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Environmental Systems > Flows of Energy and Matter > Flashcards

Flows of Energy and Matter Flashcards

1
Q

How does energy from the sun travel to the Earth and how long does it take to get there?

A

The energy is in packets called photons + it takes 8 minutes for a photon leaving the Sun to reach Earth

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2
Q

What is the Earth’s solar constant?

A

The solar energy reaching the top of Earth is 1,400 watts per second

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3
Q

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

A

The only way in which life can turn solar energy into food is through photosynthesis by green plants

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4
Q

How much of the sun’s energy is absorbed by plants? What happens to the rest of the energy?

A

40% of light that hits leaf is absorbed

[ 5% reflected // 50% lost // 5% passes straight through leaf ]

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5
Q

Of the 40% sun’s energy that is absorbed by the plant, how much can be used?

A

Plants only use red + blue wavelengths of light in photosynthesis.

Of the 40%, just over 9% can be used.

This is the GPP (gross primary productivity) of the plant

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6
Q

Of the 9% solar energy fixed by green plants, how much of this is required in respiration to stay alive?

A

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

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7
Q

How do you calculate NPP (new plant material) ?

A

New plant material = gross primary productivity - respiration

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8
Q

What is productivity ?

A

The conversion of energy into biomass over a given period of time

It is the rate of biomass increase in plants and animals

It is measured per unit area per unit time

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9
Q

What does gross refer to?

A

Gross refers to the total amount of something made as a result of an activity

e.g. salary from a job

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10
Q

What does net refer to?

A

Net refers to the amount left after deductions are made

e.g. deductions of tax from a salary

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11
Q

What does primary mean?

A

In ecology, primary means to do with plants

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12
Q

What does secondary mean?

A

In ecology, secondary is to do with animals

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13
Q

What is biomass?

A

Biomass is the living mass of an organism(s)

Sometimes refers to the dry mass

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14
Q

What is gross productivity ?

A

The total gain in energy // biomass per unit area per unit time

It is the biomass that could be gained by an organism before any deductions

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15
Q

What is net productivity ?

A

The gain in energy // biomass per unit area per unit time

That remains after deductions due to respiration

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16
Q

What is gross primary productivity ?

A

Total gain in energy // biomass per unit area per unit time by GREEN PLANTS

It is the energy fixed (converted from light to chemical energy) by green plants by photosynthesis

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17
Q

How is it possible to measure a plant’s energy uptake and why would this be difficult?

A

A plant’s energy uptake could be calculated by measuring the amount of sugar produced (GPP)

But measuring sugar produced is difficult as much of it is used by plants in respiration almost as soon as it’s produced

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18
Q

What is net primary productivity (NPP) ?

A

Total gain in energy // biomass per unit area per unit time by GREEN PLANTS

After allowing for losses to respiration

This is the increase in biomass of the plant

The biomass that is potentially available to consumers (animals) that eat the plant

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19
Q

What are the two fates of the glucose produced in respiration?

A
  • Growth, maintenance + reproduction, w energy lost as heat during respiration
  • Remainder is deposited in + around cells as new material + represents stored dry mass // this source of energy is potential food for consumers
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20
Q

The amount of plant material is the maximum amount of energy available to animals (herbivores + carnivores). It has 2 fates:

A
  • lost from food chains as it dies + decays

OR

  • eaten by herbivores so removed from primary productivity
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21
Q

The amount of biomass produced by plants varies // spatially

A

Some biomes have much higher NPP raters than others

e.g. tropical rainforest vs. tundra

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22
Q

The amount of biomass produced by plants varies // temporally

A

Most plants have seasonal patterns of productivity linked to changing availability of basic resources - light, water + warmth

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23
Q

What is assimilated food energy?

A

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

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24
Q

What are the 3 fates of assimilated food energy?

A
  1. Some is used in cellular respiration to provide energy for life processes
  2. Some is removed as nitrogenous waste as urine
  3. Rest is stored in the dry mass of new body tissue
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25
Q

What is egestion?

A

Some of the ingested plant material will pass straight through the herbivore and be release as feces

This is not absorbed and provides animals with no energy

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26
Q

How is net secondary productivity calculated?

A

Net secondary productivity = energy in the food ingested - energy lost in egestion - energy used in respiration

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27
Q

What do secondary consumers eat?

A

Herbivores

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28
Q

What is the main source of energy for tertiary consumers?

A

Other carnivores

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29
Q

Why are the diets of secondary and tertiary consumers more easily digested and assimilated?

A

They have higher protein diets (other animals)

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30
Q

Where do carnivore’s get their energy from and how do they lose it?

A
  • Assimilate 80% of the energy in their diets
  • Egest less than 20%
  • Have to chase moving animals // so higher energy intake offset by inc. respiration during hunting
  • Biomass locked up in their prey in non-digestible parts e.g. bone + antler so carnivores have to assimilate maximum amount of energy from any digestible food
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31
Q

Where do herbivores get their energy from and how do they lose it?

A
  • Assimilate 40% of the energy in their diets
  • They egest 60%
  • They graze static plants
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32
Q

What is gross secondary productivity (GSP) ?

A

Total energy // biomass assimilated by consumers

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33
Q

How is gross secondary productivity calculated?

A

GSP = food eaten = fecal loss

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34
Q

What is net secondary productivity?

A

Total gain in energy // biomass per unit area per unit time by CONSUMERS

After allowing for losses to respiration

35
Q

How is net secondary productivity (NSP) calculated?

A

NSP = gross secondary productivity - respiration

36
Q

Why is insolation not 100% efficient?

A

As solar radiation (insolation) enters atmosphere, some energy is

  • absorbed by inorganic matter or
  • reflected back into atmosphere
37
Q

What is the pathway of energy through an ecosystem?

A
  1. Conversion of light to chemical energy
  2. Transfer of chemical energy from one trophic level to another
  3. Conversion of UV + visible light to heat energy by an ecosystem
  4. Re-radiation of heat energy to atmosphere
38
Q

What are biogeochemical cycles?

A

Chemical nutrients in the biosphere cycle:

> Nutrients are absorbed by organisms from the soil + atmosphere
Circulate through trophic levels
Release back to the ecosystem, usually via the detritus food chain

39
Q

What is an organic phase of a biogeochemical cycle?

A

When the element is in a living organism

40
Q

What is an inorganic phase of a biogeochemical cycle?

A

When the element is in a simpler form outside living organisms

41
Q

Why are both organic + inorganic phases of a biogeochemical cycle vital?

A

> The efficiency of movement though the organic phase determines how much is available to living organisms
Yet major reservoir for all main elements is outside of food chain as inorganic molecules in rocks + soils
Flow in this inorganic phase tends to be much slower than movement through organic phase

42
Q

Where is carbon stored?

A

Carbon or carbon dioxide sinks?

43
Q

Carbon sinks may be ORGANIC…

A

ORGANIC (w complex carbon molecules)

> organisms // living plants + animals
fossilised life forms // e.g. fossil fuels

44
Q

Carbon sinks may be INORGANIC…

A

INORGANIC (simple carbon molecules)

> stored as sedimentary rocks + fossil fuels
carbon dissolved in oceans
locked up as carbonates in shells of marine organisms
soil
small proportion in atmosphere (0.37%)

45
Q

Carbon cycles between biotic and abiotic chemical cycles. What are they?

A
  • Carbon fixed by photosynthesis
  • Released back to atmosphere through respiration
  • Also released through combustion of fossil fuels + biomass
  • When organisms decompose, when they respire + when fossil fuels burnt, the carbon is oxidised to carbon dioxide
  • By photosynthesis, plants recapture this carbon (CARBON FIXATION) + lock it in their bodies as glucose or other molecules
  • When plants are harvested // cut down for food or firewood, carbon is released again to atmosphere
46
Q

How has human activity disrupted the balance of the global carbon cycle (carbon budget) ?

A

Increased combustion
Land use changes
Deforestation

47
Q

What are our current global emissions from burning fossil fuels?

A

About 5.5 GtC energy year

20% of this is from burning natural gas
40% from burning coal
40% from burning oil

48
Q

How many GtC are added each year from deforestation?

A

1.6GtC are added through deforestation

So 7.1 GtC enter the atmosphere each year

49
Q

Of the 7.1 GtC that enters the atmosphere each year, how much stays in the atmosphere and what happens to the rest?

A

> Only 2.4 - 3.2 GtC stay in atmosphere
Some is taken up by living things
Diffusion of co2 into oceans + uptake by phytoplankton accounts for 2.4 GtC
New growth in forests fixed 0.5 GtC

50
Q

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

A

Since the pre-industrial period, we have added 200 GtC to the atmosphere

51
Q

What does GtC stand for?

A

gigatonnes of carbon

52
Q

How many GtC are there in the atmosphere?

A

750 GtC

53
Q

How many GtC are there is standing biomass?

A

650 GtC

54
Q

How many GtC are there in soils?

A

1,500 GtC

55
Q

How many GtC are there in oceans?

A

1,720 GtC

56
Q

Why do all living organisms need nitrogen?

A

All living organisms need nitrogen as it is an essential element in proteins + DNA

Nitrogen is most abundant gas in atmosphere, but atmospheric nitrogen is unavailable to plants + animals

But some specialised microorganisms can fix atmospheric nitrogen

57
Q

Name 5 nitrogen storages or sinks

A 
Organisms
Soil 
Fossil fuels
Atmosphere
Water
58
Q

Name the 6 flows in the nitrogen cycle

A 
> Nitrogen fixation
> Nitrification
> Denitrification 
> Feeding (absorption, assimilation, consumption)
> Excretion
> Death + decomposition
59
Q

What does nitrogen need to be in the form of for plants to take it up? How do animals take in nitrogen?

A

For plants to take up nitrogen, it must be in the form of:
> Ammonium ions OR
> Nitrates

60
Q

How do animals take in nitrogen?

A

Animals eat plants + so take in their nitrogen in the form of
> amino acids
> nucleotides

61
Q

What are the three basic stages of the nitrogen cycle?

A

Nitrogen fixation
Nitrification
Denitrification

62
Q

What is nitrogen fixation?

A

When atmospheric nitrogen is made available to plants through the fixation of atmospheric nitrogen.

Conversion from gaseous nitrogen to ammonium ions

63
Q

Nitrogen fixation // the conversion from gaseous nitrogen to ammonium ions can be carried out in 1 of 5 ways

A
  1. By nitrogen-fixing bacteria living in soil
  2. By nitrogen-fixing bacteria living symbiotically in root nodules of leguminous plants. Plant provides bacteria w sugars from photosynthesis, bacteria provides nitrates
  3. By cyanobacteria living in soil or water // cause of high productivity of Asian rice fields
  4. By lightning causing oxidation of nitrogen gas to nitrate
  5. Haber process is nitrogen-fixing process used to make fertilisers. Nitrogen + hydrogen combined under pressure w iron catalyst to form ammonia
64
Q

What is nitrification? (non-living nitrogen fixation)

A

> Nitrifying bacteria in soil can convert ammonium to nitrites
Other bacteria convert nitrites to nitrates
Nitrates can then be absorbed by plant roots

65
Q

What is denitrification? (non-living nitrogen fixation)

A

Denitrifying bacteria in waterlogged + anaerobic conditions convert ammonium, nitrate and nitrite ions to nitrogen gas which escapes to the atmosphere

66
Q

How does decomposition of dead organisms provide nitrogen for uptake by plants?

A

Decomposition of organisms supplies the soil w much more nitrogen than nitrogen fixation processes

  • Important organisms in decomposition are insects, worms, fungi + bacteria
  • They break down proteins, producing ammonium ions, nitrite ions + nitrate ions
  • These ions are taken up by plants which recycle the nitrogen
67
Q

How does assimilation of nitrogen work?

A
  • Once 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 + then these join to form proteins
  • Nucleotides are building blocks of DNA and these too contain nitrogen
68
Q

How can humans alter the nitrogen cycle and upset the natural balance?

A
  • When people remove animals + plants for food, they extract nitrogen from the cycle
  • Much of this nitrogen is later lost to sea in human sewage
  • People can also add nitrogen to cycle in form of artificial fertilisers (made in Haber process) or by planting leguminous crops (enrich soil w nitrogen when decompose)
  • If soil is waterlogged near surface, most bacteria can’t breakdown detritus due to lack of oxygen, but denitrifying bacteria can so nitrogen released back into air
  • Excessive rainwater flow through porous (i.e. sandy) soil washes away nitrates into rivers, lakes, sea. This is called leaching + can lead to eutrophication
69
Q

What do energy flow diagrams show?

A
  • Energy flow diagrams allow easy comparison of various ecosystems
  • Show energy entering + leaving each trophic level
  • Show loss of energy through respiration
  • Show transfer of material as energy to the decomposer food chain
70
Q

How does a farmer determine how many animals to put in a field ?

A

Asks: How much of the grass that an animal eats can it assimilate?

Efficiency of Assimilation =
(food productivity x 100) / food eaten

71
Q

On a commercial farm, what question is asked to determine the profits?

A

Asks: How much of what is assimilated is used for productivity (turned into meat)?

Efficiency of Biomass Productivity =
(net productivity x 100) / gross productivity

72
Q

Why do trophic efficiencies vary?

A

A community of small mammals in a grassland ecosystem may only have a trophic efficiency of 0.1% as they are warm-blooded, have a high metabolic rate + large surface area compared to volume so lose a lot of energy as heat

In the oceans, zooplankton feeding on phytoplankton have a trophic efficiency of 20%, and consume most of the producer biomass

73
Q

What is trophic efficiency?

A

The efficiency of transfer from one trophic level to the next

Generally thought to be 10%

But often range from 5% to 20%

74
Q

4 reasons why trophic inefficiencies occur

A
  • Not everything is eaten
  • Digestion is inefficient (food is lost in feces as digestive system can’t extract all energy)
  • Heat lost in respiration
  • Some energy assimilated used in reproduction + other life processes
75
Q

What is an organism’s energy budget?

A

For an individual animal // population we can measure the qualities of energy entering, staying within + leaving the animal // pop.

76
Q

What does anthropogenic mean?

A

A process, effect or activity derived from humans

77
Q

Give an example of an anthropogenic effect

A

The greenhouse effect

78
Q

What is the Maximum Sustainable Yield (MSY) ?

A

The largest crop or catch that can be taken from the stock of a species (e.g. forest, shoal of fish) without depleting the stock

79
Q

Why do humans grow monocultures?

A

To maximise net primary productivity of the organisms we grow to maximise profits

80
Q

What is an energy subsidy and what is the result?

A

The additional energy we have to input into the system above that which comes from the Sun’s energy

e.g. human labour, animal labour, machines using fuel to power tractors, pump water for cattle, transport crop

The result is that some agricultural systems are very productive w high net primary productivity e.g. sugar cane

81
Q

What is the advantage of becoming more sophisticated in our farming practises?

A

We can feed more people because food production seems more efficient

82
Q

What is the disadvantage of becoming more sophisticated in our farming practises?

A
  • Energy has to come from somewhere (1st law of thermodynamics)
  • As communities become more complex, the energy subsidy increases
  • Hunter gatherers add little energy to system
  • Subsistence farming = draught animals, wind power (subsidised by human effort)
  • Commercial farming = fossil fuels to power engines, make chemicals etc
  • MEDCs use 50x energy of hunter-gather societies + it continues rising
83
Q

Does the energy : yield ratio increase // decrease with more sophisticated agriculture?

A

As agriculture becomes more sophisticated, the energy : yield ratio goes down

e.g. with a battery chicken, the ratio may be 10 : 1 so far more energy is put into the system than taken out

Environmental Systems (30 decks)

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