Topic 10.2

Question 1

Why is the nitrogen cycle so important?

Answer 1

Vital part of amino acids, hence proteins, and nucleic acids

Question 2

What does nitrosonomas spp. convert?

Answer 2

Ammonium -> nitrites

Question 3

What does nitrobacter convert?

Answer 3

Nitrites to nitrates

Question 4

What is the role of nitrogen fixing bacteria?

Answer 4

Convert nitrogen gas -> ammonium
In soil or root nodules of legumes

Question 5

What does denitrifying bacteria do?

Answer 5

Converts nitrates to atmospheric nitrogen
(Bad) (they really like waterlogged soil) (can be prevented by churning soil)

Question 6

What conditions are best for nutrient cycling? + why?

Answer 6

1. Warm (chemical reactions occur faster)
2. Moist (able to dissolve food for absorption)
3. High oxygen levels (microbes respire more efficiently)

Question 7

What is NPP and GPP?

Answer 7

Net primary productivity
Gross primary productivity

Question 8

What is the definition of GPP?

Answer 8

Rate of energy incorporated into biomass in plants
(although energy is lost through respiration, less energy is available to the primary consumer)

Question 9

What is NPP? (2 marks)

Answer 9

Rate of production of biomass
NPP = GPP - R(espiration)
In plants

Question 10

What is the unit for GPP and NPP?

Answer 10

kJ m-2 y-1
(Energy/area/time)
Or
Biomass - (g m-2 y-1)
Carbon ( gC m-2 y-1)

Question 11

Why is there energy not passed on/ lost in a food chain?

Answer 11

• losing energy from respiration like heat and movement
• stored in parts that can’t be eaten/digested
• dead organisms are not eaten

Question 12

Why does temperature and hours of sunlight affect NPP? (6 marks)

Answer 12

Correlation between NPP and light
NPP increases as light increases
Temp affects rate of enzyme activity
Light/temp could be limiting factor

Question 13

What is the risk of carrying out the experiment of measuring sand dunes? How to reduce this risk?

Answer 13

• animal bites
• allergies from plants
• Adverse weather
• wear suitable clothing
• sunscreen

Question 14

What are you looking at with Spearman’s rank?

Answer 14

Correlation

Question 15

Describe how waterlogged soil can cause nitrate to be removed from the soil.

Answer 15

Flooded wetlands give opportunity for nitrogen fixation process to take place
Nitrate converted to nitrogen gas into atmosphere
Denitrification requires aerobic conditions, useful nitrogen fixing bacteria aren’t able to survive in these conditions

Question 16

Explain why nitrogen fixing bacteria in the root nodules of leguminous plants are an example of mutualism

Answer 16

Nitrogen fixing bacteria convert nitrogen gas into nitrates.
taken up directly by the roots of the plant
bacteria themselves get glucose that the plant makes.
can be used in respiration by the bacteria.
Nitrogen fixing bacteria need lots of glucose.

Question 17

Explain why nitrogen fixing bacteria in the root nodules of leguminous plants are an example of mutualism

Answer 17

Nitrogen fixing bacteria convert nitrogen gas, which is inaccessible to plants directly, into nitrates. This can be taken up directly by the roots of the plant. The bacteria themselves get glucose that the plant makes. This is useful because it can be used in respiration by the bacteria. Nitrogen fixing bacteria need lots of glucose.