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ENV100Y5 Study Guide - Final Guide: Eutrophication, Ordovician, Disruptive Selection


Department
Environment
Course Code
ENV100Y5
Professor
Monika Havelka
Study Guide
Final

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Exam Study Guide – Module 2
What is an ecosystem?
-It integrates this idea of systems thinking and it’s an approach as to how you think of an area
-Systems thinking in ecology; ecosystems are nested and hierarchical (ex: there’s a river; this
exists in a bigger landscape and so on and so forth)
-If you look at a car, you’ll say that the engine is the whole heart of the car but if you look inside
the engine, there’s a whole lot of things that contribute and that make it what it is
-You can look at what the inputs/outputs, feedback loops are in the ecosystems
-Instead of looking at an ecosystem and saying that you only care about the trees but not the
rocks, the rocks are important if you look at it from a systems thinking point of view; they
provide habitat and do this or that; thus we must think of the abiotic and biotic features as to be
equally important
-There is no such thing as a completely closed system, as at some point, energy must get into the
system (whether it’s through solar energy, heat, etc)
-if you think of a pond, it’s more closed than looking at a river for example (where there’s more
water coming in and rushing out)
-Some systems are most closed and some are more opened but none is completely ever closed
-Feedback loops; negative feedback (e.g: density dependent, population regulation, stabilizing; a
person is in a bad mood and someone calms them down is an example) vs positive feedback (e.g:
loss of Arctic ice; destabilizing; fighting with your significant other is a positive feedback loop)
-When populations get too big, they start running out of resources and they don’t reproduce as
well, diseases come in, etc and when they get smaller, they have space and opportunities for it to
get back up (negative feedback loop)
-Positive feedback loops spiral out of control because it doesn’t keep things in a narrow bound
(ex: the more ice that is loss in the Arctic, the ratio of light to dark water changes which means it
absorbs heat and thus absorbs more Arctic ice; the worse it gets, the worse it gets)
Ecosystem Stability
-Resistance = system resists change and remains stable despite a disturbance
—> The idea that you’re able to resist for example if someone pushes you and you don’t fall
-Resilience = system changes in response to a disturbance, but later returns to its original state
—> Something happens and knocks it from its position and eventually recovers and comes back
to its position. For ex: forest fires, landslides, diseases, natural disasters
-Once you damage an ecosystem, it may not be resilient enough to recover and what comes back
may not be what it was before
-Emergent properties
—> It’s something that is not necessarily predictable from the system that emerges from the
complexity of the system
—> For ex: a blender (there’s nothing unpredictable about them; all the parts fit together and you
understand how that is so) vs an ecosystem (it’s unpredictable; a coral reef can have things
happen to it and you won’t be able to recreate a system that is exactly the same as there is
emergent properties and things that happen that will change the interactions)
-Every ecosystem is unique and is not able to be exactly replicated
-Ecosystems function whether there’s people or not; but we get our resources from them
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How do we look at ecosystems?
-Simple ecosystem model has 4 main components
a) Abiotic environment (water, soil minerals, atmospheric gases)
b) producers
c) consumers (there’s different trophic levels)
d) decomposers (return the energy stored in the biotic components to the abiotic components)
-*Soil has a abiotic and a biotic component to it* (minerals are abiotic)
How big is an ecosystem? What is the timescale of an ecosystem?
-The four components of an ecosystem is always present, no matter the size of the ecosystem
—> If you look at a grassland that mixes in with a shrub land that mixes in with the forest, then
it’s hard to draw a line on the map where you say what the ecosystem is; it’s a blurred boundary
and not easily defined boundary
-Ex: if you study a pond ecosystem, you’ll realize that the boundary is the edge area of the pond;
there’s wetlands, marsh areas, etc; thus how do you draw the line?
-Spatial boundaries can be tricky to define
-Primary production is how we get energy and it’s the basis for the engine of productivity but it’s
exactly where we see significant threat
-Net Primary productivity is a rate and is expressed per grams per meter square per year (most
often) or other sorts of measurements/there’s various possibilities
-What limits productivity?
—> Plants need sunlight, nutrients, water and CO2 for example
—> The real limiting factors are often precipitation which limit production; the reason is because
precipitation patterns change (and same with temperature, which also affects production)
—> The photic zone is the same in the coastline and in the ocean
-Decomposers break down bodies and make it available on land which makes it available for
plants to absorb it
-In oceans, when things die, they sink to the bottom and the ocean currents bring it back to the
top which tends to happen at the coastlines (this is why the fish come to the coastline so that they
can get the nutrients)
-These are systems about the major nutrients and how they move around in systems; the
substances that move around take different forms
-There’s a lot of temporal and spatial variation; how much time do they spend in these
reservoirs?
-Often, a lot of environmental problems stand from the fact that we stand in the problem and we
disturb the time in which these things happening in the reservoirs occur
-We create more of an effect on the nitrogen cycle than what it would be if we didn’t have an
effect on the cycle
Generalized biogeochemical cycle
-Ex: volcanoes are a big part of biogeochemical cycling as they liberate things in the atmosphere
at a very fast flux
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-Rocks, soils, oceans, freshwater are all potential examples of reservoirs which are potentially
connected and thus can get complex over time
-Massive changes in the hydrologic cycles happen over decades (changes in ocean temperature,
melting of ice caps, etc)
-Aquifers is where we get our groundwater from
-This is a problem of urbanization
-When it rains, the water percolates to the unconfined aquifer but the problem is that if it’s
contaminated ground, then it will pull the contaminants along with it
-Human impacts on the water cycle; damming rivers = increase in evaporation; impounding the
water behind it (i.e.: dam)
-Hard surfaces: increase in runoff creates erosion; takes in hydrocarbons and take dirt and soil
with them (i.e.: asphalt)
-Deforestation: decrease in transpiration; plants store water and they transpire as well
The Carbon Cycle
-Where is the biggest reservoir? (pay attention to that in the diagrams)
-It’s critical to life, as it functions on multitude of scale and some of them is a metabolism that is
part of the carbon cycle
-The largest carbon reservoir is the sedimentary rock. Its residence time = million of years
-Carbon cycle functions on multiple timescales: some immediate, some over long terms, etc
-Human activities could be affecting the cycle; marine systems and the temperature of the
systems; oxygen availability, metabolic rates, etc
Timescales and variations in atmospheric CO2
-Camels Often Sit Down Carefully Perhaps Their Joints Creak?
—> Refers to the 15 geological time periods: Cambrian, Ordovician, Silurian, Devonian,
Carboniferous, Permian, Triassic, Jurassic, Cretaceous
-Mid-Cretaceous Ice Age
—> Lower sea levels create land bridges for organisms to move around
Humans affect the CO2 cycle
-Carbon Mobilization
—> Burning fossil fuels (geosphere -> atmosphere): we’re burning biomass which causes
deforestation (biosphere -> atmosphere)
—> Cattle & rice production (biosphere -> atmosphere); livestock also has a big effect on the
CO2 cycle
-In Northern Canada, Peat is accumulated stuff (dead plants) is like walking on a trampoline; it’s
squishy stuff because it’s centuries of decomposed plant matter; if it warms up then it’ll dry up
and evaporate
-If the Arctic gets warmer, evaporation will take off and it’ll get dryer, which means there’ll be
more oxygen and thus the micros will decompose more and they will release CO2 more quickly
(example of a feedback loop)
-Plants or soils of northern temperate and boreal forests?
The Nitrogen Cycle
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