Ecosystems:
What Are They
and How Do They
Work?
Chapter 3
Learning Objectives

        What is ecology?
        What basic processes keep us and other
         organisms alive?
 ...
What is Ecology?

       Ecology is …
           the study of how organisms interact
            with each other and wit...
Categories of Life
Organisms and Species

    Organisms – Any form of life
    Species – Groups of organisms that resemble one
     another...
Other animals
Known species                    281,000
1,412,000




Insects
751,000                                    Fu...
Populations, Communities, &
Ecosystems

       Members of a species interact in groups
        called populations.
     ...
Universe
      Galaxies
    Solar systems          Biosphere
       Planets

        Earth

      Biosphere

     Ecosyste...
The Four Spheres
The Four Spheres

       Earth is our life support system.
       Earth is made up of interconnected
        spherical l...
The Atmosphere

       A thin envelope of air around the planet.
       The atmosphere is divided into four
        laye...
The Hydrosphere

       Consists of earth’s water
       Water can be found as liquid water, ice,
        and water vapo...
The Geosphere
   The Earth can also be divided into layers based on physical
    properties or chemical properties.
   3...
The Biosphere

       All of Earth’s living things.
       All of Earth’s ecosystems together.
Everything is linked to
everything else.
What Sustains
Life on Earth?
3 Interconnected Forces

        Solar Energy
        The Cycling of Matter
        Gravity
Biosphere




Carbon   Phosphorus   Nitrogen      Water   Oxygen
 cycle      cycle      cycle        cycle    cycle


    ...
Solar Energy

       The flow of high-quality energy from the
        sun through materials and living things
        in ...
Solar Energy

       About one-billionth of the sun’s output
        of energy reaches the earth.
       Much of the ene...
Solar
    radiation
                                     Energy in = Energy out


                              Reflected ...
Ecosystem Components
Biomes and Aquatic Life Zones

       Life exists on land systems called
        biomes and in freshwater and ocean
     ...
Biotic and Abiotic Factors

        Ecosystems consist of nonliving and
         living components.
        Biotic = liv...
Oxygen     Sun
                                                 (O2)

                        Producer
                   ...
Factors that Limit Population Growth
   Different species and their populations thrive under different physical
    and c...
Producers (Autotrophs)

        Some organisms in ecosystems can
         produce the food they need from
         chemic...
Consumers (Heterotrophs)

       Consumers get their food by eating or
        breaking down all or parts of other
      ...
Decomposers and Detritrivores

       Decomposers
           Specialized organisms that recycle
            nutrients in...
Scavengers                       Decomposers




                                Termite
         Bark beetle Carpenter   ...
Energy Flow
     in
Ecosystems
Food Chains and Food Webs

       Food chains and webs show how eaters, the
        eaten, and the decomposed are connect...
First Trophic      Second Trophic          Third Trophic          Fourth Trophic
                    Level              Le...
Blue whale                 Humans             Sperm whale



    Crabeater                                        Elephant...
Losing Energy in Food Chains and
Webs

       There is a decrease in the amount of
        energy available to each succe...
Ecological Efficiency

        The percentage of usable energy transferred as
         biomass from one trophic level to ...
Heat



                       Tertiary   Heat
                     consumers        Decomposers
                      (hu...
Ecological Efficiency

        Energy flow pyramids explain why the Earth can
         support more people if they eat at...
Biodiversity
Biodiversity

        A vital renewable resource is the biodiversity
         found in the earth’s variety of genes, spec...
Functional Diversity

  The biological and chemical
   processes such as energy
    flow and matter recycling
   needed fo...
Ecological Diversity


      The variety of terrestrial
            and aquatic
       ecosystems found in an
        area...
Species Diversity


      The number of species
        present in different
             habitats.
Genetic Diversity


       The variety of genetic
          material within a
       species or population.
Biodiversity Loss and Species
Extinction

        Human activities are destroying and degrading
         the habitats for...
Biodiversity Loss and Species
Extinction

     H = Habitat destruction and degradation
     I = Invasive species
     P = ...
Why Should We Care About
Biodiversity?

       Biodiversity provides us with:
           Natural Resources (food water, ...
In-Class Assignment

    1.   Read the Core Case Study on page 50.
    2.   Summarize the importance of insects in the
   ...
Solutions

    Goals, strategies and tactics for
     protecting biodiversity.




                             Figure 3-...
Soil: A Renewable Resource
What is Soil? Why is it Important?

        Soil is a slowly renewed resource that provides
         most of the nutrient...
What is Soil? Why is it Important?

        Over hundreds to thousands of years various
         types of life build up l...
What is Soil? Why is it Important?

        Soil helps cleanse water that flows through it.
        Soil helps decompose...
Mature Soils

        Soils that have developed over a long time.
        Arranged in soil horizons, each has a distinct...
Wood
              Oak tree   sorrel
                            Lords and   Dog violet                 Organic debris
   ...
Soil Layers

        O Horizon – Surface Litter Layer
            Freshly fallen or partially decomposed leaves

       ...
Soil Layers

        A Horizon – Topsoil
            Porous mixture of partially decomposed bodies of
             dead ...
Soil Layers

   2 Upper Layers
       Most plant roots and organic matter are located here

       As long as vegetatio...
Soil Layers

    B Horizon – Subsoil and C Horizon – Parent material
        Contain most inorganic matter

           ...
Wood
              Oak tree   sorrel
                            Lords and   Dog violet                 Organic debris
   ...
Soil

          The spaces (pores) between the solid organic
           and inorganic particles contain air and water.
  ...
Soil Properties

        Soils vary in the size of the particles they
         contain, the amount of space between these...
Sand                   Silt                 Clay
0.05–2 mm           0.002–0.05 mm      less than 0.002 mm
 diameter      ...
Mosaic of
                     closely
                     packed
                     pebbles,
                     boul...
Acidic
                            light-colored
                            humus

                            Iron and
 ...
Forest litter leaf
                        mold
                        Humus-mineral
                        mixture
    ...
Acid litter
                         and humus
                         Light-colored
                         and acidic
...
Matter Cycling in
Ecosystems
Nutrient Cycles: Global Recycling
   Global cycles recycle nutrients through the earth’s air, land,
    water, and living...
The Water Cycle
     A vast global cycle collects, purifies,
      distributes, and recycles the Earth’s fixed
      supp...
Water’s Unique Properties
    There are strong forces of attraction between
     molecules of water.
    Water exists as...
Rain clouds
                                                  Condensation


                                             ...
Surface Run Off

       Replenishes streams and lakes
       Causes soil erosion
       Sculpts the landscape
       T...
Effects of Human Activities on the
Water Cycle

        We alter the water cycle by…
            Withdrawing large amoun...
The Carbon Cycle
   Carbon cycles through the earth’s air, water,
    soil, and living organisms and depends on
    photo...
Fig. 3-27, pp. 72-73
The Carbon Cycle:
Earth’s Thermostat
    If the carbon cycle removes too much CO2
     from the atmosphere, the atmospher...
The Carbon Cycle:
How it Works
   Terrestrial producers remove CO2 from the
    atmosphere.
   Aquatic producers remove ...
The Carbon Cycle:
How it Works
   Some carbon atoms take a long time to recycle.
   Over millions of years, buried depos...
The Carbon Cycle:
The Role of Oceans
    Some of the atmosphere’s carbon dioxide
     dissolves in ocean water and the oc...
Effects of Human Activities on the
Carbon Cycle
   We alter the carbon cycle by…
       Clear trees and plants that abso...
CO2 emissions from fossil fuels
                   (billion metric tons of carbon equivalent)




         Year
          ...
The Nitrogen Cycle
   Different types of bacteria help recycle nitrogen through
    the Earth’s air, water, soil and livi...
The Nitrogen Cycle
   Two natural processes fix N2 into useful compounds
       Lightning

       Nitrogen Cycle

     ...
The Nitrogen Cycle
   Plants and animals return nitrogen-rich organic compounds
    to the environment as wastes, cast-of...
Gaseous nitrogen (N2)
                                            in atmosphere




                                      ...
Effects of Human Activities on the
Nitrogen Cycle
   We add large amounts of nitric oxide (NO) into the
    atmosphere wh...
Effects of Human Activities on the
    Nitrogen Cycle
   Nitrate ions in inorganic fertilizers can leach through
    the ...
Effects of Human Activities on the
Nitrogen Cycle
   We remove nitrogen from topsoil when we harvest
    nitrogen-rich cr...
The Phosphorus Cycle
   Phosphorus is a key component of DNA and energy storage
    molecules such as ATP in cells.
   P...
The Phosphorus Cycle
   Phosphate can be lost from the cycle for long
    periods of time when it washes from the land in...
mining       Fertilizer
excretion          Guano
                                                               agricultur...
Effects of Human Activities on the
Phosphorous Cycle

   We mine large quantities of phosphate rock to
    make commercia...
The Sulfur Cycle
   Sulfur circulates through the biosphere in the sulfur
    cycle.
   Much of the earth’s sulfur is st...
Sulfur     Water                                                   Acidic fog and
                                     Sul...
Effects of Human Activities on the
Sulfur Cycle

   We burn sulfur-containing coal and oil to produce
    electric power....
The Gaia Hypothesis
Is the Earth alive?
The Gaia Hypothesis

    Some people have proposed that the Earth’s
     various forms of life control or at least
     i...
The Gaia Hypothesis

   Life controls the Earth’s life-sustaining
    processes. (Strong)


   Life influences the Earth...
How Do Ecologists Learn About
Ecosystems?
   Ecologist go into ecosystems and learn what
    organisms live there and how...
Geographic Information Systems
(GIS)

       A GIS organizes, stores, and analyzes
        complex data collected over br...
Critical nesting site
                        locations



                       USDA Forest Service
             USDA
 P...
Systems Analysis
    Ecologists develop mathematical and other
     models to simulate the behavior of ecosystems.
    C...
Define objectives
  Systems
               Identify and inventory variables
Measurement
               Obtain baseline dat...
Importance of Baseline
Ecological Data
   We need baseline data on the world’s ecosystems so we
    can see how they are ...
All things come from
earth, and to earth
they all return.
Menander, 342 -290 BC
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Chapter 3

  1. 1. Ecosystems: What Are They and How Do They Work? Chapter 3
  2. 2. Learning Objectives  What is ecology?  What basic processes keep us and other organisms alive?  What are the major components of an ecosystem?  What happens to energy in an ecosystem?  What are soils and how are they formed?  What happens to matter in an ecosystem?  How do scientists study ecosystems?
  3. 3. What is Ecology?  Ecology is …  the study of how organisms interact with each other and with their nonliving environment.  The study of connections in nature
  4. 4. Categories of Life
  5. 5. Organisms and Species  Organisms – Any form of life  Species – Groups of organisms that resemble one another in appearance, behavior, chemistry, and genetic makeup  There are 4 million to 100 million species on Earth.  Most known species are microorganisms that are too small to be seen with the naked eye.  10 million to 15 million other species  1.4 million species have been named (most are insects)
  6. 6. Other animals Known species 281,000 1,412,000 Insects 751,000 Fungi 69,000 Prokaryotes 4,800 Plants 248,400 Protists 57,700 Fig. 3-3, p. 52
  7. 7. Populations, Communities, & Ecosystems  Members of a species interact in groups called populations.  Populations of different species living and interacting in an area form a community.  A community interacting with its physical environment of matter and energy is an ecosystem.
  8. 8. Universe Galaxies Solar systems Biosphere Planets Earth Biosphere Ecosystems Ecosystems Communities Populations Organisms Realm of ecology Communities Organ systems Organs Tissues Cells Protoplasm Populations Molecules Atoms Organisms Subatomic Particles Fig. 3-2, p. 51
  9. 9. The Four Spheres
  10. 10. The Four Spheres  Earth is our life support system.  Earth is made up of interconnected spherical layers that contain air, water, soil, minerals, and life.  Atmosphere (air)  Hydrosphere (water)  Geosphere (rock)  Biosphere (living things)
  11. 11. The Atmosphere  A thin envelope of air around the planet.  The atmosphere is divided into four layers based on temperature changes that occur at different distances above the Earth’s surface.  Troposphere  Stratosphere  Mesosphere  Thermosphere
  12. 12. The Hydrosphere  Consists of earth’s water  Water can be found as liquid water, ice, and water vapor.  Liquid water: surface and underground  Ice: polar ice, icebergs, permafrost  Water Vapor: gas in the atmosphere
  13. 13. The Geosphere  The Earth can also be divided into layers based on physical properties or chemical properties.  3 Layers (Chemical Properties):  Crust  Mantle  Core  5 Layers (Physical Properties):  Lithosphere  Asthenosphere  Mesosphere  Outer Core  Inner Core
  14. 14. The Biosphere  All of Earth’s living things.  All of Earth’s ecosystems together.
  15. 15. Everything is linked to everything else.
  16. 16. What Sustains Life on Earth?
  17. 17. 3 Interconnected Forces  Solar Energy  The Cycling of Matter  Gravity
  18. 18. Biosphere Carbon Phosphorus Nitrogen Water Oxygen cycle cycle cycle cycle cycle Heat in the environment Heat Heat Heat Fig. 3-7, p. 55
  19. 19. Solar Energy  The flow of high-quality energy from the sun through materials and living things in their feeding interactions, into the environment as low-quality energy, and eventually back into space as heat.  Solar energy flows through the biosphere, warms the atmosphere, evaporates and recycles water, generates winds, and supports plant growth.
  20. 20. Solar Energy  About one-billionth of the sun’s output of energy reaches the earth.  Much of the energy is reflected away or absorbed by the chemicals, dust, and clouds in the atmosphere.
  21. 21. Solar radiation Energy in = Energy out Reflected by atmosphere (34% ) Radiated by UV radiation atmosphere as heat (66%) Lower Stratosphere Absorbed (ozone layer) by ozone Visible Troposphere Greenhouse Light effect Heat Absorbed by the Heat radiated earth by the earth Fig. 3-8, p. 55
  22. 22. Ecosystem Components
  23. 23. Biomes and Aquatic Life Zones  Life exists on land systems called biomes and in freshwater and ocean aquatic life zones.  Biome = The terrestrial portion of the biosphere.  Aquatic Life Zones = Water parts of the biosphere
  24. 24. Biotic and Abiotic Factors  Ecosystems consist of nonliving and living components.  Biotic = living components  Producers  Consumers  Decomposers  Abiotic = nonliving components
  25. 25. Oxygen Sun (O2) Producer Carbon dioxide (CO2) Secondary consumer Primary (fox) consumer (rabbit) Precipitation Producers Falling leaves and twigs Soil decomposers Water Fig. 3-10, p. 57
  26. 26. Factors that Limit Population Growth  Different species and their populations thrive under different physical and chemical conditions.  Availability of matter and energy can limit the number of organisms in a population.  Limiting Factor Principle = Too much or too little of any abiotic factor can limit or prevent growth of a population, even if all other factors are at or near the optimum range of tolerance.  Precipitation/Amount of Water  Soil nutrients  Temperature  Sunlight  Salinity  Dissolved Oxygen Content
  27. 27. Producers (Autotrophs)  Some organisms in ecosystems can produce the food they need from chemicals in their environment.  Photosynthesis  Chemosynthesis
  28. 28. Consumers (Heterotrophs)  Consumers get their food by eating or breaking down all or parts of other organisms or their remains.  Herbivores/Primary Consumers – eat producers  Carnivores/Secondary Consumers – eat herbivores  Tertiary Consumers – eat other carnivores  Omnivores – eat both plants and animals
  29. 29. Decomposers and Detritrivores  Decomposers  Specialized organisms that recycle nutrients in ecosystems.  Digest or degrade living or dead organisms into simpler inorganic compounds that producers can take up form soil and water to use as nutrients.  Detritrivores  Insects and other scavengers that feed on the wastes or dead bodies of other organisms.
  30. 30. Scavengers Decomposers Termite Bark beetle Carpenter and engraving ant carpenter Long- horned galleries ant work Dry rot fungus beetle holes Wood reduced to Mushroom powder Time Powder broken down by decomposers progression into plant nutrients in soil Fig. 3-13, p. 61
  31. 31. Energy Flow in Ecosystems
  32. 32. Food Chains and Food Webs  Food chains and webs show how eaters, the eaten, and the decomposed are connected to one another in an ecosystem.  All organisms, whether dead or alive, are potential sources of food for other organisms.  There is little matter wasted in natural ecosystems.  Trophic Levels = Feeding Levels
  33. 33. First Trophic Second Trophic Third Trophic Fourth Trophic Level Level Level Level Producers Primary Secondary Tertiary (plants) consumers consumers consumers (herbivores) (carnivores) (top carnivores) Heat Heat Heat Solar energy Heat Heat Heat Heat Detritivores Heat (decomposers and detritus feeders) Fig. 3-17, p. 64
  34. 34. Blue whale Humans Sperm whale Crabeater Elephant seal seal Killer whale Leopard seal Adelie penguins Emperor penguin Squid Petrel Fish Carnivorous plankton Krill Herbivorous plankton Phytoplankton Fig. 3-18, p. 65
  35. 35. Losing Energy in Food Chains and Webs  There is a decrease in the amount of energy available to each succeeding organisms in a food chain or web. (2nd Law of Thermodynamics)  Each trophic level contains a certain amount of biomass.  Only a small portion of what is eaten and digested is actually converted into an organism’s biomass.  The amount available to each successive trophic level declines.
  36. 36. Ecological Efficiency  The percentage of usable energy transferred as biomass from one trophic level to the next.  It ranges from 2% to 40% or a loss of 60% to 98%.  10% ecological efficiency is typical
  37. 37. Heat Tertiary Heat consumers Decomposers (human) Heat 10 Secondary consumers (perch) Heat 100 Primary 1,000 consumers (zooplankton) Heat 10,000 Producers Usable energy (phytoplankton) Available at Each tropic level (in kilocalories) Fig. 3-19, p. 66
  38. 38. Ecological Efficiency  Energy flow pyramids explain why the Earth can support more people if they eat at lower trophic levels by consuming grains, vegetables, and fruits.  Food chains and webs rarely have more than four or five trophic levels.
  39. 39. Biodiversity
  40. 40. Biodiversity  A vital renewable resource is the biodiversity found in the earth’s variety of genes, species, ecosystems, and ecosystem processes.  4 Components  Functional Diversity  Ecological Diversity  Species Diversity  Genetic Diversity
  41. 41. Functional Diversity The biological and chemical processes such as energy flow and matter recycling needed for the survival of species, communities and ecosystems.
  42. 42. Ecological Diversity The variety of terrestrial and aquatic ecosystems found in an area or on the earth.
  43. 43. Species Diversity The number of species present in different habitats.
  44. 44. Genetic Diversity The variety of genetic material within a species or population.
  45. 45. Biodiversity Loss and Species Extinction  Human activities are destroying and degrading the habitats for many wild species and driving some of them to premature extinction.  Sooner or later all species become extinct because they cannot respond successfully to changing environmental conditions.  Current extinction rates are 100 to 10,000 times higher than natural extinction rates because of human activities.
  46. 46. Biodiversity Loss and Species Extinction H = Habitat destruction and degradation I = Invasive species P = Pollution P = human Population growth O = Overexploitation (overhunting, over consumption)
  47. 47. Why Should We Care About Biodiversity?  Biodiversity provides us with:  Natural Resources (food water, wood, energy, and medicines)  Natural Services (air and water purification, soil fertility, waste disposal, pest control)  Aesthetic pleasure
  48. 48. In-Class Assignment 1. Read the Core Case Study on page 50. 2. Summarize the importance of insects in the earth’s biodiversity. 3. Share with the class.
  49. 49. Solutions  Goals, strategies and tactics for protecting biodiversity. Figure 3-16
  50. 50. Soil: A Renewable Resource
  51. 51. What is Soil? Why is it Important?  Soil is a slowly renewed resource that provides most of the nutrients needed for plant growth and also helps purify water.  Soil is a thin covering over most land that is a complex mixture of eroded rock, mineral nutrients, decaying organic matter, water, air, and living organisms.  Soil forms when rock is broken down into fragments and particles by physical, chemical, and biological weathering.
  52. 52. What is Soil? Why is it Important?  Over hundreds to thousands of years various types of life build up layers of inorganic and organic matter on soil’s original bedrock.  Formation of 1 cm of soil can take from 15 years to hundreds of years.  Soil is the base of life on land.  Producers get the nutrients they need from soil and water.  You are mostly composed of soil nutrients imported into your body by the food you eat.
  53. 53. What is Soil? Why is it Important?  Soil helps cleanse water that flows through it.  Soil helps decompose and recycle biodegradable wastes.  Soil helps remove carbon dioxide from the atmosphere and stores it as carbon compounds.
  54. 54. Mature Soils  Soils that have developed over a long time.  Arranged in soil horizons, each has a distinct texture and composition.  Soil Profile – a cross-sectional view of the horizons in a soil.  Most mature soils have at least three of the possible horizons.
  55. 55. Wood Oak tree sorrel Lords and Dog violet Organic debris ladies Grasses and builds up Rock small shrubs fragments Earthworm Fern Millipede Moss and Honey fungus lichen O horizon Mole Leaf litter A horizon Topsoil B horizon Bedrock Subsoil Immature soil Regolith C horizon Young soil Pseudoscorpion Parent Mite material Nematode Root system Actinomycetes Red Earth Mite Fungus Mature soil Bacteria Springtail Fig. 3-23, p. 68
  56. 56. Soil Layers  O Horizon – Surface Litter Layer  Freshly fallen or partially decomposed leaves  Twigs  Crop wastes  Animal Wastes  Normally brown or black
  57. 57. Soil Layers  A Horizon – Topsoil  Porous mixture of partially decomposed bodies of dead plants and animals (Humus)  Inorganic materials such as clay, silt, sand  Fertile soil that produces high crop yields has a thick topsoil layer with lots of humus.  Helps topsoil hold water and nutrients taken up by plant roots.
  58. 58. Soil Layers  2 Upper Layers  Most plant roots and organic matter are located here  As long as vegetation anchors these layers, the soil will hold water and release it as needed  Full of bacteria, fungi, earthworms, and small insects  The color of topsoil is a clue to its ability to grow crops.  Dark brown or black = rich in nitrogen and organic matter  Gray, yellow, red = low in nitrogen and organic matter.
  59. 59. Soil Layers  B Horizon – Subsoil and C Horizon – Parent material  Contain most inorganic matter  Broken down rock  Transported by water from the A horizon
  60. 60. Wood Oak tree sorrel Lords and Dog violet Organic debris ladies Grasses and builds up Rock small shrubs fragments Earthworm Fern Millipede Moss and Honey fungus lichen O horizon Mole Leaf litter A horizon Topsoil B horizon Bedrock Subsoil Immature soil Regolith C horizon Young soil Pseudoscorpion Parent Mite material Nematode Root system Actinomycetes Red Earth Mite Fungus Mature soil Bacteria Springtail Fig. 3-23, p. 68
  61. 61. Soil  The spaces (pores) between the solid organic and inorganic particles contain air and water.  Plants need the oxygen for cellular respiration.  Precipitation that reaches the soil percolates through the soil layers and occupies many of the soil’s open spaces or pores. (Infiltration)  As the water seeps down it dissolves various minerals and organic matter in the upper layers and carries them to lower layers. (leaching)
  62. 62. Soil Properties  Soils vary in the size of the particles they contain, the amount of space between these particles, and how rapidly water flows through them.  Clay – Very small particles  Silt – Medium particles  Sand – Largest particles  Soil Texture – The relative amounts of the different sizes and types of these mineral particles.
  63. 63. Sand Silt Clay 0.05–2 mm 0.002–0.05 mm less than 0.002 mm diameter diameter Diameter Water Water High permeability Low permeability Fig. 3-25, p. 70
  64. 64. Mosaic of closely packed pebbles, boulders Weak humus- mineral mixture Alkaline, dark, Dry, brown to and rich reddish-brown in humus with variable accumulations Clay, of clay, calcium calcium and carbonate, compounds and soluble Desert Soil Grassland Soil salts (hot, dry climate) semiarid climate) Fig. 3-24a, p. 69
  65. 65. Acidic light-colored humus Iron and aluminum compounds mixed with clay Tropical Rain Forest Soil (humid, tropical climate) Fig. 3-24b, p. 69
  66. 66. Forest litter leaf mold Humus-mineral mixture Light, grayish- brown, silt loam Dark brown firm clay Deciduous Forest Soil (humid, mild climate) Fig. 3-24b, p. 69
  67. 67. Acid litter and humus Light-colored and acidic Humus and iron and aluminum compounds Coniferous Forest Soil (humid, cold climate) Fig. 3-24b, p. 69
  68. 68. Matter Cycling in Ecosystems
  69. 69. Nutrient Cycles: Global Recycling  Global cycles recycle nutrients through the earth’s air, land, water, and living organisms and, in the process, connect past, present, and future forms of life.  Nutrients –the elements and compounds that organisms need to live, grow, and reproduce  Biogeochemical Cycles  Water  Carbon  Nitrogen  Phosphorus  Sulfur
  70. 70. The Water Cycle  A vast global cycle collects, purifies, distributes, and recycles the Earth’s fixed supply of water.  Also called the hydrologic cycle.  Powered by energy from the sun and by gravity.  84% of water vapor in the atmosphere comes from oceans.  Most precipitation becomes surface runoff
  71. 71. Water’s Unique Properties  There are strong forces of attraction between molecules of water.  Water exists as a liquid over a wide temperature range.  Liquid water changes temperature slowly.  It takes a large amount of energy for water to evaporate.  Liquid water can dissolve a variety of compounds.  Water expands when it freezes.
  72. 72. Rain clouds Condensation Transpiration Evaporation Precipitation Transpiration to land from plants Precipitation Precipitation Evaporation Surface runoff from land Evaporation Runoff from ocean Precipitation (rapid) to ocean Infiltration and Surface Percolation runoff (rapid) Groundwater movement (slow) Ocean storage Fig. 3-26, p. 72
  73. 73. Surface Run Off  Replenishes streams and lakes  Causes soil erosion  Sculpts the landscape  Transports nutrients
  74. 74. Effects of Human Activities on the Water Cycle  We alter the water cycle by…  Withdrawing large amounts of fresh water  Clearing vegetation and eroding soils  Polluting surface and underground water  Contributing to climate change
  75. 75. The Carbon Cycle  Carbon cycles through the earth’s air, water, soil, and living organisms and depends on photosynthesis and respiration.  Carbon is the basic building block of the carbohydrates, fats, proteins, DNA, and other organic compounds necessary for life.  The carbon cycle is based on carbon dioxide (CO2)
  76. 76. Fig. 3-27, pp. 72-73
  77. 77. The Carbon Cycle: Earth’s Thermostat  If the carbon cycle removes too much CO2 from the atmosphere, the atmosphere will cool.  If the carbon cycle generates too much CO2 the atmosphere will get warmer.  Even slight changes in the cycle can affect climate and help determine the types of life that can exist on various parts of the Earth.
  78. 78. The Carbon Cycle: How it Works  Terrestrial producers remove CO2 from the atmosphere.  Aquatic producers remove CO2 from the water.  All producers use photosynthesis to convert CO2 into complex carbohydrates (like glucose)  The cells in consumers carry out aerobic respiration. They break down glucose and convert the glucose back to CO2 for reuse by consumers.  The link between photosynthesis and aerobic respiration circulates carbon in the biosphere.
  79. 79. The Carbon Cycle: How it Works  Some carbon atoms take a long time to recycle.  Over millions of years, buried deposits of dead plant matter and bacteria are compressed between layers of sediment, where they form carbon-containing fossil fuels.  This carbon is not released to the atmosphere as CO2 for recycling until these fuels are extracted and burned.  In the past 50 years, we have extracted and burned fossil fuels that took millions of years to form.
  80. 80. The Carbon Cycle: The Role of Oceans  Some of the atmosphere’s carbon dioxide dissolves in ocean water and the ocean’s photosynthesizing producers remove some.  As the ocean water warms, some of the dissolved CO2 returns to the atmosphere  Some ocean organisms build their shells and skeletons by using dissolved CO2 molecules.
  81. 81. Effects of Human Activities on the Carbon Cycle  We alter the carbon cycle by…  Clear trees and plants that absorb CO2 through photosynthesis faster than they can grow back  Add large amounts of CO2 by burning fossil fuels and wood.  Increased concentrations of can enhance the planet’s natural greenhouse effect.  Global warming disrupts global food production and wildlife habitats, alter temperature and precipitation patterns, and raise the average sea level in various parts of the world.
  82. 82. CO2 emissions from fossil fuels (billion metric tons of carbon equivalent) Year Low projection High projection Fig. 3-28, p. 74
  83. 83. The Nitrogen Cycle  Different types of bacteria help recycle nitrogen through the Earth’s air, water, soil and living organisms.  Nitrogen is…  The most abundant gas in the atmosphere  Crucial component of proteins, vitamins, nucleic acids  N2 cannot be absorbed and used directly as a nutrient by multicellular plants or animals.
  84. 84. The Nitrogen Cycle  Two natural processes fix N2 into useful compounds  Lightning  Nitrogen Cycle  Nitrogen-fixing bacteria in soil and aquatic environments convert (fix) gaseous nitrogen (N2 ) into ammonia (NH3) which is later converted into ammonium ions (NH4+) that can be used by plants.  Ammonia not taken up by plants undergoes nitrification. Specialized soil bacteria convert the NH3 and NH4+ into nitrite ions (NO2-) which are toxic to plants, and then to nitrate (NO3-) ions which are taken up by the roots of plants.  Animals get their nitrogen by eating plants or plant-eating animals.
  85. 85. The Nitrogen Cycle  Plants and animals return nitrogen-rich organic compounds to the environment as wastes, cast-off particles, and through their bodies when they die.  In ammonificiation, large numbers of specialized decomposer bacteria convert organic material into simple nitrogen-containing inorganic compounds such as ammonia (NH3) and water-soluble salts containing ammonium ions (NH4+).  In denitrification, nitrogen leaves the soil as specialized bacteria in waterlogged soil and in the bottom sediments of lakes, oceans, swamps, and bogs to convert NH3 and NH4+ back into nitrite and nitrate ions, then into nitrogen gas (N2) and nitrous oxide gas (N2O). These gases are released to the atmosphere to begin the nitrogen cycle again.
  86. 86. Gaseous nitrogen (N2) in atmosphere Food webs on land Nitrogen fixation Fertilizers Uptake by Loss by Uptake by autotrophs Excretion, death, autotrophs denitrification decomposition Ammonia, ammonium in soil Nitrogen-rich wastes, Nitrate in soil remains in soil Nitrification Ammonification Loss by Loss by leaching leaching Nitrite in soil Nitrification Fig. 3-29, p. 75
  87. 87. Effects of Human Activities on the Nitrogen Cycle  We add large amounts of nitric oxide (NO) into the atmosphere when N2 and O2 combine as we burn any fuel at high temperatures.  This gas can be converted to nitrogen dioxide gas (NO2) and nitric acid (HNO3) which can return to the Earth’s surface as acid rain.  We add nitrous oxide (N2O) to the atmosphere through the action of anaerobic bacteria on livestock wastes and commercial inorganic fertilizers applied to soil.  This gas can warm the atmosphere and deplete ozone in the stratosphere.
  88. 88. Effects of Human Activities on the Nitrogen Cycle  Nitrate ions in inorganic fertilizers can leach through the soil and contaminate groundwater.  This is harmful to drink, especially for infants and small children.  We release large quantities of nitrogen stored in soils and plants as gaseous compounds into the troposphere through destruction of forests, grasslands, and wetlands.  We upset aquatic ecosystems by adding excess nitrates to bodies of water through agricultural runoff and discharges from municipal waste systems.
  89. 89. Effects of Human Activities on the Nitrogen Cycle  We remove nitrogen from topsoil when we harvest nitrogen-rich crops, irrigate crops, and burn or clear grasslands and forests before planting crops.  Since 1950 human activities have more than doubled the annual release of nitrogen from the terrestrial portion of the earth into the rest of the environment.  This is a serious local, regional, and global environmental problem that has attracted little attention when compared to global warming and depletion of the ozone layer.
  90. 90. The Phosphorus Cycle  Phosphorus is a key component of DNA and energy storage molecules such as ATP in cells.  Phosphorus circulates SLOWLY through water, the earth’s crust, and living organisms through the phosphorous cycle.  On a human time scale, much phosphorus flows one-way from the land to the oceans.  Phosphate is found as phosphate salts containing phosphate ions (PO43-) in terrestrial rock formations and ocean bottom sediments.  As water runs over the phosphorus-containing rocks, it erodes away inorganic compounds that contain phosphate ions.
  91. 91. The Phosphorus Cycle  Phosphate can be lost from the cycle for long periods of time when it washes from the land into streams and rivers and is carried to the ocean.  Plants obtain phosphorus as phosphate ions directly from soil or water and incorporate it in various organic compounds.  Animals get their phosphorous from plants and eliminate excess phosphorus in their urine.  Most soils contain little phosphate so it is the limiting factor for plant growth on land unless phosphorus is applied to the soil as fertilizer.
  92. 92. mining Fertilizer excretion Guano agriculture uptake by weathering uptake by autotrophs autotrophs Marine Dissolved leaching, runoff Dissolved Land Food in Ocean in Soil Water, Food Webs Water Lakes, Rivers Webs death, death, decomposition decomposition sedimentation settling out weathering uplifting over geologic time Marine Sediments Rocks Fig. 3-31, p. 77
  93. 93. Effects of Human Activities on the Phosphorous Cycle  We mine large quantities of phosphate rock to make commercial inorganic fertilizers and detergents.  We reduce the available phosphate in tropical soils when we cut down areas of tropical forests.  We disrupt aquatic systems with phosphates from runoff of animal wastes and fertilizers and discharges from sewage treatment systems.  Human activities have increased the natural rate of phosphorous about 3.7 times since 1900.
  94. 94. The Sulfur Cycle  Sulfur circulates through the biosphere in the sulfur cycle.  Much of the earth’s sulfur is stored underground in rocks and minerals, including sulfate (SO42-) salts buried deep under ocean sediments.  Sulfur enters the atmosphere…  As H2S and SO2 from volcanoes  As particles of sulfate salts from sea spray, dust storms, and forest fires.  When produced by marine algae as dimethyl sulfide (DMS).
  95. 95. Sulfur Water Acidic fog and Sulfuric acid precipitation trioxide Ammonia Ammonium Oxygen sulfate Sulfur dioxide Hydrogen sulfide Plants Dimethyl Volcano sulfide Industries Animals Ocean Sulfate salts Metallic Decaying matter Sulfur sulfide deposits Hydrogen sulfide Fig. 3-32, p. 78
  96. 96. Effects of Human Activities on the Sulfur Cycle  We burn sulfur-containing coal and oil to produce electric power.  We refine sulfur containing petroleum to make gasoline, heating oil and other useful products.  We convert sulfur-containing metallic mineral ores into free metals such as copper, lead, and zinc. This releases large amounts of sulfur dioxide into the environment.
  97. 97. The Gaia Hypothesis Is the Earth alive?
  98. 98. The Gaia Hypothesis  Some people have proposed that the Earth’s various forms of life control or at least influence its chemical cycles and other earth- sustaining processes.  Named for the Greek goddess of the Earth.  First proposed in 1979 by English inventor and atmospheric chemist James Lovelock
  99. 99. The Gaia Hypothesis  Life controls the Earth’s life-sustaining processes. (Strong)  Life influences the Earth’s life-sustaining processes. (Weak)  The Earth is an incredibly complex system that sustains itself and adapts to changing environmental conditions to reach an optimal physical and chemical environment for life on this planet.
  100. 100. How Do Ecologists Learn About Ecosystems?  Ecologist go into ecosystems and learn what organisms live there and how they interact, use sensors on aircraft and satellites to collect data, and store and analyze geographic data in large databases.  Field Research  Geographic Information Systems  Remote Sensing  Ecologists use aquarium tanks, greenhouses, and controlled indoor and outdoor chambers to study ecosystems.
  101. 101. Geographic Information Systems (GIS)  A GIS organizes, stores, and analyzes complex data collected over broad geographic areas.  Allows the simultaneous overlay of many layers of data.
  102. 102. Critical nesting site locations USDA Forest Service USDA Private Forest Service owner 1 Private owner 2 Topography Habitat type Forest Wetland Lake Grassland Real world Fig. 3-33, p. 79
  103. 103. Systems Analysis  Ecologists develop mathematical and other models to simulate the behavior of ecosystems.  Can help us understand large and very complex systems (rivers, oceans, forests, grasslands, cities, and climate)  Researchers can change values of the variables in their computer models to project possible changes in environmental conditions, help anticipate environmental surprises, and analyze the effectiveness of various alternative solutions to environmental problems.
  104. 104. Define objectives Systems Identify and inventory variables Measurement Obtain baseline data on variables Make statistical analysis of Data relationships among variables Analysis Determine significant interactions System Objectives Construct mathematical model Modeling describing interactions among variables System Run the model on a computer, Simulation with values entered for different Variables System Evaluate best ways to achieve Optimization objectives Fig. 3-34, p. 80
  105. 105. Importance of Baseline Ecological Data  We need baseline data on the world’s ecosystems so we can see how they are changing and develop effective strategies for preventing or slowing their degradation.  Scientists have less than half of the basic ecological data needed to evaluate the status of ecosystems in the United Sates (Heinz Foundation 2002; Millennium Assessment 2005).
  106. 106. All things come from earth, and to earth they all return. Menander, 342 -290 BC
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