Chapter 21: Movement of Elements in Ecosystems Flashcards
The movement of water through ecosystems and atmosphere is known as the _________________
Hydrologic cycle
What three processes drive the hydrologic cycle?
Evaporation
Transpiration
Precipitation
The movement of water is drive by the energy of ____________, which causes evaporation from soil and water bodies and evapotranspiration from plants
the Sun
What is evapotranspiration?
Evapotranspiration changes water from a liquid to a gas in the form of water vapor
There is a limit to the amount of water vapor the atmosphere can contain. As additional water continues to evaporate, the water vapor in the atmosphere condenses into _______________, which ultimately create __________________ in the form of rain, hail, sleet, or snow
Clouds
Precipitation
___________________ that falls on land either runs off along the surface or infiltrates the soil, where it may evaporation, be taken up by plants, or enter groundwater; excess water ultimately returns to the ocean
Precipitation
The _____________ cycle is closely tied to the movement of energy
Carbon
In the carbon cycle, producers take up _________ from the atmosphere and water. They transfer assimilated carbon to consumers, detritivores, scavengers, and decomposers, and these organisms return _____________ to the atmosphere and ocens through ___________________
Carbon dioxide
Carbon dioxide
Respiration
What is a biogeochemical cycle?
The circulation of chemical elements from environment to organisms and back to the environment (inorganic to organic and back)
What are the two types of biogeochemical cycles?
- Gaesous
- Sedimentary
What is a gaseous biogeochemical cycle?
A cycle in which the resevoir is the atmosphere or ocean
What is a sedimentary biogeochemical cycle?
One in which the resevoir is usually the lithosphere (“rock”-sphere)
In ecological systems, energy __________ or passes through the system; matter, however, like nutrients, __________ through the system.
Flows
Cycles
Why is the nitrogen cycle important?
Because living organisms need nitrogen for building nucleic acids and proteins
Why is nitrogen inacessible to most animals?
Because it’s reserved in the atmosphere in a form that most living things are unable to break down - molecular nitrogen
What enzyme breaks down the triple bond between nitrogen atoms in the nitrogen molecule?
Nitrogenase
In the presence of _________, nitrogenase denatures
Oxygen
Which exceeds the other in terrestrial ecosystems? Precipitation or evaporation?
Precipitation
What’s the harm done to the hydrologic cycle when construction materials like roofing and pavement are used?
These materials are impervious to water infiltration, which reduces the amount of water available for the soil, which plants use or humans need for drinking water
These materials therefore increase the amount of surface runoff, which increases soil erosion
What’s the harm done to the hydrologic cycle as a result of logging?
The overall plant biomass is reduced, so less precipitation is taken up by plant roots and evapotranspirated
Thus surface runoff increases, which results to soil erosion and flooding
What harms are done to the hydrologic cycle when groundwater is pumped for irrigation or household use?
We reduce the amount of groundwater at a rate that exceeds its replenishment
How does global warming affect the hydrologic cycle?
As air and water temperatures rise, there will be an increase in the rate of water evaporation, which will cause water to move through the hydrologic cycle more quickly, potentially leading to increased rain and snow intensity
What are the three drivers of the hydrologic cycle?
Evaporation
Transpiration
Precipitation
What is the largest pool of water in the hydrologic cycle?
The oceans
From where does evaporation of water occur?
Bodies of water, soil, and plants that experience evapotranspiration
What provides the energy for evaporation in the hydrologic cycle?
The Sun
What are the paths that precipitation can take in the hydrologic cycle?
Falls directly onto surface of acquatic ecosystems
Falls directly onto terrestrial ecosystems, where it can travel along the surface of the ground or infiltrate the ground water (and then absorbed by plants) - the surface runoff and some of the groundwater will return to water bodies
Overview of the hydrologic cycle:
The movement of water is driven by the energy of the ________, which causes _____________________ from soil and water bodies and _______________________ from pants. Water __________________ condense into clouds that eventually return the water to Earth as ________________________ that either runs off the surface or infiltrates the soil. Runoff flows along the surface of the ground until it enters streams and rivers; water in the soil is taken up by plants or enters the groundwater. Ultimately, _________________ returns to the ocean
the Sun
Evaporation
Evapotranspiration
Vapors
Precipitation
Excess water
What are the six types of transformations carbon can undergo?
Photosynthesis
Respiration
Sedimentation/burial
Exchange
Extraction
Combustion
Producers use _______________________ in terrestrial and aquatic ecosystems to take CO2 from the air and water and to convert it into carbohydrates, which are used to make other compounds, including proteins and fats.
Photosynthesis
What does photosynthesis accomplish in the carbon cycle?
It fixes or locks up carbon in forms that are usable to consumers, scavengers, detritivores, and decomposers
Which trophic groups experience respiration?
Consumers
Scavengers
Detritivores
Decomposers
(basically anything that isn’t a producer)
How is carbon returned to the air or water in the carbon cycle?
Via respiration of consumers
In some habitats, oxygen isn’t available to serve as the terminal electron acceptor for respiration in which case some species of archaea use carbon compounds, like __________________ to produce CO2, water, and _____________
Methanol
Methane
Why is the production of methan through anaerobic respiration a concern?
Because methane is a greenhouse gas and on a per-molecule basis is 72 times more effective at aborbing and radiating infrared radiation back to Earth than CO2
What’s different between the exchange of carbon in acquatic systems and terrestrial systems?
In acquatic systems, the exchange occurs in both directions at a similar magnitude, meaning there is little net transfer over time
What happens whe CO2 diffuses from the atmosphere into the ocean?
Some is used by plants and algae for photosynthesis
Some is converted into carbonate and bicarbonate ions
To what do carbonate ions bond in water?
Calcium
What’s formed when calcium and carbonate combine?
Calcium carbonate
What’s the significance in the formation of calcium carbonate in water?
Calcium carbonate has a low solubility in water, so it precipitates out of the water and becomes part of the sediments at the botton of the ocean; over time, these calcium carbonate sediments form dolomite and limestone that humans mine for use in concrete and fertilizer
Over millions of years, the calcium carbonate sediments that accumulate in the ocean bottoms combined with the calcium carbonate skeletons from tiny marine organisms can develop into massive sources of carbon in the forms of rocks known as ________________ and _____________
Dolomite
Limestone
What does it mean to say that carbon can be “buried”?
Carbon can be buried as organic matter before it fully decomposes; some of this organic matter is converted to fossil fuels
The rate of carbon burial is slow and is offset by the rate of carbon released back into the atmosphere by the weathering of _____________________ and during _______________
Limestone rock
Volcanic eruptions
Why does carbon move slowly through sedimentary and burial pools?
Because the carbon can be locked
What represents a recent change to the carbon cycle?
The extraction of fossil fuels
____________________ of carbon sources produces CO2 that goes into the atmosphere. Some is natural, but some is human-caused.
Combustion
Like respiration and decomisition, ______________________ converts organic compounds to CO2
Combustion
Overview of the carbon cycle
In the carbon cycle, ________________ take up CO2 from the atmosphere and the water. They transfer assimilated carbon to ______________, _________________, scavengers, and _______________. These organisms return CO2 to the atmosphere and oceans through _____________________. Throughout the ecosystem, CO2 is exchanged between the atmosphere and the ocean and between the ocean and sediments. Carbon that’s been stored underground for long periods turns into ____________________, which can be extracted. CO2 is returned to the atmosphere through the __________________ of these materials, burning in terrestrial ecosystems, and volcanic activity
Producers
Consumers
Detritivores
Decomposers
Respiration
Fossil fuels
Combustion
How do researchers measure CO2 levels across time?
Ice cores
Why have CO2 levels increased in modern times?
Combustion of fossil fuels for energy
Why is the rise in atmosphere CO2 important to humans?
Because CO2 is a greenhouse gas that absorbs infrared radiation and radiates some of it back to Earth
At higher temperatures, ______________ - found in high latitude regions - thaws and decomposes under anaerobic conditions, producing methane
Peat
What are some effects that temperature increases can have around the world?
Reducing the size of the polar ice sheets
Altering the length of plant growing seasons
Changing the timing of plant and animal life histories
How does deforestation disrupt the carbon cycle?
When trees are cut down and burned or allowed to rot, their stored carbon is released into the air as carbon dioxide. And this is how deforestation and forest degradation contribute to global warming
How does agriculture affect the carbon cycle?
Plants absorb CO2 from the atmosphere through photosynthesis, and pass carbon to the ground when dead roots and leaves decompose. But human activity, in particular agriculture, can cause carbon to be released from the soil at a faster rate than it is replaced
What is the greenhouse effect?
The greenhouse effect is the process by which radiation from a planet’s atmosphere warms the planet’s surface to a temperature above what it would be without this atmosphere. Radiatively active gases in a planet’s atmosphere radiate energy in all directions
What are the five greenhouse gases discussed in class?
CO2
CH4 (methane)
O3 (ozone)
NO
CFC (chloroflourocarbons)
Under anaerobic or incomplete decompositions, _____ and methane are form, which are further _____________ to CO2 in the atmosphere
CO
Oxidized
What algae store CO2?
Coccolithophores
_____________________ sequester CO2 as calcium carbonate through their shells
Coccolithophores
What happens if too much CO2 winds up in water?
The buffer system shifts to the right, releasing carbonate and hydronium ions and decreasing the pH of the ecosystem
If too much CO2 dissolves in the ocean, the water’s pH level decreases and kills coccolithophores. Why is this a problem?
Because coccolithophores sequester excess CO2 as calcium carbonate in their shells; when they die, the excess CO2 can’t be sequester, shifting the buffer system further to the right
What do we mean by “groundwater recharge”?
Groundwater recharge or deep drainage or deep percolation is a hydrologic process, where water moves downward from surface water to groundwater. Recharge is the primary method through which water enters an aquifer; groundwater recharge also encompasses water moving away from the water table farther into the saturated zone
An ________________ is an underground layer of water-bearing permeable rock, rock fractures or unconsolidated materials (gravel, sand, or silt)
Aquifer
The _________________ describes the entire river system as a continuously integrating series of physical gradients and associated biotic adjustments as the river flows from headwater to mouth.
River Continuum Concept (RCC)
The ____________________ proposes a progressive shift, from headwaters to mouth, of physical gradients and energy inputs and accompanying shift in trophic organization and biological communities
River Continuum Concept
The River Continuum Concept is based on the theory of ___________________
Dynamic equilibrium
_________________ connectivity refers to the periodic inundation of the floodplain and the resulting exchange of water, sediment, organic matter, nutrients, and organisms. Lateral connectivity becomes especially important in large rivers with broad floodplains.
Lateral
________________ connectivity refers to the pathways along the entire length of a stream. As the physical gradient changes from source to mouth, chemical systems and biological communities shift and change in response.
___________________ connectivity, however, refers to the periodic inundation of the floodplain and the resulting exchange of water, sediment, organic matter, nutrients, and organisms. Lateral connectivity becomes especially important in large rivers with broad floodplains
Longitudinal
Lateral
The ___________________ explains how the periodic inundation and drought control the lateral exchange of water, nutrients and organisms between the main river channel and the connected floodplain
Flood pulse concept
The flood pulse concept views streams and rivers longitudinally and laterally and accepts _______________ as natural to which organisms develop
Flooding
What is a riparian zone?
A riparian zone or riparian area is the interface between land and a river or stream
Nitrogen moves through five major transformations. What are they?
Nitrogen fixation
Nitrification
Assimilation
Mineralization
Denitrification
Where is the largest pool of nitrogen located?
Atmosphere
What is nitrogen fixation?
The process of converting atmospheric nitrogen into forms producers can use
What does nitrogen fixation accomplish?
Converts nitrogen gas into ammonia (NH3) (then rapidly interconverted into ammonium NH4+) or nitrate (NO3-)
What are three ways that nitrogen fixation occurs?
Organism metabolism
Lightning
Industrial fertilizer production
What species of cyanobacteria can fix nitrogen?
Azotobacter
What mutualistic bacteria can fix nitrogen?
Rhizobium
_____________________ can fix nitrogen and lives in the root nodules of some legumes
Rhizobium
Nitrogen fixation is an important source of required _________________, especially for early succession plants colonizing habitats that have little available nitrogen
Nitrogen
The process of nitrogen fixation requires a relatively ___________ amount of energy
High
How do organisms obtain the energy required for nitrogen fixation?
Metabolizing organic matter from the environment (cyanobacteria engage in photosynthesis)
Acquiring carbohydrates from a mutualistic partner (Rhizobium is mutualistic with legumes)
Can nitrogen fixation occur via abiotic processes?
Yes via lighting and combustion
Besides the biotic and abiotic (lightning, combustion) processes, what other mechanism exists for nitrogen fixation?
Industrial production of fertilizers
What is nitrification?
The conversion of ammonium NH4+ to nitrite NO2- and nitrite to nitrate (NO3-)
What’s important about the conversion from ammonium to nitrite to nitrate in nitrification?
These conversions release much of the potential energy contained in ammonium
The conversion of ammonium to nitrites in terrestrial and acquatic ecosystems is carried out by _______________________ and _______________________ bacteria
- Nitrosomonas*
- Nitrosococcus*
The conversion of nitrite to nitrate is carried out by _________________________ and _____________________ bacteria
- Nitrobacter*
- Nitrococcus*
______________________ and ___________________ convert ammonium to nitrite; __________________ and ____________________ convert nitrite to nitrate
- Nitrosomonas*
- Nitrosococcus*
- Nitrobacter*
- Nitrococcus*
How can producers take up nitrogen?
From the soil or water as either ammonium or nitrate
Once producers take up nitrogen, they incorporate it into their tissues, a process known as ____________________
Assimilation
When primary or secondary consumers consume producers, they can either assimilate nitrogen from the producers or ___________________
Excrete it as waste
Animal waste as well as the biomass of producers and consumers that eventually die are borken down by scavengers, detritivores, and decomposers. The fungal and bacterial decomposers break down biological nitrogen into ___________________, the process of which is known as mineralization
Ammonia
What is mineralization?
The process of breaking down organic compounds into inorganic compounds
What happens to nitrates produced by nitrification?
Nitrates are quite soluble in water and readily leach out of soils and into waterways where they settle in the sediments of wetlands, rivers, lakes, and oceans. These sediments are typically anaerobic
Under anaerobic conditions, nitrates can be transformed back into nitrites, which are then transformed into ________________
Nitric oxide
What bacteria transforms nitrate to nitrite and then nitric oxide?
Pseudomonoas denitrificans
What happens to nitric oxide?
Additional chemical reactions under anaerobic conditions in soils and water subsequently convert nitric ocide to nitrogen gas
The process of converting nitrates into nitrogen gas (via nitric oxide) is known as _____________________
Denitrification
Denitrification is necessary for breaking down organic matter in oxygen-depleted soils and sediments and produces __________, which cannot be taken up by producers and thus leaves the waterlogged soils and acquatic ecosystems in the form of a __________
N2 (molecular nitrogen)
Gas
How have humans disrupted the nitrogen cycle?
During the last three centuries, humans have nearly doubled the amount of nitrogen put into terrestrial ecosystems, which produces nitric oxide that eventually reacts with water to form nitrate and returns to the ecosystem
What happens to terrestrial ecosystems when more nitrogen is added?
Producitivty increases but species loss increases; it’s believed that the increased nitrogen, a limiting nutrient, caused a few plant species to grow very large and to dominate the community
Overview of the nitrogen cycle:
The nitrogen cycle begins with nitrogen gas in the _________________. The process of ____________________converts it into a form that producers can use. The _________________ can then be ________________ into producers and consumers; it ultimately decomposes into ammonium through the process of ____________________. The ammonium can be converted into nitrite and then nitrate through the process of __________________________. Under anaerobic conditions, the nitrate can be converted into nitrogen gas through the process of _________________
Atmosphere
Nitrogen fixation
Fixed nitrogen
Assimilated
Mineralization
Nitrification
Denitrification
Why is the atmosphere NOT an important component of the phosphorus cycle?
Because phosphorus doesn’t exist in a gaseous phase
How does phosphorus generally travel?
As the phosphate ion; it rarely changes physical form
What’s the major source of phosphorus?
Phosphate rocks
Over time, calcium phosphate precipitates out of ocean water and slowly forms ____________________, which is uplifted by geologic forces and weathering, thereby releasing phosphate ions
Sedimentary rocks
____________ take up phosphate ions from soil or water and incorporate them directly into various organic compounds. _____________ eliminate excess phosphorus in their diets by excreting urine containing either phosphate ions or phosphorus compounds that are converted to phosphate ions by phosphatizing ______________
Plants
Animals
Bacteria
What ecosystems act as phosphorus sinks?
Marine and freshwater sediments because they remove phosphorus from the water column - in well-oxygenated waters, phosphorus readily binds with calcium and iron ions, precipitating out of the water
Under _______________ conditions, iron tends to combine with ____________ rather than phosphorus, so phosphorus remains more available in the water column
Low-oxygen
Sulfur
Overview of phosphorus cycle:
Phosphate __________ are uplifted by geologic forces and are naturally weathers over time to release ______________, which is used in fertilizer and detergents. Phosphorus is taken up by producers and moves through the food chain until it is released either through waste or _________________. Excess phosphorus on land runs off the surface or leaches out of the soil into acquatic habitats. In the ocean, phosphorus combines with _____________ or iron and precipitates out of the water column, ultimately reforming phosphate rocks again.
Rocks
Phosphorus
Decompisition
Calcium
An increase in the productivity of acquatic ecosystems is called ______________________
Eutrophication
Why is too much phosphorus a bad thing?
Because in combination with excess nitrates contributes to harmful algal bloods that lead to dead zones
An increase in the productivity of acquatic ecosystems caused by human activities is called ________________________
Cultural eutrophication
Eutrophication can lead to ________________ in acquatic ecosystems
Dead zones
What enzyme’s responsible for breaking apart N2?
Nitrogenase
Who developed a way to commercially produce ammonia?
Frtiz Haber
Does nitrogenase require a lot or a little energy?
A lot of energy - it’s very energy expensive to use, but nitrogen is a limiting nutrient and important to life, so it’s a justifiable expense
Both symbiotic and free-living organisms can fix nitrogen. What are the symbiotic ones?
Rhizobium and Bradyrhizobium
Actinomycetes associated with alder roots
Lichens
Anabaena azollae
Both symbiotic and free-living organisms can fix nitrogen. What are the free-living ones?
- Clostridium*
- Azotobacter*
Some cyanobacteria
Free-living organisms that can fix nitrogen include the anaerobic ________________ and the aerobic _______________
- Clostridium*
- Azotobacter*
Because nitrogenase, which fixes nitrogen, denatures in the presence of oxygen, what must organisms exposed to oxygen do in order for nitrogenase to function?
Adapt
What adaptations did Azotobacter develop for reducing oxygen?
High respiratory rate
Production of extracellular polysaccharide
Why does Azotobacter have such a high respiratory rate?
Because nitrogenase denatures in the presence of oxygen - by respiring quickly, little oxygen can remain in cells, and therefore nitrogenase can continue working
Why does Azotobacter produce an extracellular polysaccharide?
It protects cells from oxygen
How does Rhizobium accomplish nitrogen fixation in the presence of oxygen?
Via leghemaglobin, which scavengers O2
In the process of _______________, organic nitrogen is oxidized to CO2, H20, and NH3
Ammonification
Does ammonification produce or consume energy?
Produces energy
Why is the process of ammonification important?
Because plants can use ammonium
Why are seabirds important to the phosphorus (and nitrogen) cycles?
Seabirds drastically transform the environmental conditions of the sites where they establish their breeding colonies via soil, sediment, and water eutrophication
What’s the role of phosphorus in Florida red tides?
The Gulf of Mexico receives iron dust from the Sahara Desert; this iron stimulates Trichodesmium bloom, a nitrogen fixer; and with nitrogen and phosphorus from run-off, a phytoplankton blood results
What happens when zooplankton populations increase?
They eat the non-toxic algae, leaving behind toxic dinoflagellates
In the interaction between nitrogen and phosphorus, which is likely the limiting element?
Phosphorus
IIn 1977, Schindler showed, using whole-lake experiments, that natural biological mechanisms can compensate for deficiencies in ____________ and _______________ in lakes affected by eutrophication, but no such mechanisms exist for _________________. Based on his findings, Schindler recommended that management of lakes should focus on control of ________________levels
Carbon, nitrogen
Phosphorus, phosphorus
What is the GAIA hypothesis?
The Gaia hypothesis, also known as the Gaia theory or the Gaia principle, proposes that living organisms interact with their inorganic surroundings on Earth to form a synergistic and self-regulating, complex system that helps to maintain and perpetuate the conditions for life on the planet.
Why can ecosystems more easily adjust their carbon and nitrogen levels than their phosphorus levels?
Because carbon and nitrogen can exist in gaseous forms; phosphorus can only exist in a solid
What’s the main biologically available form of sulfur?
Sulfate
_____________________ is reduced by autotrophs to make ________________
Sulfate (SO4)
Amino acids for proteins
____________________ are formed in sediment, and _______________ is converted from its insoluble to soluble form; therefore, the sulfur and phosphorus cycles regulate one another
Iron sulfides
Phosphorus
What are the three reservoir pools for sulfur?
Lithosphere
Atmosphere
Ocean
What is the turnover rate?
The amount of a substance that gets fixed
What’s turnover time?
How long it takes for a substance to be fixed
