Carbon cycle

What human activities increase carbon dioxide? (3)

burning fossil fuels releases carbon dioxide into the atmosphere, deforestation removes large quantities of photosynthesising biomass, so less carbon dioxide is removed from the atmosphere

How is respiration a biological process of the carbon cycle? (2)

carbon dioxide is added to the air by respiring animals, plants and micro-organisms, and by combustion of fossil fuels

How is photosynthesis a biological process of the carbon cycle?

photosynthesis reuses almost as much carbon dioxide as is released into the atmosphere by respiration

How is decomposition a biological process of the carbon cycle?

dead remains of plants and animals are acted upon by detritivores and saprobionts in the soil, releasing carbon dioxide back into the atmosphere

In what form is carbon dioxide present in aquatic ecosystems? (2)

bicarbonate ions, involved in the same processes as terrestrial organisms

What are bicarbonate ions incorporated into in aquatic ecosystems?

incorporated into magnesium and calcium carbonate in mollusc shells and arthropod exoskeletons that sink after the animal’s death

How are carbonates lost from the biosphere?

carbonates become components of chalk, limestone and marble

What happens if geological processes expose carbonates to the atmosphere? (2)

they are eroded, releasing carbon dioxide back into the air

How does deforestation impact the carbon cycle? (2)

cutting down forests reduces the rate at which carbon dioxide is removed from the atmosphere by photosynthesis, sometimes cut down trees are burnt or left to decay both releasing carbon dioxide into the atmosphere

How is climate change related to the carbon cycle? (3)

average temperature, wind patterns and rainfall are caused by an increase in carbon dioxide and other greenhouse gases, caused by burning fossil fuels due to increased industrialisation, deforestation reduced global forest area by 40%

Global warming

increase of average global temperature, in excess of the greenhouse effect caused by the atmosphere’s historical concentration of carbon dioxide

What are some examples of greenhouse gases? (6)

carbon dioxide, methane, nitrous oxide, CFCs, ozone and water vapour

Explain the first stage of the greenhouse effect

all greenhouse gases allow high energy, short wavelength solar radiation to pass through to the earth’s surface

Explain the second stage of the greenhouse effect (3)

earth absorbs the energy and warms up the earth, lower energy is re-radiated, this lower energy is longer wavelength infra-red radiation which is absorbed and trapped by greenhouse gases in the atmosphere

Explain the third stage of the greenhouse effect (2)

gases re-radiate the energy in all directions and energy absorbed again by Earth, planetary surface and atmosphere warm up

What is important to note about the greenhouse effect? (2)

it is a natural process, without the greenhouse effect the Earth would be -20 degrees celsius too low to sustain life

What are some significant consequences of global warming? (6)

polar ice melting causes floods in local areas, increased frequency of extreme weather conditions, increased frequency of forest fires, decreased water availability in tropical areas, animals have to move to find a more suitable habitat, plants can only disperse so may become extinct

What is a result of these plants possibly becoming extinct as a consequence of global warming?

dependent animals may become extinct so ecosystem collapses

What are some other consequences of global warming? (5)

movement of fishing areas and crop growing belts, increased crop yields as warmer temperatures allow more photosynthesis, increase in pests, world food production may decrease reducing grain crop in North America and Central Asia, causing serious economic and political consequences

What are the consequences of increasing carbon dioxide in the oceans?

decreases pH, threatens organisms, such as fish populations secrete mucus to protect gills so unable to perform gas exchange, coral reefs external skeleton made of calcium carbonate is soluble in acid

Why is freshwater critical?

to sustain food production and provide food for the world’s growing population

What is a problem with decomposition of soil organic matter in farming?

carbon dioxide

What farming practices are altered to reduce carbon dioxide emission? (3)

conservation tillage, cover cropping, crop rotation

What is conservation tillage? (2)

leave crop residues on the soil surface to reduce erosion, improve water use and organic matter to the top soil

What is cover cropping? (2)

use clover to cover soil to protect and improve it between crops, enhances soil structure and adds organic matter to topsoil

What is the result of crop rotation?

reduces pest numbers and mineral depletion

What is a problem related to digestive activities of farm animals used in the meat and dairy industries and decomposition of wet soils?

methane

What farming practices are altered to reduce methane gas emission? (4)

change human dietary intake, change cow food, use different varieties, ammonium sulphate addition

What changes can be made to human dietary intake to reduce methane gas emission?

reduce dietary intake of meat and dairy products

What changes can be made to cow dietary intake to reduce methane gas emission?

high-sugar grasses, oats, rapeseed and maize silage in cows diets reduce the methane they release

What changes can be made to rice varieties to reduce methane gas emission? (3)

use rice varieties that grow in drier conditions, select varieties that have a higher yield, ammonium sulphate addition can favour non-methane producing micro-organisms in paddy fields in same conditions

What is a problem with waterlogged and anaerobic soils?

nitric oxide and nitrous oxide

What farming practices are altered to reduce nitric oxide and nitrous oxide gas emissions?

improve drainage to remove water and aerate soil

What is a problem related to low rainfall and high temperature?

low and fluctuating water supply

What farm practices are altered to prevent low and fluctuating water supply? (2)

use drought tolerant crops, like in Kenya drought tolerant sorghum, millet and cowpea have increased yields significantly

What is a problem related to cultivated land inundated by saltwater?

raised sea level

What farming practices are altered to deal with raised sea levels? (3)

salt-tolerant crops, like a salt-tolerant potato, durum wheat yields 25% more grain than the parent variety

Carbon footprint

The total amount of carbon dioxide produced by a person, product or service in a year

How do crops incur indirect sources of greenhouse gases? (4)

production of farming tools, production of insecticides, herbicides, fungicides and fertilisers, farm machinery powered by fossil fuels, transport of produce as most crops are shipped hundreds of miles to processing plants before distribution

How can you reduce the production of greenhouse gases? (6)

recycle packing material, drive less, use less air conditioning and heating, choose a diet to reduce animal protein, rice, food from far distances, heavily processed and packaged foods, avoid food waste and turn it into compost if possible, plant trees in deforested regions