Ecosystem Ecology Ecosystems:  What  Are  They  and  How  Do  They  Work?  

Ecology: Levels • Multiple levels of ecology:

•  Organisms •  Populations: groups of

individuals of same species in same place

•  Communities: populations in same place

•  **Ecosystems: community interacting with environment

•  Biosphere: parts of earth’s air, water, and soil where life is found

Ecology • Ecosystems

survive on the: •  FLOW of

energy • CYCLING

of matter

Ecology: Three Important Factors

} Life  depends  on  3  interconnected  factors:  1.  The  one-­‐way  flow  of  energy  from  the  sun  à  

organisms  à    the  environment  as  heat  à  back  out  into  space  as  heat  (open  system)  Governed  by  laws  of  thermodynamics!  

 

2.  The  cycling  of  maKer  through  parts  of  the  biosphere  (closed  system)  

3.  Gravity:  allows  the  planet  to  hold  onto  its  atmosphere  and  enables  movement  of  chemicals  in  their  maKer  cycles  

Ecology: Ecosystems } Ecosystems  Have  Living  and  Nonliving  Components  } AbioNc:  nonliving  component  

} Water  } Air  } Nutrients  } Rocks  } Heat  } Solar  energy    

} BioNc  } Living  and  once  living  } Plants,  animals,  microbes  

 

• Producers & Consumers Are the Living Components of Ecosystems

• Each assigned a trophic level (feeding level) • Producers aka autotrophs are the 1st trophic level

•  Producers / autotrophs make the nutrients they need from compounds and energy from their environment •  Perform Photosynthesis:

• Or Chemosynthesis: make nutrients without sunlight (specialized bacteria can do this; hydrothermal vents)

• Autotrophs/producers are found at the bottom of the “food chain” – have the most energy

• Types of Autotrophs:

• Terrestrial: § Nonvascular plants: Mosses § Vascular plants: Ferns, Gymnosperms (conifers),

Angiosperms (flowering plants) § Some algae (not plants, are protists!)

• Aquatic: § Phytoplankton: = floating producers

§  Algae (diatoms, seaweed) §  Cyanobacteria

§ Freshwater & marine plants

http://www.planktonchronicles.org/en/episode/plankton

• Consumers aka heterotrophs: must consume other organisms for energy (and nutrients) • Primary consumers = eat autotrophs • Secondary consumers = eat the autotroph-

eaters • Tertiary consumers = eat the eaters of the

autotroph-eaters

} Types  of  Heterotrophs:  } Herbivore  (Ex:  elephants,  caterpillars,  zooplankton)  

§  Energy/nutrients  from  plant/algae  material    

} Carnivores  (Ex:  spiders,  lions,  fish)  §  Energy/nutrients  from  animals/meat    

} Omnivores  (Ex:  pigs,  rats,  bears,  humans)  §  Energy/nutrients  from  both  plant  and  animal  maKer    

} Types  of  Heterotrophs  conNnued:  } Scavengers  (Ex:  vultures,  hyenas)  

§  Energy/nutrients  from  large  pieces  of  dead  and  decaying  animal/meat    

} DetriNvore  (Ex:  worms,  insects,  small  crabs)  §  Energy/nutrients  from  medium  pieces  of  dead  organic  maKer  (plant  or  animal)    

} Types  of  Heterotrophs  conNnued:  } Decomposers:  consumers  that  digest  on  a  molecular  scale  &  release  nutrients  (BUT  NOT  ENERGY!)  back  into  the  environment  §  Includes:  Bacteria  &  Fungi  § Are  present  basically  at  every  trophic  level  

 

• Both Producers & Consumers Perform Respiration

• Aerobic respiration: making energy from sugar in the presence of oxygen

• Anaerobic respiration/ fermentation: energy gained in absence of oxygen. End products include methane gas (CH4), ethyl alcohol, acetic acid, and hydrogen sulfide

ATP

• As energy flows through ecosystems in food chains and webs, the amount of chemical energy available to organisms at each succeeding trophic level decreases.

•  Food Chain: One way-flow of energy (always lost has heat back out to space)

Photosynthesis → feeding → decomposition

} Usable  Energy  Decreases  with  Each  Link  in  a  Food  Chain  or  Web  

} Biomass:  Dry  weight  of  all  organic  maKer  of  a  given  trophic  level  in  a  food  chain  or  food  web  }  Chemical  energy  is  stored  in  biomass  

 

}  Ecological  Efficiency:  %  of  usable  energy  transferred  as  biomass  from  one  trophic  level  to  the  next  } Typical  is  10%  efficient  (90%  of  energy  is  lost)  }  Is  diagramed  as  the  Pyramid  of  Energy  Flow  

Practice Problem!

•  If a primary producer captures 5,000 units of energy from the sun, how much usable energy will be available to a tertiary consumer in the ecosystem?

• Answer: •  5 units

•  5000 units x 0.1 = 500 units for primary consumers à

•  500 units x 0.1 = 50 units for secondary consumers à

•  50 units x 0.1 = 5 units for tertiary consumers

•  How Fast Can Producers Produce Biomass? = Productivity

•  Gross primary productivity (GPP): the rate at which producers in an ecosystem convert solar energy into biomass •  Measured in Kcal/m2/year

•  Net primary productivity (NPP): the rate at which producers use photosynthesis to store energy minus the rate at which they use some of this stored energy

R is the amount of energy used in respiration

•  GPP vs. NPP:

•  Some ecosystems have higher NPP than others:

} MaKer,  in  the  form  of  nutrients,  cycles  within  and  among  ecosystems  and  the  biosphere,  and  human  acNviNes  are  altering  these  chemical  cycles.  

} Biogeochemical  cycles/  nutrient  cycles  } Hydrologic  (water)  } Carbon  } Nitrogen  } Phosphorus  } Sulfur    

 

•  Hydrologic Cycle •  Only cycle in which nutrient does not undergo chemical change

Water into vapor Evaporation from plant leaves Water vapor into liquid droplets

Rain, sleet, snow

Movement of water through soil & rock to aquifers

Surface movement down slopes to the sea

• Alteration of the hydrologic cycle by humans: •  Withdrawal of large amounts of freshwater at rates faster

than nature can replace it •  Clearing of vegetation from land & cover it with buildings

& asphalt à increases runoff, erosion •  Draining wetlands for farming and urban development à

increases flooding •  Water Pollution •  Warmer climate à change precipitation patterns

Cycling of Carbon •  CO2 in

atmosphere •  à converted to

carbohydrates by producers during photosynthesis

•  à producers & consumers break down carbs during aerobic respiration, release CO2 back into atmosphere

•  Decomposers release carbon stored in bodies

•  CO2 is also dissolved in the oceans (major sink/reservoir)

• à used in photosynthesis by marine producers

• à involved in marine food webs

•  Stored in limestone or sediments

Ecology: Cycling of Carbon •  Over millions

of years, buried deposits of dead plant matter & bacteria are compressed between layers of sediment

• à high pressure and heat convert them to fossil fuels

} AlteraNon  of  the  carbon  cycle  by  humans:  } Burn  fossil  fuels  à  releases  carbon  dioxide  into  atmosphere  

}  Electricity  (burn  coal)  }  TransportaNon  (burn  oil)  

} Clearing  forests  }  Removes  carbon-­‐absorbing  trees  }  Burning  trees  puts  out  CO2  

} CO2  is  a  greenhouse  gas  that    traps  heat  in  our  atmosphere  

http://www.youtube.com/watch?v=8oblMClD2oU

Cycling of Nitrogen •  Important

component of proteins & nucleic acids

•  Atmosphere is major reservoir for nitrogen (N2)

•  But N2 cannot be taken in by organisms

} Steps:  1.  Nitrogen  fixa8on:  nitrogen-­‐fixing  bacteria  convert  N2  to  ammonia  (NH3)  }  Can  dissolve  to  form  ammonium  (NH4

+)  

} Steps:  2.  Nitrifica8on:  bacteria  convert  NH4

+  to  nitrite  (NO2

-­‐)  à  nitrate  (NO3

-­‐)  3.  Assimila8on:  Nitrate  is  taken  up  by  plants  (cycles  in  food  web)  

} Steps:  4.  Ammonifica8on  Decomposer  bacteria  convert  nitrogenous  wastes  &  dead  organisms  back  into  NH3  and  NH4

+  

5.  Denitrifica8on:  Bacteria  convert  NO3

-­‐  in  soil  back  into  N2  or  N2O  (nitrous  oxide)    

Cycling of Nitrogen • Since 1950, human

activities have more than doubled the annual release of nitrogen from the land into the environment

• Alteration of the nitrogen cycle by humans: •  Add nitric oxide (NO) to atmosphere when burning

fuel •  NO à NO2 and HNO3 (nitric acid; part of acid rain)

• Add nitrous oxide (N2O) to atmosphere through anaerobic bacteria feeding on fertilizers

• Remove nitrogen from topsoil when growing & irrigating crops

• Alteration of the nitrogen cycle by humans: • Add excess nitrates to aquatic systems through

agricultural runoff of fertilizers & manure or sewage •  Causes Eutrophication – growth of cyanobacteria &

phytoplankton = algal blooms •  Especially in marine ecosystems like estuaries •  Results in oxygen depletion & biodiversity loss •  Creates “Dead Zones”; examples:

•  Gulf of Mexico •  Chesapeake Bay Estuary

•  Can create “Red Tide” – toxic algal bloom •  Can poison fish, mammals, birds

Cycling of Phosphorus •  Does not

include the atmosphere

•  Reservoir: salts containing phosphate (PO4

3-) in rock formations & bottom of oceans

https://www.youtube.com/watch?v=6LAT1gLMPu4

•  As water erodes rock, phosphate ions enter soil à

•  Phosphate taken up by plants & enter food web •  Important for

nucleic acids and energy transfer molecules (ATP)

•  Most soils contain little phosphate, so limits plant growth (limiting factor!)

•  That’s why fertilizers have phosphate

• Alteration of the phosphorus cycle by humans: • Removing phosphate salts from mining

• Phosphate-rich runoff enters aquatic systems (esp. freshwater) & causes algal blooms (eutrophication)

Cycling of Sulfur •  Much of world’s

sulfur is in rocks & minerals & sulfate (SO4

2-) salts in ocean sediments

•  S enters the atmosphere from: •  Volcanoes & break

down of organic matter by anaerobic decomposers à hydrogen sulfide (H2S)

•  Sulfate (SO42-)

particles come from dust storms & forest fires

}  In  atmosphere,  sulfur  dioxide  (SO2)    

is  converted  to  sulfur  trioxide  gas  (SO3)  &  sulfuric  acid  (H2SO4)    -­‐Sulfate  cycles  through  food  webs  

• Alteration of the sulfur cycle by humans: •  Factory emissions: sulfur in coal is

released into atmosphere when we burn it •  Leads to acidic precipitation

(sulfuric acid) •  Refining petroleum •  Smelting metallic ores (copper, lead, zinc)

•  Smelt: To melt or fuse (ores) in order to separate the metallic constituents.

Biomes & Aquatic Life Zones

} Large  regions  of  similar  ecosystems:  }  Terrestrial  areas  are  called  biomes:    large  

regions  characterized  by  a  disNnct  climate  and  specific  species  adapted  to  it  

} Forests  (conifer,  deciduous,  rain  forest)  } Deserts  } Grasslands    

} AquaNc  areas  are  called  aquaNc  life  zones:  } Freshwater  (lakes,  ponds,  rivers,  streams,  wetlands)  } Marine  (coral  reefs,  coastal  regions,  deep  ocean)  

Ecology: Biomes & Aquatic Life Zones

Biozone Assignments: Lab Review for Unit 5 •  Food Web worksheet •  Nitrogen Cycle page (p. 75-76) •  Phosphorus Cycle (p.80) •  Sulfur Cycle (p. 81)

•  Once done – work on Study Guide

• Warm-Up Video: Should We All Be Eating Insects? https://www.youtube.com/watch?v=iM8s1ch5TRw&list=UUC552Sd-3nyi_tk2BudLUzA)