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EARTH’S LIFE SUPPORT SYSTEMS > 4.1 > Flashcards

4.1 Flashcards

1
Q

IMPORTANCE OF WATER IN SUPPORTING LIFE ON PLANET

A

Helps create benign thermal conditions on Earth:
- oceans moderate temperatures by absorbing, storing + releasing heat slowly
water moderates environment in other ways:
- clouds made up of tiny water droplets + ice crystals reflect around 1/5th of incoming solar radiation + lower surface temperatures
- at same time water vapour (potent greenhouse gas) absorbs long-wave radiation from Earth helping to maintain average global temperatures almost 15C higher than they would be otherwise

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2
Q

Oceans occupy how much of Earth’s surface

A

71%

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3
Q

Water makes up how much % of all living organisms

A

65-95%
- water crucial to their growth, reproduction, + other metabolic functions

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4
Q

Uses of water for flora, fauna + people

A

Plants need water for photosynthesis, respiration, transpiration
- photosynthesis takes place in leaves of plants, combining CO2, sunlight, water to make glucose + starches
- respiration in plants + animals converts glucose to energy through its reaction with oxygen, releasing water + CO2
- plants require water to maintain their rigidity (plants wilt when run out of water) + to transport mineral nutrients from soil
- in people + animals, water is medium used for chemical reactions in body (circulation of oxygen + nutrients)
- transpiration of water from leaf surfaces cools plants by evaporation
- sweating is cooling process in humans
- in fur-covered mammals, reptiles + birds, evaporative cooling achieved by panting

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5
Q

How is water essential resource for economic activity

A

Used to generate electricity, irrigate crops, provide recreational facilities + satisfy public demand (drinking water + sewage disposal)
- Industries including food manufacturing, brewing, paper + steel making

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6
Q

Importance of carbon to life on Earth (biological)

A

Stored in carbonate rocks (such as limestone), sea floor sediments, ocean water (as dissolved CO2), atmosphere (as CO2 gas) + in biosphere
- life is carbon based: built on large molecules of carbon atoms (proteins, carbohydrates, nucleic acids)

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7
Q

How is carbon used as economic resource

A

Fossil fuels (coal, oil, natural gas) power global economy
- oil used as raw material in manufacture of products ranging from plastics to paint + synthetic fabrics
- agricultural crops + forest trees store large amounts of carbon available for human use as food, timber, paper, textiles

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8
Q

Global water cycle

A

Consists of 3 stores: atmosphere, oceans, land
- oceans - biggest store , atmosphere - smallest store
Water moves between stores through processes of precipitation, evapotranspiration, run-off, groundwater flow
(Evapotranspiration is flow from land to atmosphere)

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9
Q

Global carbon cycle

A

global carbon cycle is similar in comprising series of stores + flows. Long-term storage in sedimentary rocks holds 99.9% of all carbon on Earth
In contrast, most of carbon in circulation moves rapidly between atmosphere, oceans, soil + biosphere.
- main pathways between stores followed by carbon in this cycle include photosynthesis, respiration, oxidation (decomposition, combustion) + weathering

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10
Q

water and carbon cycles as open + closed systems

A

On global scale water + carbon cycles are closed systems driven by Sun’s energy (which is external to Earth).
Only energy (+ not matter) cross boundaries of global water + carbon cycles - hence we refer to these systems as ‘closed’

At smaller scales (drainage basin/forest ecosystem), materials as well as Sun’s energy cross system boundaries (so are open systems)

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11
Q

Global stores of water

A

Oceans (contain 97% of all water on planet)
Polar ice + glaciers
Groundwater (aquifers)
Lakes
Soils
Atmosphere
Rivers
Biosphere

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12
Q

Stores of water explained (fresh water + atmosphere)

A
  • Fresh water comprises only tiny proportion of water in store + 3/4 is frozen in ice caps of Antartica + Greenland
  • water stored below ground in permeable rocks amounts to just 1/5th of all fresh water
  • only minute fraction of Earth’s water found in atmosphere - explained by rapid flux of water into + out of atmosphere: average residence time of water molecules is 9 days
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13
Q

Inputs + outputs of water

A
  • Inputs of water to atmosphere include water vapour evaporated from oceans, soils, lakes + rivers, + vapour transpired through leaves of plants. Together these processes known as evapotranspiration.
  • Moisture leaves atmosphere as precipitation (rain, snow, hail) + condensation (e.g fog)
    ~ Ice sheets, glaciers + snowfields release water by ablation (melting + sublimation).
  • Precipitation + meltwater drain from land surface as run-off into rivers. Most rivers flow to oceans though some, in continental drylands like southwest USA, drain to inland basins.
    ~ large part of water falling as precipitation on land reaches rivers only after infiltrating + flowing through soil.
  • after infiltrating soil, water under gravity may percolate into permeable rocks/aquifers
    ~ this groundwater eventually reaches surface as springs/seepages + contributes to run-off
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14
Q

Global carbon cycle stores

A

Sedimentary (carbonate) rocks
Oceans
Sea floor sediments
Fossil fuels
Soils + plants
Atmosphere

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15
Q

Biggest carbon store

A

Sedimentary rocks
- most of carbon that is not stored in rocks + sediments is found in oceans as dissolved CO2
- relatively small carbon storage in atmosphere, plants, soils (but play crucial part in cycle + represent most of carbon in circulation at any 1 time

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16
Q

SLOW CARBON CYCLE

A
  • carbon stored in rocks, sea-floor sediments + fossil fuels locked away for millions of years
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17
Q

Typical residence times for carbon held in rocks in SLOW CARBON CYCLE

A

around 150 million years

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18
Q

total amount of carbon circulated by SLOW CYCLE

A

between 10 + 100 million tonnes a year

19
Q
  1. IN SLOW CARBON CYCLE CO2 diffuses from atmosphere into oceans…
A
  • where marine organisms (e.g. clams + corals) make their shells + skeletons by fixing dissolved carbon together with calcium to form calcium carbonate
  • on death, remains of these organisms sink to ocean floor
  • there they accumulate + over millions of years, heat + pressure convert them to carbon-rich sedimentary rocks
20
Q
  1. CARBON-RICH SEDIMENTARY ROCKS
A
  • Some carbon-rich sedimentary rocks (subducted into upper mantle at tectonic plate boundaries) are vented to atmosphere in volcanic eruptions
    ~ Others exposed at/near surface by erosion + tectonic movements attacked by chemical weathering
21
Q
  1. CHEMICAL WEATHERING PROCESSES SUCH AS CARBONATION…
A
  • are result of precipitation charged with CO2 from atmosphere, which forms weak acid.
    ~ acid attacks carbonate minerals in rocks, releasing CO2 to atmosphere, + in dissolved form to streams, rivers + oceans.
22
Q
  1. ON LAND, PARTLY DECOMPOSED ORGANIC MATERIAL MAY BE…
A
  • buried beneath younger sediments to form carbonaceous rocks (coal, oil + natural gas)
    ~ Like deep-ocean sediments, these fossil fuels act as carbon sinks that endure for millions of years
23
Q

FAST CARBON CYCLE

A

Carbon circulates most rapidly between atmosphere, the oceans, living organisms (biosphere) + soils. These transfers are between ten + 1000 times faster than those in slow carbon cycle.

24
Q
  1. LAND PLANTS + MICROSCOPIC PHYTOPLANKTON IN OCEANS = KEY COMPONENTS OF FAST CYCLE
A
  • through photosynthesis they absorb CO2 from atmosphere + combine it with water to make carbohydrates (sugars/glucose)
  • respiration by plants + animals is opposite process + results in release of CO2
  • decomposition of dead organic material by microbial activity also returns CO2 to atmosphere
25
Q
  1. IN FAST CYCLE, CARBON EXCHANGE ALSO OCCURS BETWEEN ATMOSPHERE + OCEANS
A
  • atmospheric CO2 dissolves in ocean surface waters while oceans ventilate CO2 back to atmosphere
  • through this exchange, individual carbon atoms stored (by natural sequestration) in oceans for 350 on average
26
Q

Processes of water cycle: Water balance

A

Water balance equation summarises flows of water in drainage basin over time
- states that precipitation = evapotranspiration + streamflow +/- water entering/leaving storage:
Precipitation (P) = Evapotranspiration (E) + Streamflow (Q) +/- storage

27
Q

Flows in water cycle

A

Precipitation, evaporation, transpiration, run-off, infiltration, percolation(movement of surface + soil water into underlying permeable rocks), throughflow (water flowing horizontally through soil to stream + river channels)

28
Q

What is Precipitation

A

water + ice that falls from clouds towards ground. It takes several forms: most commonly rain + snow, but also hail, sleet + drizzle.

29
Q

When does precipitation form

A

forms when vapour in atmosphere cools to its dew point + condenses into tiny water droplets/ice particles to form clouds. Eventually these droplets/ice particles aggregate, reach critical size + leave cloud as precipitation.

30
Q

Precipitation also varies in character + this impacts water cycle at drainage basin scale

A
  • Most rain on reaching ground flows quickly into streams + rivers
    ~ But in high latitudes + mountainous catchments, precipitation often falls as snow + may remain on ground for several months. So there may be time lag between snowfall + run-off.
  • Intensity: amount of precipitation falling in given time. High-intensity precipitation (e.g. 10-15 mm/hour) moves rapidly overland into streams + rivers, as it is falling at rate that exceeds infiltration capacity of soil.
  • Duration: length of time that precipitation event lasts. Prolonged events, linked to depressions + frontal systems, may deposit large amounts of precipitation + cause saturation of soil which leads to overland flow + river flooding.
  • In some parts of world (e.g. East Africa, Mediterranean) precipitation concentrated in rainy season. During this season river discharge is high + flooding common. In dry season rivers may cease to flow altogether.
31
Q

Transpiration

A

diffusion of water vapour to atmosphere from leaf pores (stomata) of plants.

  • responsible for around 10% of moisture in atmosphere
  • Like evaporation, transpiration influenced by temperature + wind speed. - also influenced by water availability to plants
    ~ E.g, deciduous trees shed their leaves in climates with either dry/cold seasons to reduce moisture loss through transpiration.
32
Q

Condensation

A

phase change of vapour to liquid water
- occurs when air is cooled to its dew point.
- At this critical temperature air becomes saturated with vapour resulting in condensation.
- Clouds form through condensation in atmosphere
- condensation at/near ground produces dew + fog
~ both types of condensation deposit large amounts of moisture on vegetation + other surfaces

33
Q

Cumuliform clouds

A

Have flat bases + considerable vertical development
- most often form when air heated locally through contact with Earth’s surface
- this causes heated air parcels to rise freely through atmosphere (convection), expand (due to fall in pressure with altitude) + cool.
- As cooling reaches dew point, condensation begins + clouds form.

34
Q

Stratiform/layer clouds

A

develop where air mass moves horizontally across cooler surface (often ocean)
- this process, together with mixing + turbulence is known as advection

35
Q

cirrus clouds

A

Wispy, consist of tiny ice crystals
- form at high altitude
do not produce precipitation + so have little influence on water cycle

36
Q

Formation of clouds

A

Clouds: visible aggregates of water/ice/both that float in free air
Form when water vapour cooled to its dew point

37
Q

Cooling occurs when…

A
  • Air, warmed by contact with ground/sea surface, rises freely through atmosphere. As air rises + pressure falls it cools by expansion (adiabatic expansion). This vertical movement of air is convection.
  • Air masses move horizontally across relatively cooler surface (advection)
  • Air masses rise as they cross mountain barrier/as turbulence forces their ascent.
  • relatively warm air mass mixes with cooler one.
38
Q

Adiabatic expansion

A

Expansion of parcel of air due to decrease in pressure
- Expansion causes cooling

39
Q

Advection

A

Horizontal movement of air mass which often results in heating/cooling

40
Q

Convection

A

Motion of gas/liquid which when warmed rises until eventually cools + sinks in continuous circulation

41
Q

Lapse rates

A

Describes vertical distribution of temp in lower atmosphere + temp changes that occur within air parcel as it rises vertically away from ground
3 types: ELR, DALR, SALR

42
Q

ENVIRONMENTAL LAPSE RATE (ELR)

A

Vertical temperature profile of lower atmosphere at any given time
- on average, temp falls by 6.5C for every km of height gained

43
Q

DRY ADIABATIC LAPSE RATE (DALR)

A

Rate at which parcel of dry air (less than 100% humidity so condensation not taking place) cools
- cooling (caused by adiabatic expansion) is 10C/km

44
Q

SATURATED ADIABATIC LAPSE RATE (SALR)

A

Rate at which saturated parcel of air (one in which condensation occurring) cools as it rises through atmosphere
- as condensation releases latent heat, SALR, at around 7C/km is lower than DALR

EARTH’S LIFE SUPPORT SYSTEMS (2 decks)

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