Earths life support systems


reasons why water is ciritical for life

  • as a habitat for organisms- water insulates well from extreme temperatures. the surface may freee but this protects the water below from the cold, keeping it liquid. when hot, water  remains cooler than many other liquids. thus water is a good protective habitat
  • as a reagent in bio-chemical reactions- water reacts with other chemicals in important reactions in living organisms e.g. it is the source of hydrogen for photosynthesis
  • for transport in organisms- water molecules are very cohesive due to their hydrogen bonds. water is therefore very efficient at transporting materials in organisms e.g. products of digestion in blood plasma
  • as a coolant in organisms- water molecules have a high freezing and boiling point to compared to other molecules of similar mass. they can absorb a lot of energy before turning into a liquid or gas, animals use this property to cool themselves down via sweating
  • to maintain a constant temperature in organisms- it has a high specific heat capacity (it warms up and cools down slowly). as cells are mostly made up of water they can keep their temperatures relatively constant
  • as chemical solvent- ions, alcohols and sugers are easily dissolved in water. this allows them to be moved around in cells/organisms to facilitate essential chemical reactions e.g. respiration
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the importance of Carbon

Critical for life on earth as it is the buildings blocks for all organic chemicals:

  • carbohydrates- sugers are used in respiration, complex carbohydrates like starch are energy stores and cellulose is used to reinforce cell walls in plants
  • lipids- these are organic oils and fats. lipids form hormones and are an essential part of cell membranes, provide animals with insulation and storage
  • proteins- amino acids form proteins. proteins catalyse bio-chemical reactions, form structural elements in organisms and can cause energy conversion reactions for motor functions
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carbon has other important non-biological function

  • raising earths temeperature- CO2 and methane CH4 are two important GHG in the atmosphere. without GHG in the atmosphere earths mean temperature would be about 29°C lower, meaning that water would not be in liquid form, so life as we know it would not exist
  • a fuel source with high energy density- organic matter can undergo the geological processes of maturation and coalification to form fossil fuels of oil, coal and natural gas. these fossil fuels have a high energy density and are the main fuel source world-wide
  • carbon and water is stored in particular resevoirs and flow between these stores. on a planetary scale, these cycles are closed, on a smaller scale, they are open
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the water cycle stores

earth has 1.4 billion km cubed of water

  • oceans- 97%
  • ice caps and glaciers- 2%
  • sub soil and rocks- 0.7%
  • rivers and lakes- 0.01%
  • top soil- 0.005%
  • atmosphere- 0.001%
  • living organisms- 0.00004%
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water cycle- definitions

  • ablation- snow and ice melts of vaporises realising water
  • evaporation- energy from the sun turns liquid water into a gas
  • transpiration- plants take water from the soil and give it off through their leaves
  • condensation- water vapour turns into droplets of liquid water
  • transport- water vapour and clouds are moved by wind
  • precipitation- water falls from the atmosphere to the surface of the earth
  • surface runoff- water runs across the surface of the ground into rivers and lakes
  • aquifer- sub-soil of rock that is permbeable and holds groundwater
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carbon cycle and stores

there are 48,500 Gt of Carbon in various resevoirs on Earth not counting the sedimentary rocks of the earth's crust where over 100,000,00Gt is found


  • earths crust- 99.95%
  • other carbon resevoirs- 0.05%
  • Oceans- 78%
  • fossil fuels- 10%
  • living organisms- 4%
  • soil- 3%
  • atmosphere- 1.5%
  • sea floor sediments- 0.3%
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Carbon Cycle definitions and residence time

  • photosynthesis- plants take in CO2 is emitted from volcanoes
  • sedimentation- dead organic matter from the ocean biomass forms carbonate sediments
  • decomposition- dead organic matter is broken down releasing CH4 and CO2
  • respiration- animals break down carbohydrates for energy releasing CO2
  • diffusion- CO2 dissolve into the upper oceans and is released from solution
  • uplift- ocean sediments are raised up by tectonic processes
  • denudation- chemical weathering and erosion remove CO2 from the atmosphere

Residence time- the amount of time that either water or carbon in one of the stores

check table on notes

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slow and fast carbon cycle

check photos on notes

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similarities between the water and carbon cycle

  • difference in amount of it
  • most stores are the same- oceans, atmosphere, living organisms, soil, rock
  • some differences in stores- little carbon found in ice caps and glaciers, lots of water
  • amount found in each store differ greatly
  • plants play a key role in both
  • carbon cycle can be split into fast and slow cycle, water cannot
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processes in the water cycle- drainage basin

Drainage basins- an area of land that is drained by a river and its tributaries. they interlock so thats all the land is drained

  • all precipitation that falls into a drainage basin will, if it not evapo-transpired back into the atmosphere, end up in the main river channel of that drainage basin as river run-off and moved to the ocean. a small amount of groundwater may leak through aquifers into the sub-soil and rocks of adjoining drainage basins
  • thus, in a drainage basin system precipitation is the input, river run-off, evapotranspiration and groundwater leakage are the outputs
  • watershed- edge of the draiange basin
  • mouth- end point of the river, where it meets the sea. may have mudflats or a delta
  • confluence- where two tributaries join up, or where it joins the main river
  • source- start point of the river
  • tributary- a stream that flows into the main river channel
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drainage basin hydrological cycle

  • DCP- precipitation falling straight into the river channel
  • surface storage- water stored in puddles on surface
  • infiltration- water sinking into the soil from surface
  • soil water storage- water stored in soil pores above the top of water table
  • percolation- water moving down through the soil from above the water table to below it
  • groundwater storage- water stored in the soil below the top of the water table
  • through flow- water moving sideways through the soil, above the top of the water table
  • base/groundwater flow- water moving sideways through the soil, below the top of the water table
  • interception- water hitting vegetation
  • vegetation storage- water stored on plant leaves or in plant tissues and cells
  • stem flow and through fall- water going down stems or falling leaves from vegetation to ground
  • channel storage- water stored in the river channel
  • channel flow- water moving down the river channel
  • river run-off- water in the river leaving the drainage basin to the ocean
  • groundwater leakage- water leaving the drainage basin from aquifers via groundwater flow
  • uptake- plant roots taking in water from the soil store
  • water table- the zone of the soil where all the soil spores are full of water
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factors influencing drainage basin water cycle

slope angle- steep slopes encourage surface runoff and limit infiltration

  • precipitation amount- more precipitation = more surface run off as top layer of soil will become saturated, so infiltration will stop
  • precipitation intensity- heavy rainfall will slam into the soil surface, closing the soil pores
  • preceding levels of precipitation- if lots, water table will be high as soil will be mostly saturated
  • geology- thin soils and impermeable bedrock will lead to little or no infiltration and percolation
  • type of vegetation- large plants will intercept and transpire more, slowing down movement of water to river, no plants at all will speed it up
  • draiange intensity- if basin has lots of tributaries, distance water must flow to get into one is small, so more will get into river quicker
  • rime of year- winter- ground frozen and impermeable. summer- hard baked ground and heavy rainfall will limit infiltration
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lapse rate

  • environmental lapse rate- way temperature chnges as you move up into the troposphere from the earths surface- -6.5°/km
  • the dry adiabatic lapse rate- way the temperature of a rising parcel of dry air chages as you move up into the troposphere from the surface. -10°/km
  • the saturated adiabatic lapse rate- way the temperature of a rising parcel of air where condensation is occurring changes as you move up into the troposphere from the earths surface

base of clouds form when dep point is reached -8°C

  • convectional precipitation- caused by air rising in hot places- solar radiation heats earth, heats air above, warm air less dense so rises, cools and water vapour condenses, clouds form and precipitation
  • orographic (relief) precipitation- caused by mountains forcing air to rise- air can't pass mountains, rises and cools, clouds form and precipitation, air falls other side and warms, water evaporate
  • frontal precipitation- caused by warm air meeting cold air- warm and cold air meet head on, warm air rises over, rising air cools and water vapour condenses
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processes in the carbon cycle

  • living organisms affect the carbon cycle on a short-term basis through the processes of photosynthesis and respiration
  • photosynthesis- CO2 is taken in by plants and phytoplankton via photosynthesis and turned into carbohydrates
  • respiration- animals consume the plants and respire using up the carbohydrates gained, giving off CO2 in the process. plants respire at night
  • atmospheric CO2 levels variation over a year- as there is more land and therefore more plants in the northern hemisphere, the global atmospheric CO2 levels reflect the season changes in the northern hemisphere. during the growing season, photosynthesis outweights respiration so atmospheric CO2 levels fall leading to a CO2 minimum in October. during the winer, many plants have dropped their leaves and temperatures are colder, so photosynthesis is less and so atmospheric CO2 levels rise as respiration outweighs photosynthesis leading to a CO2 maximum in May
  • atmospheric CO2 levels variation in a day- during the daytime, the presnece of light means that photosynthesis can take place, this outweights respiration so CO2 levels fall to a minimum at about 3pm. at night photosynthesis is not taking place so it is outweighted by respiration, therefore CO2 levels rise to a maximum at about 3am
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processes in the carbon cycle

Carbon storage in biomass- tropical forest- 548Gt, Tropical grassland- 285Gt, Tundra- 155Gt

  • the amount of carbon stored in biomass is dependent on two factors: the productivity of the biome and the area of land covered by the biome

Decomposition- removes carbon from the biomass store and returns it to the atmosphere or ocean

  • decomposers (bacteria and fungi) break down dead organic matter producing chelates (soluble organic acids) that cause weathering of rock, and CO2 in aerobic conditions and CH4 in anaerobic conditions, which is released into the atmosphere via the soil
  • warmer the temperature, more rapid the decomposition, its also affected by oxygen availability, a lack of oxygen will stop decomposition as decomposers will not be able to respire
  • methane is formed instead of carbon dioxide where oxygen levels are low, for example bogs
  • decomposition is affected by water availability- dry areas have fewer decomposers
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processes in the carbon cycle

Maturation-geological process that forms crude oil and natural gas

  • sea creatures die and fall to the ocean floor. over millions of years they are buried and exposed to increased levels of heat and pressure forming oil and natural gas

Coalification- geological process that forms coal and natural gas

  • dead organic matter builds up in swamps and bogs, over millions of years, these are buried and exposed to increased levels of heat and pressure forming coal and natural gas

Combustion- the process where a substance containing carbon is burnt and energy along with CO2 is produced

  • humans can cause combustion through the ignition of crude oil or its products, coal and/or natural gas. combustion can occur naturally when lightening strikes cause forest and grassland fires
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processes in the carbon cycle

Weathering- break up of rock in situ. two forms connected to the carbon cycle- chelation and carbonation, however other forms of weathering can increase these by increasing the surface area

  • Carbonation- CO2 dissolves in rainwater forming a weak acid- carbonic acid. this dissolves rocks such as limestone and chalk producing calcium bicarbonate which is soluble and makes its way initally into rivers and then into oceans
  • Chelation- decomposition produces chelates that are organic acids, these react with metal ions in rock producing more soluble organic chemicals that again eventually move to rivers and then into the oceans
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the water cycle in a tropical rainforest

  • tropical rainforest biome- a biome is an ecosystem that covers large areas of the earths surface. an ecosystem is a community of plants and animals linked to the climate and soil by flows of energy and nutrients
  • the abiotic component of the tropical rainforest is made up of the climate and soil. tropical rainforest climate is hot and wet. there is at least 60mm of precipitation every month and the mean temperature is over 25°C every month
  • tropical rainforest soils are a type of oxisol called a latosol. latosols have a thin topsoil layer that is thick in decomposed organic matter and is where all the plant nutrients are situated. high temperatures and high levels of precipitation cause rapid weathering of bedrock, so the subsoil is a thick layer- up to 30m deep. it is lacking in nutrients as the precipitation leaches them away leaving only iron and aluminium oxides, which give the soil a distinctive red colour. Latosols have a regolith layer of broken up material where the bedrock is being weathering a few metres in thickness
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the water cycle in a tropical rainforest- Congo

The biotic component of the tropical rainforest is made up of the plants and animals

tropical rainforests are very biodiverse- this means that they have large numbers of different species of plants and animals. the dominant species is the tree. most trees are about 30m tall and form a mostly continuous canopy. where gaps are in the canopy due to tree die-back, fast growing tall species called emergents (50m) can break through. at around 20m under canopy species can be found, these individual trees are awaiting a gap to form in the canopy when they will grow to fill the gap. very little light reaches the forest floor so there are few plants in the shrub layer

emergent trees in the Congo rainforest include the great Maobi tree. examples of canopy special are limba. about 25% of biomass is comprosed of lianas and vines. plants that grow on other plants include orchids. around 11,000 plant species are found in the Congo rainforest

animal species are abundant and more than 60% of African's butterfly species, more than 60% of Africa's bird species and more than 80% of Africa's primate species are found in the Congo rainforest including Gorillas and Bonobos. 400 species of mammals, 216 species of amphibian, 280 species of reptiles are found in the Congo rainforest

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the water cycle in a tropical rainforest- The cong

  • the Congo makes up 18% of the worlds tropical rainforest. this makes it the second largest continuous area of rainforest in the world. 2/3 of the Congo rainforest is found in DRC and 57% of the area of the DRC is rainforest. the Congo river flows through the rainforest and is the second largest river in the world
  • the Congo river basin is the 2nd largest in the world covering 3.4million km2 in area
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the water cycle in the Congo

  • precipitation- the Congo recieves high amounts of precipitation all year round, with an average of 1553mm per year. there are 2 wetter seasons roughly lasting 3 months each peaking in April and October. the precipitation amount and pattern is caused by the COngo lying under the low pressure inter tropical convergence zone where convectional rainfall occurs every day
  • evapotranspiration- interception rates are high in the rainforest. therefore, most evaporation is from leaf surfaces rather than the soil surface. water is quickly cycled from the soil back into the atmosphere by transpiration. high temperatures mean large and fast evapotranspiration rates. about 55% of precipitation is recycled water from evapotranspiration rates. about 55% of precipitation is recycled water from evapotranspiration. ET makes up 78% of incoming precipitation
  • runoff- the annueal discharge of the Congo river has 2 peaks, one in May and one in December, following the two slightly wetter seasons that occur each year
  • soil storage- latosols are loose and deep so through flow and groundwater flow is faster than in many other soils, taking water to the nearest tributary relatively quickly
  • geology- most of the Congo basin is underlain by thick layers of unconsolidated alluvial Quaternary sedimentary rocks. thesr rocks allow a large amount of infiltration and percolation to occur
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the water cycle in the Congo

  • relief- the congo basin is mostly flat with an altitude of between 300m and 1000m. the areas to the south and east of the basin are undergoing uplift due to tectonic processes
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the carbon cycle in tropical rainforest

  • tropical rainforests are highly protective ecosystems. this is because sunlight is plentiful, and precipitation and temperature rates are high, so photosynthesis rates are high
  • eco system productivity is measured using net primary productivity, this is a procy measure of the amount of energy stored in plants per year and is expressed as the mass of new growth produced each year. tropical rainforest has the most, Desert has the least
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the human impact on rainforest water and carbon cy

Deforestation and farming in the Congo

  • the Congo rainforest has lower rates of deforestation than the Amazon or SE Asian Rainforests
  • GIS data is used to calculate deforestation rates. satellite images from different dates are compared to examine chang in canopy coverage. advantages for using GIS for deforestation data are that it enables you to visualise deforestation data at a range of scales providing opportunities to detect and quantify patters, analysis can show hot spots and cold spots, distances can be computed to establish relationships between different spatial features and different layers of data can be added to see whether deforestation  is greater on particular soil types or near particular land uses
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the human impact on rainforest water and carbon cy

Reasons for deforestation in the Congo:

  • civil unrest/war- civil war has occured twice in the last 3 decades in DRC. this caused civilians to flee into the rainforest to seek shelter
  • increase in demand of agricultural land- as population rises there is more demand to clear the forest to provide land for subsistence agriculture via slash and burn techniques
  • mining- Gold, Diamonds, Cobalt, copper, oil are mined. most mines are small scale, but associated roads and settlements also cause deforestation
  • logging- 30% of the area of the Congo is covered by industrial logging concessions, some of which are sustainable selective logging, howeber illegal logging is prevalent in DRC
  • despite being the second largest river basin in the worl after the amazon, the hydrology of the Congo has been rarely studied. most of the studies use GIS data gathered from satellites to esimate the water balance of the Congo and its tributaries. while deforestations of the Congo is less of a problem than of the Amazon, it is predicted that the discharge of the Congo would increase greatly if 30% of the rainforest was deforested
  • deforestation- there will be less interception and less transpiration, so evapotranspiration rates will fall. as a consequence, there will be more surface runoff and river discharge levels will rise
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the human impact on rainforest water and carbon cy

How tropical deforestation of the Congo basin would affect the water cycle of the region

  • precipitation- rates would fall because transpiration and evaporation rates would fall in the absence of the trees and precipitation is 55% recycled water from the Congo basin itself
  • evaporation- rates would fall because there would be reduced interception and increased infiltration rates, so water would quickly sink into the soil so not be available for evaporation
  • transpiration- rates would fall because there would not be trees to carry out the large amount of transpiration that previously took place
  • river runoff- rates would increase despite the reduction in precipitation because ET rates will have declined rapidly too. surface runoff will increase as there is less interception. more infiltration will mean through flow, which will increase discharge and slow lag times
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Management of tropical rainforests

  • the DRC has more than 50% of the Congo rainforest in its borders. about 40 million people in DRC rely on the forests for their food, income and shelter
  • in 2012 the DRC Government agreed to a United Nations REDD+ strategy to protect the rainforest. REDD+ is the UN programme Reduce Carbon Emissions from Deforestation and Degradation of Forests. in 2015 the DRC Government also signed up to the central african forest initiative (CAFI)
  • CAFI provides funding for government programmes to increase the use of sustainble farming strategies in forest regions, provide energy alternative to fuel wood, minimise the impact of mining, urbanisation and communications routes in the forest
  • CAFI aims to increase rural household income by 10-20% whilst reducing emissions by 20%
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Management of Tropical Rainforests

  • a number of sustainable strategies can be used to manage tropical rainforests. One area of the Congo where sustainable strategies are being put into place is Mai Ndombe, DRC. It has one of the highest rates of deforestation in the DRC as ti is close to the large population centre of Kinshasa
  • threats in the area to the forest include: unplanned deforestation via slash and burn to create agricultural land, illegal logging and deforestation to provide fuel wood for the residents of Kinsaha and forest loss for mining ad infrastructure e.g. roads and power lines
  • solutions that are in place include: creating community forest areas, strengthening control of logging, re-afforestation and use of sustainable logging
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Management of tropical rainforests

  • the Mai Ndombe prpject is funded by REDD+ using money gained from Carbon Trading schemes. it covers 300ha of tropical rainforest and 26 villages with a total population of 50,000
  • the area was covered by 2 legal concessions which were revoked by the DRC Governent in 2011
  • a key aspect of the project was improving quality of life for the locals. Schools, hospitals and wells have been built, this reduces local population growth rates
  • education on more efficient agricultural practices and funding to provide the tools and seeds to implement the practices has reduced the amount of forest land cleared for agriculture as yields on existing plots have increased
  • jobs have been created for local villagers connected to forestry- 'forestry police- to ensure illegal deforestation is not happening and forest nursery workers growing trees and enacting reforestation
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the human impact on the water cycle

during the Holocene both the carbon and water cycle have been in the dynamic equilibrium. dynamic equilibrium is when a system maintains stability and resists overall change through constant fluctuations in inputs, flows, stores and outputs

Urbanisation- building of towns and cities- can have a big impact on the water cycle both in terms of type and speed of flows and amount of water in stores

Impact: remove of vegetation.

Explanation: less transpiration as buildings replace vegetation

Impact: construction of buildings and roads.

Explanation: ground surface is made impermeable so less infiltration and more overland flow. buildings intercept water, which quickly travels through the sewage system to local streams, increasing river discharge. urban areas are 'heat islands' due to reduced albedo and the energy given off by heating/air conditioning systems. this will increase rates and could cause more local convectional rainfall

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the human impact on the water cycle


  • impact- vegetation changes
  • explanation- the natural vegetation is removed and replaced with grassland for livestock farming or crops with bare ground after harvesting. this will reduce interception and reduce transpiration rates and so there will be more surface runoff and infiltration. therefore, there will be more water in the soil store and river discharge will increase
  • impact- agricultural practices
  • explanation- ploughing breaks up the soil and increases infilitration rates. irrigation removes water from aquifers or rivers


  • impact- deforestation
  • explanation- there will be less interceptio and less transpiration, so evapotranspiration rates will fall. consequently, there will be more surface runoff and river discharge levels will rise
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