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159 Cards in this Set
- Front
- Back
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Problem: Malaria is carried by mosquito
Solution: Sprayed village huts with DDT & dieldrin
What are the repercussions and why did they occur? |
Effects - Reduced mosquito pop'n and malaria - Roofs on huts collapsed
Reasons - Parasitic wasps DDT sensitive causing mortality - Moth larvae pop'n increased (pop'n not controlled by wasps) -Rat pop'n increase (typus!) because of bioaccumulation of DDT from cockroaches to Geckos to Cats, in which the cats were unable to control rat pop'n
Response - importing cats |
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Define: Ecology |
Ecology The scientific study of relationships between organisms and their environment |
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Define: Environment |
Environment Physical and biological conditions in which an organism lives |
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Define: Ecosystem |
Ecosystem - interacting system with biotic and abiotic objects in a specified volume of space
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List 4 features that make ecosystems complex |
- Structured and hierachy organized, ex trophic levels - Large number of species with interactions with biotic and abiotic factors - Open systems (external conditions exert influence on ecosystems over space and time) - Lots of feedback responses due to circulation of information, energy and materials
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Describe 3 Ecosystem functions |
1) continuous energy source to maintain biochemical and physical integrity 2) Capture, store and release energy 3) Biotic and abiotic processes transform and circulate energy |
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True or false.
The correct level of organization in ecology is the following:
Individuals |
True |
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Why do we study ecosystems? |
1) To understand our planet and learn how to sustain life 2) Satisfy curiosity 3) Management due to human pressures |
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Compare Coniferous and Deciduous trees. |
Coniferous 1) softwood 2) Produce cones 3) Needle-like leaves
Deciduous 1) Hardwood 2) Broad, flat leaves 3) Flowers and fruits |
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Define: System |
System A set of inter-related parts that work together to perform a function within an environment
Note: 1) Not all components are essential for function 2) Ecosystem may not operate optimally |
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Define: positive feedback |
Positive Feedback: Reinforcement; allows the system to continue in the same direction (upwards continues upwards; downwards continues downwards).
Ex, Utricularia eat periphyton which eat zooplankton. As there are more space and nutrients available, the zooplankton keep increasing thus supporting periphyton and Utricularia. |
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Define: Direct effect/ Direct feedback |
Direct Effect Change due to an explicit direct transaction of energy and/or matter between two components
Ex. Fish eat planktivores (plankton-eaters) |
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Define: Indirect effect/ Indirect feedback |
Indirect effect A change in one component caused by a change in another component without direct transaction of energy and/pr matter between
Ex. Photoplankton pop'n affects fish populations because the pop'n of all the other organisms in between will change |
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How do scientists study ecosystems? |
1) Natural history/Observations 2) Long-term studies; research (allows us to learn about the slow processes) 3) Cross-ecosystem comparisons (variation of ecosystem structure and function to help generate hypothesis) 4) Manipulative experiments (controlling cofounding factors; ex. field experiments like Schindler's lake 226, precipitation and nitrogen in forested/deforested areas) 5) Theory and Conceptual models |
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Describe Schindler's Lake 226 Experimental Lake Experiment |
Proving: Phosphorous controls eutrophication Lake: Lake 226, Kenora, Ontario Control: +N, +C (Clear) Test: +N, +C, +P (Turbid) Result: Algae blooms occur with P, so we know that it induces eutrophication |
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Define: Geomorphology |
Geomorphology
The development, evolution, or relief (topography) and landforms on Earth
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True or false.
Erosion, transportation and deposition involves physical, chemical and biological processes. |
True
Physical - Mechanical erosion and transport Chemical - hydrolysis, hydration, oxidation, sol'n Biological - Catalysts of physical and chemical processes |
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Explain how soils impact life. |
- product of weathering and actions of living organisms Influenced by: - Parent material, history, climate (freeze-thaw, wind), biota, topography, time Affects: Water-holding properties, soil fertility |
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Explain how climate impacts life |
Climate: Long-term average pattern of weather and described on a local, regional or global scale
- Determines the type of ecosystem - Derives directly or indirectly from solar radiation |
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Explain how solar energy impacts life |
Solar energy: Electromagnetic energy released from the sun
- Subject to various fates before intercepting with Earth surface - Range of wavelengths (short wave length = high energy; long wavelength low energy) |
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Explain how photosynthetically Active Radiation (PAR) impacts life |
- Wavelengths range from 380-740 nm - Plants use these wavelengths for photosynthesis - ~42 of solar radiation reaching Earth's surface is PAR (photosynthetically active radiation) |
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How does latitude affect the amount of solar energy (affecting radiation and temperature)? |
1) Angle of incidence: Affects the amount of energy received per unit area of Earth (lower at high latitude
2) Distance of travel through the atmosphere (higher at high latitudes)
Ex. The North pole receives less light than the Equator as the angle from the sun is increased and the energy has to travel a longer distance.
3) The amount of energy intercepting by any point on Earth varies greatly with season, due to the tilt to Earth on its rotational axis |
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Using the tilts of the Earth's axis explain how this causes changes in the amount of solar energy received (thus affecting radiation and temperature). |
1) Vernal and autumnal equinoxes: Solar radiation falls directly on the equator
2) Summer solstice: Solar radiation falls directly on the Tropic of Cancer, with increased input and day length in the N-hemisphere
3) Winter solstice: Solar radiation falls directly on the Tropic of Capricorn, with increased input and day length in the S-hemisphere |
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Explain how rainfall and humidity impact life on Earth |
- Earth's atm is in constant motion; influences patterns of rainfall and humidity - Air cools and eventually descends to the surface, where it moves across the equator - Warm surface air at the equator rises and moves north and south - precipitation affects the distribution of biota and ecosystems - varies with latitude, corresponding to the rise and fall of air masses associated with the belts of prevailing winds - Seasonal shifts |
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What is the Inter-tropical convergence zone? |
Area around the Earth's equator where the NE and SE trade winds come together
Affecting wet and dry seasons in the tropics and warm seasons of higher latitudes. Long term changes in ITCZ can result in severe droughts |
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How does wind affect life? |
- Caused by differences in air pressure across the Earth's surface - Plays an important role in water cycle - Exceptional events (hurricanes, tornadoes) influence ecosystems - Important agent of erosion and transport of particles (sediment, animals, nutrients, pollutants) - Controls the currents, and water movements that affect thermal stratification in aquatic ecosystems (Affecting light distribution, chemicals and biota) |
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Describe how currents and water movements work in the mixing layer, the layer above the thermocline. |
- The wind moves across the surface of the water body, causing the water to lose heat, thus becoming more dense - the dense water enters a convection cell in which it is replaced with warmer water above - this cycling affects the distribution of light, chemicals and biota in the body of water |
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Explain how light and structure of aquatic ecosystems affects life. |
- Light energy is attenuated exponentially with water depth due to absorption by water and scattering by suspended particles - quality of light changes with depth as some wavelengths are absorbed more readily than others |
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Explain how fire affects life in ecosystems. |
- Plays important role in structure and function 1) Transform vegetation and animal communities 2) Opens up tree canopy, allowing pioneer species to grow 3) Kills pests and pathogens 4) Releases nutrients and speeds up rates of nutrient cycling 5) Releases pollutants and speeds up rates of pollutant cycling |
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Explain how the water cycle affects life in ecosystems. |
- All life is linked (directly or indirectly) by the hydrologic cycle - Solar energy heats the atm and provides the energy to evaporate water, which drives precipitation and water flow
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Energy exists in two forms. What are they? |
1. Potential energy = stored energy or energy at rest; it is available to perform work but is not doing work at this time
2. Kinetic energy = energy in motion; performs work at the expense of potential energy |
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What is the 1st Law of Thermodynamics? |
- Energy (and matter) cannot be created or destroyed but can be transfered or change form -potential energy lost from the molecular bonds equals the kinetic energy as released by heat, light, noise etc. - In photosynthesis, solar energy accumulated from chlorophyll accessory pigments equals the energy stored as sugars - potential energy during rxns degrades into entropy (energy that is incapable of doing more work; disorder) |
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What is the 2nd Law of Thermodynamics? |
- With every energy transfer, some energy is lost which increases entropy (disorder) - heat, noise, etc. - As energy is transferred between two organisms, a portion is stored in tissue and some is dissipated as heat - applies to closed systems - Ecosystems maintain structure (order) due to continuous inputs of solar energy |
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Define Primary production |
Primary Production - The storage of energy through formation of organic matter from inorganic carbon compounds - by autotrophic organisms (plants, algae, microbes) or chemoorganotophs - first step in capture, storage and transfer of energy |
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Name 2 ways in which primary production occurs. |
1) Photosynthesis - CO2 incorporated into organic matter using energy from the sun (photoautotrophs)
2) Chemosynthesis - chemical energy to convert inorganic compounds into organic matter (chemoautotrophs) - includes nitrifyinf bacteria that and bacteria that oxidize H, CH3, S, Fe, Mn - Often occurs at the interface between oxic and anoxic env (soils, sediments) |
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True or False.
Primary production is a rate, with units of mass per unit area per time (or volume for water bodies) |
True
Often presented as g C m^-2 d^-1 |
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True or False.
Biomass and production are always correlated. |
False. Usually, but not always
Biomass - yield; standing crop |
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Define: Gross Primary Production (GPP) |
Gross Primary Production Rate of photosynthetic energy assimilated by autotrophs per unit time |
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Define: Net Primary Production (NPP) |
Net Primary Production Thee rate of energy stored by autotrophs in organic matter after respiratory losses (Ra)
NPP = GPP - Ra
Represents the energy available to support organisms at high trophic levels |
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Define: Ecosystem respiration |
Ecosystem respiration Re = Ra + Rh
Where Ra is the respiration of autotrophs Where Ra is the respiration of heterotrophs |
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Define: Net Ecosystem Production |
Net Ecosystem production The difference between accumulation and net export
Residual production that accumulates in biomass, is exported, or is lost via fire and photooxidation
NEP = HPP - Re
NEP = GPP - Ra - Rh = NPP-Rh |
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Measuring Primary Production Terrestrial.. |
Ex, grass lands: Measure mass of above-ground plant material at the end of growth season
- Measures NPP, not GPP, because Ra has occurred - Losses to herbivores not measured (assumed negligible) -Mass of root growth not included (estimation of above ground NPP)
Ex. Forest Ecosystems - Leaf fall (foliar production) and wood production (tree diameter) - Estimates above gound NPP (no roots, branches, fruits) |
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Measuring Primary Production in Aquatic systems... |
- In-situ incubation of photoplankton in light and dark bottles - Measure rate of oxygen production or carbon dioxide consumption
- Oxygen concentrations increase during the day due to photosynthesis, decreases at night due to respiration - Oxygen exchanges with atm due to differences between concentration between water and air
GPP = change in oxygen concentration in day + Respiration at night concentration + concentration of water and air |
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Name factors that regulate primary production |
1) Light, temperature, growing season length (increased light to maximum rate of photosynthesis; longer growing season, more primary production) 2) Precipitation (= water availability, gas exchange via stomata - more precip longer stomata can remain open) 3) Nutrients (primary production is nutrient limited: Macronutrients including C,N,H and Micronutrients including Fe, Mn. Zn). Relative uptake affects stochiometric composition |
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What is Liebig's Law of the minimum? |
Liebig's Law of the minimum: The factor supplied at lowest level relative to the demand determines primary production
Limiting terrestrial: K, Ca, N, P Limiting aquatic: N, P
Useful, but simplistic because: 1) Organisms can use one resource to obtain another (growing roots to access more water) 2) Variation across space and time means that several factors can be limiting in different places at different times (changes of season) |
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Define: Authochthonous organic matter |
Authochthonous organic matter Produced within the system (phytoplankton, attached algae, macrophytes) |
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Define: Allochthonous organic matter |
Allochthonous organic matter Produced outside the system and transported in (Coarse debris, particulate matter, dissolved organic matter) |
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Describe the fates of primary production |
1) Consumed by herbivores 2) Converted to detritus 3) Stored in biomass 4) Consumed by fire or photo-oxidation 5) Exported |
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Define: Secondary Producer |
Secondary producer: rate of energy assimilated by all heterotrophs per unit area (or volume) per time. g C m^2 d^-1
Secondary Producers gain energy from available autotrophs (NPP) This includes the rest of the food web: animals, fungi, heterotrophic bacteria etc.
Herbivores (eat plant material) and Decomposers (non-living organic matter) directly consume primary production.
Carnivores (herbivores + decomposers) and Omnivores (more than one category) |
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What are the two main roles that Secondary Producers are involved in ecosystem energetics? |
Secondary Producers... 1) Capture energy from primary production into growth and reproduction (secondary production). Support higher trophic levels
2) Respiration destroys organic matter that serves as the medium of energy exchange in ecosystems, regenerating nutrients trapped in organic matter |
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Define Ingestion |
Ingestion : describes the effect of consumers on the food resource
I = assimilation + egestion |
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Define: Egestion |
Egestion is input into the detrital pool (poop) |
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Define: Respiration |
Respiration: energy lost from the ecosystem |
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Define: Production |
Production The energy available to support growth and reproduction of the consumer, which can support growth and reproduction of predators |
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List 3 factors that affect the magnitude of ingestion, assimilation, production and respiration. |
1) Body size: Metabolic rates higher in smaller organisms (lower mass)
2) Temperature: Metabolic rates increase ~2X for each 10 degree rise
3) Respiration higher in homeotherms than poikilotherms |
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Define: Assimilation efficiency |
Assimilation efficiency Ability to extract energy from the ingested food A/I |
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Define: Net growth efficiency |
Net growth efficiency Partitioning of growth and respiration
P/A |
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Define: Gross growth efficiency |
Gross growth efficiency Overall efficiency of converting food to consumer tissue
P/I |
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Describe how diet impacts Consumer Efficiency |
1) Diet (food quality), -require 30-40 chemical elements for growth, development and reproduction. -Macro and Micronutrients. -All nutrients are essential but can be toxic at high conc. - Maintaining C:N ratios is difficult for herbivores and decomposers; lots more C than N
2) Overcome physical and chemical defenses of plants - Physical: thorns, hard to chew cellulose and lignin - Chemical: low nutrition (high C:N in ligin and cellulose), toxins, digestion of reducing substances (ex. phenolic compounds inhibit enzyme digestion) |
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True or false:
Carnivores' prey are usually similar in nutrient content. Therefore, they do not face the same challenges as herbivores and detriviores to balance nutritional demands vs. energy demands |
True |
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Name a few mechanisms in which prey protect themselves from predators. |
- Anatomical defenses (spines, shells, poisions, repellants) - Behavioural defenses (flight, refuge, grouping, colouration, camoflauge); mimicry |
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Describe 4 factors that affect consumer efficiency. |
1) Diet (food quality) 2) Temperature 3) Metabolic type: Homeothermy vs poikilothermy; body size/ mass 4) Physiological status (stage in development) |
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How do we estimate Secondary production? |
1) measure uptake of labeled substances (radioactive tracers)
2) Use turnover rates of consumer tissue with biomass estimates
3) Demographic info with individual growth (= pop'n growth)
4) Empirical models |
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Define: Consumption efficiency |
Consumption efficiency Ratio of energy available at one trophic level that is consumed by the next
(=In/Pn-1
A method of quantifying energy flow |
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Define: Trophic efficiency |
Ratio of productivity between two trophic levels
Pn/Pn-1
A method of quanitifying energy floe |
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True or False.
Energy/biomass pyramids provide a way to assess efficiency of transfer through ecosystems |
True
Note: the pattern will differ among ecosystems |
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Define: Decomposition |
Decomposition The breakdown of the chemical bonds within complex organic molecules
- Key in nutrient cycling & transport - Organic molecules into inorganic molecules - Processes: Leaching, fragmentation, alteration of physical and chemical structure - Macro-scale: Conversion from large forms to smaller particles, soluble compounds & gases - Molecular scale: Conversion of complex organic molecules to simpler forms (eventually to inorganic compounds = mineralization) |
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Define: Saprophages |
Saprophages = organisms that feed on dead organic matter
- Inculdes detritivores: animals (invertebrates & vertebrates) that fragment organic matter thus increasing surface area, also able to feed from microbivores (exploiting mineralization) - Decomposers or microflora: diverse group of bacteria and fungi; perform mineralization step |
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True or false:
Fungal decomposition is done extracellularlly and involves hyphal filaments to contact with organic mater.
Decomposers are obligate and facultative aerobes and anaerobes |
True |
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Describe the succession of plant tissue decomposition (explain first 3 here) |
1) Epiphytic fungi: aerobic yeast and yeast-like fungi that tolerate stressful conditions on leaf surface (high UV, low moisture & nutrients, varying temperature). Start when plant is still alive (feeds on dead cells and soluble nutrients that leak from the plant)
2) Endophytes, weak parasites and pathogens: Consume soluble substrates, colonies internal tissues. Able to tolerate plant defenses which weaken with aging
3) Pioneer saprophytic fungi (sugar fungi) colonize plant tissue after death, consume sugars and storage compounds (but not structural compounds like cellulose) |
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Describe the succession of plant tissue decomposition (explain last 3 here; after saphrophytic fungi) |
4) Polymer-degrading fungi: Degrade cellulose and hem-cellulose - Extracellular digestion
5) Lignin-degrading fungi (aerobic only; oxidative decay) - lignin = highly resistant group of compounds - These fungi rarely use lignin as a major energy source - rely on the digestion of cellulose for energy, but modify lignin with a few enzymes that release cellulose
6) Secondary opportunistic fungi: Colonize dead fungal tissue, insect exoskeletons, living fungi; decompose the most plant organic matter |
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Measuring decomposition by using litterbags that we measure the weight before, during the experiment and after
What is the challenges of using this process? |
Challenge is that it is hard to identify the processes causing loss of mass
Mass loss depends on: 1) Fragility of original material 2) Physical stresses in the system 3) Activities of animals (physical breakage) |
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Describe the 2 controls on decomposition |
1. Intrinsic factors (quality of nutrients, lignin, secondary compounds)
2. Extrinsic factors (climate, temperature & moisture) |
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Define: Mineralization |
Mineralization Transformation of organic matter to inorganic compounds |
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Define: Immobilization |
Immobilization Uptake & assimilation of the inorganic compounds |
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Define: Net mineralization |
Net mineralization = mineralization - immobilization |
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Describe what an ideal pattern change in nitrogen content of detritus (Mineral release: time trend) |
Phase A: Water-soluble compounds leached (short lived)
Phase B: Decomposers immobilize nutrients external to the litter & grow
Phase C: Mineralization exceeds immobilization |
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True or false, the decomposition cycle is an example of a positive feedback. |
True
High nutrient availability, more primary production and mineralization rate, etc.
Low nutrient availability, low net primary production and low mineralization rate etc. |
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Define: Element cycling |
Element Cycling: The transport and transformation of chemicals within and among ecosystems
- Involves the movement and transformation of abiotic and biotic forms of elements - Includes inputs, outputs and internal cycling - Obeys the 1st law of thermodynamics: matter cannot be created nor destroyed |
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Compare Gaseous cycles and Sedimentary cycles |
1) Gaseous cycle: main reservoirs are the atm and ocean (Ex, N, O)
2) Sedimentary cycles: main reservoir is the lithosphere (Ex. P) - tend to be more localized, mineral form supplied by weathering
Some cycles are a hybrid of gaseous and sedimentary (Ex, S, C) |
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Element cycles are linked by... |
1) Structural stoichiometry: Ratio of elements Living and nonliving need to be built with particular ratios of elements (C:N:P)
2) Chemical reactivity & material and energy flow linked due to joint movement together down physical gradients or during chemical reactions Example: Redox rxns: anoxic environments Mn is used as an electron acceptor for the oxidation of C Example: movement of materials as acidic precipitation percolates through soil |
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"Aquatic osteoporosis" or "Jellification" of lakes |
"Aquatic osteoporosis" or "Jellification" of lakes - decline in [Ca] in softwater boreal lakes - Long-term leaching of calcium from drainage basin soils by acid rain, logging, climate change - Daphnia requires relatively high [Ca] for its tissues. Can't reproduce when [Ca] < 0.5 mg/L - Holopedium can live in low Ca environments and populate the lake |
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Describe the "Move, stick & Change" phrase to explain the framework of elemental cycling |
Materials:
Move within and between ecosystems (through physical, chemical gradients and biological vectors/ food web)
Stick for periods of time within "pools" or "reservoirs". Residence time depends on solubility, charge, size, reactivity and specific gravity
Change from one chemical state to another (and the form it is in influences its movement and sticking). Phase changes, dissolved, chelation, biologically mediated (ex. ammonia dissolved and taken up by plant for the incorportation into protein, sulfate reduced by bacteria to H2S to gain energy) |
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Carbon Chemistry |
Carbon Chemistry - exist in different oxidation states (-4 to +4) - Oxidation state increases if C is bound to more Oxygen (less hydrogen) - Methane highly reduced form - CO2 highly oxidized form - To move C to a more reduced state requires input of energy. To move C to a more oxidized state releases energy - Chemical oxidants (e- receptors) include O2, SO4 2-, NO3-, Fe 3+ - Biological enzymes speed up the rate of redox reactions by reducing the amount of activation energy required |
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Explain the reduction of carbon dioxide to organic matter |
A. OXYGENIC PHOTOSYNTHESIS modern plants and photosynthetic microbes. Appeared 2 bya cyanobacteria
CO2 + H2O + light -> (CH2O) + O2
B. ANOXYGENIC PHOTOSYNTHESIS early type of photosynthesis by bacteria (purple sulfur bacteria)
CO2 + H2S + light -> CH2O + H2O + 2S Anoxic environments
C. CHEMOSYNTHESIS energy to reduce CO2 comes from oxidation of reduced chemical compounds (ammonium, methane, hydrogen sulfide, iron). Most chemosynthetic reactions rewquire O2 to oxidize these compounds |
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Explain the methods in which oxidation of organic matter can occur. |
A. OXIC RESPIRATION the major energy-generating reaction in aerobic organisms C6H12O6 + 6O2 -> 6Co2 + 6H2O + energy output
B. ANAEROBIC RESPIRATION oxidation of OM using something other than oxygen. Restricted to bacteria. Common in soils, sediments and anoxic water. Accounts for about half of all decomposition
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Dissolved inorganic carbon (DIC) includes... |
Cabon dioxide, bicarbonate and carbonate ion
- Usually most abundant form of C in water - readily exchanges with atm, but usually the atm is saturated with carbon from respiration, groundwater CO2 and CaCO3 precipitation - Inorganic C is involved in acid-base rxns in soil and water. Bicarbonate and carbonate are the main buffers of pH change in natural waters |
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True or false.
Inorganic carbon on land and sediments is commonly found in limetsone and dolomite and are the largest reservoir of C. |
True |
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True or false.
Carbon dioxide is the only abundant form of inorganic carbon in the atmosphere. |
True
It comes from the decomposition and burning of organic material (can be anthropogenic sources) |
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Human activities influencing the carbon cycle |
- CO2 to rise rapidly (30% since 1958), and stored in terrestrial and ocean ecosystems - [CO2] was constant until the last interglacial period (200 years ago) - Atm [CO2] fluctuated over a narrow range; high during interglacials, low during glacial times (due to high Fe on Southern Ocean plankton) |
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C cycle in a temperate hardwood forest |
C cycle in a temperate Hardwood forest - Autochthonous PP dominates; allochtonous inputs tiny - NEP << GPP, most ends up in detrital pools - soil organic pool is very large, but constant overtime |
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C cycle in a tidal freshwater river (Hudson R.) |
Pre-zebra musscles - Allochthonous inputs > autochthonous PP; Net heterotropic (GPP < R), so NEP is -ve - No storage in C in sediments - River exports less C than it imports
Post-zebra mussels - reduced C exports slightly (increased C retention) - greately increased Rh (x2) and reduced NPP (>3-fold by eating alage), so NEP became more -ve |
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Features of Nitrogen |
Nitrogen - Limits PP over large areas of the Earth, especially in temperate forest and saltwater ecosystems - N is an integral part of proteins, enzyme and DNA/RNA - Oxidation states of N range from -3 (in ammonia)to +5 (NO3-) - Humans have greatly the N cycle via fertilizer use and fossil fuel combustion, with cascading negative effects on ecosystems |
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True or false
The main reservoir of N is the atmosphere |
True
79% of atmosphere is N2
But N2 is not available to most organisms because it is a very stable molecule (triple bond) |
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True or false
Conversion of nitrogen gas to a form that plants can take up - ammonium or nitrate - requires a lot of energy |
True |
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True or false
All N that is available to biota was originally derived from nitrogen fixation - either by lightning or specialized microbes |
True |
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Describe the process of nitrogen fixation |
Nitrogen Fixation Biological: N2 -> ammonia Abiotic: N2 -> NOy (various forms of reactive N)
- requires a lot of energy, so the process only occurs where it is available - abiotic fixations occur during lightning -discharges - Cyanobacteria, relationships between primary producers and microbes with the requires enzymes provide the energy subsidy needed - Nitrogenase (soil bacteria = Rhizobia, Frankia; legume and alder plants) and cyanobacteria (blue-green algae) -spend atleast half of their energy on N-fixation; reduces growth and competitive ability - occurs in env when N-fixation conveys a competitive advantage |
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Describe nitrogen mineralization and immobilization |
Mineralization (or ammonification): Organic N to ammonium
Immobilization: ammonium or nitrate -> organic N
- the balance between mineralization and immobilization regulates the size of the soluble (bioavailable) N pool (for uptake by primary producers or hydrologic loss) - substrates with C:N rato less or equal to 25 is net mineralization - Substrates with C:N ratio greater than 25 is net immobilization
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Describe nitrification
Which bacteria can perform nitrification? |
- chemoautotrophs
ammonium to nitrite by Nitrosomonas nitrite to nitrate by nitrobacter
- gain energy by oxidizing more reduced forms of inorganic N -occurs in aerobic environments - Nitrite is highly reactive and rapidly converts to nitrate (NO3-) - End products are taken up by plants (NO3- preferred) - NO3- is more mobile than ammonium so it leads to greater hydrologic loss of N - Fosters denitrification (causing loss of N2 to atm) - competes with NH4+ uptake by plants and immobilization by heterotrophs (ammonium abundant areas)
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Describe denitrification |
NO3- -> NO2- -> NO -> N2O -> N2
- anaerobic respiration - factultative anaerobes - strongly regulated by availability of NO3- - Dry-wet cycles of wetland soils: if dry increase of NO3- by nitrification; wet denitrification in anaerobic wet soils -NO leads to ozone pollution in troposhere; N2O is a Greenhouse gas and destoys ozone in stratosphere |
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Other dissimilatory processes |
Where anaerobic processes where N-oxides serve as electron acceptors to gain energy
- Dissimilatory nitrate reduction to ammonia (DNRA): NO3- + e- -> NH3 - favoured over dentrification where the ratio of energy sources to electron receptor is high (consumes more electrons)
- Anaerobic oxidation of NH3 (anamox): is coupled to reduction of NO2 (electron acceptor) to form N2 - Anamox important to anaerobic environment with low supply of organic energy (oceans) |
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Describe the human impact on the global nitrogen cycle |
Increase of global nitrogen from: - Deforestation - CO2 emissions - Increasing human populations - Industrial fertilizer (largest impact) |
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Features of phosphorous... |
Involved in: - Energetics (ADP, ATP) - Genetics (RNA/DNA) - Structure (membranes)
- exists as an orthophosphate: PO4 3-, HPO4 2-, H2PO4-, H3PO4 - oxidation states -3 to 5 - most oxidized form PO4 3- - no gaseous phase; main reservoirs are rock, soil and sediments - released slowly by weathering, leaching and erosion - readily binds to clays, humic materials and Fe/Al oxides which slows the release of P from soils and sediments |
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Name the two Soluble forms of phosphorous (0.45 micrometer filter) |
1) Soluble reactive P (SRP) is mainly inorganic phosphate (PO4 3-), the form is directly taken up by plants and algae
2) Soluble unreactive P (SUP) consists of organic P and polyphosphate (chains of P) |
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True or false
Particulate P is another form of phosphorous that includes organic and inorganic particles and colloids. |
True |
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True or false
Rate of P release by weathering increases with temperature, precipitation, slope and acidity |
True |
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True or false
Dissolved P in soil moisture and water can be assimilated by primary producers, and it is either passed up the food chain (and excreted) or decomposed and mineralized |
True |
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True or false
Particulate P makes up most of the P that is transported and it has very low reactivity |
True |
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Discuss human impact on the phosphorous cycle |
- phosphate mining - fertilizers - increased run off from deforestation - Landfills/sewage |
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P cycling in terrestrial ecosystems |
- P moves to plant roots via diffusion (concentration gradient) - Slower diffusion rate than N
- Symbiotic relationships between roots and fungi: plants supply carbon and fungi excrete phosphatase to mineralize organic P, excrete acids that increase weathering - Prolific root growth (no symbiosis) increases P uptake rate |
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P cycling in Aquatic Ecosystems |
- Most P delivered to sediments as sinking particles (algae, zooplankton fecal pellets) - Sediment P can return to the water column in dissolved form or through resuspension - Sediment P that is not resuspended undergo decomposition and chemical reactions -When sediments are oxic, most P is bound to Fe - When sediments are anoxic, dissolved P becomes released (positive feedback known as accelerated eutrophication) |
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Describe the sulfur cycle |
- Hybrid cycle: has sedimentary and gaseous phases - Sedimentary S tied up in organic and inorganic deposits; released by weathering and decomposition, and carried to terrestrial systems in salt solution -Main pools of S: pyrite-rich (FeS2) igneous and sedimentary shale rock - S moves to terrestrial systems naturally via weathering and volcanic acitivity, and gas from oceans (dimethylsulfide) - Main sink of S: oceans as SO2 (oxidizing agent) - short residence time in atmosphere - S enters the atm through volcanic activity, exchange at ocean surface and decomposition, and from fossil fuels - atm as hydrogen sulfide, interacts with water to make sulfuric acid - sulfate SO4 2- taken up by plants |
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True or False
Bacterial transformations are involved in sulfur cycling. |
True
Anoxic conditions, sulfate reducing bacteria oxidize organic compounds, releasing H2S
Colourless S bacteria (chemoautotrophs) gain energy by oxidizing H2S to elemental sulfur to sulfate ion (through NO3-)
green & purple sulfur bacteria are photoautotrophs that use H2S as an electron acceptor in photosynthesis releasing elemental S which is the oxidized to SO4 2- |
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Biomagnification of metals |
Ex. MeHg and organic contaminants too (DDT, PCBs) biomagnify (concentrate with trophic level), because they are fat-soluble (hydrophobic) and degrade slowly
Species at high trophic levels are most vulnerable |
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Has Alberta oil sands development increased supply of contaminants to the Peace-Athabasca Delta? |
Not from the river or atm
No evidence that oil sands development is increasing deposition of contaminants via the atm to the delta
Lack of pre-industrial baseline data has impeded our ability to disentangle natural vs industrial contributions |
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Budgets and Boundaries are used to track the inputs and outputs of an ecosystem (flow) to help answer a question.
What are the components? |
Inputs: Output + storage If storage = 0, inputs = outputs; ecosystem is at steady state
If storage is +ve, inputs are accumulating in the ecosystem If storage is -ve, outputs > inputs and there is net loss from the system |
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Hubard Brook Experimental forest (Calcium mass balance) |
- Watershed boundary is easily defined - bedrock is water-tight - Calcium enters the ecosystem via precipitation and weathering and exits via stream outflow - Within the system, there is uptake, exchange and cycling of Ca
Precipitation + weathering = stream outflow + net storage inputs = outputs
Losses of Ca >> inputs of Ca
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Challenges of setting boundaries for experiments |
- size, shape and spatial heterogenity can influence ecosystems - generalizations are possible, ex. mixed layer depth is influenced by water clarity; relation differs for small and large lakes |
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Generality and Prediction Steps in an experiment |
1. Synthetic perspective - Evaluates multiple alternatives - strives for synthesis and interegration of the knowledge gained - integrates multiple disciplines, or a range of spatial and temporal scales, to discover new knowledge - Generally emerges as a consequence of synthesis - often uses models and chooses the one(s) generating the best predictions
2. Deductive hypothesis testing: -Attempts to eliminate alternative explanations to evaluate underlying causes of phenomena - Predictions areise via deduction from hypotheses that are tested, and refuted or supported - generally develops when a hypothesis becomes widely supported by various tests
- both approaches are complementary
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Define: Structural heterogeneity |
Structural heterogeneity
Refers to complexity and variability of a property of an ecosystem in three dimensional space and over time |
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Define: Spatial heterogeneity |
Spatial heterogeneity
Occurs when a property (ex. plant cover, air temperature) has different values in different places within an ecosystem |
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Define: Temporal heterogeneity |
Temporal heterogeneity
Occurs when values of a property recorded at a single place in an ecosystem change over time |
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How are heterogeneity boundaries formed? |
- Through strong abiotic forces that lead to sharp boundaries - Plant neighbourhoods harsh environments, conditions can differ markedly beneath shrubs (organic matter content of soils, nutrients, moisture, wind, temperature, predation) - Stream patchiness pool, riffles, woody debris alternate with another; contrast in current velocity, sediment, habitat types - Boundary effects differ across a boundary: light, moisture, wind, aerosols, nutrients, biota and creates distinctive habitat zones |
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Define: Landscape ecology |
Landscape ecology The study of landscape structure and process |
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Define: Landscape |
Landscape An area of the earth containing a patchwork of ecosystems |
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Define: Landscape elements
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Landscape elements
Individual ecosystems within a landscape (forests, wetlands, lakes, meadows, bogs, hillslopes) |
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Define: Landscape process |
Landscape process The exchange of materials, energy or organisms among the ecosystems (or elements) that make up a landscape |
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Define: Landscape structure |
Landscape structure The size, shape, composition, number and position of ecosystems within a landscape |
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Define: Metapopulation |
Metapopulation A group of subpopulations living in seperate locations with active exchange of individuals among the subpopulations |
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Explain two types of temporal heteogeneity |
1) Dinural cycles - photoperiod, temperature, moisture etc. - photosynthesis/respiration - Vertical and horizontal migrations (lakes, nocturnal animals)
2) Annual variability Seasonal variation in climatic factors, Ex. flood pulse |
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Discuss causes and trends of temporal heterogeneity |
1) Disturbance 2) Animal movement and activity 3) Vegetation dynamics of succession 4) Climate variation and change 5) Human activities |
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Disturbances and responses affecting temporal heterogeneity |
- perturbations in ecosystems consists of a sequence of 2 events: disturbance and response shown by the biota to the damamge inflicted by the disturbance |
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Name 3 Disturbance types |
1) Pulse sudden onset, sort-lived, ends soon after onset.
2) Press Once instigated remains in a place a long time (ex. climate shift to new regime; exotic species invasion)
3) Ramp Steadily increase in time without an endpoint (ex. acid rain, eutrophication) |
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Name two types of resoponses |
1) Resistance: a measure of the capacity of a system to withstand a disturbance
2) Resilience: a measure of capacity of the system to recover from disturbance |
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Define: Succession |
Succession The gradual change in biological communities over time in an area following disturbance or the creation of new geological substrate |
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Define: Primary succession |
Primary succession Succession that occurs on newly exposed geological substrate (ex. glacier recession, volcanic activity, island emergence from sea, new sand dunes)
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Define: Secondary Sucession |
Secondary Succession Succession that occurs after a disturbance destroys the biological communities but does not destroy the soil (ex. fire, abandoned agricultural areas, forest clearance, wind throw) |
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Discuss the steps in which Secondary Succession occurs after forest clearance |
1) undisturbed ecosystem 2) following disturbance, the ecosystem will reorganize, Reorganization phase, 0-20 years. Forest loses biomass (and water and nutrients) 3) Aggradation, biomass will increase, >100 years (water and nutrients strongly retained) 4) Transition phase, biomass will decline during transition (expect loss of nurtients and water to increase), duration unspecified 5) Steady state phase, duration unspecified, biomass fluctuates around some mean value |
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Define: Control |
Control - occurs when a change in factor causes a change in size or nature of an ecosystem component or flow -depends on the scales of time and spaces that are being considered |
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Why do we care about ecosystem controls? |
1) Helps us understand how and why different ecosystems work the way they do
2) Predict or evaluate consequences of various management strategies
3) Anticipate how ecosystems will respond to future changes in climate, land-use, species invasions, etc. |
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Trophic cascade example: |
- biotic control via energy and nutrient uptake and waste production - top predators influence lower trophic levels and abiotic properties (water chemistry, clarity etc.) |
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Ecologic engineers cause physical and structural changes in an ecosystem |
- Involved 4 cause and effect relations
1) Engineering species cause structural changes which;
2) Causes changes in abiotic conditions, which;
3) Causes biological changes (ie other organisms and associated ecological processes), which
4) Causes further feedbacks to other abiotic and biotic changes
Example: Beavers! |
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Ecosystems can be controlled either through "bottom-up" or "top-down" processes |
Think about what happens to different organisms that are affected in the trophic system.
What happens if there are more nutrients in the lake; or if there are more fish in the lake? |
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Control can come from outside or inside the ecosystem. |
- controlled by inputs from outside their boundaries (light, materials, disturbances) - also controlled by their own internal structure - Ex. Forests with shallow or deep soil differ in PP, decomposition, nutrient cycling - Ex. Lakes with different basin morphometry differ in thermal stratification, habitats for biota, biogeochemical cycles, etc. |
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Control of ecosystems can follow mathematical functions |
- linear relationships - log-log scales - curves - hysteretic relationships, which means that different stable states under the same variables or parameters |
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Shallow Lake Example: Hysteresis
Clear-water state vs turbid water state |
1. Clear-water state - Dominated by submersed weeds when P loading is low - Weeds protect zooplankton from predation - low phytoplankton biomass - Weeds decreases sediment mixing
2. Turbid-water state - Dominated by photoplankton when P loading is high - Predation on zooplankton is higher, thus increasing phytoplankton - wind can mix sediments |
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Human activities control many ecosystems, name a few ways in which humans control different aspects of an ecosystem |
Humans - Appropriate 24% of global terrestrial primary production - Control >50% of available runoff water - Increase sediment moving in rivers by billions of tons, but cause an overall decline in sediment export to oceans (retention by dams) -Pollution, spreading species, toxins and nutrients around - Alter disturbance regimes |
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Define: Paleoecology |
Paleoecology The study of past ecosystems and how they have changed over time
- often as centered on assessing the past ditricution and abundance of species and their relation with environmental conditions - Term often used for studies of past terrestrial ecosystems |
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Define: Paleolimnology |
Paleoliminology The branch of science that uses physical, chemical and biological information preserved in aquatic sediments to reconstruct past changes in aquatic ecosystems |
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Define: Paleoocreanography |
Paleooceanography The study of past changes in ocean ecosystems |
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True or false
Allochthonous materials contribute to the paleorecord. |
True
Able to view: - Pollen (palynology) - Mineral particles - Insect remains - Algae (diatoms, chrysophytes, pigments) - Invertebrates (Chrionomids) -atmospheric conditions (carbon particles from combusiton, fly ash from coal combustion, metals and other pollutants) |
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Name a few biological indicators that are seen in the paleorecords. |
Terrestrial indicators (pollen, plant microfossils, conifer stomata, charcoal)
Algal indicators (diatoms, chrysophytes, pigments)
Zoological indicators (sponges, branchiopod crustations, midges) |
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Describe the Paleoecological approach |
1. Define Research Questions 2. Select study system(s) 3. Select coring site and get the sediment core 4. Section and date the sediment core (lead, cesium, carbon radioactive) 5. Sub-sample sediments and isolate indicator of itnerest 6. Collect proxy data 7. Analyze and interpret data
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Example of paleoecology
Using pollen to track postglacial changes in terrestrial vegetation |
looking at seeds to determine the changes of tree vegetation over time |
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Example of Paleoecology
Using pollen to map migration of trees in response to long-term climatic changes |
climate affecting precipitation and weather thus changing the type of trees and distribution
Spruce moving northwards in North america; moving towards optimal climate
Wite pin moving too |
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Example of paleoecology
Using pollen and transfer functions to estimate past changes in climatic variables (big lake) |
Transfer function = quantitative model based on the relation between community composition and an environmental variable |
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Example of paleoecology
Using pollen to assess human impacts on forests |
looking at the type of vegetation in the area through pollen and the size of the bands to determine duration og time |
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Example of Paleoecology
Addressing controversy Disentangling the roles of river regulation and climate change on the Pace-Athabasca Delta |
infrequent flooding vs frequently flooding - Concern over drying of the delta has developed due to consturction of the WAC Bennett Dam on the Peace river and the absence of major flood for over 20 years - Flooding frequency is reduced since the late 1800s - Hydrological and ecological consitions since 1968 are not outside the range of natural variability observed during the past 300 years - Evdidence from lake sediments incate that the 1700s were the driest periods over the past 300 years |
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Lake sediment analysis steps |
1. Chronology (measuring 210 Pb and 137 Cs, 14C)
2. Paleoenvironmental reconstruction a. geochemical analaysis - aquatic plant cellulose oxygen isotope contamination (hydrologic change) - Bulk organic C and N elemental and stable isotope composition
b. Biological analyses - diatom algar - plant macrofossils -pigments
c. Physical analyses - Magnetic susceptibility - Structure, texture and mineralogy |
