Carbon Cycle

Question 1

What is the carbon cycle ?

Answer 1

The carbon cycle is a nutrient cycle that shows how carbon is passed from the atmosphere (where it is in the form of carbon dioxide) into plants (during photosynthesis) and on to animals as they feed on plants.

Question 2

Significance of photosynthesis in carbon cycle

Answer 2

photosynthesis: plants absorb carbon, in the form of carbon dioxide, from the atmosphere during photosynthesis.
- Plants then use this carbon dioxide (combined with water) to form carbohydrates like starch

Question 3

Significance of respiration in carbon cycle

Answer 3

respiration: all organisms respire. This process uses the carbohydrates (such as glucose) and produces carbon dioxide. This carbon dioxide is released back into the atmosphere. Remember that plants, animals and the decomposers all respire.

Question 4

Significance of combustion in carbon cycle

Answer 4

combustion: this is burning, when any fuel (coal, oil, gas, wood) is burnt it releases carbon in the form of carbon dioxide back into the atmosphere.

Question 5

Significance of decomposition in carbon cycle

Answer 5

decomposition: this process breaks down any dead or decaying matter ensuring that the carbon contained within these molecules is released back into the atmosphere as carbon dioxide or released as minerals into the soil.

Question 6

Significance of fossilisation in carbon cycle

Answer 6

fossilisation: under certain circumstances (e.g. when it is very cold or there’s a lack of oxygen) dead organisms do not become fully decomposed. Over millions of years these partially decomposed materials are converted into fossil fuels such as coal, oil and gas.

Question 7

Significance of feeding in carbon cycle

Answer 7

feeding: as described on our work on food chains, plants are producers which are then consumed by animals. When this occurs the carbon in the biomolecules in the plants are passed into the animals

Question 8

Explain how environmental changes affect the distribution of organisms (3)

Answer 8

• Deforestation causes there to be fewer plants to absorb carbon dioxide during photosynthesis and loss of habitats for animals
• Melting ice caps leads to increased sea levels which disrupts sea life
• Rapid global warming means certain species’ do not have time to adapt to different climates

Question 9

What has caused climate change ?(2)

Answer 9

• Humans rely heavily on the combustion of fossil fuels in order to generate electricity, heat our homes and for transport. This results in a greater amount of carbon dioxide being released into the air which cannot all be absorbed by plants
• Humans have cleared a great deal of forested areas in order to provide wood for industry and housing. As a result of deforestation, there are fewer plants to absorb carbon dioxide during photosynthesis.
• CO2 and Some other gases in the atmosphere form a ‘greenhouse blanket’ trapping the head from the sun’s rays within the atmosphere

Question 10

How we can prevent global warming or reduce it (3)

Answer 10

• Reduce carbon dioxide emissions from combustion of fossil fuels (use of renewable energy sources like wind power)
• Planting of more trees
• conserving existing forest to reduce deforestation.

Question 11

Effects of global warming (5)

Answer 11

• climate change, extreme weather
• polar ice caps melt
• sea levels to rise and increased flooding
• More land to become desert
• loss of habitats