Cycles

Question 1

Why do plants and animals need nitrogen?

Answer 1

To make proteins and nucleic acids.

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Question 2

“The over-application of fertiliser increases the rate of leaching. Explain the consequences of leaching of fertiliser into ponds or lakes.”

Answer 2

1 There is an Increase algae (algal bloom) and so light is blocked out;
2. Plants can’t photosynthesise and plants and algae die;
3. Bacteria/saprobionts, breakdown dead
organisms;
4 Bacteria/saprobionts/ use up oxygen
via respiration.
5. Conc of oxygen in water reduced and so oxygen is a limiting factor, fish and other organisms die.

Question 3

What is leaching?

Answer 3

Leaching is when nutrients are removed from the soil

Question 4

What is Eutrophication?

Answer 4

The process by which nutrients build up in bodies of water.

Question 5

Describe the role of bacteria in making the nitrogen in dead leaves available to growing plants.

Answer 5

1. Saprobionts digest or break down proteins
2. Extracellular digestion occurs/release of enzymes;
3. Ammonia produced and converted to nitrite and then into nitrate by Nitrifying bacteria. (nitrification)

Question 6

What does the Haber process do?

Answer 6

It produces ammonia from atmospheric nitrogen which is used to make things like fertilisers.

Question 7

What is denitrification?

Answer 7

• denitrification is when nitrates in the soil are converted into nitrogen gas by denitrifying bacteria (they use nitrates in the soil to carry out respiration) and produce nitrogen gas.
• This happens under anaerobic conditions e.g. waterlogged soils.

Question 8

What is nitrification?

Answer 8

• Nitrification is when ammonium compounds are changed into nitrogen compounds that can be used by plants.
• First nitrifying bacteria change ammonium compounds into nitrites.
• The other nitrifying bacteria change nitrites into nitrates.

Question 9

What is ammonification?

Answer 9

-Ammonification is when nitrogen compounds from dead organisms are turned into ammonium compounds by decomposers.
-Animal waste also contains nitrogen compounds. These are also turned into ammonium compounds by decomposers.
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Question 10

The relationship between the bacteria and plant?

Answer 10

They provide the plant with nitrogen compounds and the plant provides them with carbohydrates.

Question 11

What is nitrogen fixation?

Answer 11

When nitrogen gas in the atmosphere is turned into ammonia by bacteria. The ammonia can then be used by plants.
The bacteria are found inside root nodules of leguminous plants.

Question 12

What is saprobiontic nutrition?

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Answer 12

The feeding on dead organic matter. (the feeding is done by microorganisms called decomposers)
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Question 13

“Dead leaves contain starch. Describe how microorganisms make carbon in starch available.”

Answer 13

Carbon is taken up by plants in photosynthesis as carbon dioxide.

• Extra-cellular digestion occurs, enzymes aid the digestion of the starch into monosaccharides.
• Respiration occurs and carbon dioxide is produced from respiration.

Question 14

“Microorganisms make the carbon in polymers in a dead worm available to cells in a leaf”. Describe how.

Answer 14

Microorganisms are saprobionts that secrete enzymes onto dead tissue (extra ceullular digestion)

• Respiration (by microorganisms) produces carbon dioxide.
• Carbon dioxide taken into leaves through the stomata.

Question 15

Clearing the forests and burning the vegetation affects the carbon dioxide
concentration in the atmosphere.
Describe how and explain why

Answer 15

1. Carbon dioxide concentration increases;
2. Less vegetation so less photosynthesis
   photosynthetic organisms
3. Less carbon dioxide removed (from the atmosphere)
4. Burning/combustion releases carbon dioxide;

Question 16

Global warming affect on wild animals and plants:

Answer 16

-affect the distribution of many wild animal and plant species.
- affect the number of wild animals and plants.
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Question 17

Global warming affect on Insect Pests:

Answer 17

Some insects will go through their larval stage quicker and emerge as adults earlier.
-Some species become more abundant (the species adapted to warmer and wetter species)
-Other species may become less abundant (e.g. some tropical insect species can only thrive in specific temperature ranges, so if it gets too hot fewer insects may be able to reproduce successfully.
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Question 18

Global warming affect on crop yield:

Answer 18

Increase in crop yield as CO2 is a limiting factor for photosynthesis and so increasing glocal CO2 concentration could mean crops grow faster, increasing crop yields.

Question 19

What is carbon fixation?

Answer 19

It involves the reduction of carbon dioxide to large organic molecules. Simply:
CO2 + 4H > CH2O + H2O
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Question 20

What is happening to Carbon Dioxide conc:
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Answer 20

CO2 conc is increasing as more fossil fuels like coal, natural gas and petrol are burnt.

Question 21

Another factor in increasing carbon levels

Answer 21

the destruction of natural sinks (things that keep carbon dioxide out of the atmosphere by storing carbon. e.g. Trees. they store the carbon as organic compounds).

Question 22

Why is methane conc increasing

Answer 22

more methane is being released into atm- because more fossil fuels are being extracted + more decaying waste + more cattle give off methane as a waste gas.
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Methane can also be released from natural stores ( frozen ground). As temperatures increase—> thaw + release large amounts of methane into the atmosphere.

Question 23

All living organisms including decomposers, carry out respiration. What does this mean?

Answer 23

This means carbon and water are returned to the air as respiration produces CO2 & water

Question 24

What is combustion?

Answer 24

When the carbon in fossil fuels is released when they are burnt.

Question 25

Daily change in carbon dioxide concentration

Answer 25

1. Respiration is carried out constantly through the day AND the night.
2. But photosynthesis only takes place during daylight hours.
3. So carbon dioxide is removed during the day as its being removed by plants as they carry out photosynthesis.
4. This means carbon dioxide concentration increases at night as photosynthesis ceases, so no CO2 is being removed from the atmosphere. All the organisms are still respiring and adding CO2 to the atmosphere.
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Question 26

Yearly change in Carbon dioxide concentration

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Answer 26

1. Most plant life exists in the northern hemisphere because that’s where most land is.
   2.Most plant growth occurs in the summer (June-August) because that is when the light intensity is greatest, more photosynthesis can occur, which means there is more energy to grow.
2. CO2 concentration falls during summer because more is being removed from the atmosphere as more plants are photosynthesising.
3. However, in the winter, CO2 conc increases throughout autumn-winter because less is being removed via photosynthesis.
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Question 27

What is global warming?

Answer 27

The term for the increase in average global temperature over the last century.
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Question 28

How has human activity contributed to global warming?

Answer 28

by enhancing the greenhouse effect. (deforestation/fossil fuels etc)