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EcosystemsEcosystems
Structural & Functional aspectsStructural & Functional aspects
• Atom Atom • C, N, P – chief constituents of building blocks of life C, N, P – chief constituents of building blocks of life
MoleculeMolecule• A molecule of DNAA molecule of DNA
OrganelleOrganelle• Mitochondria Mitochondria
Cell Cell • Nerve cellNerve cell
Tissue Tissue • Nervous tissueNervous tissue
Organ System Organ System • Nervous systemNervous system
Organism Organism • Fish Fish
Population Population • Group of same type of Fish say Salmon FishGroup of same type of Fish say Salmon Fish
Community Community • Complete under water sea lifeComplete under water sea life
Ecosystem Ecosystem • Complete ocean including living and non-living Complete ocean including living and non-living
mattermatter
Levels of organization Levels of organization
Ecosystem • A community of organisms and it’s corresponding abiotic
environment through which matter cycles and energy flows Types
• Natural / wild • Managed / artificial
Common features• Energy flow • Nutrient cycling
Biosphere• The sum total of all the ecosystems on the planet
Biome• Areas of predominant flaura & fauna
Ecotone• Areas of transition
Basics Basics
Basics Basics Food chainFood chain
• Path of energy exchange Path of energy exchange through..through..
Food websFood webs• Interconnected feeding Interconnected feeding
relationships in an relationships in an ecosystemecosystem
Trophic levelTrophic level• Feeding relationshipsFeeding relationships• Individuals positionIndividuals position
Ecological pyramidEcological pyramid Recyclers of biosphereRecyclers of biosphere
Energy flow in an ecosystem
Primary ProductivityPrimary Productivity Secondary productivitySecondary productivity
GPP (Gross Primary GPP (Gross Primary Productivity)Productivity)
NPP (Net Primary NPP (Net Primary Productivity)Productivity)
Rs (Respiration)Rs (Respiration)
NPP = GPP – RsNPP = GPP – Rs Biomass: Reflection of
primary productivity
What is A Niche?What is A Niche?Set of conditionsSet of conditions within which an organismwithin which an organism can maintain a viablecan maintain a viable populationpopulation
Multi-dimensionalMulti-dimensional with as manywith as many dimensions as theredimensions as there are limiting conditionsare limiting conditions temperature
light intensity
okay
salinity
ecologicalniche
The NicheThe Niche
Ecological niche:Ecological niche:• The sum total of an The sum total of an
organisms use of biotic organisms use of biotic & abiotic resources in & abiotic resources in its environment with its environment with unique ecological roleunique ecological role
Fundamental NicheFundamental Niche Realized NicheRealized Niche Co-existance vs Co-existance vs
Identical niches Identical niches
Nutrients…what are they? The basic chemical building blocks of all life Recycled in a living system. Key nutrients - 95% of all living matter.
Factors effecting Nutrient cycling Factors effecting Nutrient cycling &/or availability &/or availability
Transformation / cycling – oxidation or reduction reactions
Metabolism related Mineralization Immobilization Rates of decomposition Presence of nitrogen fixers Microbial activity Fire Precipitation patterns Soil drainage Soil temperature, moisture
Residence Time• Length of time taken for a nutrient to be completely
decomposed or recycled from the forest floor Nutrient Use Efficiency (NUE)
• Selective advantages in low nutrient conditionsNUE = A / L
A – the nutrient productivity (dry matter production per unit nutrient in the plant)
L – nutrient requirements per unit of plant biomassTypes of relationships
based on Nutrient limitations
• A - Production - independent of resource availability
• B - Production - a linear function of resource availability
• C - At some point, another resource becomes limiting
Nutrient Pools and Nutrient FluxNutrient Pools and Nutrient Flux
Nutrient pool – a specific Nutrient pool – a specific component or compartment where component or compartment where a nutrient residesa nutrient resides• Can be a single organism, a population, Can be a single organism, a population,
a community, a trophic level, and an a community, a trophic level, and an abiotic feature (e.g., lake, soil, abiotic feature (e.g., lake, soil, atmosphere, etc.)atmosphere, etc.)
Nutrient flux – the rate of exchange Nutrient flux – the rate of exchange (e.g., unit of material per unit time) (e.g., unit of material per unit time) of nutrients between poolsof nutrients between pools
Biogeochemical CyclingBiogeochemical Cycling
Vernadsky 1934Vernadsky 1934• The cycling of nutrients through ecosystems via
food chains and food webs, including the exchange of nutrients between the biosphere and the hydrosphere, atmosphere and geosphere (e.g., soils and sediments)
Biotic / Organic phaseBiotic / Organic phase Abiotic phaseAbiotic phase ReservoirReservoir Major categories
• slowest-changing pool(=reservoir): Sedimentary phaseSedimentary phase Atmospheric phaseAtmospheric phase
FeaturesFeatures• Biological & Chemical processesBiological & Chemical processes• Nutrient transformation by Oxidation, Reduction Nutrient transformation by Oxidation, Reduction
reactionsreactions• LinkedLinked• Metabolism related transformationsMetabolism related transformations• Global impactGlobal impact
Water cycleWater cycle
Hydrologic cycle• Medium for introducing
nutrients• Means of thermal regulation• Means of removal/transport-
local ecosystems Route of water escape
• Evapotranspiration Average rainfall-81.1cm Land precipitation>evaporation
(84% vs.77%) Rapid cycling
• Surface runoff Erosion, weathering
• Ground water Catchment area, Springs, Aquifer
Carbon cycle Relative percentage in atmosphere – 0.03
Route of escape into atmosphere• Photosynthesis /
respiration• Fermentation• Methane
Aquatic form• Carbonic acid,
Bicarbonate, Carbonate
P: photosynthesis, PR: plant respiration, SR: soil respiration, SF: Soil P: photosynthesis, PR: plant respiration, SR: soil respiration, SF: Soil formation, FFF: fossil fuel formation, FFB: fossil fuel burning, formation, FFF: fossil fuel formation, FFB: fossil fuel burning, DEF: deforestation, W:weathering, V: Volcanic eruption, E: DEF: deforestation, W:weathering, V: Volcanic eruption, E: evaporation, D: dissolution evaporation, D: dissolution
Carbon cycleCarbon cycle
Nitrogen cycleNitrogen cycle Key stepsKey steps
• Nitrogen fixationNitrogen fixation• NitrificationNitrification• DenitrificationDenitrification• MineralizationMineralization
Nitrogen FixationNitrogen Fixation Biological or chemical process where gaseous nitrogen Biological or chemical process where gaseous nitrogen
is converted into solid forms of nitrogen. is converted into solid forms of nitrogen. Biological fixation Biological fixation
N N 22 + 8e + 8e -- + 8H + 8H ++ + ATP -----> 2NH + ATP -----> 2NH 33 + H + H 22 + ADP + Pi + ADP + Pi• OrganismsOrganisms
Free livingFree living SymbiontsSymbionts
• Enzymes for nitrogen fixation require anoxic conditionsEnzymes for nitrogen fixation require anoxic conditions Chemical fixationChemical fixation
N N 22 + H + H 22 2 NH 2 NH 33 Physical process Physical process in Naturein Nature
NITRIFICATIONNITRIFICATION The biochemical oxidation of ammonium to nitrite and The biochemical oxidation of ammonium to nitrite and
nitrite to nitrate. nitrite to nitrate. Microbes Microbes
• ChemoautotrophsChemoautotrophs• Aerobes Aerobes • Nitrifiers: Nitrifiers: NitrosomonasNitrosomonas and and NitrobacterNitrobacter
ReactionsReactions• Nitrification I:Nitrification I:
NHNH44 + 1 ½ O + 1 ½ O22 NO NO22- - + H+ H22O + O + Energy
• Nitrification II: Nitrification II:
NO 2 - + ½ O NO 2 - + ½ O 22 NO NO33-- + + Energy
RequirementsRequirements• OxicOxic• N abundancyN abundancy
DENITRIFICATIONDENITRIFICATION
Denitrification Denitrification • Reduction of nitrate (NO3-) to nitrogen Reduction of nitrate (NO3-) to nitrogen
gas or to organic nitrogen compounds. gas or to organic nitrogen compounds. Two types Two types
• Dissimilative Dissimilative Returns nitrogen atoms to the atmosphere Returns nitrogen atoms to the atmosphere
by reducing nitrate to nitrogen gas. by reducing nitrate to nitrogen gas.
NONO33-- NO NO22
-- NO NO N N22O O N N 22 Facultative anaerobes: Pseudomonas,
Bacillus, and Micrococcus spp. Oxygen for respirationOxygen for respiration
• Assimilative. Assimilative. Conversion of nitrate to ammonium ionConversion of nitrate to ammonium ion
MINERALIZATION / AMMONIFICATION
Organic nitrogen from decaying plant and animal residues (proteins, nucleic acids, amino sugars, urea) is converted to ammonia (NH3) and ammonium (NH4
+) In Dry soils
• Proteins Amino acids NH3 NH3 Moist soils
• Proteins Amino acids NH3 NH3+H2O NH4+OH- NH4
+ + OH-
Microbes: Bacillus, Clostridium, Streptomyces
Nitrogen fixing bacteria & enzymes they produce
Nitrifying bacteria
Nitrate reductase (Fe, Mo)
Nitrite reductase (Fe)
Nitrogenase(Fe, Mo or V)
Denitrifying bacteria
N2 NH4+
NO3-NO2
-
Nitrogen
All the major N assimilation enzymes require Fe.
R-NH2
Ammonium assimilation
Ammonification
Assimilatory NO3
- reduction
Dissimilatory NO3- reduction
Nit
rite
oxi
dati
on
Nit
rite
Am
mon
ific
atio
n
Ammonium oxidation
NH4+ NO2
-
NO3-NO2
-
NO
N2O
ANAEROBIC PROCESSES
AEROBIC PROCESSES
Den
itri
fica
tion
N2 Nitrogen fixation
Amino groups in cell protein
Sulfur cycleSulfur cycle Sulfur in soil
• 90% - Organic 50% as C-O-S linkages (sulfate esters) 20% as S-amino acids 20% other compounds
In living tissue • S-containing amino acids and sulfate esters
Phosphorous Phosphorous cyclecycle
Changes in the amounts of tracer phosphorous being exchanged within an aquatic food web
The Potassium CycleThe Potassium CycleAnimal
manuresand biosolids
Mineralfertilizers
Crop harvest
Runoff anderosion
Leaching
Soil solution potassium (K+)
Plant residues
Plantuptake
Mineralpotassium
Fixedpotassium
Exchangeable potassium
Input to soilComponent Loss from soil
Bioaccumulation & BiomagnificationBioaccumulation & Biomagnification
Bioaccumulation:• Increase in concentration
of a pollutant from the environment to the first organism in a food chain
Biomagnification:• Increase in concentration
of a pollutant from one link in a food chain to another
DDT has a half-life of 15 years This means, if you use 100 kg
of DDT today (consider this the zero time), it will break down in such a manner that after 100 years from now, there will still be over a pound of DDT in the environment. If it does bioaccumulate and biomagnify, much of the DDT will be in the bodies of organisms
DDT has brought in the "age of resistance" - a high price to pay to have no mosquitoes.
Year Amount Remaining
0 100 kg
15 50 kg
30 25 kg
45 12.5 kg
60 6.25 kg
75 3.13 kg
90 1.56 kg
105 0.78 kg
120 0.39 kg
Gaia HypothesisGaia Hypothesis
James Lovelock, Lynn Margulis - 1970 Our planet functions as a single organism that
maintains conditions necessary for its survival. A complex entity involving the Earth's biosphere,
atmosphere, oceans, and soil; the totality constituting a feedback or cybernetic system which seeks an optimal physical and chemical environment for life on this planet.
Life, regulates or maintains the climate and the atmospheric composition at an optimum for itself.
Gaia, therefore, can be viewed as a study of the physiology of the Earth, where the oceans and rivers are the Earth's blood, the atmosphere is the Earth's lungs, the land is the Earth's bones, and the living organisms are the Earth's senses.
Ecosystem services - UNEPEcosystem services - UNEPThe UNEP programme focuses on ecosystem services comprising:Regulating services: climate, water, natural hazard and disease regulation, water purification and waste treatment, which are often strongly affected by the overuse of provisioning services;Provisioning services: freshwater, energy (especially the emerging issues around biofuel production) and capture fisheries;Cultural services: Recreation and ecotourism service;Supporting services: nutrient cycling and primary production which underlie the delivery of all the other services but are not directly accessible to people.
Ecosystem servicesEcosystem services
For detailed information on biogechemical cycles For detailed information on biogechemical cycles and information related to the slides in this lecture, and information related to the slides in this lecture, refer to:refer to:
Chapter 4 “Ecology” from the text book Chapter 4 “Ecology” from the text book “Environmental Studies” by Benny Joseph“Environmental Studies” by Benny Joseph
Unit 3 “Ecosystems” from the text book Unit 3 “Ecosystems” from the text book “Environmental Studies” by Erach Bharucha“Environmental Studies” by Erach Bharucha