Ecology - 2.3 Biogeochemical cycles

Question 1

3 main biogeochemical cycles

Answer 1

• carbon cycle
• nitrogen cycle
• hydrological cycle

Question 2

Store

Answer 2

They are “reservoirs” where elements are held for varying periods of time
* represent areas where the element remains in equilibrium with the environment
* i.e. the total input of the element is equal to the total output
* can be natural or artificial

Question 3

Sinks

Answer 3

Represent parts of the cycle where a particular element accumulates over time
* areas where the total input of the element is greater than the total output

Question 4

Sources

Answer 4

Release elements into the cycles
* Represent parts of the cycle where the total output of the element is greater than the total input

Question 5

Stages of the carbon cycle

Answer 5

1. Photosynthesis
2. Decomposition/Fossilisation - breaking down of plants leads to creation of fossil fuels (due to pressure and heat from Earth’s crust)
3. Stored underground
4. Combustion - released into air when fossil fuels are burned
5. Feeding - animals consume carbon dioxide through plants
6. Respiration - released into air
7. Defecation - returned to the soil through waste product
8. Death and decomposition - break down dead organism and release carbon into the soil

Question 6

Carbon sequestration

Answer 6

Carbon sequestration is the process of capturing atmospheric CO2 and storing it in solid or liquid forms

Question 7

Human impacts on carbon cycle (2)

Answer 7

• Fossil fuel burning - increases atmospheric CO2
• Deforestation - reduces carbon storage capacity

Question 8

Human impacts on nitrogen cycle (3)

Answer 8

• Industrial fertiliser use disrupts natural cycling
• Agricultural runoff causes eutrophication
• Factory farming concentrates nitrogen waster

Question 9

Carbon cycle use

Answer 9

Essential for organic molecules and energy storage

Question 10

Water cycle use

Answer 10

Essential for cellular processes and transport

Question 11

Nitrogen cycle use

Answer 11

Essential for protein and DNA synthesis

Question 12

Human impacts on the water cycle (3)

Answer 12

• Urbanisation alters natural draining patterns
• Dam construction disrupts riber flow regimes
• Groundwater depletion from irrigation

Question 13

Biological factors affecting biogeochemical cycles (3)

Answer 13

• microbial activity varies with conditions (temp, light)
• plant uptake changes seasonally
• animal migration moves nutrients

Question 14

Physical factors affecting biogeochemical cycles (3)

Answer 14

• Temperature affects reaction rates
• Moisture levels influence mineral solubility
• Rock type determines weathering rates

Question 15

Chemical factors affecting biogeochemical cycles (3)

Answer 15

• pH affects mineral availability
• Oxygen levels control decomposition
• Salinity influences solubility

Question 16

Residence time

Answer 16

The average period that a carbon atom remains in a store without human interference

Question 17

Examples of carbon sinks in agricultural systems (3)

Answer 17

(overall: regenerative agriculture techniques)
* crop rotation
* cover cropping
* no-till farming

Question 18

Examples of carbon sources in agricultural systems (3)

Answer 18

• drainage of wetlands
• monoculture farming
• intensive tillage

Question 19

Ocean acidification

Answer 19

Increased concentrations of dissolved CO2 in oceans lowers the pH of the sea water, leading to ocean acidification

Question 20

Affects of ocean acidification (2)

Answer 20

• Small decreases in ocean pH reduce calcium carbonate deposition in mollusc shells and coral skeletons
• Weakened shells, increased vulnerability to predators and smaller and less diverse reef structures

Question 21

Ways to reduce human impacts on the carbon cycle (name 3)

Answer 21

• low carbon technologies (e.g. renewable energy sources)
• reduction in fossil fuel burning
• using biomass as a fuel source
• reduction in soil production
• reduction in deforestation
• carbon capture through reforestation
• artificial sequestration
• enhancing carbon dioxide absorption