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EOSC 112 MIDTERM 3
Question | Answer |
---|---|
What is is the most important contributor to global warming ? | Increase in atmospheric CO2 from anthropogenic activities |
How significant is the increase in solar radiation to global warming? Compare to anthropogenic GHG? | Increase in solar radiation has also contributed to global warming but its effect is much smaller that the effect of anthropogenic greenhouse gases |
T/F? - Increase in troposheric ozone concentration also contributes to greenhouse warming | TRUE |
Does an increase in cloud albedo have a net warming or a net cooling effect? | net cooling effect |
T/F? - The effect of change in cloud cover is more precisely known than the effect of greenhouse gas concentration | FALSE - have large uncertainties and low LOSU |
What controls the concentration of water vapor at saturation in the atmosphere? | air temperature |
What is the most powerful GHG? | CH4 |
In today’s atmosphere, what greenhouse gas produces the most warming? | CO2 |
What greenhouse gas drives global warming? | CO2 |
why was the concentration of methane in the atmosphere low? | because it was rapidly oxidized to CO2 by oxygen |
T/F? - Even though CH4 has a lower atmospheric concentration than CO2 today, it contributes more than CO2 to greenhouse warming | FALSE - CO2 contributes more |
During early stages of Earth's history, before O accumulated in the Earth's atmosphere, what was the most important GHG? | methane |
Can changes in the water content of the atmosphere DRIVE climate change? | No, water content of Earth’s atmosphere cannot change independently of its temperature; instead it is changes in temperature (or climate) that drive changes in the water vapor content of the atmosphere |
What is being exchanged in the Carbon cycle? What elements of earth does it include? | continuous exchange of carbon between the atmosphere, biosphere, hydrosphere and lithosphere by a range of processes (e.g. volcanism, weathering, photosynthesis, respiration, etc.) |
What does the carbon cycle control? | atmospheric concentration of CO2 and CH4 |
What drives climate change? and why? CO2 vs H20 | Changes in atmospheric CO2 can drive climate changes because atmospheric CO2 concentration can change independently of climate (e.g. burning fossil fuel) |
When chemically bound to hydrogen (H), carbon is : (organic vs inorganic)? | organic |
Is limestone organic or inorganic? | inorganic |
Is the living tissues of organism is a form of (a) organic (b) inorganic carbon | organic |
Is CO2 dissolved in seawater is a form of (a) organic (b) inorganic carbon | inorganic |
Is Fossil fuel is a form of (a) organic (b) inorganic carbon ? | organic |
Size of largest carbon reservoirs (decreasing) | inorganic carbon in sedimentary rocks -> sedimentary organic carbon -> inorganic carbon dissolved in seawater -> atmospheric CO2 -> living organisms |
Explain CO2 + H2O -> H2CO3 | Dissolution of CO2 in water produces carbonic acid |
Explain H2CO3 -> (H+) + HCO3- | Carbonic acid dissociates to produce hydrogen ions and bicarbonate ions |
Explain (HCO3-) ->(H+) + CO3 | Bicarbonate ions dissociate to produce hydrogen ions and carbonate ions |
T/F? Methane is a very potent greenhouse gas | TRUE |
Where is Carbon found in marine sediments? | dissolved inorganic carbon and carbonate minerals |
Is there more carbon dioxide gas in the atmosphere than dissolved inorganic carbon in seawater ? | No, more dissolved than in atmosphere |
Marine sediments accumulating on the seafloor contain? (organic vs inorganic) | inorganic carbon only |
what is involved in Organic C cycle? | - Organic carbon (organic matter) finely dispersed in sedimentary rocks - Fossil fuels - Organic matter in soils and sediments - Organic matter in living biomass - Atmospheric methane |
what is involved in Inorganic C cycle? | - The limestone reservoir - Inorganic carbon dissolved in seawater - Carbonate minerals in marine sediments - CO2 in the atmosphere |
Atmospheric CO2 is controlled by different processes on what timescales: | multi-million year timescales |
atmospheric CO2 is affected by exchange of carbon between the atmosphere and...._________ which is controlled by_________? | the earth's crust; tectonic processes |
Exchanges with large reservoirs produce (i) rapid or (ii) slow changes in atmospheric CO2 because the processes controlling the exchanges are (iii) fast or (iv) slow | slow; slow |
Exchanges with smaller reservoirs produce (v) small or (vi) large changes in atmospheric CO2 | large |
Why do exchanges with smaller reservoirs produce large changes in atmospheric CO2? | because even the smallest reservoirs which exchange carbon with the atmosphere are much larger than the atmospheric reservoir |
The residence time of CO2 in the atmosphere with respect to respiration/photosynthesis is 12.7 years. This means that: | Molecules of CO2 produced by heterotrophs and released to the atmosphere remain ON AVERAGE 12.7 years in the atmosphere before being taken up by phototrophs for photosynthesis |
On seasonal timescale, atmospheric CO2 increases from ___________ in the southern hemisphere when ___________ exceeds ___________? | May - September; respiration of organic matter on continents exceeds photosynthesis by land plants |
on seasonal timescale, atmospheric CO2 increases from __________ in the northern hemisphere? | October - April |
What causes a negative feedback loop during the CO2 fertilization effect? | higher atmospheric CO2 increases the photosynthetic rate of land plants |
are seasonal variations in atmospheric CO2 larger or smaller in the southern hemisphere? | smaller because there are less continents |
what causes seasonal fluctuations in atmospheric CO2? | exchange of carbon with land biomass -> balance between CO2 uptake during photosynthesis by land plants and CO2 release by land heterotrophs that produces seasonal variations in atmospheric CO2 |
Which components of the Earth’s system is involved in the Carbonate – Silicate Geochemical Cycle? | Atmosphere/Biosphere/ Hydrosphere/Lithosphere |
On multi-million year timescales, what controls atmospheric CO2? | the balance between uptake of CO2 from the atmosphere during weathering and addition of CO2 to the atmosphere by volcanism |
If volcanism increases: - atms co2? - rain water? - uptake by weathering? | - Atmospheric CO2 increases and stabilizes at higher level - Rain water becomes more acidic - Rate of CO2 uptake by weathering increases until it matches the rate of CO2 release by volcanism |
what causes a negative feedback loop stabilizes atmospheric CO2 on multi-million year timescales? - acidity? uptake by weathering? | higher atmospheric CO2 increases the acidity of rain water, the reaction rate between carbonic acid and silicate minerals and the uptake rate of atmospheric CO2 by weathering |
Lower rates of seafloor spreading.. - volume of basins? - mid ocean ridges? sea level? - SA of continent? | increase the volume of ocean basins by producing thinner mid ocean ridges, thereby lowering sea level, increasing the surface area of continent subjected to weathering and increasing uptake of atmospheric CO2 by this process |
Higher rates of seafloor spreading.. - mid ocean ridges? - time to cool and contract? - volume? | produce broader mid ocean ridges because seafloor at a given distance from the ridge has had less time to cool and contract.the resulting mid ocean ridges occupy a larger volume of the ocean basins and sea level increases |
Increasing the rate of seafloor spreading.. - atms co2? influences | increases atmospheric CO2 because of higher rate of CO2 addition to the atmosphere by volcanism and hydrothermal activity at the mid ocean ridges AND lower rate of CO2 uptake by weathering due to continental flooding |
Mountain ranges formed when two continental plates are colliding.. - contribute to atms co2 by? | contribute to decreasing atmospheric CO2 by increasing the uptake rate of atmospheric CO2 by weathering because glacier abrasion and increased erosion fragment rocks and increase the surface of contact with rain water |
During the maximum of the last ice age, about 20 ka ago, large amount of ice accumulated on land. This resulted in a sea level: | a sea level 130 m lower than today |
What factors affect the rate of removal of atmospheric CO2 by weathering? | A) Sea level B) Formation of mountain ranges (uplift) C) Atmospheric CO2 level |
If sea level rises, while the rate of outgassing by volcanoes stays the same.. What is going to happen to atmospheric CO2? | It will increase and stabilize at a higher level when the rate of removal by weathering matches again the rate of input from volcanoes |
Which factor controls sea level by changing the volume of water in the ocean? | The volume of ice accumulating on continents |
a ____fraction of this organic carbon is consumed by heterotrophs and oxidized back to CO2, but a _______ proportion is buried in marine sediments | large; small |
The organic carbon buried in marine sediment is slowly transported to subduction zones by _________ | seafloor spreading and incorporated into sedimentary rocks |
Uplift of sedimentary rocks bring the buried organic carbon to the surface of continents where it is subjected to_________ | weathering |
Weathering of rocks on the surface of continents produces a net ________ of CO2 from the atmosphere | a net removal of CO2 from the atmosphere because removal by the weathering of silicates exceeds addition by oxidation of organic carbon in sedimentary rocks |
The long-term evolution of the oxygen content of the atmosphere is controlled by | the balance between the amount of organic carbon produced by photosynthesis and buried, and the oxidation of organic carbon during the weathering of sedimentary rocks |
The amount of oxygen in the atmosphere is largely dictated by: | The amount of organic carbon buried in sedimentary rocks |
If we were to burn all the fossil fuel available in the Earth’s crust, which of the following we would : | A) increase the concentration of CO2 in the atmosphere B) increase the acidity of the ocean C) increase global warming D) decrease the level of oxygen, but by a very small fraction |
Vast swamps covered large areas of land during the Carboniferous, increasing the burial of organic carbon. This resulted in an atmosphere with.. - O2? - CO2? | higher O2 content and lower CO2 content |
How have we measured changes in atmospheric CO2 during the last 800,000 years? | by analyzing old air confined in air-tight bubbles trapped in the ice covering Antarctica a Snow gradually compresses as new snow falls on top b Bubbles get trapped at around 50m below surface |
atmospheric CO2 was _______ during ice ages and _______ during interglacial periods | lower; higher |
Do CO2 and CH4 move in the same direction? or different? | same |
why was the Antarctic ice finding significant? | Recorded changes in atmospheric CO2 and temperature in Antarctic ice support the notion that the level of atmospheric CO2 can significantly affect global climate |
Changes in atmospheric CO2 recorded in ice cores during the last 800,000 years are mainly a result of.. | exchange of carbon between the atmosphere and the ocean |
. Changes in atmospheric CO2 recorded in ice cores during the last 800,000 years are: ______ to be explained by exchange of carbon between the atmosphere and the terrestrial biota | too small |
. Changes in atmospheric CO2 recorded in ice cores during the last 800,000 years are: _______ to be explained by exchange of carbon between the atmosphere and sedimentary rocks | too slow |
Lowering atmospheric CO2 during ice ages could be achieved by? | increasing the biological pump and decreasing the rate of the thermohaline circulation |
In HNLC (High Nutrient Low Chlorophyll) regions, the surface water concentration of nitrate and phosphate is _______ because.... | high because productivity in these oceanic regions is limited by a lack of Fe, or because of light limitation from deep vertical mixing and shallow light penetration |
Export production in these regions could be increased by _______ the wind supply of continental dust to surface waters | increasing |
How can you increase the biological pump? | A) increasing the utilization of nutrient in HNLC regions B) supplying more continental dust and iron to the southern ocean C) increasing “New Production” |
Phytoplankton growing in the southern ocean around Antarctica cannot use all the nitrate and phosphate available in surface water because: | i. Vertical mixing is too deep ii. Euphotic zone is too shallow iii. Another essential nutrient is missing |
The formation of calcium carbonate by marine plankton results in..... | the production of carbon dioxide in seawater i when 2 molecules of CO2 are removed from the atmosphere by weather, one co2 is returned to the atmosphere when CaCO3 is formed and one is removed to |
Coccolithophorids and diatoms are common types of phytoplankton in the ocean. Which of these two types of phytoplankton is more effective at driving a flux of CO2 from the atmosphere to the ocean? and why? | Diatoms because they produce organic matter and do not produce calcium carbonate |
Decreasing atmospheric CO2 during the ice ages could be achieved by: | a) increasing surface nutrient utilization in HNLC regions by increasing the flux of continental dust b) increasing nitrate and phosphate concentration in the deep sea |
The P cycle includes: release of _____ from ______________ during weathering and uptake of _____ by land plants | release of phosphate from continental rocks during weathering and uptake of phosphate by land plants |
The P cycle includes: recycling in terrestrial ecosystems and ____________________ to the ocean by rivers | recycling in terrestrial ecosystems and supply of dissolved phosphate to the ocean by rivers |
The P cycle includes: burial of ________ molecules containing ________ in marine sediments | burial of organic molecules containing phosphorus in marine sediments |
The P cycle includes: Inclusion of phosphorus in _________________________ and ____________ | Inclusion of phosphorus in sedimentary and metamorphic rocks and uplift |
The phosphate inventory of the ocean can be increased by: | a) decreasing the burial efficiency of phosphorus reaching the seafloor with sinking organic matter b) increasing the rate of addition of dissolved phosphate from the continents by runoff |
Phosphorus is always found in what form in the environment? | oxidized (phosphate) |
What is the most reduced form on N? the most oxidized? | FALSE - most reduced form: ammonia most oxidized: nitrate |
What species are able to fix N2? | prokaryotes |
Some nitrogen fixers live in ________ with other organisms | symbiosis |
What is the main species of N fixers? Where do they thrive? | FALSE - Main N fixers are cyanobacteria, which thrive in low latitudes where thermal stratification of the water column limits nitrate supply by vertical mixing from deeper water |
Does denitrification requires the presence of oxygen ? | no |
What marine phytoplankton species can use N from the atmosphere? | cyanobacteria or methanogens |
T/F? Nitrifying bacteria decompose organic matter to regenerate nitrate in deep water | ammonia -> nitrate |
T/F? Nitrate (NO3-) is reduced to ammonia (NH3) during denitrification | (NO3-) -> atmospheric N2 |
T/F? Nitrifying bacteria oxidize ammonia (NH3) to nitrate (NO3-) and use the energy released in this exothermic reaction to produce organic matter from CO2 dissolved in seawater | TRUE |
transformation vs process: (NO3-) ---> organic nitrogen (proteins) | nitrate uptake |
transformation vs process: organic nitrogen -> NH3 | decomposition |
transformation vs process: N2 -> organic nitrogen (proteins) | nitrogen fixation |
transformation vs process: (NO3-) -> N2 | denitrification |
transformation vs process: NH3 -> NO3- | nitrification |
processes and marine environments: nitrogen fixation | euphotic zone |
processes and marine environments: nitrate uptake | thermally stratified surface water |
processes and marine environments: nitrification | aphotic zone in presence of oxygen |
processes and marine environments: denitrification | anoxic zones |
processes and types of marine organism: nitrogen fixation | cyanobacteria |
processes and types of marine organism: nitrate uptake | phytoplankton |
processes and types of marine organism: nitrification | chemoautotrophic bacteria |
processes and types of marine organism: denitrification | anaerobic heterotrophic bacteria |
processes and types of marine organism: NH3 excretion | zooplankton |
The nitrate inventory in the ocean is regulated by the balance between: | Denitrification and nitrogen fixation |
Considering that (1) nitrogen fixation demands a lot of energy, which limits the growth rate of nitrogen fixers and (2) the distribution of surface nitrate concentration in the world ocean, where would expect to find nitrogen fixers? | subtropical gyrens |
What happen to ammonia released by the decomposition of organic nitrogen in the water column? | i) it is taken up by phytoplankton in the euphotic zone ii) it is oxidized to nitrate in the aphotic zone by nitrifying bacteria; |
Most seawater samples have a nitrate to phosphate concentration ratio of 16 (Redfield Ratio). In seawater where denitrification occurs, the nitrate to phosphate concentration ratio is: | <16 because nitrate is reduced to N2 which escapes to the atmosphere |
Most seawater samples have a nitrate to phosphate concentration ratio of 16 (Redfield Ratio). In seawater where nitrogen fixation occurs, the nitrate to phosphate concentration ratio is: | >16 because nitrogen fixation adds nitrogen from the atmosphere to the ocean but not phosphate. Nitrogen is first incorporated in biomass, heterotrophy releases it as ammonia (NH3) in seawater, and NH3 gets oxidized to nitrate by nitrification |
Negative feedback if N2 fixation increases: the ocean’s nitrate inventory and nitrate concentration in deep water ___________ | increases |
Negative feedback if N2 fixation increases: export production _________ | increases |
Negative feedback if N2 fixation increases: O2 consumption in intermediate depth waters ___________ because of the_______ sinking flux of organic matter and its oxidation by ________ | increases; large; heterotrophs |
Negative feedback if N2 fixation increases: the anoxic zones of the ocean ________ and denitrification rates ________ until they match the higher level of N2 fixation. | expand, increase |
Negative feedback if N2 fixation increases: this stage, the nitrate concentration of seawater will have stabilized at a ________ value | higher |
Which one of the following could possibly contribute to lowering the level of CO2 in the atmosphere? | a) Higher rate of deep water renewal b) Higher rate of weathering on continents c) Higher supply rate of wind-blown continental dust to the ocean d) More diatoms growing at the expense of carbonate producing phytoplankton |
Stromatolites are | fossilized remains of bacterial communities that form layered mats of minerals |
The morphology of the stromatolites implies that they were | photosynthetic organisms |
the first photosynthetic organisms were.. | sulfide oxidizing bacteria which used sunlight to oxidize hydrogen sulfide (H2S) to sulfur (S) and produce organic matter from CO2. This process is called anoxygenic photosynthesis. Anoxygenic photosynthetic bacteria are still found today in hot springs |
how can we explain the long delay (> 1 billion years!) between the rise of atmospheric O2 and the appearance of the first photosynthetic organisms? | O2 produced by photosynthesis reacted with reducing chemical species (reduced iron, sulfide, CH4, etc.) |
How can we explain the long delay (several hundred million years!) between the rise of atmospheric O2 and the appearance of the first oxygenic photosynthetic organisms? | O2 produced by photosynthesis reacted with reducing chemical species (reduced iron, sulfide, CH4, etc.) |
What happened before oxygenic photosynthesis? | anoxygenic photosynthesis |
T/F? during anoxygenic photosynthesis _____ are used instead of H2O to produce organic matter from CO2 | H2S or H2 |
Does anoxygenic photosynthesis produce oxygen ? | No |
where can we still find anoxygenic photosynthetic bacteria? | in hot springs |
Organisms on Earth are subdivided into what three super-kingdoms? | Archaea, Bacteria, Eucarya |
What super kingdom(s) contain Monera? | archaea and bacteria -> single cell prokaryotes |
What super kingdom(s) contain Protista, Fungi, Metaphyta and Metazoa? | eucarya -> all eukaryotes |
The “tree of life”, based on the genetic code of organisms living today, indicates that all the organisms closest to the “common ancestor” (i.e. the “trunk of the tree”) are.. | thermophiles (archaea or bacteria), i.e. prokaryotic cells living in water as hot as 80°C. This suggests that life started in hot springs or near hydrothermal vents |
T/F? The genetic code of methanogens indicate that they are primitive organisms that evolved at a very early stage of life of Earth | TRUE |
what do methanogens do? | use energy produced from oxidation of H2 by CO2 and produce CH4 as a by-product |
Can some methanogens can fix nitrogen (N2) in addition to CO2 to produce organic matter? | yes |
The first ecosystems were based on the production of organic matter by what species? | anoxygenic photosynthesis and methanogens? |
T/F? The organic matter produced by these primitive organisms was consumed by aerobic heterotrophic bacteria | FALSE |
The first organisms that started oxygenic photosynthesis 2.3 billion years ago were: | cynaobacteria or methanogens |
what type of organisms are methanogens? | chemoautotrophs |
why are prokaryotes more resistant to ultraviolet radiations? | Because there was no oxygen in the atmosphere when they first evolved - No oxygen = no ozone = stronger UV radiations |
considering that there was no oxygen in the atmosphere at the start of the evolution of life on Earth, what type of heterotrophs must have evolved within the first ecosystems? | fermenting bacteria |
what are Banded Iron Formations (BIFs)? | BIFs are laminated sedimentary rocks that consist of alternating layers of iron-rich and silica-rich minerals. |
How did BIFs form? | The iron-rich layers were produced by the oxidation of reduced Fe (added to seawater from hydrothermal vents and continental runoff) by oxygen produced by cyanobacteria |
(a) Ediacaran metazoans (b) shelled multicellular organisms (c) Oxygenic cyanobacteria (d) methanogens. Sequence them in order of first appearance on Earth (starting with those that appeared first and finishing with those that appeared last)? | Methanogens -> oxygenic cyanobacteria -> Ediacaran metazoans -> shelled multicellular organisms |
t/f? multicellular organisms first evolved after the “Cambrian Explosion” | false- when multicellular organisms started developing hard shells |
the accumulation of oxygen in the atmosphere was essential to allow the evolution of the ___________ | early metazoans |
The evolution of organisms able to produce _______ produced the “Cambrian Explosion” and it is believed that atmospheric oxygen reached a level similar to today during that period for the first time in Earth history | hard shells and skeletons |
when did prokaryotes become present after life on earth appeared? | approx 1 billion years after |
why was there a long delay between the appearance of oxygenic photosynthesis and the accumulation of oxygen in the atmosphere ? | because the oxygen that was initially produced by cyanobacteria was used to oxidize Fe2+ and form large deposits of iron oxides |
We know that the oxygen content of the atmosphere must have been at least as high as 13% throughout the Phanerozoic because... | combustion of organic matter is impossible if the oxygen level drops below 13% and charcoal is found in the entire geological record of the Phanerozoic |
The amount of oxygen in the atmosphere is equivalent to.. | The total amount of organic carbon on Earth (mostly found in sediments and sedimentary rocks) |
* GO LEARN NEGATIVE FEEDBACK OF OXYGEN IN ATMOSPHERE | OK |