UIC BioS 101 Nyberg

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ECOSYSTEM Material Cycles

Ultimately material (elements) must cycle among the compartments in which it is found. The global paths that an element takes is referred to as its biogeochemical cycle.

Speaker Notes:

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Material is conserved in total but the proportions found in different compartments can change.

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UIC BioS 101 Nyberg

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Reading

• Chapter 54

• Today we concentrate on 54.2.

• Figure 54.14 and 54.16 describe the Carbon and Nitrogen cycles, the two major element cycles.

• The water cycle, cycling of a molecule, ignores the formation and destruction of water.

Speaker Notes:

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UIC BioS 101 Nyberg

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Ecosystem

• We used the word ecosystem to include not only the living organisms of a community, but also the abiotic components that are important to functioning of organisms.

• Abiotic components include:

  • Atmosphere and its molecules.

  • Water and molecules dissolved in it.

  • Any other non-living part important to function.

Speaker Notes:

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Ecosystem is more inclusive than community.

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UIC BioS 101 Nyberg

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Ecosystem Ecology

• Ecology that focuses on the flow of energy and materials is called ecosystem ecology.

• Typically, ecosystem ecologists are not interested in species, but rather groups aggregated by trophic level such as plants or carnivores.

Speaker Notes:

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The capacity to store and process information has changed dramatically in the last few years. Maybe future ecosystem studies will not have to rely on aggregated groups.

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UIC BioS 101 Nyberg

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Material Cycles (but energy flows)

• Energy moves from a source (and eventually is dissipated).

• Elements (material) are not gained or lost, the constant total amount does move among compartments holding different forms.

• The movement of an element among its compartments is called a cycle as an individual atom eventually moves among all comparments.

Speaker Notes:

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Biogeochemical, bio means organisms are involved, geo reflects that fact that the earth, ocean and atmosphere is involved, and chemical focus our attention on chemical elements.

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UIC BioS 101 Nyberg

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Biomass ‘Pyramids’

• If the producers grow rapidly, it may be possible for there to be more biomass of consumers than of producers.

• Oligotrophic aquatic systems frequently have a greater mass of zooplankton than of phytoplankton.

• Terrestrial systems almost always have mass pyramids close to energy pyramid (which always has less at subsequent levels).

Speaker Notes:

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UIC BioS 101 Nyberg

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Biomass shown by width

Biomass shown by width

AQUATIC SYSTEM

With rapidly growing autotrophs

Terrestrial System

Speaker Notes:

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High growth rate and low biomass imply a high flux.

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UIC BioS 101 Nyberg

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Ingestion and Excretion

• Not all the food that is eaten is absorbed –some is excreted.

• Not all the compounds that are absorbed are metabolized (broken down) equally efficiently.

• Compounds/elements that are absorbed, but not metabolized accumulate in the body. The amount an individual has is called the ‘body burden’.

Speaker Notes:

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UIC BioS 101 Nyberg

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Heavy Metals

• Some metals are essential nutrients.

• Lead (Pb) and mercury (Hg) have a variety of negative effects on organisms.

• Lead and mercury are excreted very slowly, so they tend to accumulate in the body.

• Lead and mercury continue to be major health concerns for humans.

Speaker Notes:

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UIC BioS 101 Nyberg

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BIOMAGNIFICATION

• Toxicity of compounds increases with increasing concentration.

• Concentration increases

at each trophic level.

Compound that is absorbed but not metabolized.

Example DDT, PCB

Speaker Notes:

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Because the biomass at higher levels is less the concentration of the non-metabolized compound increases.

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UIC BioS 101 Nyberg

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Biogeochemical Cycling

• Bio – stands for the biosphere, the living organisms,

• Geo – stands for the geological compartments, the earths crust, ocean and atmosphere,

• Chemistry is involved because the elements frequently are transformed among a variety of compounds, e.g. NH3, N2, NO2- & NO3-

Speaker Notes:

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UIC BioS 101 Nyberg

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Material Cycles

• Compartments are also called reservoirs.

• Movement into a compartment is input.

• Movement (=flow) out of a compartment is called output.

• Amount in the compartment called pool size.

• If the rate of flow out of the pool is low, the pool size is likely to be large.

Speaker Notes:

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At equilibrium inputs equal outputs, but the world is far from equilibrium for most variables.

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UIC BioS 101 Nyberg

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Turnover or Residence Time,
the length of time in the pool

• Compounds that can be made by biological systems can be broken down by biological systems (otherwise those compounds would build up indefinitely).

• Simple sugars are rapidly metabolized and turnover quickly.

• Lignin,a part of wood, is broken down slowly and therefore lasts for a long time.

Speaker Notes:

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Lignin is even tougher to break down than cellulose.

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UIC BioS 101 Nyberg

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Biosphere Recycling

• Dead animals and plants are called detritus.

• Dead animals and plants are recycled by organisms called decomposers.

• Some parts are recycled quickly, others take a lot longer to break down.

• Microorganisms are a necessary part of recycling.

Speaker Notes:

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Hardly any individuals end up as fossils because the dead are eaten by the living.

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UIC BioS 101 Nyberg

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Detritus

• Detritus is dead organic mater.

• The leaves that fall from deciduous trees are the classic example of detritus.

• Detrivores eat detritus, e.g. shred and chew it.

• In Illinois, oak leaves take about 3 years to completely disappear – leaves of other trees take less time.

Speaker Notes:

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The length of time for leaves to disappear has a big influence on the amount of leaves on the ground.

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UIC BioS 101 Nyberg

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Decomposers

• Most of the difficult to digest compounds are broken down by fungi or bacteria.

• Decomposition is faster with high levels of moisture at higher temperatures because fungi and bacteria need high moisture.

• Decomposition is therefore usually more rapid in the tropics than at higher latitudes.

Speaker Notes:

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What fungi do to know?

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UIC BioS 101 Nyberg

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Animals that use wood have symbionts

• Termites eat wood and extract energy from it.

• The termite gut has flagellates (Protista) that harbor bacteria. The termites chews the wood into pieces so small that the flagellates can engulf them and then the bacteria make the enzymes that digest the wood.

• Ruminants, e.g. Cows, also are dependent on protista and prokaryotes in their rumen for much digestion.

Speaker Notes:

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Termites are social insects. What is a ‘rumen’?

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UIC BioS 101 Nyberg

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Local cycling of material

• Rain tends to leach nutrients from the soil into the ground water.

• Plant roots capture these nutrients and transport them to the leaves.

• When the leaves die and fall to the ground the nutrients again enter the soil.

  • See the following figure (54.10)

Speaker Notes:

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UIC BioS 101 Nyberg

Exam 3 #11

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Speaker Notes:

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Plants reduce the loss of elements they need by pumping the elements upward, eventually depositing them on the surface.

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UIC BioS 101 Nyberg

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Losses and Gains of Nutrients

• Local systems can lose or gain substantial amounts of various nutrients. Changes in the local amount of nutrient can dramatically impact the local system, i.e. eutrophication of lakes.

• At the global scale we used to think local losses and gains balanced out, but humans have increased the amount of many elements in the biosphere.

Speaker Notes:

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Eutrophic could be translated to ‘good eating’, but it is algae that have good eating in such systems. The organisms humans fish for decline with eutrophic conditions.

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UIC BioS 101 Nyberg

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Global Carbon Cycle

• Carbon dioxide in atmosphere.

  • 370 ppm = parts per million.

• Carbon dioxide dissolved in ocean is 50 times the amount in atmosphere.

• Living organisms generate flux thru respiration.

• Geological forms of carbon:

  • Oil Graphite

  • Coal Diamond

Speaker Notes:

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Carbon has a diverse and therefore interesting chemistry.

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UIC BioS 101 Nyberg

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Global Carbon Cycle

Gigaton = one billion tons = 109 metric tons

SI units 1 gigaton = 1018g = 1 petagram

Speaker Notes:

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UIC BioS 101 Nyberg

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Global Nitrogen Cycle

• While the concentration of carbon dioxide has increased considerably since 1800, the percent increase is much less than N.

• The amount of nitrogen added to the biosphere by humans is almost equal that of natural sources.

• N2 is the most common gas of our atmosphere, but it is very unreactive.

Speaker Notes:

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Haber developed the process of making ammonia. Haber also developed gas as an offensive weapon for his German homeland in WWI. Though he served the German war effort he was stripped of his academic position when the Nazis came to power because he was a Jew.

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UIC BioS 101 Nyberg

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Amounts of Nitrogen moving into biosphere each year

Speaker Notes:

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Fertilizer is changing crop yields worldwide. It is also having those inevitable ‘side effects’.

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UIC BioS 101 Nyberg

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VOCABULARY

• Abiotic

• Ecosystem

• Decomposer

• Detritus

• Lignin

• Biomagnification

• Biogeochemical cycling

• Global carbon cycle

• Nitrogen fixation

• Nitrogen fertilizer

Speaker Notes:

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