ENERGY TRANSFERS IN + BETWEEN ORGANISMS

Question 1

PHOTOSYTHESIS EQUATION

Answer 1

6CO2 + 6H2O → C6H12O6 + 6O2

Question 2

ADAPTIONS OF LEAVES TO PHOTOSYNTHESIS

Answer 2

.Large surface area
.Thin so diffusion distances are short and to capture light as only penetrates few mm
.Transparent cuticle to let light through
.Long narrow layer of palisade mesophyll cells allows many cells packed close to surface for light absorption
.Cells packed w/chloroplasts around edge that collect light
.Stomata on lower surface for gas exchange
.Air spaces in lower mesophyll layer for diffusion of gases
.Xylem brings water and phloem carries away sugar in form of sucrose

Question 3

CHLOROPLAST STRUCTURE

Answer 3

.Chloroplasts are transducers: convert energy of light photons into ATP chemical energy

.composed of double membrane w/ stroma inside-Stroma is site of Calvin cycle – light independent reactions of photosynthesis

.Membrane thylakoids are composed of flattened sacs called lamellae-Grana are several stacked thylakoids containing photosynthetic pigments e.g. chlorophyll-absorb light for light dependent reactions of photosynthesis

.Chloroplasts also often contain starch grains- amyloplasts and lipid droplets which are products of photosynthesis

Question 4

PHOTOSYSTEMS

Answer 4

.Chloroplasts contain photosystems embedded in thylakoid membranes
.Photosystem I contains chlorophyll w/light absorption peak at wavelength of 700nm and Photosystem II contains chlorophyll w/light absorption peak at wavelength of 680nm

Question 5

WHY DO LEAVES CONTAIN DIFFERENT TYPES OF PIGMENT

Answer 5

.maximise absorption of light
.absorption spectrum is graph of light absorption against wavelength of light
.action spectrum is graph of rate of photosynthesis against wavelength of light

Question 6

LIGHT DEPENDANT REACTION IN THYLAKOIDS/GRANA

Answer 6

1. Photoionisation- Light absorbed by chlorophyll in photosystems I and II-electrons of chlorophyll are excited to higher energy level
2. Photosystem II Photolysis also occurs-Light used indirectly to split water to produce protons electrons and oxygen gas: H2O → H+ + OH-
3. Electrons replace those previously lost by chlorophyll in Photosystem II
4. Photolysis raises concentration of protons in thylakoid space
5. High energy electrons released from chlorophyll are accepted by electron acceptors and are then transferred between electron carriers and used in manufacture of ATP (chemiosmosis)
6. reduction of NADP is brought about by addition of electrons and H+ ions
7. Electrons emitted from Photosystem II are used to replace those lost from Photosystem I

Question 7

HOW CHEMIOSMOSIS PRODUCES ATP

Answer 7

1. ATP is produced across thylakoid membranes- Hydrogen can be split into proton
   and an electron
2. Proton pumps fuelled by high energy electrons from electron transfer chain in membrane pump protons into thylakoid space to maintain their high concentration
3. membrane is impermeable to protons but they diffuse down their electrochemical gradient through enzyme ATP synthase on stalked particle from thylakoid space into stroma
4. causes ADP + Pi to form ATP

Question 8

PRODUCTS OF LIGHT DEPENDANT REACTION

Answer 8

Oxygen-used in respiration or diffuses out of leaf through stomata
ATP and reduced NADP- which are used in Light Independent Reactions

Question 9

LIGHT INDEPENDANT REACTION IN STROMA

Answer 9

1. CO2 combines RuBP using rubisco enzyme
2. which produces 2 glycerate phosphate
3. 2 Glycerate Phosphate are reduced to form 2 Triose phosphate using energy from ATP → ADP + Pi and reducing power and H supply of reduced NADP
4. Triose Phosphate can then be converted to make 6C hexoses eg. glucose
5. 5C from Triose Phosphate is used to regenerate RuBP using more energy from ATP → ADP + Pi

Question 10

GROSS VS NET PHOTOSYNTHESIS

Answer 10

gross: total rate of CO2 uptake
net: difference between CO2 uptake and release
-gross is always bigger than net

Question 11

LIMITING FACTOR MEANING

Answer 11

factor which if increased rate of overall reaction also increases

Question 12

FACTORS THAT AFFECT RATE OF PHOTOSYNTHESIS: LIGHT INTENSITY

Answer 12

.light intensity increases, rate of photosynthesis increases
.light saturation point now another factor is limiting photosynthesis
.high light intensities rate of photosynthesis-remains constant-limiting reagent is something else (temp or CO2)

If reduced, levels of ATP and reduced NADP would fall
LDR limited - less photolysis and photoionisation
GP cannot be reduced to triose phosphate in LIR

Question 13

FACTORS THAT AFFECT RATE OF PHOTOSYNTHESIS: CO2 CONCENTRATION

Answer 13

.increase in CO2 increases rate of photosynthesis
.at low concentration CO2 is limiting factor
.at high concentration CO2 is no longer limiting factor could be temp or CO2

If reduced, LIR inhibited
less CO2 to combine w/RuBP to form GP
less GP reduced to TP
less TP converted to hexose and RuBP regenerated

Question 14

FACTORS THAT AFFECT RATE OF PHOTOSYNTHESIS: TEMPERATURE

Answer 14

At low temperatures, there is not enough kinetic energy for successful collisions between enzyme and substrate
At too high temperature, enzymes denature, active site changes shape and enzyme- substrate complexes cannot form so limiting factor light intensity or CO2

Question 15

FACTORS THAT AFFECT RATE OF PHOTOSYNTHESIS: LIGHT WAVELENGTH

Answer 15

Provides energy for light dependent reaction
Only certain wavelengths are absorbed: red and blue
Green is reflected

Question 16

COMPENSATION POINT

Answer 16

point at which photosynthesis and respiration are taking place at same rate

Question 17

EVALUATING DATA ABOUT ARGICULTURE PRACTICES USED TO OVERCOME LIMITING FACTORS IN PHOTOSYTHESIS

Answer 17

.Use of glass houses to control temperature, light intensity, wavelength of light and carbon dioxide levels- increased temperature may increase rate of respiration, so no further increase in biomass of plant

.Use of pesticides removes unwanted pests: decreases biodiversity as affects feeding relationships

.Removal of hedgerows to reduce competition/shade from crops: decreases biodiversity as decreases variety of food sources and habitats

.Atrazine-herbicide is weedkiller used to reduce competition-Atrazine binds to proteins in electron transfer chain in chloroplasts of weeds reducing transfer of electrons down chain: decreases variety of food sources, habitats and therefore biodiversity

.Use of genetically modified crops which are e.g., give higher yield or resistance to herbicides-Issues
w/transferring modified genes to wild plants

Question 18

RP7-USE OF CHROMATOGRAPTHY TO INVETSTIGATE PIGMENTS ISOLATED FROM LEAVES OF DIFFERENT PLANTS

Answer 18

1. Draw line on paper using ruler and pencil
2. add chlorophyll/solution to line
3. Add solvent below line
4. Remove before solvent reaches end
5. Calculate rf value by Distance moved by
   pigment/Distance moved by solvent

Question 19

RP7-EXPLIAN ADVANTAGES OF CALCULATING RF VALUES

Answer 19

RF values can be compared to known values to identify compound

Question 20

RP7-WHEN CALCULATING RF VALUE,MIDDLE OF SPOT IS USED-WHY?

Answer 20

Allows comparison as it standardises readings

Question 21

EXPLAIN WHY STUDENT MARKED ORGIN USING PENCIL RANTHER THAN INK

Answer 21

Ink and leaf pigments would mix

Question 22

WHY DOES SOLVENT FRONT HACE TO BE MARKED BEFORE PAPER CHROMATOGRAPHY DRIES

Answer 22

stood in solvent as before and left until solvent front gets close to top of paper

Question 23

RP8-INVESTIGATE INTO EFFECT OF NAMED FACTOR ON RATE OF DEHYDROGENASE ACTIVITY IN EXTRACTS OF CHLOROPLASTS

Answer 23

1. In photosystem I, during light-dependent stage of photosynthesis, NADP acts as an electron acceptor and is reduced- reaction is catalysed by dehydrogenase enzyme
2. activity of enzyme can be investigated using redox indicator eg. DCPIP and adding it to extracts of chloroplasts
3. DCPIP acts as an electron acceptor and becomes reduced, changing colour from blue to colourless
4. End point of a colour change is subjective- absorption of solution could be measured using colorimeter every unit of time- end point could be identified by point when absorption no longer changes

Question 24

RP8-WHY ARE LEAVES BLENDED

Answer 24

release chloroplasts by breaking open cells

Question 25

RP8-WHY ARE LEAVES FILTERED

Answer 25

remove any large piece of cell debris

Question 26

RP8-AMMONIUM HYDORXIDE IS USEF AS WEEDKILLER AS IT IS AN PROTON ACCEPTOR WHY?

Answer 26

Less ATP Less reduced NADP Less light independent reactions Less reduction of GP to TP Less organic products eg. glucose Less respiration

Question 27

RESPIRATION

Answer 27

series of enzyme-catalysed catabolic reactions which release chemical energy from organic molecules in order to synthesise ATP

Question 28

TYPES OF COENZYMES

Answer 28

NAD: Can accept hydrogen to form reduced NAD FAD: Can accept hydrogen to form reduced FAD

Question 29

PHOSOHORYLATION

Answer 29

Adding an inorganic phosphate- Pi to ADP to form ATP

Question 30

OXIDATION + REDUCTION

Answer 30

O: removing hydrogens/electrons R: adding hydrogens/electrons

Question 31

SUBSTRATE LEVEL PHOSPHORYLATION

Answer 31

synthesis of ATP by transfer of phosphate group from phosphorylated intermediate to ADP

Question 32

OXIDATION PHOSPHORYLATION

Answer 32

synthesis of ATP from reduced coenzymes and oxygen in electron transfer chain of aerobic respiration

Question 33

WHAT ARE 4 STAGES FOR AREOBIC RESPIRATION

Answer 33

1. glycolysis 2. link reaction 3. Krebs cycle 4. oxidation phosphorylation

Question 34

GLYCOLYSIS

Answer 34

cytoplasm and anaerobic 1. Phosphorylation of glucose using ATP 2. oxidation of Triose phosphate to pyruvate 3. net gain of ATP 4. reduced NAD .Net gain from 1 x glucose: 2 x ATP 2 x reduced NAD 2 x Pyruvate

Question 35

LINK REACTION

Answer 35

.Dehydrogenation: Pyruvate is actively transported to mitochondria from cytoplasm and is oxidised as hydrogen is removed and transferred to NAD which is reduced to form reduced NAD .It is also decarboxylated CO2 is removed to form acetate .Acetate then combined w/CoA to form Acetyl CoA .Net gain from 1 x glucose: 2 x reduced NAD 2 x Acetyl Coenzyme A

Question 36

KREBS CYCLE

Answer 36

.2C Acetyl CoA enters the cycle and acetyl is accepted by 4C acid to form 6C acid regenerating CoA for link reaction .Cycle turns twice for each original glucose molecule .2C acetate fragment is completely broken down and 4C acid is regenerated via 6C and 5C intermediates in series of oxidation-reduction reactions .1 x ATP is produced directly by substrate level phosphorylation of ADP .2 x C atoms are released in 2 x CO2 molecules by decarboxylase .3 x reduced NAD and 1 x reduced FAD are produced as 4 pairs of H atoms are removed to these hydrogen carriers by dehydrogenase .Net gain from 1 x glucose: 6 x reduced NAD 2 x reduced FAD 4X carbon dioxide 2X ATP

Question 37

OXIDATIVE PHOSPHORYLATION

Answer 37

.Enzymes remove hydrogen from reduced NAD/FAD and split it into H+ and high energy e- .e- flow through electron transfer chain of carriers releasing energy at each lower energy level-This energy is used to power proton pumps .Proton pump: H+ pumped across inner membrane to inter membrane space H+ diffuse down an electrochemical gradient back to matrix through ATP synthase synthesising ATP from ADP and Pi by chemiosmosis .Reduced NAD powers 3 pumps, reduced FAD powers 2 pumps .O2 acts as final H+ and e- acceptor forming H2O which maintains flow of electrons

Question 38

DESCRIBE HOW ATP IS MADE IN MITOCHONDRIA

Answer 38

1. substrate level phosphorylation 2. link reaction produces reduced coenzymes 3. electrons released from coenzymes 4. electrons pass along carrier 5. energy released 6. ADP + Pi 7. protons move into membrane space 8. ATP synthase

Question 39

HOW MANY ATP FORM EACH NAD + FAD

Answer 39

2.5 ATP made from each NAD 1.5 ATP made from each FAD

Question 40

ANAEREOBIC RESPIRATION

Answer 40

.Under anaerobic conditions reduced NAD cannot be re-oxidised and so made available to pick up more hydrogen .there is no oxygen to act as final electron acceptor at end of electron transport chain .link reaction, Krebs cycle and oxidative phosphorylation stop .without NAD being re-oxidised, glycolysis will stop and no ATP will be formed .Need to re-oxidise reduced NAD back to NAD for glycolysis to continue anaerobic respiration, much less ATP is formed compared to aerobic respiration-ATP formed is from glycolysis

Question 41

OXIDATION OF NAD IN ANIMAL MUSCLE TISSUE-LACTATE FERMENTATION

Answer 41

.H from reduced NAD combines w/pyruvate to form lactate .Lactate causes cramp in muscle and builds up an oxygen debt .Lactate is eventually oxidised back to pyruvate when O2 is available by rapid breathing Pyruvate ↓ ↓ (Reduced NAD → NAD) ↓ Lactate

Question 42

OXIDATION OF NAD IN YEAST-ALCOHOLIC FERMENTATION

Answer 42

.Pyruvate is decarboxylated to ethanal .Carbon dioxide is produced .Ethanal is reduced as it accepts H from reduced NAD and is converted to ethanol Pyruvate ↓ ↓ (→CO2) ↓ Ethanal ↓ ↓ (Reduced NAD → NAD) ↓ Ethanol

Question 43

ANAEROBIC RESPIRATION IS RELATIVELY INEFFICIENT COMPARED TO AEROBIC

Answer 43

.Pyruvate is used to form lactate or ethanol .Under anaerobic conditions, link reaction/Krebs cycle/oxidative phosphorylation cannot take place so only ATP formed is from glycolysis .Only 2 x ATP synthesised per molecule of glucose, about 2% efficiency as there is still lots of energy contained within lactate or ethanol .More anaerobic respiration is needed to produce same amount of ATP

Question 44

DESCRIBE WHAT HAPPENS TO PYRUVATE IN ANAEROBIC CONDITIONS + EXPLAIN WHY ANAEROBIC RESPIRATION IS ADVANTAGEOUS TO HUMAN SKELETAL MUSCLE

Answer 44

Forms lactate Use of reduced NAD Regenerates NAD NAD can be re-used to oxidise more respiratory substrate

Question 45

ALTERNATIVE RESPIRATORY SUBSTRATES

Answer 45

.carbohydrates are in short supply fats and proteins may be used as respiratory substrates .Lipase digests fats to fatty acids and glycerol by hydrolysing ester bonds .Glycerol is converted to 3-carbon sugar, triose phosphate, an intermediate of glycolysis .Long fatty acid chains molecules are split into 2C fragments which enter pathways as acetyl coenzyme A- This generates lot of ATP as chains can be very long .Endopeptidases, exopeptidase and dipeptidases digest proteins to amino acids by hydrolysing peptide bonds .Amino acids are deaminated in liver .amine group is converted to urea and excreted by kidneys .rest of amino acids are converted into various organic acids which can enter respiratory pathways

Question 46

RP9-INVESTIGATE TO EFFECT OF NAMED VARIABLE ON RATE OF RESPIRATION OF CULTURES OF SINGLE-CELLED ORGANISM

Answer 46

.Methylene blue is an artificial acceptor of H+ and changes colour from blue to colourless when reduced .Yeast, when respiring produce H+ due to their dehydrogenase enzymes .A: Control tube B: Experimental tube .Measure time to go colourless at eg. range of temperatures

Question 47

RP9-WHY ARE TUBES LEFT FOR __ MINUTES IN WATER BATH BEFORE ADDING METHYLENE BLUE

Answer 47

allows yeast mixture to equilibrate/ reach temperature of water bath

Question 48

RP9-HOW WOULD TEMPERATURE BE CONSTANT

Answer 48

use thermostatically controlled water bath-temperature would cool using beaker of water as water bath

Question 49

RP9-WHY SHOULD YOU NOT SHAKE TUBES

Answer 49

Oxygen would act as final electron acceptor instead of methylene blue

Question 50

RP9-EXPLAIN HOW END POINT FOR THIS PRACTICAL IS STANDARDISED

Answer 50

Set up control to compare results to – yeast and glucose solution w/no methylene blue

Question 51

RP9-SUGGEST ONE SOURCE OF ERROR

Answer 51

Colour change end-point is difficult to determine

Question 52

USING RESPIROMETER

Answer 52

.Measures rate of O2 consumption by aerobic respiration .Choose temperature normal for organism which will be optimum for enzymes .Set up and leave for 10 minutes to reach equilibrium, allow for volume changes and respiration rate of seeds to stabilise .CO2 given out is absorbed by KOH solution so volume in B decreases .liquid moves as O2 is taken up by organism .Measure distance moved by liquid in a set period of time e.g. every 10 minutes .Calculate volume of oxygen absorbed using πr2h per unit of time where r is radius of capillary tube lumen, and h is distance moved by dye

Question 53

RESPIRTOMETER-EXPLAIN WHY RESPIROMETER APPARATUS IS LEFT OPEN FOR 10 MIN

Answer 53

Allows apparatus to equilibrate, allows for respiration rate to stabilise following handling

Question 54

RESPIRTOMETER-WHY TEMPERATURE RANGE WOULD BE SUITABLE AND WHY

Answer 54

20-40 ⁰C – optimum for respiratory enzymes

Question 55

ECOSYSTEMS

Answer 55

area comprising living organisms, biotic, and non-living, abiotic, components w/which they interact, plants synthesise organic compounds from atmospheric, or aquatic CO2 Most of sugars synthesised by plants are used by plant as respiratory substrates- rest are used to make other groups of biological molecules- biological molecules form biomass of plants

Question 56

BIOMASS

Answer 56

total mass of organisms in given area or volume formed from biological molecules

Question 57

HOW TO CALCULATE BIOMASS

Answer 57

sample from known area is dried in a low temperature oven-mass is weighed regularly, and when this is constant, all water has been removed Scale up answer to kg m-3

Question 58

ENERGY

Answer 58

.chemical energy store in dry biomass can be estimated using calorimetry .Burn plant matter in calorimeter and use energy to heat known volume of water .amount of energy needed to raise 1cm3 water by 1°C is 4.2 joules so Energy content (J) = temperature increase of water (°C) X volume of water in cm3 X 4.2

Question 59

ENERGY FLOW THROUGH ECOSYSTEMS-SUN

Answer 59

source of energy for ecosystem

Question 60

CALORIMETER INCLUDES:

Answer 60

.Chamber is sealed so all heat energy produced is transferred to surrounding water .Stirrer distributes heat energy .Chamber is insulated to prevent heat loss to surroundings

Question 61

ENERGY FLOW THROUGH ECOSYSTEMS-PRODUCERS

Answer 61

.Green plants trap solar energy in photosynthesis and convert it to chemical energy in sugars .Energy hitting leaf is lost due to reflected light, light passing through leaf and energy lost as heat- Some of this heat energy evaporates water from surface of leaf

Question 62

GROSS PRIMARY PRODUCTIVITY (GPP)

Answer 62

.biomass per area or volume .rate at which light energy is converted into chemical energy products by photosynthesis eg glucose are formed by plants- substantial amount of gross production is respired by plant and lost as heat

Question 63

NET PRIMARY PRODUCTIVITY (NPP)

Answer 63

which is left over and represents potential food available to primary consumers

Question 64

FOOD WEB CHAIN

Answer 64

Shows feeding relationships-Arrow shows direction of energy flow

Question 65

NPP EQUATION

Answer 65

NPP=GPP-respiration

Question 66

TROPHIC LEVEL

Answer 66

Level of feeding Eg. Producer / herbivore / carnivore

Question 67

ENERGY TRANSFERRED

Answer 67

through trophic levels from plants to animals when eaten, animals to animals and plants and animals to decomposers through food webs

Question 68

ENERGY LOST

Answer 68

transfer from one trophic level to next due to heat loss in respiration, egestion of non-digestible parts, excretion of waste products, and not eating all parts- loss limits food chain to 4 or 5 steps

Question 69

HERBIVORES (PRIMARY CONSUMERS)

Answer 69

receive about 10% of energy-Eg. Some parts of plants are not eaten/are egested so are passed to decomposers instead

Question 70

CARNIVORS (SECONDARY/TERTIARY CONSUMERS)

Answer 70

more efficient at energy conversion because they are able to digest their high protein diets more efficiently so less egestion

Question 71

NET PRODUCTION OF CONSUMERS EQUATION

Answer 71

N = I – (F + R) I represents chemical energy store in ingested food F represents chemical energy lost to environment in faeces and urine and R represents respiratory losses to environment

Question 72

DECOMPOSERS

Answer 72

feed as saprobionts gaining energy from organic compounds in dead producers and consumers

Question 73

ENERGY FROM RESPIRATION IN CONSUMERS IOS USED THEN LOST AS HEAT

Answer 73

eg. Movement, active transport, maintaining body temperature, anabolic/catabolic reactions

Question 74

EXCREATION

Answer 74

Consumers lose energy excreting eg. Urea Energy in faeces/urine is passed to decomposers

Question 75

FARMING PRACTICES INCREASE EFFICIENCY OF ENERGY TRANSFER BY:

Answer 75

.Simplifying food webs to reduce energy losses to non-human food chains Eg. Reducing pests w/chemical pesticides, eg weeds that compete for light/water/minerals w/herbicides, greenfly that eat crops w/ insecticides- increase crop NPP .Reducing respiratory losses within human food chain .Restrict movement of animals as this uses energy .Keep animals warm indoors to reduce energy lost maintaining body temperature

Question 76

CALCULATE EFFICIENCY OF ENERGY TRANSFER

Answer 76

net productivity/ energy supplied x 100

Question 77

RABBITS INGEST 20,000 KJ M-2 OF ENERGY. THEY LOSE 12,000 KJ M-2YR-1 IN FEACES AND URINE AND USE 6000 KJ M-2YR-1 FOR RESPIRATION CALCULATE EFFICIENCY % FOR ENERGY TRANSFER

Answer 77

N = I – (F + R) 20,000-12,000 + 6000=2000 2000/20,000 x100= 10%

Question 78

SAPROBIONTS FEED ON DEAD ORGANISMS AND THIER WASTE PRODUCTS

Answer 78

.Extracellular digestion: secrete enzymes and digest their food externally-they absorb products of digestion .During this process, organic molecules are broken down to inorganic ones

Question 79

MYCORRHIZAE

Answer 79

.Some fungi form symbiotic relationships w/plants .long, thin hyphae of fungi connect to plant roots .increase surface area enabling plant to obtain more water and inorganic ions .fungi get useful organic compounds from plants eg. Sugars

Question 80

NITROGEN CYCLE

Answer 80

1. Ammonification/Putrefaction .Saprobionts hydrolyse proteins from dead matter into ammonium compounds 2. Nitrogen Fixation .N2 ‘fixed’ to NH4+ and then amino acids .Symbiotic nitrogen fixing bacteria in root nodules of leguminous plants- pass on compounds to plant-plant can then grow in low fertility soils-plant provides anaerobic conditions for bacterium and passes on carbohydrates 3. Nitrification .Requires aerobic conditions as is oxidation .Nitrifying bacteria convert NH4+ to NO2- then- to NO3- -require O2 to oxidise NH4+ ions 4. Conversion to Organic Nitrogen .Plants absorb NO3- by taking them up by their roots from soil by active transport and use nitrogen to produce amino acids then proteins eg enzymes and ATP .Animals eat plants, digest proteins to amino acids make more proteins 5. Denitrification .Requires anaerobic conditions so often problem in waterlogged soil .Denitrifying bacteria convert nitrate to atmospheric nitrogen gas 6. Ammonification .Organic nitrogen in dead organisms, faeces, nitrogenous excretory products eg. urea decayed by decomposers .Proteins hydrolysed to amino acids

Question 81

AFTER HARVESTING REMAINS OF CROP PLANTS ARE OFTEN PLOUGHED INTO SOIL. EXPLAIN HOW MICRO-ORGANISMS IN SOIL PRODUCES SOURCE OF NITRATES FROM THESES REMAINS

Answer 81

1. Protein into ammonium compounds 2. By saprobionts 3. Ammonium into nitrite 4. Nitrite into nitrate 5. By nitrifying bacteria

Question 82

ROLE OF SAPROBIONTS IN NITROGEN CYCLE

Answer 82

1. use enzymes to decompose proteins 2. releasing ammonium ions

Question 83

PHOSPHOROUS CYCLE

Answer 83

1. PO43- in soil through weathering rocks 2. plants absorb inorganic phosphate and use it to form inorganic compounds eg.ATP 3. animals digest organic matter and form animal compounds 4. saprobionts digest organic matter eg.DNA and release inorganic phosphates in soil 5. PO43- in rocks weathering of rocks also releases PO43- into seas, lakes,rivers to aquatic food chains

Question 84

FERTILISERS

Answer 84

.Nutrients are lost from soils on agricultural land .Plants absorb nutrients then are harvested and taken away .Animals eat plants, then are taken away and slaughtered .Fertilisers replace these nutrients, so that more energy can be used for growth .Artificial fertilisers are inorganic eg. Ammonium nitrate- more soluble in water than organic fertilisers .Natural fertilisers are organic eg. Manure, composted vegetables

Question 85

NATURAL FERTILISER ADVANTAGE + DISADVANTAGE

Answer 85

ADVANTAGES .Cheaper than artificial fertilisers .often free if farmer has own animals - recycle manure organic molecules have to be broken down first by saprobionts so leaching less likely DISADVATAGES Exact minerals and proportions cannot be controlled

Question 86

ARTIFICIAL FERTILISER ADVANTAGE + DISADVANTAGE

Answer 86

ADVANTAGES .Contain pure chemicals in exact proportions more water-soluble, so more ions dissolve in water surrounding soil .higher absorption DISADVATAGES .High solubility means larger quantities can leach away w/rain .risking eutrophication reduce species diversity as favour plants w/higher growth rates e.g., nettles

Question 87

LEACHING

Answer 87

When water-soluble compounds are washed away into rivers for nitrogen fertilisers, this can lead to eutrophication

Question 88

EUTROPHICATION CAUSE ALGAL BLOOMS IN RIVERS/LAKES

Answer 88

.Mineral ions e.g nitrate and phosphate are soluble and leach into rivers after rainfall on agricultural land .Algal bloom: single celled plants rapidly grow due to high nutrients .General decrease in diversity as light cannot reach larger submerged plants which die .Algae are short lived and are decomposed by saprobiotic bacteria which respire aerobically and create high biological oxygen demand so fish die due to lack of oxygen .Anaerobic bacteria may then reduce nitrates to nitrites

Question 89

NITRATE FROM FERTILISER APPLIED TO CROPS MAY ENTER PONDS AND LAKES. EXPLAIN HOW NITRATE MAY CAUSE DEATH OF FISH IN FRESH WATER

Answer 89

1. Growth of algae blocks light 2. Reduced / no photosynthesis so plants die 3. Saprobiotic bacteria 4. Aerobically respire 5. Less oxygen for fish to respire