nitrous oxide)

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Effects of Human Activities on the Nitrogen Cycle

• We alter the nitrogen cycle by
• 1) Adding gases that contribute to acid rain.
• 2) Adding nitrous oxide to the atmosphere through
  farming practices which can warm the atmosphere
  and deplete ozone.
• 3) Contaminating ground water from nitrate ions
  in inorganic fertilizers.
• 4) Releasing nitrogen into the troposphere
  through deforestation.

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Effects of Human Activities on the Nitrogen Cycle

• Human activities such as production of
  fertilizers now fix more nitrogen than all
  natural sources combined.

Figure 3-30
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The Phosphorous Cycle
Figure 3-31
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Effects of Human Activities on the Phosphorous
Cycle

• 1) We remove large amounts of phosphate from the
  earth to make fertilizer.
• 2) We reduce phosphorous in tropical soils by
  clearing forests.
• 3) We add excess phosphates to aquatic systems
  from runoff of animal wastes and fertilizers.

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The Sulfur Cycle
Figure 3-32
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Effects of Human Activities on the Sulfur Cycle

• We add sulfur dioxide to the atmosphere by
• 1) Burning coal and oil
• 2) Refining sulfur containing petroleum.
• 3) Convert sulfur-containing metallic ores into
  free metals such as copper, lead, and zinc
  releasing sulfur dioxide into the environment.