Biogeochemical cycles

Question 1

Where can carbon be found?

Answer 1

In all organic matter (living things)

Question 2

What expression is used to describe carbon?

Answer 2

“The backbone of life on Earth”

Question 3

Would life exist if there was no carbon?

Answer 3

No. Living things are all made of carbon.

Question 4

What type of reactions happen in the carbon cycle? (transform/transfer)

Answer 4

The transformation of energy

Question 5

Name the reactions in the carbon cycle.

Answer 5

• Photosynthesis
• Respiration
• Combustion

Question 6

Write the equation for photosynthesis.

Answer 6

6CO2 + 6H20 + light/energy—–> C6H12O6 + 6O2

carbon dioxide + water + light/energy —-> sugar + oxygen

Question 7

Write the equation for respiration.

Answer 7

C6H12O6 + 6O2 —–> 6CO2 + 6H20 + energy

Question 8

What is a combustion reaction?

Answer 8

burning - reaction of an element or compound with oxygen to form an oxide and produce heat

Question 9

Is combustion an oxidation reaction?

Answer 9

Yes

Question 10

What is an oxidation reaction?

Answer 10

A reaction where oxygen is one of the reactants

Question 11

Draw a carbon cycle.

Answer 11

Check notes for answer

Question 12

What does having more carbon in the atmosphere mean?

Answer 12

An increase in global warming

Question 13

Name the greenhouse gasses

Answer 13

• CH4
• CO2
• H2O
• N2O

Question 14

Describe the greenhouse effect (how it happens)

Answer 14

• solar radiation powers the climate system
• some solar radiation is reflected by the Earth and the atmosphere
• about half the radiation is absorbed by the Earth’s surface and warms it
• infrared radiation is emitted from the Earth’s surface

Question 15

What is the greenhouse effect?

Answer 15

Some of the infrared radiation passes through the atmosphere but most is absorbed and re-emitted in all directions by greenhouse gas molecules in the clouds. The effect of this is to warm the Earth’s surface and and the lower atmosphere.

Question 16

What is eutrophication?

Answer 16

The enrichment of a waterbody with nutrients, resulting in excessive growth of photosynthetic organisms (ex: algae) and depletion of dissolved oxygen via decomposition (decomposers need lots of O2)

Question 17

Describe eutrophication (how it happens)

Answer 17

• Excess use of chemical fertilisers leads to run off and ground water contamination + the inorganic salts dissolved groundwater eventually enter lakes, ponds, and rivers
• Increased nutrients absorbed by algae
• Increased growth of algae shading out other plants.
• Increased decomposition of dead algae uses up oxygen in the water
• Fish begin to die as oxygen levels fall

Question 18

What is a better alternative to fertiliser use to replace nutrients in agriculture?

Answer 18

Compost

Question 19

Describe the nitrogen cycle (what happens)

Answer 19

• Atmospheric nitrogen is absorbed into soil
• Ammonification: nitrogen becomes ammonium
• Nitrification: Ammonium becomes nitrites
• Assimilation: nitrates are absorbed by plants
• Animals eat plants containing nitrites. When the animals and plants die they are decomposed by decomposers, and are transformed back into ammonium
• Dentrifying bacteria transforms nitrates into atmospheric nitrogen
  (check picture to see an example)

Question 20

Describe the phosphorus cycle (what happens)

Answer 20

• Phosphate is mined
• Fertiliser containing phosphate is put on crops and eaten by animals
• Animal waste and decomposition goes into bodies of water
• Phosphate rocks erode into bodies of water
• Dissolved phosphates are absorbed by algae and become marine sediments
• Marine sediments become phosphate rocks
• Algae is eaten by animals. Their excretion and decomposition is released into the body of water
  (check picture for example)