nutrient cycles

Question 1

what is denitrification?

Answer 1

the loss of nitrates from the soil under anerobc conditions

Question 2

what happens in the process of denitrification?

Answer 2

nitrates are converted into nitrogen gas

Question 3

what carries out denitrification?

Answer 3

denitrifying bacteria

Question 4

describe an organic molecule

Answer 4

large, complex molecules that all contain the element carbon

Question 5

describe an inorganic molecule

Answer 5

simple, small molecules and tend to be found in the abiotic

phase.

Question 6

Name two nucleic acids

Answer 6

DNA & RNA

Question 7

Name two other organic compounds which always contain nitrogen

Answer 7

Amino acids / proteins / ATP / ADP

Question 8

What does inert ’ mean?

Answer 8

unreactive

Question 9

how much nitrogen makes up the earths atmosphere?

Answer 9

80%

Question 10

Why will lack of nitrogen lead to stunted growth?

Answer 10

Organism is unable to make proteins which are needed for growth

Question 11

name the 5 main stages in the nitrogen cycle

Answer 11

1. Nitrogen fixation
2. Nitrification
3. Denitrification
4. Nitrogen flow through food webs
5. Ammonification (during decomposition

Question 12

describe nitrogen fixation

Answer 12

This is a process by which
nitrogen gas is converted into a nitrogen containing
compound that is more useful to organisms.

Question 13

what carries out nitrification?

Answer 13

nitrifying bacteria

Question 14

how does nitrogen fixing bacteria work?

Answer 14

They convert the nitrogen into ammonia using a reduction reaction catalysed by the enzyme
nitrogenase

Question 15

where can nitrogen fixing bacteria be found?

Answer 15

• Some of these bacteria live in special swellings on the roots (known as root nodules of plants called legumes .
• free living in the soil

Question 16

describe the mutually beneficial relationship

between the bacteria and the plant is an example of

Answer 16

The bacterium receives water and sugars

from the plant and in return supplies the plant with ammonia.

Question 17

Name some types of legumes

Answer 17

Clover, soy beans, pea plants

Question 18

when the ammonia is dissolved in water in the soil. what is produced?

Answer 18

ammonium ions

Question 19

what carries out nitrification?

Answer 19

nitrifying bacteria

Question 20

what do nitrifying bacteria do?

Answer 20

transform ammonium ions into nitrates.

Question 21

why are nitrifying bacteria described as autotrophs?

Answer 21

when they transform ammonium ions into nitrates, it releases energy which they use for the synthesis of organic molecules such as carbohydrates. For this reason, these

Question 22

Green plants are also called autotrophs. What is the difference between green plants and nitrifying bacteria autotrophs?

Answer 22

• Green plants use light energy to synthesise organic matter(= PHOTOautotrophs)
• Some bacteria oxidise chemical compounds (e.g. nitrites) to release energy they need to synthesise organic matter (= CHEMOautotrophs

Question 23

describe the two stages of nitrification

Answer 23

1. The oxidation of ammonium ions to nitrite by nitrifying bacteria
2. The oxidation of nitrites to nitrates by nitrifying bacteria

Question 24

describe the two stages of nitrification

Answer 24

1. The oxidation of ammonium ions to nitrite by nitrifying bacteria
2. The oxidation of nitrites to nitrates by nitrifying bacteria

Question 25

how do plants take up nitrogen from the soil in the form of nitrates?

Answer 25

through their roots by active transport

Question 26

what are sabrobiotic microorganisms and how do they cause decay?

Answer 26

Fungi/bacteria that perform extracellular digestion. They secrete enzymes on to the detritus so the nitrogen-containing compounds (e.g. DNA/proteins/urea) are digested externally. They absorb some of the products of digestion and use them, but some (e.g. ammonia) are released into the environment

Question 27

name the process that converts nitrogen into ammonia

Answer 27

nitrogen fixation

Question 28

name the process that converts ammonium ions into nitrates and then into nitrites

Answer 28

nitrification

Question 29

name the process when nitrates are converted into nitrogen gas

Answer 29

denitrification

Question 30

describe the role of nitrogen fixing bacteria

Answer 30

reduce nitrogen gas to ammonia/ ammonium ions

Question 31

describe the role of sabrobiotic bacteria

Answer 31

decompose dead/waste material by extracellular digestion | -convert nitrogen containing organic molecules into ammonia

Question 32

describe the role of nitrifying bacteria

Answer 32

oxidise ammonia to nitrates | oxidise nitrates to nitrites

Question 33

describe the role of denitrifying bacteria

Answer 33

concert nitrates in the soil to nitrogen gas in the atmosphere the bacteria work in anaerobic conditions

Question 34

how can crop rotation involving legumes increase crop yield

Answer 34

Nitrogen-fixing bacteria in the clover convert nitrogen gas to ammonia. The clover uses the N in ammonia to make proteins etc. When left to decay, saprobiotic bacteria will convert the proteins in dead clover to ammonia, and nitrifying bacteria will convert it to nitrates. different crops grown after the legumes will then absorb different nutrients from different soil depths (due to different requirements and different root lengths). Different crops will have different pest species. Those from the previous year’s crop are unlikely to affect the new crop

Question 35

where can the phosphate element be found?

Answer 35

Phospholipids, Nucleic Acids (DNA and RNA), ATP, ADP, NADPH

Question 36

describe the role of saprobionets

Answer 36

Saprobionts decompose dead animals / plants / algae/ waste materials using extracellular digestion

Question 37

explain the phosphorus cycle

Answer 37

-Saprobionts decompose dead animals / plants / algae/ waste materials using extracellular digestion -Saprobionts absorb the products of digestion and release phosphate ions into soils, lakes, rivers and oceans where they dissolve. -some of these phosphate ions are absorbed by plants and algae and are used to form organic biological molecules used in growth, such as phospholipids, ATP and nucleic acids. -The phosphate ions are then passed to the animals that feed on the plants and algae. The phosphate-containing organic compounds are digested then absorbed and assimilated.

Question 38

what does the word Mycorrhizae mean ?

Answer 38

fungus root

Question 39

why does mycorrhizae help increase growth?

Answer 39

it Increases growth beacuse the presence of fungus which, due to their large surface area, allow a more efficient absorption of water and the minerals that are essential for growth (and are often the limiting factors in plant growth )

Question 40

give examples of mutualistic relationship

Answer 40

- legumes and nitorgen fixing bacteria | - lichens (a fungus and an algae)

Question 41

what ions are needed to produce proteins?

Answer 41

nitrites

Question 42

what ions are needed to produce nucleuic acids?

Answer 42

Nitrates and phosphates

Question 43

what ions are needed to produce ATP?

Answer 43

Phosphates (and nitrates)

Question 44

what ions are needed to produce phospholipids ?

Answer 44

Phosphates

Question 45

what do natural fertilisers consist of?

Answer 45

orgainic plant or animal matter, containing complex orgainc compounds

Question 46

what do articfical fertilisers consost of?

Answer 46

concentrated mineral ions in an in orgain, soluble ready to use form

Question 47

give the advantages of artifical fertiliser

Answer 47

- nutrients in concentrated form can be applied in smaller amounts (cost effective) - nutrients relesed rapidly into soil - clean chemicals that lack odur

Question 48

give the disadvantages of artifical fertiliser

Answer 48

- readily leached from soil so u can damage ecosystems of ponds and lakes - rick of fertiliser spray spreading to ther areas - expensive to buy/ maufacteur

Question 49

give the advantages of natural fertiliser

Answer 49

- slow release of nutrients - adds humus to soil improves structure and drainage - nutrients not readily leeched - useful, cheap mean disposable of farm waste

Question 50

give the disadvantages of natural fertiliser

Answer 50

- may be difficult to spread - minerals only released slowly - unknown concentration of nutrients

Question 51

why may crop yeild fall when there is too much fertiliser?

Answer 51

higher concentration of ions may reduce water potential of the soil plants may loose water through their roots via osmosis

Question 52

describe the process of leeching

Answer 52

the process by which nutrients are removed from the soil

Question 53

why does leeching occur?

Answer 53

inorganic fertilisers are very soluble in water | -so rain water dissolves them and washes them out of the soil

Question 54

describe eutrophication

Answer 54

- rapid algal growth - a dnese layer of algal forms on the surface of the water, absorbing light and preventing it from penatrating to lower depths, so plants below the surface cannot photosynthesise and therefore die - increased competition between algea results in death of algae too - When the algae and plants die, they are decomposed by bacteria and other saprobiotic organisms, whose populations suddenly increase. - The increase in aerobic respiration by bacteria uses up oxygen. - The dissolved oxygen in the water becomes depleted, causing many species of invertebrates and fish to die

Question 55

pollution of a river with sewage can also cause eutrophication explain how?

Answer 55

the orgainic material in sewage is fed upon by bacteria, which will respire areobically, using up the oxygen in the river If detergents are present, these contain phosphates which will encourage algal growth.

Question 56

why does adding fertilisers reduce species diversity?

Answer 56

they increase the growthof species such as nettles and grasses . these rapidly growing species outcompete many other species, which die as a result

Question 57

what do the different species compete for?

Answer 57

- light - minerals - water