2.3 Flows of energy and matter

what are the names of the packets in which energy leaves the sun

photons

what is the energy leaving the sun per second per square metre

63 million joules per second per square meter

what is the solar energy reaching the top layer of the atmosphere of the earth

1,400 J s^-1 m^-2 or 1,400 watts per second

what is the only way that life can turn solar energy into food

through photosynthesis by green plants

how much energy that hits a leaf is absorbed

40%

how much solar energy is reflected by a leaf

about 5%

how much solar energy passes straight through a leaf

about 5%

what colour lights do plants use in photosynthesis

red and blue wavelengths

of the 40% of solar energy absorbed by a leaf, how much can be used

about 9%

what is the GPP of a plant

the 9% of energy that can be used by the leaf

how much of the GPP of a plant is needed in respiration

just under half

how much of the energy hitting the leaf becomes new plant material

5.5%

how much of the solar radiation hitting the earth do plants capture

0.06% of it

what is the efficiency of the conversion of energy to food in terrestrial systems

2-3%

what is the efficiency of conversion of energy to food in aquatic systems

about 1%

what does net productivity result 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

why do we usually talk about productivity and not production in ecology

so we know the area and time period to which we refer

how do autotrophs produce energy

light energy is converted into chemical energy by photosynthesis using chlorophyll within the cells of plants

what are the first organisms in the the production chain

plants and algae

how can you theoretically calculate a plants energy uptake

by measuring the amount of sugar produced

why is sugar production difficult to measure

much of it is used up by plants almost as soon as it is produced

what is an ecosystems NPP

the rate at which plants accumulate dry mass

what is NPP usually measured in

g/m^2

what are the two main uses for glucose produced in photosynthesis

to provide for growth, maintenance and reproduction with energy being lost as heat, and deposited in cells as new material and represents stored dried mass

what does NPP represent

the difference between the rate at which plants photosynthesize and the rate at which they respire

what is the accumulation of dry mass usually termed

biomass

what is the theoretical maximum amount of energy that is available to all the animals

the total amount of plant material

what can happen to plant material in food chains

lost from food chains as it dies and decays, eaten by herbivores which means it is removed from primary productivity

what are the two ways the amount of biomass produced varies

spatially, temporally

biomass produced varies spatially because

some biomes have much higher NPP rates than others

biomass produced varies temporally because

many plants have seasonal patterns of productivity linked to changing availability of basic resources

what is assimilated food energy

the food that crosses the gut wall of animals and is absorbed and used to power life processes

how is the assimilated food energy used

in cellular respiration, removed as nitrogenous waste, in most animals urine, the rest is stored in the dry mass of new body tissue

what happens to the ingested material that passes straight through the herbivore

it is released as faeces and provides the animal with no energy

net productivity of herbivores =

energy in food digested - the energy lost in egestion - energy used in respiration

how much of the energy in their diets do carnivores assimilate

80%

how much of their diet do carnivores egest

less than 20%

how is the higher energy intake of carnivores offset

by increased respiration during hunting

how much of the energy in their diet do herbivores assimilate

about 40%

how much of the energy in their diet do herbivores egest

60%

which is more efficient, transfers or transformations

transfers

describe the flow of energy through an ecosystem

energy flows through an ecosystem in one direction, starting as solar radiation and leaving as heat energy

what are biogeochemical cycles

Pathways by which a chemical substance moves through both biotic & abiotic compartments of earth

how many elements cycle through the ecosystem

about 40

what phases do all biogeochemical cycles have

organic and inorganic phases

which phase of biogeochemical cycles determines how much is available to living organisms

the efficiency of movement through the organic phase

where does the major reservoir for all the main elements tend to be

outside the food chain as inorganic molecules in rock and soils

which phase of biogeochemical cycles is slower

the inorganic phase

what are the major biogeochemical cycles

carbon, water, nitrogen, sulphur, phosphorous

what are some organic carbon sinks

organisms in the biosphere, fossilized life forms

what are some inorganic carbon sinks

sedimentary rocks, the oceans, soil, atmosphere

where does the carbon cycle occur

in the ecosphere

how is carbon fixed

by photosynthesis

how is carbon released back into the atmosphere

through respiration, through the combustion of fossil fuels and biomass, when dead organisms decompose, when plants are harvested for food, firewood or processing

how has humanity disrupted the balance of the carbon cycle

through increased combustion, land use changes and deforestation

what are our current global carbon emissions from fossil fuels

5.5 GtC

how much of our global fossil fuel emissions is from burning natural gas

20%

how much of our global fossil fuel emissions is from burning coal

40%

how much of our global fossil fuel emissions is from burning oil

40%

how many GtC enter the atmosphere each year due to deforestation

1.6 GtC

how much of the carbon that enters the atmosphere stays in the atmosphere

about 2.4-3.2 GtC

how many GtC is fixed by new growth in forests per year

0.5 GtC

how many GtC are stored in the atmosphere

750

how many GtC are stored in biomass

650

how many GtC are stored in soils

1,500

how many GtC are stored in oceans

1,720

how many GtC have we added to the atmosphere since the pre-industrial period

200 GtC

is atmospheric nitrogen available to plants and animals

no

what are some nitrogen stores

organisms, soil, fossil fuels, the atmosphere, in water

what are the flows in the nitrogen cycle

nitrogen fixation, nitrification, denitrification, feeding (absorption, assimilation, consumption), excretion, death and decomposition

what form must nitrogen be in for plants to take it up

ammonium ions or nitrates

what form to animals obtain nitrogen from plants

in the form of amino acids and nucleotides

what are the three main stages of the nitrogen cycle

nitrogen fixation, nitrification, denitrification

what is nitrogen fixation

when atmospheric nitrogen is made available to plants through the fixation of atmospheric nitrogen

what are the five ways nitrogen can be fixed

bacteria in soil, bacteria in roots, cyanobacteria, lightning, the haber process

give an example of a nitrogen fixing bacteria that lives in the soil

azotobacter

give an example of a nitrogen fixing bacteria that lives symbiotically in the root nodules of plants

rhizobium

what is the cause of high productivity of rice fields

cyanobacteria

how does lighting fix bacteria

by causing the oxidation of nitrogen gas to nitrate which can be washed into the soil

what are nitrifying bacteria

those that can convert ammonium to nitrates

give an example of a nitrifying bacteria

nitrosomonas

give an example of a bacteria that converts nitrites to nitrates

nitrobacter

what do denitrifying bacteria do

convert nitrate and nitrite ions to nitrogen gas in waterlogged and anaerobic conditions

give an example of a denitrifying bacteria

pseudomonas denitrificans

what are some important organisms in decomposition

insects, worms, fungi, bacteria

what do decomposers do

break down proteins, producing different ions: ammonium, nitrite, nitrate

what do organisms do once they have taken in nitrogen

assimilate it into more complex molecules

what does protein synthesis do

turns inorganic nitrogen compounds into more complex amino acids and then these join to form proteins

how do people remove from the nitrogen cycle

when people remove animals and plants for food, and in human sewage

how can humans add to the nitrogen cycle

by using the haber process, by planting crops with root nodules containing nitrogen fixing bacteria

what is one way eutrophication may occur

excessive flow of rainwater through a porous soil will wash away the nitrates into rivers, which can cause eutrophicationi

what do energy flow diagrams allow

easy comparison of various organisms

what do energy flow diagrams show

the energy entering and leaving each trophic level and the loss of energy through respiration and transfer of material as energy to the decomposers

what are the quantities we need to know to establish 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 is trophic efficiency

the efficiency of transfer from one trophic level to the next

what is the average trophic efficiency

10%

what is the range of trophic efficiencies

5-20%

a community of small mammals in a grassland may only have a trophic efficiency of 0.1%, why might this be

they are warm blooded, have a high metabolic rate and have a large surface area compared to their volume, this means they lose a lot of heat to the environment

what is the trophic efficiency of zooplankton

up to 20%

cold blooded animals have ...... assimilation rates than warm blooded animals

slower