Biology 213 Chapter 55

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Biology 213 Chapter 55

• Ecosystems and the Biosphere

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You will be able to

• Compare contrast food chains, webs, and
  pyramids
• Explain Bioaccumulation magnification
• Describe C cycle, N cycle, P cycle H2O cycle in
  the biotic and abiotic environment.
• Examine human influence on natural cycles
• Describe role of the sun in
• Creating seasons
• Weather systems
• Developing ocean currents
• Creating a climate and weather

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• Energy flow through an ecosystem
• Linear
• Sun to producer to consumer to decomposer

Is the sun the only source of energy for food
webs?
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Energy flow through an ecosystem A food chain
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Food chains, webs, trophic levels.
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Food chains, webs, trophic levels.
Trophic relationships important in endangered
wildlife management e.g. DDT ? Bald Eagle
Condors
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• Ecological pyramids
• Express progressive reduction in s of
• Organisms
• Biomass
• energy
• found in
• successive
• trophic levels

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Food chains, webs, trophic levels.
Not all animals or plants are eaten. Portions
(beaks, shells, bones, etc.)
not digested. Matter energy transfer not
efficient.
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Pyramids of biomass
Usually amount of fixed energy in an ecosystem is
measured in quantity of living material biomass
Generally amount of biomass decreases at
successively higher trophic levels. Why?
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Pyramid of biomass
If you want to support a lot of humans, what
should you feed them?
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Pyramids of energy

• What happens to the energy?
• Undigested parts
• Entropy
• Energy
• expended in
• hunting
• processing food

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Bioaccumulation build up of toxins in an
organism Biological magnification increasing
concentration in successive trophic levels
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• Gross primary productivity (GPP)
• Rate at which photosynthesis captures energy
• Net primary productivity (NPP)
• Energy remaining after plants and other producers
  carry out cellular respiration

What do you think are the most productive
ecosystems?
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NPP for selected ecosystems

• Ecosystem Avg NPP (g dry matter/m2/yr)
• Algal beds reefs 2,500
• Tropical rain forest 2,200
• Swamp marsh 2,000
• Estuaries 1,500
• Temperate evergreen forest 1,300
• Temperate deciduous forest 1,200
• Savanna 900
• Boreal (northern) forest 800

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NPP for selected ecosystems

• Ecosystem Avg NPP (g dry matter/m2/yr)
• Woodland shrubland 700
• Agricultural land 650
• Temperate grassland 600
• Upwelling in oceans 500
• Lake and stream 250
• Arctic and alpine tundra 140
• Open ocean 125
• Desert and semi-desert scrubland 90
• Extreme desert (rock, sand, ice) 3

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Why is Carbon important in the ecosystem?

• What form is carbon used by plants?
• CO2 absorbed / O2 released
• Sugars (starch) formed
• Sugar used for Energy (cellular respiration)
• What form is carbon used by animals?
• Sugar used for Energy (cellular respiration)
• CO2 released / O2 absorbed
  (see Joseph Priestlys experiments)
• Remember
• C forms the skeleton for every biomolecule

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How does Carbon cycle in the environment?

• Biotic factors
• plants and animals gaseous form
• Trees store carbon
• Seashells solid form calcium carbonate
• Abiotic factors
• Atmospheric gas circulates globally
• Mineral compounds limestone
• Fossil fuels remnants of ancient plants
• and marine critters

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• Biogeochemical Cycles
• The Carbon cycle
• Carbon dioxide is the most important gas (0.038
  of air)
• gas phase allows for global circulation
• Carbon enters plants as CO2

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• Biogeochemical Cycles
• The Carbon cycle
• CO2 returned to the environment
• Cellular respiration
• Combustion volcanoes
• Erosion of limestone
• Decomposition

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Carbon cycle
Carbon Reservoirs in billions of metric tons
Atmosphere 720 Fossil fuels 4,000
Ocean 39,000 Soils 1500 Carbonates
100,000,000 Land plants 560

• most C is in rocks (carbonates sediments)
• most C not in rocks is dissolved in ocean
• 3 x more C in soils than in land plants
• Methane hydrates under sea floor

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Carbon Cycle
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Nitrogen cycle
Why is nitrogen important to living things? How
is it used? Proteins, DNA, Chlorophyll
formation.
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• Nitrogen cycle
• Five steps
• Nitrogen fixation
• Nitrification
• Assimilation
• Ammonification
• Denitrification

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Nitrogen fixation 2 moles of ammonia produced
by prokaryotes from 1 mole of N2 gas

• N2 8H 8e- 16 ATP 2NH3 H2 16ADP 16
  Pi

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Combustion, volcanoes, industry, and lightning
can fix N2 as nitrates nitrites
Lightning N2 O2 --------------gt 2 NO (nitric
oxide) Nitric oxide free radical combines with
O2 to form NO2. 2 NO O2 ---------------gt 2NO2
Nitrogen dioxide dissolves in water to produce
nitric and nitrous acids 2 NO2
H2O -------gt HNO3 HNO2 These acids readily
release NO3 NO2 ions - utilized
by plants micro-organisms. HNO3 --------gt H
NO3- (nitrate ions) HNO2 --------gt H NO2-
(nitrite ions)
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Nitrification

• Ammonia converted to ammonium to nitrate

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Assimilation

• Roots absorb
• Ammonia (NH3)
• Ammonium ions
• Nitrate ions
• Make plant proteins, nucleic acids, chlorophyll

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Ammonification

• Nitrogen compounds
• released as wastes
• Urea in urine
• Uric acid in bird poop
• Compounds are decomposed into ammonia by bacteria

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Denitrification

• Nitrate ions reduced to gaseous nitrogen by
  denitrifying bacteria
• Reverse nitrogen fixing process
• Anaerobic environments deep soil, swamps,
  deep ocean

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Nitrogen cycle
Both Carbon Nitrogen cycles involve gas,
biological, geochemical reservoirs
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• Phosphorus cycle
• Phosphorus erodes from rock as inorganic
  phosphate
• Animals obtain it from their diet
• Plants obtain it from the soil
• Does not have a gaseous phase,
  so cycles more locally

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Phosphorus cycle no gas phase
N and P are the major limiting factors for plant
growth
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Guano happens!

• Sea bird deposits
• Bat caves
• Used extensively in agriculture as a fertilizer
• Used in detergents
• Run-off enters streams

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Eutrophication enhanced phytoplankton growth due
excess supply of nutrients

• High concentrations of nutrients as run-off from
• Sewage
• Agriculture
• Lawns

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Eutrophication enhanced phytoplankton growth due
excess supply of nutrients

• Phytoplankton bloom
• Phytoplankton die and are eaten by bacteria
• Oxygen levels depleted fish die

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• Dr. David Schindler is an ecologist who
• worked at the Experimental Lakes Project in
• northern Ontario

• performed several experiments on eutrophication
  that led to ban on phosphates in detergents

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Phosphates are the culprit
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• Hydrologic cycle
• Renews supply of water
• Involves exchange of water btwn land, ocean,
  atmosphere, and organisms
• Water enters atmosphere by evaporation and
  transpiration
• Water leaves atmosphere as precipitation
• Distillation purifies water

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Water Basins Lakes, Oceans, Ice
How much fresh water is there?
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Transpiration and Evaporation

• Solar energy drives evaporation
• Evaporation ocean surface is main reservoir
• Transpiration plants release over 95 of water
  they absorb back into air

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Condensation and precipitation

• Solar E drives surface winds
• Winds carry moist air inland and up over
  mountains
• Cooling air loses moisture as condensation
• Precipitation rain, sleet, snow, hail, fog

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Storage percolation and ground water

• Aquifers may take hundreds of years to replenish
• Underground aquifers
• supply water for
• Streams
• Agriculture
• Wells

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Ogallala Aquifer 95 used for irrigation.
High Plains 65 of total irrigated acreage
in USA. Overuse 175,000
wells, irrigating gt 15 million acres.
Depleted much faster than natural rate of
recharge. Some states 40 x
higher.
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Hydrologic cycle
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Bottom-up processes Availability of resources
e.g. nutrient minerals controls of producers,
which
controls of herbivores,
which controls of predators, etc.
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Top-down processes Increase in top predators
cascades down food web
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• Sunlight primary source of energy
• Combo of Earths spherical shape
  
• axis tilt concentrate solar E at equator.
• Inclination of Earths axis primarily determines
  
• the seasons

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Amount of solar radiation reaching Earth

• 30 reflected back
• 47 absorbed by atmosphere
• 23 runs hydrologic cycle
• 1 drives wind and ocean currents
• 0.02 captured
• by photosynthesis
• 0.0001 used by Culhane for tanning

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Seasonal changes in temperature
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• Visible light IR radiation warm surface and
  lower part of atmosphere
• Atmospheric heat produces air movement, which
  moderates the climate

Hadley cells
Global wind map
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• Coriolis effect
• Tendency of moving air or water to be deflected
• Right in the Northern Hemisphere
• Left in the Southern Hemisphere

Does your toilet really flush straight down on
the equator?
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Atmospheric circulation
Trade winds
Doldrums
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Oceanic currents

• Generated by uneven heating of ocean surfaces
• Salinity differences
• Surface winds

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Major surface ocean currents
Modifies temperatures and affects precipitation
patterns
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• Regional precipitation differences
• Influenced by latitude, elevation, topography,
  vegetation, distance from large bodies of water,
  and location
• Precipitation greatest where warm air passes over
  ocean then cools

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Small D in sea surface temp D trade winds, which
D sea temp, which continues until
atmospheric circulation patterns precipitation
are disrupted across Pacific Indian Oceans,
surrounding continents
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Look at the geography of major deserts
Why are they found in these locations?
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Rain shadow
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Sierra Nevadas

• California side
• Moist and lush
• Nevada side
• Dry and desert-like plant communities

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Much of the suns heat is trapped in the
atmosphere by CO2

• How has man influenced global climate?
• Increased CO2 from burning fossil fuels
• What are fossil fuels?
• CO2 reservoir depleted deforestation
• Surface algae polluted
• What will happen globally? Very complex!
• What are the alternatives?