2.3 - Flows Of Energy And Matter Flashcards
What happens when solar ratification enters earths atmosphere
As solar radiation insolation enters the Earth’s atmosphere some energy becomes unavailable for ecosystems as the energy is absorbed by inorganic matter or reflected back into the atmosphere.
What does energy pathways through ecosystems include
• conversion of light energy to chemical energy
• transfer of chemical energy from one trophic level to another with varying efficiencies
• overall conversion of ultraviolet and visible light to - - -heat energy by an ecosystem re-radiation of heat energy to the atmosphere.
What is productivity measured as
The conversion of energy into biomass for a given period of time is measured as productivity.
How is net primary productivity calculated
is calculated by subtracting respiratory losses (R) from gross primary productivity (GPP]. NPP = GPP - R
How is gross secondary productivity calculated
is the total energy / biomass assimilated by consumers and is calculated by subtracting the mass of fecal
loss from the mass of food eaten. GSP = food
eaten - fecal loss
How is net secondary productivity calculated
is calculated by subtracting respiratory losses (R] from GSP. NSP = GSP - R
What are maximum sustainable yields
Maximum sustainable yields are equivalent to the net primary or net secondary productivity of a system.
Where else can matter flow and what does it involve
Matter also flows through ecosystems linking them together. This flow of matter involves transfers and transformations.
What are the carbon and nitrogen cycle used to illustrate
The carbon and nitrogen cycles are used to illustrate this flow of matter using flow diagrams.
These cycles contain storages (sometimes referred to as sinks] and flows which move matter between storages.
What does stores in the carbon cycle include
Storages in the carbon cycle include organisms and forests (both organic], or the atmosphere, soil, fossil fuels and oceans (all inorganic).
What does flows in the carbon cycle include
Flows in the carbon cycle include consumption (feeding), death and decomposition, photosynthesis, respiration, dissolving and fossilisation.
What do stores in the nitrogen cycle include
Storages in the nitrogen cycle include organisms (organic), soil, fossil fuels, atmosphere and water bodies (all inorganic).
What do flows in the nitrogen cycle include
Flows in the nitrogen cycle include nitrogen fixation by bacteria and lightning, absorption, assimilation, consumption (feeding), excretion, death and decomposition, and denitrification by bacteria in waterlogged soils.
What human activities impact energy flows as well as the carbon and nitrogen cycle
Human activities such as burning fossil fuels, deforestation, urbanization and agriculture impact energy flows as well as the carbon and nitrogen cycles.
How old is the sun and what has it burned
Our Sun is about 4.5 billion years old and halfway through its lifespan.
It has burned up about half of its hydrogen in nuclear fusion to make helium and release energy. This energy is in packets called photons and it takes eight minutes for a photon leaving the Sun to reach the Earth.
How fast does energy leave the sun
The energy leaving the Sun is about 63 million joules per second per square metre (Js-‘ m 2). The solar energy reaching the top of the atmosphere of Earth is 1,400 J s-‘ m 2 (or 1,400 watts per second).
How much of solar radiation is absorbed
69% total
- 17% by molecules and dust
- 3% of clouds
- 49% by ground
How much of solar radiation is reflected
Total 31%
- 3% by scatter
- 19% by clouds
- 9% by ground
How can life turn solar energy into food
The only way in which life can turn solar energy into food is through photosynthesis by green plants.
What are the nerdy conversion figures for a crop such as wheat
It can absorb about 40% of the energy that hits a leaf. About 5% is reflected, 50% lost and 5% passes straight through the leaf. But plants only use the red and blue wavelengths of light in photosynthesis and reflect the other colours (which is why plants look green). So of the 40%, just over 9% can be used. This is the GPP of the plant. Just under half of this is required in respiration to stay alive so 5.5% of the energy hitting a leaf becomes NPP (new plant material).
Define productivity
Productivity is the conversion of energy into biomass over a given period of time. It is the rate of growth or biomass increase in plants and animals. It is measured per unit area per unit time, eg per metre? per year. (m-? yr 1).
What happens to all of the solar radiation falling on earth
Of all the solar radiation falling on the Earth, plants only capture 0.06% of it (GPP) and use some of that to stay alive. What is left over (NPP) is the amount of food available to all the animals including humans.
In general the efficiency of conversion of energy to food is low at about 2-3% in terrestrial systems but even lower at about 1% in many aquatic systems as water absorbs more of the light before it reaches the plants, though it is variable and there are exceptions (such as marine zooplankton feeding on phytoplankton).
What does gross productivity refer to
Gross refers to the total amount of something made as a result of an activity, eg profit from a business or salary from a job.
What does net productivity refer to
Net refers to the amount left after deductions are made, eg costs of production or deductions of tax and insurance from a salary. It is what you have left and is always lower than the gross amount.
Define biomass
Biomass is the living mass of an organism or organisms but sometimes refers to dry mass.
What happens in net productivity
results from the fact that all organisms have to respire to stay alive so some of this energy is used up in staying alive instead of being used to grow.
What happens in primary productivity
autotrophs are the base unit of all stored energy in any ecosystem. Light energy is converted into chemical energy by photosynthesis using chlorophyll within the cells of plants.
What happens in gross primary productivity
plants are the first organisms in the production chain. They fix light energy and convert it to sugars so it is theoretically possible to calculate a plant’s energy uptake by measuring the amount of sugar produced (GPP).
An ecosystem’s NP is the rate at which plants accumulate dry mass (actual plant material) usually measured in g m 2. This glucose produced in photosynthesis has two main fates, what are they?
• Some provides for growth, maintenance and reproduction (life processes) with energy being lost as heat during processes of respiration.
• The remainder is deposited in and around cells as new material and represents the stored dry mass - this store of energy is potential food for consumers within the ecosystem.n
What does NPP represent
So, NPP represents the difference between the rate at which plants photosynthesize, GPP, and the rate at which they respire. This accumulation of dry mass is usually termed biomass and provides a useful measure of both the production and the utilization of resources.
What’s the equation for NPP
NPP = GPP - R where
R = respiratory loss
The total amount of plant material is the theoretical maximum amount of energy that is available to all the animals, both the herbivores and the carnivores that feed on them. It has two fates, what are they?
• lost from food chains as it dies and decays OR
• eaten by herbivores which means it is removed from primary productivity.
What are the 2 ways biomass produced varies
• Spatially: some biomes have much higher NPP rates than others - eg tropical rainforest vs tundra.
• Temporally: Many plants have seasonal patterns of productivity linked to changing availability of basic resources - light, water and warmth (see succession 2.4).
What are the different fates of energy produced by plants in net secondary productivity
• Only food that crosses the wall of the alimentary canal (gut wall) of animals is absorbed and is used to power life processes (assimilated food energy):
• Some of the assimilated food energy is used in cellular respiration to provide energy for life processes.
• Some is removed as nitrogenous waste, in most animals as urine.
• The rest is stored in the dry mass of new body tissue.
• Some of the ingested plant material will pass straight through the herbivore and be released as feces (egestion). This is not absorbed and provides animals with no energy.
net productivity of herbivores (net secondary productivity) = energy in the food ingested - the energy lost in egestion energy used in respiration
What is the equation for net productivity of herbivores
net productivity of herbivores (net secondary productivity) = energy in the food ingested - the energy lost in egestion - energy used in respiration
Define gross secondary productivity
Gross secondary productivity
(GSP] is the total energy / biomass assimilated (taken up by consumers and is calculated by subtracting the mass of fecal loss from the mass of food eaten.
Where is the very small percentage of the original NPP of plants turned into secondary productivity
Only a very small percentage of the original NPP of plants is turned into secondary productivity by herbivores and it is this secondary productivity, which is available to consumers at the next trophic level.
This change of primary productivity to secondary productivity follows the general conditions of energy transfer up the trophic levels.
State 4 facts about carnivores diet
• On average they assimilate 80% of the energy in their diets.
• They egest less than 20%.
• Usually they have to chase moving animals so higher energy intake is offset by increased respiration during hunting.
• Biomass is locked up in the prey foods - non-digestible skeletal parts, such as bone, horn and antler - so they have to assimilate the maximum amount of energy that they can from any digestible food.
State 3 facts about herbivores diet
• Assimilate about 40% of the energy in their diet.
• They egest 60%.
• They graze static plants.
How to matter and energy move or flow through the ecosystem
Both types of flow use energy - transfers, being simpler, use less energy and are therefore more efficient than transformations.
How does energy flow through and ecosystem and where does it start
Energy flows through an ecosystem in one direction, starting as solar radiation and finally leaving as heat released through the respiration of decomposers.
How does chemical nutrients move through the ecosystem
chemical nutrients in the biosphere cycle: nutrients are absorbed by organisms from the soil and atmosphere and circulate through the trophic levels and are finally released back to the ecosystem, usually via the detritus food chain. These are the biogeochemical cycles.
What is the organic and inorganic phase in the nitrogen cycle
organic phase determines how much is available to living organisms. Yet the major reservoir for all the main elements tends to be outside of the food chain as inorganic molecules in rock and soils. Flow in this inorganic phase tends to be much slower than the movement of these nutrients through organisms, the organic phase.
What is routes of the major biochemical cycles (water, carbon, nitrogen, sulphur, phosphorus)
• Movement of matter, such as nutrients, through an ecosystem is very different from the movement of energy.
• Energy travels from the Sun, through food webs and is eventually lost to space as heat.
• Nutrients and matter are finite and are reccled and reused (via the decomposer food chain).
• Organisms die and are decomposed and nutrients are released, eventually becoming parts of living things again, when they are taken up by plants. These are the biogeochemical cycles.
Where is carbon stored
In carbon or carbon dioxide sinks. These may be:
Organic (with complex carbon molecules):
• Organisms (biomass) in the biosphere - living plants and animals.
• Fossilized life forms, eg fossil fuels.
Inorganic (simple carbon molecules):
• Locked up or fixed into solid forms and stored as sedimentary rocks and fossil fuels. Most carbon is stored here and locked up for millions of years.
• The oceans where carbon is dissolved or locked up as carbonates in the shells of marine organisms.
• Soil.
• A small proportion is carbon dioxide in the atmosphere (0.37%).
Where does the carbon go in the carbon cycle
The carbon cycle, in which carbon circulates through living and non-living systems occurs in the ecosphere. Here carbon is found in four main storages: the soil, living things (biomass), the oceans and the atmosphere. Carbon not in the atmosphere is stored in carbon dioxide sinks (soil, biomass and oceans), as complex organic molecules or dissolved in seawater.
How is carbon realised back into the atmosphere throughout the carbon cycle
it is fixed by photosynthesis and released back to the atmosphere through respiration. Carbon is also released back to the atmosphere through combustion of fossil fuels and biomass. When dead organisms decompose, when they respire and when fossil fuels are burned, the carbon is oxidized to carbon dioxide and this, water vapour and heat are released. By photosynthesis, plants recapture this carbon - carbon fixation - and lock it up in their bodies for a time as glucose or other large molecules. When plants are harvested and cut down for food, firewood or processing, the carbon is also released again to the atmosphere. As we burn fossil fuels and cut down trees, we are increasing the amount of carbon in the atmosphere and changing the balance of the carbon cycle. Carbon can remain locked in either cycle for long periods of time, ie in the wood of trees or as coal and oil.
What is the carbon budget
The amount of carbon on Earth is a finite amount and we have a rough idea of where it goes. The diagram of the carbon cycle in figure 2.3.7 shows carbon sinks (storages) and flows in gigatonnes of carbon (GtC).
A gigatonne is one billion tonnes (10° tonnes).
What is our anual global emisión of carbon and where is that carbon going
Our annual current global emissions from burning fossil fuels are about 5.5
GtC. About 20% of this is from burning natural gas, 40% from burning coal and the other 40% from burning oil. Another 1.6 GtC are added through deforestation. So 7.1 GtC enter the atmosphere each year. Only about 2.4-3.2 GtC of this stay in the atmosphere. Some is taken up by living things. Diffusion of carbon dioxide into the oceans and uptake by oceanic phytoplankton accounts for 2.4 GtC. New growth in forests fixes about 0.5 GtC a year. But this still leaves between 1 and 1.8 GtC - a large amount - unaccounted for. We are not sure where it goes because of the complexity of the system.
What are the amounts of carbon stored in some reservoirs
• atmosphere 750
• standing biomass 650
• soils 1,500
• oceans 1,720.
What is the nitrogen cycle
All living organisms need nitrogen as it is an essential element in proteins and DNA. Nitrogen is the most abundant gas in the atmosphere but atmospheric nitrogen is unavailable to plants and animals, though some specialized microorganisms can fix atmospheric nitrogen.
What are the nitrogen sinks
- organisms
- soil
- fossil fuels
- the atmosphere
- in water
What are the nitrogen flows
- nitrogen fixation
- nitrification
- denitrification
- feeding
- absorption
- assimilation
- consumption
- excretion
- death and decomposition
What is nitrogen fixation
when atmospheric nitrogen (N,) is made available to plants through the fixation of atmospheric nitrogen. This conversion from gaseous nitrogen to ammonium ions
What are 5 ways nitrogen fixation can be carried out
- By nitrogen-fixing bacteria free-living in the soil (Azotobacter).
- By nitrogen-fixing bacteria living symbiotically in root nodules of leguminous plants (Rhizobium). The plant provides the bacteria with sugars from photosynthesis, the bacteria provide the plant with nitrates.
- By cyanobacteria (sometimes called blue-green algae) that live in soil or water. Cyanobacteria are the cause of the high productivity of Asian rice fields, many of which have been productive for hundreds or even thousands of years without nitrogen -containing fertilizers.
- By lightning also causing the oxidation of nitrogen gas to nitrate which is washed into the soil.
- The industrial Haber process is a nitrogen-fixing process used to make fertilizers. Nitrogen and hydrogen gases are combined under pressure in the presence of iron as a catalyst (speeds up the reaction) to form ammonia.
Define nitrification
some bacteria in the soil are called nitrifying bacteria and are able to convert ammonium to nitrites (Nitrosomonas) while other convert the nitrites (NO, ) to nitrates (Nitrobacter) which are then available to be absorbed by plant roots.
Define denitrification
denitrifying bacteria (Pseudomonas denitrificans), in waterlogged and anaerobic (low oxygen level) conditions, reverse this process by converting ammonium, nitrate and nitrite ions to nitrogen gas which escapes to the atmosphere.
What is the decomposition of dead organisms
decomposition of dead organisms also provides nitrogen for uptake by plants. Decomposition of dead organisms supplies the soil with much more nitrogen than nitrogen fixation processes. Important organisms in decomposition are animals (insects, worms among others), fungi and bacteria. They break down proteins, producing different ions: ammonium ions, nitrite ions and finally nitrate ions. These ions can be taken up by plants which recycle the nitrogen.
What is assimilation
Once living organisms have taken in nitrogen, they assimilate it or build it into more complex molecules. Protein synthesis in cells turns inorganic nitrogen compounds into more complex amino acids and then these join to form proteins. Nucleotides are the building blocks of DNA and these too contain nitrogen.
How can people add nitrogen to the cycle
But people can also add nitrogen to the cycle in the form of artificial fertilizers, made in the Haber process, or by planting leguminous crops with root nodules containing nitrogen-fixing bacteria.
How do leguminous crops add nitrogen to the cycle
These plants enrich the soil with nitrogen when they decompose. The soil condition also aflects the nitrogen cycle. It it becomes waterlogged near the surface, most bacteria are unable to break down detritus because of lack of oxygen but certain bacteria can. Unfortunately they release the nitrogen as gas back into the air. This is called denitrification. Excessive flow of rainwater through a porous soil, such as sandy soil, will wash away the nitrates into rivers, lakes and then the sea. This is called leaching and can lead to eutrophication.
What’s an energy flow diagram
Energy flow diagrams allow easy comparison of various ecosystems. These show the energy entering and leaving each trophic level. Energy flow diagrams also show loss of energy through respiration and transfer of material as energy to the decomposer food chain.
What are the 2 quantities we need to establish for the assimilation and productivity efficiencies
- What proportion of the NPP from one trophic level is assimilated by the next?
- How much of this assimilated material is turned into the tissues of the organism and how much is respired?
What are the 2 quantities we need to establish for the assimilation and productivity efficiencies for a animal raised for meat
- How much of the grass that an animal eats can it assimilate (absorb into its body)? This will determine how many animals the farmer can put in a field.
- How much of what is assimilated is used for productivity (turned into meat)? On a commercial farm this will determine the profits.
State the efficiency of assimilation equation
Efficiency of assimilation = gross productivity × 100/
food eaten
State the efficiency of biomass productivity equation
efficiency of biomass productivity = net productivity x 100/ gross productivity
What is tropic efficiency
The efficiency of transfer from one trophic level to the next, eg the ratio of secondary productivity to primary productivity consumed, is considered, on average, to be about 10%. As always, things are not quite as straightforward as they at first appear. While the 10% rule is a generalization and a helpful aid to our understanding of energy flow, there are considerable variations. Trophic efficiencies generally range from 5% to 20%, ie only 5% to 20% of primary producer biomass consumed is converted into consumer biomass.
Why do trophies inefficiencies occur
• Not everything is eaten (if it were, the world would not be green as all plants would be consumed).
• Digestion is inefficient (food is lost in feces because the digestive system cannot extract all the energy from it).
• Heat is lost in respiration.
• Some energy assimilated is used in reproduction and other life processes.
What is an energy budget
For an individual animal or population, we can measure the quantities of energy entering, staying within and leaving the animal or population.
This is its energy budget. It can be measured in the laboratory for a population of silk worms or locusts and it is useful for farmers to know what stocking rate of animals per hectare they can use.
What is a process called when its derived from humans
Anthropogenic
Define maximum sustainable yield
Maximum sustainable yield [MSY\ see also 4.3l is the largest crop or catch that can be taken from the stock of a species (eg a forest, a shoal of fish) without depleting the stock. Taken away is the increase in production of the stock while leaving the stock to reproduce again. It is often used in managing fisheries. The MSY is equivalent to the net primary or net secondary productivity of a system.
How do humans affect the ecosystem
Generally, when humans have an influence on an ecosystem, be it farming or living within it, we tend to simplify it and make it less diverse. Usually, this is on purpose. We cut down forest to grow crops and often this is just one species, eg wheat. So the complex food web that may have been there in a deciduous temperate forest becomes:
wheat -
> human
ОГ
improved pasture grasses
> cattle -
> human
What are humans trying to maximise when simplifying an ecosystem
Our aim is to maximize the NPP of the organisms we grow to maximize our profit. What happens is that we have to become ever more sophisticated in our farming practices - agribusiness - so we use artificial means to maintain the system. The Green Revolution which brought improved varieties of rice and other crops also brought the need to buy fertilizers for them or pesticides to kill the pests to which they were susceptible.
What is an energy subsidy
All farming practices require an energy subsidy which is the additional energy that we have to put into the system above that which comes from the Sun’s energy. It may be the human labour, animal labour or machines using fuel to power the tractors and plows, pump water for cattle, make fertilizers and other chemicals, transport the crop. The result is that some agricultural systems are very productive with high NPP, particularly, eg, sugar cane.
What are the advantages and disadvantages of an energy subsidy
The advantage of an energy subsidy is that we can feed more people because food production seems more efficient but the energy has to come from somewhere (first law of thermodynamics).
As communities become more complex, the energy subsidy increases. Hunter-gatherers have to add little energy to the system apart from their own work. Subsistence farming may involve draught animals, wind-power or water-power to irrigate or grind corn. All these are subsidized by human effort. Commercial farming now involves major use of fossil fuels to power machines, make chemicals to put on the crops or produce feedstuffs for animals. It is estimated that we use 50 times as much energy in MEDs as a hunter-gatherer society and it is rising all the time.
What is an energy:yield ratio
we can look at energy in and energy out in the form of food. It seems that as agriculture has become more sophisticated, the ratio goes down. A simple slash and burn type agriculture (when land is cleared in the rainforest and then a variety of crops grown by a subsistence farmer) may have an energy:yield ratio of 1:30. With increasing input of energy, this could reduce to 10:1 for battery chicken or egg production, so far more energy is put in to the system than taken out. But the important thing is that the energy is in the form of high energy foods - concentrated energy such as protein and meat, not lower energy cereals. We are producing high energy foodstuffs.
What’s the issue with lower energy
The issue to remember is that energy has to keep flowing through ecosystems whether natural or influenced by humans. If it does not, the svstem alters rapidly. Blocking sunlight from reaching a plant stops photosynthesis and the plant dies. Stopping the energy subsidy to agriculture will result in chaos. In a natural ecosystem, the large number and variety of food chains and energy paths mean the system is complex and less likely to fail completely. If one species goes, others can take its role. The system is resilient. If there is only one species in an ecological niche, eg wheat, its failure can have a bigger impact.
