Nutrient, Nitrogen, phosphorus cycle

Question 1

What is the carbon cycle

Answer 1

Carbon is taken out of the atmosphere in the form of carbon dioxide by plants and algae during photosynthesis (the carbon is used to make glucose, which can be turned into carbohydrates, fats and proteins – biomass – within plants and algae)
This carbon is passed on to animals (and microorganisms) when they feed on plants and algae
It is returned to the atmosphere in the form of carbon dioxide, during respiration by plants, animals and microorganisms (that release CO2 during decomposition)
If animals and plants die in conditions where decomposing microorganisms are not present, the carbon in their bodies can be converted, over millions of years and significant pressure, into fossil fuels
When wood or fossil fuels are burned (a process is known as combustion), the carbon within them combines with oxygen and carbon dioxide is released into the atmosphere

Question 2

What is the nutrient cycle?

Answer 2

the continuous movement of nutrients from the environment, through living organisms, and back to the environment. The cycles involve the transformation of these nutrients from one form to another as they are taken up, used, and released by different organisms.

Question 3

Describe the nutrient cycle? Draw a diagram to show this..

Answer 3

Simple inorganic molecules:
e.g. carbon dioxide, phosphate ions and nitrogen are assimilated (or fixed) from the environment.
Complex organic molecules:
E.g. carbohydrates, proteins, nucleic acids and lipids. These organic molecules pass through the food chains and Eventually return to the environment as simple inorganic molecules by saprobionts (decomposers)

Question 4

What are the two main types of saproboints?

Answer 4

bacteria and fungi

Question 5

what are scavengers?

Answer 5

first to feed on dead animals

Question 6

What are detrivores?

Answer 6

invertebrates which feed on partly broken down dead matter (DETRITUS). Most are unable to digest cellulose.

Question 7

What are saprobionts?

Answer 7

organisms which secrete enzymes outside their bodies then absorb the products of digestion

Question 8

what is decomposition?

Answer 8

Decomposition is the breakdown of dead organic material (or waste material) into simpler compounds by saprobiotic micro-organisms e.g. Bacteria/fungi (known as saprobionts, formerly saprophytes).

Question 9

what is saprobiotic nutrition?

Answer 9

Saprobiotic nutrition is how decomposers e.g. Rhizopus or Mucor (bread moulds) obtain their energy.

Question 10

what do these saprobiotic organisms do?

Answer 10

They detect the composition of surrounding
dead organic material and activate the genes that make the correct digestive enzyme.

Question 11

What is hyphae?

Answer 11

secrete digestive enzymes, which hydrolyse the substrates. digested products can then be absorbed and used for respiration

Question 12

what is extracellular digestion?

Answer 12

They release hydrolytic enzymes, which break down complex organic molecules. (extracellular digestion). The digested
products (e.g.??) can then be absorbed and used for respiration.

Question 13

what is Mycorrhizae?

Answer 13

Means ‘fungus-root’ - Mutualistic, threads grow in and around the roots.

Question 14

what is the role of Mycorrhizae?

Answer 14

they increase the SA may be more efficient at absorbing minerals (some plant roots couldn’t get phosphate ions without it)

Fungus gets sugars from the plant, plant benefits from enhanced absorption of water and minerals

when they absorb minerals, water potential decreases, so water follows by osmosis

Question 15

Why is nutrient recycling in a natural
ecosystem vital for plant growth?

Answer 15

Nutrient recycling is vital because there is only a limited supply of nutrients and so
they must be recycled, otherwise they would all become locked up in biological
material.

Question 16

Describe how the method of digestion used by saprobionts results in some nutrients being made available to plant roots.

Answer 16

Saprobionts hydrolyse biological molecules by secreting enzymes into their surrounding environment. Some of the products of hydrolysis are then absorbed by the saprobionts, but many remain in their surroundings and may then be absorbed by other organisms.

Question 17

The Nitrogen cycle

Question 18

What is the nitrogen cycle?

Answer 18

The nitrogen cycle demonstrates the movement of nitrogen from the atmosphere into the soil, where is it utilised by bacteria and plants.

Question 19

what is the importance of the nitrogen cycle?

Answer 19

There is 78% nitrogen in the air, however plants and animals can not obtain the nitrogen through gas exchange, and so obtains it through the nitrogen cycle.

Question 20

What is nitrogen?

Answer 20

nitrogen is an inert gas, contains a triple bond and is really hard to break these bonds

Question 21

What is needed to convert nitrogen gas into nitrogen containing compounds?

Answer 21

microorganisms so plants and animals can absorb them

Question 22

Which biological molecules contain Nitrogen?

Answer 22

proteins - AA, ATP, nucleic acids, such as DNA, RNA

Question 23

What are the four/five key stages in the Nitrogen cycle?

Answer 23

1. Saprobiotic nutrition + microbes
2. Ammonification
3. Nitrification
4. Nitrogen fixation
5. Denitrification

Question 24

What is Nitrogen Fixation?

Answer 24

Where Nitrogen gas from the atmosphere is converted into Nitrogen containing compounds (soluble form)

Question 25

What are the 3 ways nitrogen can be fixed?

Answer 25

1. Lightning 2. free living Nitrogen fixing bacteria naturally occuring in the soil or water. 3. mutualistic Nitrogen fixing bacteria in the nodules on roots of legumes (peas, beans, clover).

Question 26

where is energy supplied from to split nitrogen molecules?

Answer 26

from oxidation of organic molecules found in the soil, the organic molecules may be from the plant or as a product from the bacteria's own photosynthesis

Question 27

how is nitrogen fixed through lightning?

Answer 27

The high temperature of a lightning bolt can break the bonds of atmospheric nitrogen molecules. Free nitrogen atoms in the air bond with oxygen in the air to create nitrogen oxides, which dissolve in moisture to form nitrates

Question 28

Why is bacterial present in leguminous roots able to fix nitrogen?

Answer 28

the root nodules, contain mutualistic bacteria that is able to convert nitrogen into ammonia and then into nitrites to nitrates (via nitrification). however not all plants have root nodules

Question 29

which Mutualistic bacteria is able to convert N2 in atmosphere into Ammonia?

Answer 29

Azotabacter bacteria

Question 30

what is the relationship described as?

Answer 30

symbiotic - both bacteria and plants are gaining benefit from co-existing together

Question 31

how can nitrogen be fixed by free-living bacteria?

Answer 31

free-living nitrogen fixing bacteria is naturally occurring in soil, which is able to react with the nitrogen in the air and convert it into ammonium

Question 32

give the name of a free-living nitrogen fixing bacteria?

Answer 32

Rhizobium

Question 33

In order for plants to absorb the ammonia what needs to happen?

Answer 33

Nitrification - so plants can absorb

Question 34

What is nitrification?

Answer 34

the process in which ammonium compounds are converted into nitrites and nitrates NH4+ ----> NO2- -----> NO3-

Question 35

What is nitrification carried out by?

Answer 35

nitrifying bacteria which are chemotrophic bacteria that obtain their energy from oxidising ammonium ions

Question 36

what process is nitrification?

Answer 36

Nitrification is an oxidation reaction, so converting ammonium ions into nitrate + nitrites is oxidation and so denitrification will be reduction.

Question 37

what type of nitrifying bacteria coverts ammonium ions into nitrites?

Answer 37

nitrosomonous (bacteria)

Question 38

where does energy from nitrification come from, and what else is this energy used for?

Answer 38

Bacteria get energy from nitrification rather than respiration, then use the energy for chemosynthesis (synthesise own organic compounds)

Question 39

what type of nitrifying bacteria converts nitrites into nitrates?

Answer 39

nitrobacter (bacteria)

Question 40

in order for nitrifying bacteria to oxidise ammonium into nitrites + nitrates, what does it need?

Answer 40

oxygen - so will need aerated soil

Question 41

how do plants get nitrates? By which process? To make?

Answer 41

Through absorption and assimilation. nitrates, could be dissolved in the water within the soil and are able to be absorbed into the plant by active transport , then they're assimilated into cells - so used to create Amino acids, ATP + DNA

Question 42

how does waterlogged soil affect how the nitrifying bacteria?

Answer 42

no oxygen can get in - so an insufficient supply of oxygen - will be under anaerobic conditions - denitrification will occur - so nitrates are converted back into N2 gas

Question 43

what are the nitrates made into when absorbed into the plant?

Answer 43

made into biological molecules such as proteins, DNA, RNA, ATP

Question 44

How do animals get nitrates/ nitrogen?

Answer 44

animals eat the plants, and will also absorb the nitrates + assimilate biological molecules such as DNA, proteins

Question 45

what happens when animals eat the plants?

Answer 45

they produce waste (faeces) which will contain ammonia - as well as when they decompose. - ammonification

Question 46

what happens when plants and animals die?

Answer 46

AMMONIFICATION - the proteins, DNA, ATP that is made within them can be broken down by saprobiotic microorganisms back into ammonia.

Question 47

what can the saprobiotic microorganisms do to the proteins, amino acids, DNA or even detritus (waste or debris)? Results in two processes

Answer 47

stage 1 - can digest, break down the proteins into amino acids (nitrogen containing compounds) using extracellular protease enzymes - (also into ammonia- ammonification) stage 2 - removal of the amino group from the amino acids using a deaminase enzymes - deamination

Question 48

What is Denitrification?

Answer 48

is the process in which nitrates are converted back into atmospheric nitrogen gas. NO3- ------> N2

Question 49

What type of bacteria is denitrification carried out by?

Answer 49

anaerobic denitrifying bacteria uses nitrates as electron acceptors in respiration to produce nitrogen gas

Question 50

when does denitrification occur?

Answer 50

in conditions with no oxygen so tends to take place in waterlogged soil

Question 51

how can farmers prevent denitrification?

Answer 51

plow the soil to aerate the soil using a garden fork to make sure there is oxygen

Question 52

Phosphorus cycle

Question 53

what is the phosphorus cycle?

Answer 53

The phosphorus cycle shows how phosphorus is recycled in ecosystems and explores the role of mycorrhizae in facilitating the uptake of water + inorganic ions by plants.

Question 54

what is phosphorus needed for to make?

Answer 54

- Phospholipids (phosphate group) - ATP (phosphate ion) - Nucleotides -> DNA/RNA (phosphate ion)

Question 55

what are mycorrhizae?

Answer 55

fungal associations between plant roots and beneficial fungi

Question 56

why are mycorrhizae beneficial for plant growth?

Answer 56

1. the fungi increase the surface area for water and mineral absorption 2. the mycorrhizae acts like a sponge so holds water and minerals around the roots 3. this makes plants more drought resistant and able to take up more inorganic ions

Question 57

so overall what is their part in nutrient cycles?

Answer 57

improving the uptake of relatively scarce ions, such as phosphate ions - act mutalistically

Question 58

Draw a diagram of the phosphorus cycle

Question 59

describe the phosphorus cycle, including all the stages

Answer 59

1. Phosphate ions in sedimentary rocks are released into oceans, rivers and soil b weathering 2. Phosphate ions are taken into the plants through the roots by active transport. Mycorrhizae increase the rate at which phosphorus can be assimilated 3. Animals will then eat, absorb and digest the plants, and then also assimilate these phosphate ions into their biological molecules such as phospholipids, DNA 4. Phosphate ions are lost from animals through waste products via excretion 5. Guano - waste products by birds is rich in phosphate ions, and returns phosphate ions back to the soil. 6. when plats and animals die, saprobionts are involved in breaking down organic compounds, releasing phosphate ions into the soil for the assimilation of plants. these microorganisms also release the phosphate ions from urine and faeces 7. some phosphate ions remain in the shells/bones of animals and so go through a slow break down of phosphates and release into oceans and rivers. some of this will go towards creating phosphorus in rocks called deposition. 8. And through sedimentation, the build up of phosphate ions and sediment in oceans and rivers build up creating sedimentary rocks (over thousands of years)

Question 60

Fertilisers And Eutrophication

Question 61

Why do we need fertilisers?

Answer 61

Fertilisers are added to the soil to replace the lost nitrates and phosphate ions when plants are harvested and removed from nutrient cycles as crops.

Question 62

when we remove crops...? Also when we remove animals..?

Answer 62

- they can no longer can die and decompose, and return the mineral ions/nutrients they contain back to the soil - when animals are removed from land, they used to eat grass + plants from and take in their nutrients, phosphates and nitrates are also lost, the urine, faeces and dead matter is not returned to the same area of land.

Question 63

So farmers use fertilisers to..?

Answer 63

replace the lost minerals, so more energy from the ecosystem can be used for growth, increasing the efficiency of energy transfer

Question 64

What are the two types of fertilisers?

Answer 64

Natural (organic) and artificial (inorganic)

Question 65

What are natural fertilisers?

Answer 65

Natural fertilisers are organic material – which consist of dead and decaying plants and animals as well as animal wastes such as manure, slurry and bone meal

Question 66

what are Artificial fertilisers?

Answer 66

Artificial fertilisers are made up of inorganic matter which are mined from rocks and deposits and then converted into different forms and blended together to give the appropriate balance of minerals for a particular crop. (usually containing NPK)

Question 67

How do fertilisers increase productivity?

Answer 67

nitrogen + phosphorus is needed to make proteins, AA, DNA and chlorophyll which is needed for plant growth. without/ less will limit plant growth and so it's addition increases productivity.

Question 68

why after a certain point, the addition of more fertilisers no longer improves the productivity of a crop?

Answer 68

some other factor is limiting photosynthesis. e.g light, co2, and only the addition of this factor will increase photosynthesis and hence productivity

Question 69

explain the consequences of the addition of too much fertiliser?

Answer 69

- reduced species diversity - because nitrogen-rich soils favour the growth of grasses, nettles + other rapidly growing species. - species-rich Hay Meadows, only survive when nitrogen conc. in soil is low enough to allow other species to compete with the grasses - Leeching - leads to pollution of rivers, pond (watercourses - Eutrophication -

Question 70

What is Leeching?

Answer 70

leaching is the process by which excess water-soluble compounds in the soil are washed away by rain water or irrigation systems. They're often washed away into nearby rivers and ponds. and can lead to eutrophication

Question 71

why is leeching less likely by natural fertilisers?

Answer 71

the nitrogen and phosphorus are still contained in organic molecules that need to be decomposed by microorganisms before they can be absorbed by plants. this means their release into the soil for uptake by plants is more controlled.

Question 72

why is the leeching of nitrogen more likely than phosphorus?

Answer 72

nitrates are more water-soluble than phosphates

Question 73

what is Eutrophication?

Answer 73

the process by which excess nutrients end up in freshwater lakes and rivers.

Question 74

Describe the process of eutrophication

Answer 74

1. excess fertiliser/ mineral ions is leached from the soil causing algae to bloom 2. large amounts of algae block the sunlight from reaching bottom dwelling plants 3. plants end up dying from not being able to photosynthesise 4. increased dead matter means saprobiontic bacteria feed on the dead plant matter, and so population of bacteria grows. 5. these bacteria will then use the oxygen in the water in order to undergo aerobic respiration, reducing the oxygen concentration in the water 6. Aerobic animals such as fish and other aquatic organisms die as there isn't enough dissolved oxygen in the water. 7. the anaerobic organism further decompose dead material, making water putrid

Question 75

what are the factors which affect eutrophication: when is it more likely to happen? when is it least likely to happen in?

Answer 75

more likely to occur in hot weather - because metabolic processes are speeded up due to increased enzyme activity less likely to occur in moving water - because water is re-oxygenated continually and mineral ions are diluted rapidly

Question 76

Advantages of Natural fertilisers?

Answer 76

ADV: - nutrients not readily leached from the soil - add structure to the soil in the form of humus - provides a useful means of disposing of animal/ farm waste - provides a steady supply of nutrients to plants and contain both macro + micro nutrients

Question 77

Disadvantages of natural fertilisers?

Answer 77

DISADVANTAGES - Offensive smells - mineral release is slow - unknown quantity of minerals - may be difficult to spread and store

Question 78

Advantages of Artificial fertilisers?

Answer 78

ADVANTAGES - easy to apply to fields - nutrients in concentrated form and can therefore be applied in smaller amounts so cost effective - clean chemicals that lack odor of organic manure - nutrients released rapidly into the soil (more soluble)

Question 79

Disadvantage of Artificial fertilisers?

Answer 79

DISADVANTAGES: - risk of fertiliser spray being spread to other areas - expensive to manufacture and buy - increased risk of eutrophication - readily leached from soil

Question 80

DONE